[HN Gopher] Myths in cycling: wider tires are slower
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Myths in cycling: wider tires are slower
Author : jmilloy
Score : 165 points
Date : 2021-06-14 18:45 UTC (4 hours ago)
(HTM) web link (www.renehersecycles.com)
(TXT) w3m dump (www.renehersecycles.com)
| wolverine876 wrote:
| Can anyone recommend serious science and engineering sources on
| bicycles? I've looked hard and only found a couple:
|
| * _Bicycling Science_ by David Gordon Wilson: Book by MIT
| mechanical engineering professor, going back four editions to the
| 1970s. https://mitpress.mit.edu/books/bicycling-science-fourth-
| edit...
|
| * "Bicycle Technology" by SS Wilson in Scientific American (Mar
| 1973): Great starting point on the technology and it's
| development. PDF:
| http://veterancycleclublibrary.org.uk/ncl/pics/Bicycle%20Tec...
|
| Here's a few more I haven't yet pursued:
|
| * Journal of Science and Cycling: Open access online journal
| https://www.jsc-journal.com/
|
| * International Human Powered Vehicle Association (IHPVA) and
| World Human Powered Vehicle Association (WHPVA): Apparently one
| association that split acrimoniously in the 2000s. I haven't
| pursued this.
|
| * Cycle Engineers Institute (CEI) (UK)
|
| * European Cyclists Federation (ECF)
|
| I'd love to find other publications, and a community and forum.
| When I ask around at bike shops, most people refer me to Park
| Tools, which isn't what I'm after.
| sam wrote:
| If you're interested in wheels, check out _The Bicycle Wheel_
| by Jobst Brandt. If you 're building wheels it's a must have.
| adolph wrote:
| https://sheldonbrown.com/
| dnhz wrote:
| I don't believe it. When I had a cheapo mountain bike, I could
| hear the tires on the road, especially at higher speeds. With my
| current road bike, the tires are a lot quieter. That noise
| translates into lost energy, including lost energy that can't be
| heard. Sure the bikes differ a lot, but the difference in rolling
| resistance is stark to me. The road bike also can roll for a lot
| longer a distance.
| msandford wrote:
| It sounds like you haven't read even a paragraph or two.
| They're talking about road slicks vs road slicks, not mtb tires
| vs road tires.
| discreteevent wrote:
| Mountain bike has knobbly tread. This article is taking about
| wide smooth tires.
| geocrasher wrote:
| Wider tires are not slower. They are heavier. Heavier tires are
| slower than light tires because they take significantly more
| energy to get them up to speed.
| wiredfool wrote:
| Yes, but the effect is rather small, because the rotating mass
| is small compared to the combined mass of bike and rider.
|
| Also, a typical trick is to go to a smaller diameter wheel and
| a larger tire, so that the handling and moment of inertia are
| similar.
|
| For example, I've got two rim brake wheels, one 700c 16 spoke
| aero front wheel with a 23mm tire on it, and one 26" 36 spoke
| tandem/mtb front wheel with a 44mm tire, and the difference in
| weight is 200g. (1200 vs 1400)
|
| Even on the road bike, that's only a 0.4% difference. (Not that
| they're compatible wheels, it's just the only decent comparison
| I have on hand)
| thrwyoilarticle wrote:
| This is not the conclusion the article reaches.
| toxik wrote:
| In particular their inertia is higher, and the tire is the
| worst place to put heavy things physically speaking.
| carl_dr wrote:
| Not disagreeing with you at all - it is true.
|
| But for most people, whether or not you went to the toilet
| before starting your ride, or had that bit of cake at the
| cafe stop, has a bigger impact than the additional grams on
| the tyres.
| dheera wrote:
| Wider tires also usually inflate to lower pressures, so you
| lose a lot of energy to that as well.
|
| Road bikes can be inflated to 100psi or more, you can't do that
| on a mountain bike.
| durkie wrote:
| wider tires also let you run lower pressures, which puts you more
| in the comfort zone of being able to convert to tubeless. not
| every rim/tire combination works with tubeless, but if you are
| able to pull it off, it's among my personal top 5 list of cycling
| innovations of the past 30 years.
| wolverine876 wrote:
| I'm missing something: How do lower pressures lead to tubeless?
| durkie wrote:
| 'davisoneee covered it pretty well, but mostly lower
| pressures mean it's less of a pressure differential that the
| sealant has to withstand. "Road tubeless" setups exist for
| narrower tires, but a lot of them have upper pressure limits
| around 80 psi / 5.4 bar. Running wider tires / lower
| pressures gives you a bit more margin of error.
| et-al wrote:
| It's the other way around: tubeless (and wider tires) allows
| one to run tires at lower pressures with minimal risk of
| pinch flats.
| davisoneee wrote:
| Narrow tyres tubeless is a no-go as the high-psi required to
| get the tyre seated and shaped can cause blowouts, especially
| if you get impact such as a pothole.
|
| Going for wider tyres means you naturally can go lower PSI,
| but if you drop PSI with tubes you risk pinch-flats
| ('snakebites'), where striking a hard edge causes both edges
| of the tyre to puncture (like X___X on the cross section,
| rather than \\__x_/ of a normal puncture). If you go wide,
| you can then drop the pressure more as you don't have a tube
| to pinch. This gives you the great comfort, the pliability to
| absorb road imperfection (which improves speed), and less
| likelihood of puncture.
|
| As an approximate pressure guide: # weight
| in kg. front load probably 0.45 (45%). tyre width in mm
| weight_front = weight * front_wheel_load weight_rear
| = weight * (1 - front_wheel_load) psi_front =
| (338.14 * weight_front / tyre_width ** 1.5785) - 7.1685
| psi_rear = (338.14 * weight_rear / tyre_width ** 1.5785) -
| 7.1685
|
| This should ballpark you 15% tyre deflection under load,
| which was a guide from an old bike magazine on a balance of
| rolling resistance and comfort.
| [deleted]
| onethought wrote:
| How is this a test if they didn't measure energy expenditure?
| Using a human rider feels like a flaw here.
| KeplerBoy wrote:
| It's a flaw, but also a feature. If the enhanced comfort of a
| wider tire reduces the perceived extertion, even though the
| actual power needed increases, it's a net win in my view.
| falcolas wrote:
| So, I wouldn't expect them to be slower (except in the most
| extreme cases with aerodynamics), since you can make anything go
| fast with enough power.
|
| But along that line of thinking, I would expect larger tires to
| require more energy to keep at speed. A larger tire with a a
| larger contact patch implies a greater deformation of the tire,
| which in turn implying greater energy loss.
|
| Cars, using a measurement of gas mileage, have shown this.
| Smaller contact patches (a condition created with over-inflated
| tires) result in higher gas mileage, whereas larger contact
| patches (under-inflated tires) lower gas mileage.
|
| I didn't see this addressed directly, that I saw.
| marwatk wrote:
| Wouldn't the size of the contact patch be dictated entirely by
| tire pressure and not tire size? A 100lb person+bike and 100psi
| inflation means 1 sq inch of contact regardless of tire
| dimensions.
|
| They're circles on a plane, after all. In ideal conditions
| they'd only contact at a single point.
| bri3d wrote:
| No, because the tire has substantial structure and isn't a
| latex balloon, for lack of a simpler explanation. In the case
| of automotive tires, the carcass (structure) of the tire
| governs the contact patch much more than the inflation
| amount.
| wiredfool wrote:
| So, part of the point of the Rene Hearse tires is that
| they're as supple as they can possibly make them. They are
| producing essentially the same best tire that they can in a
| huge range of sizes.
|
| (Well, at least until they started doing endurance casing
| and knobbies, so now it's more like 4 of the best tires
| they can, aimed at slightly different target users/races)
| quietbritishjim wrote:
| In this article, "slower" clearly means "slower [when putting
| the same amount of power in]". Or, equivalently, "need less
| power to get the same speed". Of course any tires are the same
| speed if you adjust the power input to compensate.
| bserge wrote:
| Does it really matter? Unless 1 extra mile per hour will make
| or break your commute or you're racing, just go with the most
| comfortable choice.
|
| I've been planning an E-Bike conversion and it looks like wider
| tires would be a better choice, as would shock absorbers which
| everyone says are less efficient.
|
| I'll give up that efficiency in a second if it means my ass and
| legs aren't sore when I get to my destination.
| PragmaticPulp wrote:
| If you're going a short distance: No, it doesn't matter.
|
| For a longer ride or a trail ride, the loss from the tires
| adds up. One extra MPH means a lot when you're doing a
| multiple hour ride at an average of 10-15MPH.
|
| Tire pressure influences rolling resistance significantly on
| larger tires. I'll some times increase pressure on longer
| rides or for uphill portions. Lower pressures have more
| traction, so I'll let air out for the downhills.
|
| It doesn't seem like much, but everything adds up as you push
| into longer and higher effort rides. Non bikers roll their
| eyes when we talk about saving small amounts of weight, for
| example, but it makes a difference over time with less weight
| to throw around. Again, you won't notice on short rides
| around town but when you're spending tens of hours every week
| on the bike in increments of 1-3 hour rides, it's worth
| optimizing these things.
| TheAlchemist wrote:
| Is the data available somewhere ?
|
| It doesn't match my experience at all. I have a road bike and a
| gravel bike - same quality range (gravel slightly higher). At low
| speeds, that may be true - the difference is negligible. But at
| higher speeds / power outputs, the road bike beats the gravel
| hands down - by a significant margin (big enough to be felt,
| without a power meter)
| derbOac wrote:
| My impression from reading articles and technical reports about
| this is that there's a couple of things going on.
|
| First, I think the wider-tires-are-faster argument has to be
| appreciated in the context of the narrow-tires-are-faster
| argument that dominated for a long time. With the latter
| paradigm, you wanted your tires as narrow as possible, with
| some lower boundary constraint due to wheel and tire thinness
| limitations, maybe around 20-21mm. The former paradigm emerged
| in part in contrast to that, in that "wider" doesn't mean
| "infinitely wide" but rather "wider than what's typical for
| people striving for narrower tires". Some of the arguments
| about rolling surface area are maybe understood in that context
| -- the patch of tire in contact with the road maintains the
| same area as a minimal area under the narrow tire paradigm, and
| then it starts to become larger, at which point you start
| increasing friction theoretically with more tire surface area
| in contact.
|
| The other argument for wider tires is about impedance gains due
| to wider tires -- decreased vibrations basically. This is
| different than decreased or equal rolling resistance per se.
| However, there are eventual aero losses for wider tires, as
| well as weight increases (which then increase rolling
| resistance). Eventually these aero losses and weight increases
| overshadow any impedence gains, and the wider tires' costs
| exceed their benefits.
|
| This is the sort of thing about cycling that is frustrating to
| me. I love cycling, but so many mechanical factors get really
| oversimplified: costs aren't often realistically assessed
| against actual gains, and sometimes gains are very restricted
| in the circumstances under which they apply. Disc brakes, for
| example, are safer, but you see little discussion about whether
| the safety margin they afford actually would make any practical
| difference in scenarios in which accidents typically occur
| (e.g., where a car is coming from the side or a blindspot), and
| they're often heavier and less aero (so yes, they save your
| carbon wheels, but you almost have to have deep section carbon
| wheels to make up for their weight and aero costs to begin
| with). I'm not saying disc brakes are a bad thing, but I think
| in practice their gains are more complex than is often made out
| to be. In the same way, wider tires are probably more optimal
| than a lot of people thought in, say, 1985. But I think the
| pendulum has swung a bit too indiscriminately in the other
| direction at the moment. What's probably most accurate is to
| say you want the widest tire that affords some impedence gains
| given your typical riding surface, and not anything wider.
|
| Aero effects increase exponentially (?? polynomially?) with
| speed (that is, as your speed increases, aero effects become
| more of a factor in further speed increases), which would match
| your experience. As your speed increases, the wider tires
| become more and more of a burden, and require higher wattage to
| compensate for.
|
| All sports with any significant tool involved are full of
| misperceptions and myths, not supported by science. Cycling is
| full of them, but it's not the only athletic discipline like
| that.
| sjburt wrote:
| This is an old article that compares tires in the 20-25mm
| range. The bike industry has moved to wider tires and 25 or
| 28mm tires are now quite common on road bikes, and gravel bikes
| have much wider tires. I would be the optimum is around 25 or
| 28 for road bikes on typical roads, especially as aerodynamics
| become a bigger factor.
| brianwawok wrote:
| Does your gravel bike have road slicks? Is your geometry the
| same, i.e. your reach and drop is the same?
| TheAlchemist wrote:
| No. Fair point indeed - the tires are not the only
| difference. I suspect they are one of the biggest though
| (based on subjective feeling - for what it's worth).
| wiredfool wrote:
| They (Jan and the RH crew) have done several versions of this
| over the years, and the takeaway is that some gravel bikes feel
| slower due to geometry, rider position, Q factor, and so on,
| but the tire width isn't a factor.
|
| (I think one was testing the open vs firefly, with similar
| riding positions but drastically different wheels)
| et-al wrote:
| Don't forget Jan's signature word: _planing_.
|
| This is prob the Open vs Firefly test you're thinking of:
| https://www.renehersecycles.com/what-makes-a-bike-fast/
|
| In the test, they apparently isolated the wheel weight
| variable by swapping out wheels on the slower-on-paper
| Firefly and according to them, the bike didn't ride up the
| hill significantly faster.
|
| However Jan Heine's experiments are often pseudo-sciencey and
| subject to rider effort. In this test, there were no power
| meters to show the difference in rider efforts between the
| two bikes. But somehow planing gives you free watts.
| louthy wrote:
| If that were the case, surely Tour de France riders would use
| wider tyres to gain more grip going around corners, especially in
| time-trials or stages with sprint finishes.
|
| Doesn't a greater surface area touching the floor means more
| frictional effects when pushing against the road?
| dredmorbius wrote:
| Static friction being constant regardless of contact surface
| presumes a uniform surface consistency (uniform frictional
| coefficient).
|
| Large (an knobby) tyres are a statistical bet that there will
| be _sufficient_ friction _somewhere_ on the contact patch. When
| riding over nonuniform surfaces (dust, loose pebbles, twigs,
| mud, leaves, and embedded rock), that 's a gamble the large and
| contoured tyre is far more likely to win.
|
| On a velodrome deck, not so much, and cross-sectional area,
| thermal losses from compressive deformation, angular momentum,
| etc., favour thinner tyres and higher inflation pressures.
| bernulli wrote:
| Is the static friction what is going on with wheels? Why do
| race cars (dragster, F1, etc) have wide, smooth (un-knobby)
| tires if it's so disadvantageous (no gain, but higher weight
| and moment of inertia)?
| dredmorbius wrote:
| For your standard street-car tyres ... _mostly_ , modulo
| variations in surface, rain, snow, mud, etc. On reasonably
| fresh dry clean tarmac though, yes.
|
| For racing tyres ... you're getting into a differet set of
| circumstances and uncomfortably far from my knowledge and
| experience, though my understanding is that the rubbers are
| specifically engineered to be sticky, more so at high
| temperatures (hence why drag racers spin out, it warms the
| tyres). That's no longer the domain of static friction.
|
| There's also the matter of thermal management, where tyres
| at high speeds generate a _lot_ of heat. How much size
| affects and /or is determined by this, I don't know. I am
| aware that street-tyre speed ratings are based on thermal
| properties, however.
|
| Knobby tyres are most effective on non-uniform surfaces:
| dirt/rock and mod most notably.
| bretthopper wrote:
| The one caveat this article doesn't mention is worse handling
| but they replied in the comments about it. And handling matters
| way more at higher speeds, plus they commented the extra weight
| matters more for steep climbs too.
| loeg wrote:
| I was a little surprised: the weight difference isn't huge.
| It is about +27% between Conti 5k 25mm and 32mm, or 60 grams
| per tire.
|
| Aerodynamics are the only real reason, I think.
| Cockbrand wrote:
| This, and a wider tire also has a larger front surface,
| resulting in more aerodynamic resistance. As every watt
| counts in the pro peloton, this is an important factor. For
| us amateur riders, probably not so much.
| mantas wrote:
| They're already using wider tyres than a decade ago.
| scoofy wrote:
| Yes. Much, much wider.
|
| I nearly passed by this comments section because i assumed
| everyone already knew this was true.
| at-fates-hands wrote:
| I think you're exaggerating a bit.
|
| From 2018:
|
| https://www.businessinsider.com/tour-de-france-wider-
| tires-l...
|
| _" It depends on the road surface, but 10 years ago the
| standard was 23mm tires at 8 or 8.5 bar, or 115, 120 psi,"
| Brown said. "And now it's 25mm for regular road racing and
| 7 to 7.5 bar for front and rear, so a little less than 100
| to 110 max on the bikes."_
|
| 2mm and 10psi less is not that huge a difference.
| mantas wrote:
| It's pretty big when you take into account whole context.
| Stuck up "socks size is a rule" UCI, historical norms,
| technical limitations (25mm is a limit for caliper
| brakes), tire tech (wider tires used to be heavy)....
|
| My prediction is 27mm being the norm in next 5 years.
|
| Currently I'm riding a decade-old road bike. It was fancy
| at the time because it fit 25mm tires without issues.
| People would give me shit for "slow" tires on group
| rides. But 25mm tyres improved a lot in that time. Now I
| wish it could take 27mm :(
| loeg wrote:
| 25mm is not a limit for caliper brakes? No idea why you
| claim that. One of my bikes has calipers and can fit 33mm
| tires.
|
| Also 28mm is extremely common; 27mm doesn't exist.
| wizzwizz4 wrote:
| 8% width and 13% pressure is significant.
| taude wrote:
| Here's a pretty interesting article discussing Le Tour slowly
| getting wider and wider tires, compared to a decade ago [1].
| Granted their use case is going to be at a very different scale
| than most rec/serious non-pro riders. But I know that most all
| my friends and I ride 28s on our road bikes these days compared
| to 23s a long time ago. More comfort and more forgiving.
|
| My current road bike maxes out at 28, but I'd probably go a
| little wider if I could due to the nature of the roads around
| here (lots of potholes, chunks, crappy shoulders, etc...)
|
| [1] https://www.businessinsider.com/tour-de-france-wider-
| tires-l...
| bombcar wrote:
| You also have the theoretical perfect tire vs the actual best
| for the rider - the more comfortable tire may be better
| overall as it allows the rider to perform better and for
| longer.
| kazinator wrote:
| Regardless of whether it is the case or not, Tour de France
| riders would not use wider tires to gain more grip around
| corners because ... wider tires do not add more grip.
|
| You get a larger contact patch from a wider tire, but that
| patch has less pressure.
|
| Grip (static friction) is coefficient of friction, times
| weight. The coefficient of friction is a constant which depends
| on the materials. Rubber on road is no exception.
| Retric wrote:
| That's the first order effects, however substances deform
| under pressure which is just one of many complexities
| involved. For car tires on dry pavement you get maximum grip
| from racing slicks. Unfortunately they need to swap in the
| rain.
| datameta wrote:
| I might be missing something here but I believe slick tire
| compounds are geared toward longevity at the expense of
| lower grip. Unless you are referring to racing tires in
| general which are grippier than their street equivalents.
| [deleted]
| kazinator wrote:
| Believe it or not, I have actually researched the "do
| wider tires grip more" topic (though not recently). I'm
| not simply extrapolating from high school physics class
| on friction. But, that's the executive summary.
| kazinator wrote:
| First order effects are the only effects which matter in
| cycling. This isn't aerospace.
|
| Racing slicks are a different _material_.
|
| In Formula 1 racing, you go through multiple tires in one
| race.
|
| In consumer driving, tires are expected to last 100,000 km
| or more.
|
| There is even the practice, in racing, of using chemicals
| to attack the rubber to soften it.
| carl_dr wrote:
| > In Formula 1 racing, you go through multiple tires in
| one race.
|
| They could easily make a tyre which lasts the length of a
| race, but they mandate pit stops and two different tyre
| compounds to add interest - teams can use the mandatory
| pit stop to "undercut" or "overcut" competitors.
|
| In fact, IIRC, for the 2005 season, changing tyres mid
| race for anything other than safety reasons was banned.
|
| > In consumer driving, tires are expected to last 100,000
| km or more.
|
| This is much closer to 25,000-50,000km, and peaking at
| 70,000km. Source: https://www.pirelli.com/global/en-
| ww/road/how-many-kilometre...
| Retric wrote:
| Using a different material is in effect irrelevant, they
| still get maximum grip from maximizing contact area
| because of how rough roads are. Ultra narrow tries need
| higher internal pressures, which limits how much the
| deform and thus reduces grip.
|
| Also, F1 cars are going up to 246 mph and doing heavy
| acceleration and breaking throughout the races, which
| seriously heats up the tires. Normal road tires would
| actually die sooner under those conditions. Just read up
| on who long tires last when people are doing street
| racing, burnouts, etc.
| wizzwizz4 wrote:
| > _The coefficient of friction is a constant which depends on
| the materials._
|
| This is an approximation. It holds here, but it doesn't hold
| for (say) figure skates on road.
| [deleted]
| kazinator wrote:
| That is false; you might be thinking of figure skates on
| ice. Steel on road obeys coefficient of friction.
|
| (I promise I will keep that in mind the next time I attach
| skates to a bicycle frame.)
| wizzwizz4 wrote:
| Steel on road obeys the coefficient of friction... until
| it starts cutting into the road. Unless you're very
| light, that's going to happen if you're going an
| appreciable speed wearing figure skates and then try to
| stop.
| kazinator wrote:
| Yes; anything cuts into anything else if you concentrate
| enough weight into enough of a small area, or there are
| other extreme factors involved like things melting.
|
| E.g. A carbide bit milling a stainless steel object is
| clearly not following carbide-on-stainless coefficient of
| friction.
| [deleted]
| carl_dr wrote:
| From TFA: " We tested our tires on smooth pavement at 29.5 km/h
| (18.3 mph), and found no speed difference between narrow and
| wide tires."
|
| A professional peloton rides at 28-30mph on the flat and
| significantly faster towards the end of a flat stage - I bet at
| higher speeds, for professionals where every percent matters,
| it does make a difference.
|
| Certainly for my level (and I have ridden for an hour at 18mph
| average) it doesn't.
| bmj wrote:
| It is worth noting that tires used by the pros have used
| slightly wide tyres over the years, and for events like
| Paris-Roubaix and Flanders, they absolutely use wider rubber
| on frames with more clearance.
| periheli0n wrote:
| The problem is that wide tyres tend to eat lots of momentum in
| corners.
|
| When going mainly straight and/or on uneven ground, use wide
| tyres. When cornering a lot, use narrow tyres.
| outside1234 wrote:
| Also, they have higher raw weight, so thinner is better
| uphill.
| mijamo wrote:
| This is actually not really true. Competition bikes have a
| minimum weight nowadays, and technology is that advanced
| that it wouldn't be a problem to add some weight here or
| there because the bike would stay the same weight in total
| as they have so much margin else to keep in track with the
| minimum weight. This is why most teams have switched to
| disk brakes btw, and that they can have all the electronics
| onboard with power meter, bike computer etc.
| localhost wrote:
| But there's rolling "sprung" vs. static "unsprung" weight
| (the examples you listed). You care a lot more about
| rolling weight as that affects the acceleration
| characteristics of the wheel - that's really important at
| the limits.
| gameswithgo wrote:
| Tour De France riders do use wider tires than they used to
| these days. At some point the width starts imparting
| aerodynamic drag penalties that are worse than the handling
| gains.
| CalChris wrote:
| You can't really rely on the Tour de France peloton for
| guidance. They're pretty conservative and, to a degree, ruled
| by fashion and sponsors.
| [deleted]
| carl_dr wrote:
| I guarantee the masters of marginal gains, Sky (now Ineos
| Grenadiers), will have spent some resources on looking at
| which tyres are actually faster for them, regardless of
| fashion or sponsors.
|
| I think it's safe to say that whatever they ride on are the
| fastest options - and every other team would follow - or that
| within a certain set of parameters, it doesn't matter.
|
| I just tried to search to see if Ineos run different tyres on
| different race and stages, and found nothing conclusive.
| idoubtit wrote:
| Cycling teams spend tens of millions each year, with Ineos
| going over EUR 50m some time ago. Are they conservative? They
| benchmark their material in wind tunnels. Sometimes they bend
| the rules with high-tech material[^1]. There's no way a team
| competing in Tour de France would choose fashion over
| performance.
|
| [^1]:
| https://www.theguardian.com/sport/blog/2017/jul/03/vortex-
| su...
| dahart wrote:
| > Doesn't a greater surface area touching the floor means more
| frictional effects when pushing against the road?
|
| Good question because at first I thought it might be negligible
| due to the tire normally being in a state of static friction
| relative to the road. But some quick searches showed me that
| rolling resistance is related to how large the contact point
| is, like you suggest, along with a variety of other factors.
| https://en.wikipedia.org/wiki/Rolling_resistance
|
| I don't know how reliable this is, but googling brought me to
| this site which compares bicycle tire brands according to
| rolling resistance on their test machine. Apparently, some 25s
| have all the 23s beat. If true, the variability range for
| bicycle tires is a lot wider than I expected.
| https://www.bicyclerollingresistance.com/
| Cockbrand wrote:
| I've bought a few tire models after researching at
| bicyclerollingresistance.com, and while I certainly don't
| have the means to do proper scientific research, I feel like
| I did buy the right stuff.
| jeffbee wrote:
| Same. I don't have any rational basis for it, but I've been
| happy with my tires. I think the best thing I learned from
| that site is even slightly larger sizes have a much bigger
| effect on puncture resistance than better construction.
| davisoneee wrote:
| One thing every person has missed so far is that often the TDF
| riders are on rather narrow bikes with very little clearance.
|
| This helps give an aerodynamic profile. Even at a few watts,
| this is considered worth it. You would likely have to do a lot
| of research to go with bigger wheels, as that would been wider
| fork, and thus throw off aerodynamics.
|
| A bit daft, in my opinion, given that it's mainly the
| domestiques who are in the wind and the ones behind, and in the
| peloton, can be putting out significantly less energy. May even
| be better for recovery having a bit more comfort on the bike
| through wider tyres with a bit lower pressure.
| soperj wrote:
| Another one is that clip in pedals make you faster.
| caturopath wrote:
| Compared to cages or straps, you mean?
|
| This is shockingly unintuitive if you mean compared to flats.
| The theory is that the force you use pulling up will always
| have a reduction in the force you use pushing down?
| soperj wrote:
| Compared to flats! I also couldn't believe it at first. I'm
| not sure the theory of it, but I've done long rides with
| people in both (80+km) and there was no difference in speed.
| I also would do a 16km route as fast as I could, and there
| was no discernible difference in avg speed or time.
| mumblemumble wrote:
| Huh. I had never heard anyone say that, _per se_.
|
| For my part, I like clipless pedals because they ensure that my
| feet are positioned optimally, which reduces fatigue and strain
| on my joints. Which, in turn, probably does mean I can maintain
| a faster pace for longer, but it's not like I've ever timed
| myself.
|
| Back when I was mountain biking, I also liked them for better
| control over the bike, and easier mount/dismount than toe
| clips.
| soperj wrote:
| I also like them for feet placement. They just aren't faster
| from my experience. It was not something I expected.
| salty_biscuits wrote:
| No data other than anecdotal but totally agree. I use flats on
| my road bike and look like an idiot but I go just as fast. I
| prefer to be able to wear normal shoes so I have less to carry.
| The whole "you can push while you pull" thing makes no sense,
| my quads are way more powerful than my hamstrings and you never
| need that much force when pedalling anyway, cardio fitness is
| always the limiting factor for me, not leg strength/power.
| mumblemumble wrote:
| "You can push while you pull" never made much sense to me on
| the road. Because, you're right, those muscles aren't as
| efficient, so you're just going to have to pay the
| expenditure back with interest.
|
| But, off-road, it can occasionally be useful to give 'er one
| or two extra firm strokes to help power over a small rise or
| whatever.
| salty_biscuits wrote:
| Off road the trade-off for me has always been "how quickly
| can I bail when things go wrong?". With spiky flats and
| sticky shoes I don't really have any problems with making
| enough power.
| aeharding wrote:
| Do you have a source? Anecdotally I've found clipless to make
| my power transfer more efficient. Some quick googling shows
| this seems to be true:
|
| "Mean power output was higher using clipless pedals ( = 617
| watts, SD = 112) than toe-strap ( = 572 watts, SD = 77), and
| flat ( = 566 watts, SD = 83)." [1]
|
| [1]
| https://scholars.fhsu.edu/cgi/viewcontent.cgi?article=1118&c...
| at-fates-hands wrote:
| I was a life long flat pedal rider.
|
| Started working at a bike shop during college and one of the
| first things roadies told me was they are indeed much more
| efficient because you can push AND pull on your pedals -
| generating a lot more power and making the ability to sustain
| that power a lot easier.
| [deleted]
| soperj wrote:
| I use clip ins now, have for about 5-6 years. I don't think
| you actually pull up.
| fsckboy wrote:
| you should actively pull up your leg so the down leg is
| not working extra to lift it, and the pull up muscles are
| different muscles so your idle down muscles are still
| getting a rest.
|
| The pulling up of your leg results in easier pedaling
| overall, and it is relatively as if you are pulling up on
| the pedal. Should you actually then pull up? You should
| go for the most natural sustainable pedal motion for you.
| When I pedal I "visualize" my feet going in circles, not
| up and down, it helps me on the "over the top" and
| "across the bottom" parts of the circle. keeps me
| sinusoidal!
|
| If you never pull up at all and you are pedaling and
| feeling tired, try pulling enough to remove the dead
| weight leg from the equation and you'll feel rejuvenated.
| soperj wrote:
| Honestly, go try biking by only pulling up. You don't
| pull up.
| carl_dr wrote:
| I think this is a myth - you don't pull on your pedals to
| make you more efficient, I think it's the fact you are not
| continuously having to adjust your feet as you would on
| flat pedals.
|
| See https://www.bikeradar.com/advice/fitness-and-
| training/stop-p... for instance.
| fsckboy wrote:
| a better way to say what you might be saying is, "without
| locking your feet to the pedal, you expend significant
| energy with lateral muscle movements to keep your feet on
| the pedals"
| carl_dr wrote:
| In cycling, clipless = clipped in, which is of course
| confusing - I think the GP is referring to the same thing as
| you are.
|
| Clipped pedals refer to pedals with toe straps. Clipless are
| pedals without a strap, but you clip into. And flat are ones
| you just rest your feet on.
| Nav_Panel wrote:
| From what I've read, although I can't remember the source,
| the difference doesn't really matter on flat surfaces, but
| clipless perform far better on inclines. I believe this has
| to do with the angle of the stroke relative to gravity
| causing some efficiency loss without a clip.
| mikestew wrote:
| My first impulse, given the loads of data to the contrary, was
| to just hit that down arrow and move on. But that's not fair,
| so I'll instead throw out: "got a citation for that?"
| soperj wrote:
| There's been studies from Bath University, but
|
| https://gearmashers.com/clipless-pedals-vs-flat-pedals-
| faste...
|
| Here are 2 dudes that did a trial, they produced more watts
| going up hill in flats, sprints were a big difference though.
| These were people used to being clipped in, and not using
| flats.
|
| Where's the studies to the contrary? Nothing I've seen has
| been more than marginal at best.
| jcarpio wrote:
| An opinion piece on the matter of being clipped in vs street
| shoes: https://www.rivbike.com/pages/the-shoes-ruse
| fsckboy wrote:
| the so-called "half toe clip" is the way to go. I wish I
| could find pedals that were clipless on one side and would
| let me install the half toe clip on the other (need the screw
| holes which usually hold the orange reflectors)
|
| for regular street shoe convenience, they are amazing and
| much easier to get out of than straps.
| louthy wrote:
| You can pull up and push down. Also if you get a pro fitting
| then the position of your foot will be optimised to get the max
| power through the pedal.
|
| Anecdotally they're faster.
| soperj wrote:
| Foot placing definitely, I love clipped in shoes for that.
| You don't pull though. I can ride equally as fast on flats,
| as I can clipped in. I've gone on 80km bike rides with people
| who are clipped in while I'm using flats, and it's the same.
| Clipped in is more comfortable, in my experience, it's not
| faster.
| louthy wrote:
| I've done many 100 mile+ sportives and have done both
| pushing down and pulling up.
| soperj wrote:
| You've done it just pulling up?
| matthewowen wrote:
| I mean, they do, in the sense that they give a stronger and
| more secure connection to the pedals which lets riders commit
| more power.
|
| This is relative to casual toe clips or flats. Compared to old
| school clips + tightly fastened straps with dedicated shoes
| they aren't a huge difference performance wise but no one rides
| those any more because they're much more dangerous and much
| less convenient.
| soperj wrote:
| Once you're used to flats, this isn't an issue. If you have
| good pedals and good shoes, your feet don't normally move at
| all.
| MarkusWandel wrote:
| Cheap tires are slower. Reliable tires are slower. It's obvious
| from the pictures that the fatties they're testing are special,
| with paper thin skinwalls. I can totally see that a high
| performance fattie would be just as good as a high performance
| narrow tire. It's the inelastic deformation of the tire casing
| (and inner tube) that eats power.
|
| Unfortunately thin-walled high performance tires are also
| delicate. I've seen people ride tires that can't even survive a
| couple of kilometers of dirt road.
| wiredfool wrote:
| I've ridden their extra lights into some pretty ridiculous
| places, and commuted on them in a city, and they're as trouble
| free as any other tire I've had. (In about 7k miles)
|
| I would recommend taking them on technical single track, but
| they rock for any sort of road riding. They're certainly fine
| for the gravel I've seen.
|
| (And by trouble free, I mean no flats that I can blame on the
| tire or some damage to it. I've had one slow leaky valve that I
| had to change on a ride. I'd normally get a flat every 1-2
| thousand miles or so with my older tires)
| carl_dr wrote:
| I've ridden 25mm to 32mm tyres on the same bike, in the same
| season, and my (absolutely amateur, I'm 250lb and did 125 miles
| at 16mph) experience is that 32mm tyres are no slower, but are
| significantly more comfortable, and allow me to ride
| significantly longer with less fatigue.
|
| Does anyone else have any other data points?
| matsemann wrote:
| Lots of the wattage gains in tests are often only noticeable
| when the speed approaches 40km/h. Wonder about the effect at
| pro levels, if 32mm is viable there.
|
| My longest is 300km with 35km/h avg (185 miles, ~22mph) running
| 25mm. No problems with comfort. Never tested other wheels on
| this bike. But I do have a gravel in same price range with
| wider tires. That I can follow easily in a group, but alone my
| speed is slower for the same wattage. Might be the more upright
| position though.
| twoWhlsGud wrote:
| This is all anecdotal, but a couple of decades ago I was riding
| road bikes with standard 622 rims shod with 23 mm tires. In the
| 2000s I shifted to riding road bikes with 584 rims and 42mm
| tires because they were frankly just more fun for me (lower
| pressure = greater comfort and better suspension meant better
| handling on our rough Northwest roads). The outer diameter was
| about the same, so I didn't have to do something weird with the
| geometry of the bikes.
|
| When Jan came out with 55mm super-supple tires on 559 rims
| (again that would keep the outer diameter the same) I thought
| what the heck and got Seven Cycles to build me a custom around
| the new tires. Now that road bikes run disk brakes, you can run
| multiple rim size on the same frame so I figured I could always
| go back to 584/42mm if I didn't like the crazy wide tires. (I
| was worried enough that I actually got somebody to build me a
| new set of 584 rims for the new frame.)
|
| I've had that bike for about 3 years now and have ridden
| several thousand miles on it. Only a few tens of those miles
| have been on the fancy 584 rims with the (equally nice) 42mm
| tires - the 55mm tires are even more fun than the 42's were for
| me. If you ride on mixed surfaces, the extra suspension you get
| from running low pressures (I run around 26 PSI front/32 back)
| makes a big difference (or at least it does for me) - both in
| handling and comfort.
|
| Downsides are increased weight (the 55mm tires weigh about 420
| g a piece which is impressively light given the amount of
| material, but still a lot heavier than those old 622/23 mm
| tires back in the day) and the increased maintenance of running
| them tubeless (though of course you can run them with tubes-
| though given that I haven't had a flat in 3 years and I'm
| riding on Seattle streets, I'll put up with having to monitor
| the sealant levels every month or so).
| kazinator wrote:
| I suspect that 42mm is already into diminishing returns for
| road cycling.
| carl_dr wrote:
| I am definitely slower - 4.5mph or so - on my 42mm gravel
| bike on road than I am on my 32mm road bike.
|
| But my road bike has slick tyres and the gravel bike's
| tyres are more knobbly, and I run the gravel bike's tyres
| at much lower pressure. (And there is the difference in
| geometry of each bike, too.)
|
| I'm not even sure you can buy 42mm slick tyres, so a like-
| for-like comparison is probably very hard.
| kazinator wrote:
| Slick tires, by which I mean minimal treat pattern, do
| exist in 42mm or even wider widths.
|
| (Source: I have seen them on bicycles.)
| wiredfool wrote:
| Rene Hearse sells tires from 26 mm to 55 mm all with the
| same tread and casings.
|
| That's part of why they can do this test with some level
| of accuracy.
| wiredfool wrote:
| Yes.
|
| I swapped RH tires onto my road tandem, 26x44 on the front and
| 26x54 on the back (from schwable 40mms), and the average ride
| speed I saw went from the 16mph range to the 17mph range, and
| the first time out on the new tires we increased our fastest
| average ride ever speed from 17.25 to 18.25 mph.
|
| And, the stoker is happier because the ride is that much
| better.
| haswell wrote:
| I've spent a lot of time with 28mm tires, but I'm absolutely in
| love with my 38mm GravelKing slicks. I don't really notice much
| speed difference (if any), and the comfort level makes up for
| it if there is. I ride for fitness, so I'm happy.
|
| More details in my other comment (I actually ride a gravel bike
| so I have the extra clearance for big fat tires if I need).
| kazinator wrote:
| The comfort level you feel is also a form of efficiency that
| makes you faster. Vibration absorbs energy and saps your
| momentum.
| periheli0n wrote:
| Years ago I switched from 1" tyres to 2.5" inch ones for my
| commuter bike and I can confirm that they are not slow at all...
| as long as you ride in a straight line! As soon as you turn, they
| suck up all momentum.
|
| The fact that they provide decent straight-line rolling even at
| 2bar pressure is nice though, especially in a city where
| cobblestone paving is common. Fat tyres provide some suspension,
| and a ton of grip.
|
| Still, narrow tyres are the choice for fast riding if you need a
| bit of agility.
| kazinator wrote:
| I completely believe you, but the issue is likely not width
| _per se_.
|
| Might it be that your tires have a smooth profile down the
| middle for going in a straight line, but edges that have a more
| aggressive tread pattern, which engages the road surface when
| you tilt into a turn?
|
| There are true fat road slicks that have the same smooth
| profile all over.
|
| I think, tire pressure is also a factor in turning because of
| the way the tire deforms on the rim. If you have the pressure
| way down (which you can easily get away with in 2.5 inches),
| that could be a factor.
| japanuspus wrote:
| A great source of data on bike tires is [0], which has been doing
| systematic tests on a dedicated test rig for many years and
| appears to be independent of any tire manufacturer.
|
| After finding this site a few years back, I bought a high-
| pressure floor pump and Schwalbe Marathon tires for all the
| commuter bicycles in the family. Haven't seen a flat tire since,
| even though we have four bikes on the road almost every day.
|
| [0]: https://www.bicyclerollingresistance.com/the-test
| oliwarner wrote:
| They're great tyres for commuting but they're _so_ heavy. When
| you swap back to regular or race tyres your bike weighs half as
| much.
|
| Again, I'm not saying they're good tyres, but perhaps best if
| you have a spare wheelset so you can keep a "fun" set for the
| weekend.
| draw_down wrote:
| Seems reasonable that more tire contact = more friction.
| crawdog wrote:
| Makes my day to see this company on HN. Their Barlow Pass tires
| in tubeless setup have been an excellent addition to my commute
| bike. Supple, great handling. There's an efficiency lost on a
| gravel setup vs road bike, but that's mostly the geometry than
| the tire.
| wiredfool wrote:
| There is another article with a newer batch of tire tests here.
| https://www.renehersecycles.com/bq-tire-test-results/
|
| Basically, they looked at even wider tires 40+mm and they still
| aren't any slower.
| kazinator wrote:
| Narrower tires, necessarily inflated to a high pressure, are
| actually inefficient on a bumpy surface.
|
| A tire's job is to absorb surface defects in the road, and that
| is not only for comfort, but rolling efficiency.
|
| The extreme example of this occurs off-road. Off-road vehicles
| benefit from wider tires that are inflated to a lower pressure.
| If you have an off-road vehicle, it behooves you to take some of
| the air out of the tires when you go off-road.
|
| 25mm road bike tires basically require a polished velodrome; real
| roads consist of pitted, eroded and cracked asphalt.
|
| If your bike is vibrating from the crappy road, you're probably
| not going as fast as you could be. Letting some of the air out
| for a more efficient, smoother ride is risky, if the tires a
| narrow; you risk snakebite flats and damage to the rim.
|
| For commuting in run-down city with aging infrastructure, you
| want at at least 38 mm tires. 40 mm is a nice round number. You
| can vary the pressure for the kinds of roads you're riding on
| with a lot of margin, and can take it quite low for dirt roads.
|
| I've commuted around town with pressures as low as 45 psi in the
| back, 35 in the front, in 45 mm tires.
|
| I have story in relation to that. One time I was riding along NW
| Marine Drive in Vancouver, from UBC down to Spanish Banks. I came
| down from the hill and then along the flats there were some
| Spandex-clad road cyclists ahead of me. I pulled up to them and
| we were neck and neck. There was road work going on up ahead and
| the pavement had been scraped, leaving it horribly bumpy. I stood
| on the pedals and just cranked right through it, hardly slowing
| down. I saw in the mirror mounted on my eyeglasses that road bike
| guys dropped off as if a sniper had taken them out.
|
| What is the use of narrow tires? It's just fashion, like stiletto
| heels.
| fsckboy wrote:
| You're commenting on a article that says "we started to
| question many of the things we had accepted as 'facts'... we'll
| look at some of these myths. We'll explain why we (and
| everybody else) used to believe them, and how things really
| work"
|
| But you aren't qualifying what you're saying: Are you telling
| us what everybody used to believe? Are you saying you see
| through what everybody says even without empirical testing? Are
| you agreeing or disagreeing with the test results presented in
| the article?
| kazinator wrote:
| > _Are you telling us what everybody used to believe?_
|
| No; pretty much everything in my comment is undisputed old
| hat, so it is kind of tangential.
|
| The main myth is not that any of that is false, but rather
| than thin tires more than compensate for these effects due to
| their reduced air drag and weight and so always end up being
| advantageous anyway.
|
| (And they almost certainly are on a polished indoor velodrome
| track, where the effect of surface imperfections is next to
| nonexistent.)
| haswell wrote:
| This is one of the reasons I love the emergence of the "Gravel"
| category of bikes. They look and have geometry similar to a road
| bike, but they have enough clearance for nice fat gravel tires.
|
| I ride in Chicago (shitty roads, potholes & construction are
| everywhere), and love that I can put nice 38mm+ GravelKing Slick
| tires on the bike, and still have no problem keeping up with most
| road bikes. I've gotten funny looks from folks who're unfamiliar
| with the concept, but it's such a great setup.
|
| Comfy/soft ride too.
|
| Edit: Cannondale Topstone if anyone is curious.
| alistairSH wrote:
| Dont tell my wife. She'll want me to sell 3-4 of my bikes! ;)
| krono wrote:
| Yeah, my roady friends are jealous because I get to use my
| gravelbike off-road, and my mountainbike friends are jealous at
| me for being able to keep up with roadies. And all that for the
| price of one bike and an extra set of wheels with slicks!
|
| Canyon Grail here, yes the one with the weird cockpit :)
| jasonvorhe wrote:
| I got my Cannondale CAADX in 2015 right before the gravel hype
| started. I've put WTB Riddler 37 on it and it's close to a
| gravel bike but a bit more direct and maneuverable - I love it.
| If I was in for a new bike right now, I'd be very tempted to
| get a Canyon Grail with electronic shifting though. After
| Cannondale's manufacturing error put me in the hospital for a
| night followed by a broad recall of a lot of their carbon fiber
| forks and they new minimalist logo I'm just not a fan of
| Cannondale anymore. But the Topstone is a great bike!
| dharmab wrote:
| Similarly in the motorcycle world, dual sport and adventure
| models originally designed for on road/off road mix are now
| quite popular as commuter machines. Their long suspension makes
| them quite comfortable over potholes, cracks, curbs and
| generally poor road surfaces. And many models are narrow enough
| to filter between lanes with ease.
| ultrarunner wrote:
| I would argue that "designed for [off] road mix" is pretty
| charitable. A 500-pound dirt bike with a comfortable seating
| position wins the tough-aesthetics competition, but off road
| performance is meager at best. I built decent off-road skills
| on a DL1000, but the weight was always such a liability as to
| make it impracticable. I moved to a smaller and lighter bike
| and have more fun, but 99% of people I met in Arizona are
| happy with their big ADV bikes-- with zero interest in going
| off road.
|
| I think the most interesting take-away is that there is a
| segment of people who value being given an excuse for
| something rugged-- I heard lots of "I just like the peace-of-
| mind that I _could_ go anywhere if I needed to " whether they
| believe themselves or not.
| plorkyeran wrote:
| Yeah, when I first got my gravel bike I thought I'd be
| sacrificing some road performance for better flexibility and
| comfort, but that didn't happen. The actual result was that my
| times on smooth segments were unchanged and I've beaten many of
| my personal bests on rougher roads (and obviously it's much
| better on dirt).
|
| It's not a perfectly fair comparison because I did upgrade to a
| nicer bike in the process, but my previous bike was already
| into the territory of significant diminishing returns for
| someone who doesn't race and doesn't actually care about saving
| seconds.
| germinalphrase wrote:
| Rumor has it that a very prominent British Tour de France
| competitor rides a re-badged/stealth gravel bike because he
| finds it more comfortable.
| jasonvorhe wrote:
| Who is that rider?
| CalChris wrote:
| Slicks themselves are under-appreciated.
| jaypeg25 wrote:
| I bought a Specialized Diverge over a year ago. It was mostly
| to commute to and from work, but also to have the ability to
| take gravel paths and trails on the weekends. It's been awesome
| but friends have suggested I take off the stock tires and add
| some new ones. Is it really worth it? The tires are already
| fairly fat already, at least compared to road bike tires.
| haswell wrote:
| The Diverge was on my shortlist when I got the Topstone. At
| the time (2019), I think the Diverge defaulted to skinnier
| smoother tires. Can't remember which tires specifically.
|
| The Topstone shipped with some pretty knobby WTBs that
| definitely had an impact on rolling resistance. If your tires
| are knobby/optimized for off-road, putting a slicker tire
| (the GK slicks are quite popular for good reason), I suspect
| you'll notice quite a difference, but I'd look more at the
| knobbiness than the fatness if you're considering a change.
|
| Also worth noting that some knobby tires have a hard line
| down the middle that keeps resistance minimal until you start
| to turn, at which point you hit the high traction portion of
| the tire. Takeaway: even if it looks knobby, it might not be
| as slow as it looks.
|
| 32mm+ is already getting into "fat" territory for a road
| bike, and for me personally, 38mm seems to be my sweet spot.
| jaypeg25 wrote:
| They came with 35mm "roadsport flak jacket" https://www.spe
| cialized.com/us/en/roadsport/p/155765?color=2....
|
| They're pretty smooth overall, perhaps why I never really
| had an issue commuting with them, but I'm always looking to
| go faster!
| haswell wrote:
| Found the details - I went from 40mm WTB Nanos [0] to
| these 38mm GravelKing Slicks [1]. If you look at the
| product pages, the difference is pretty striking. I don't
| know much about the RoadSports, but at least when it
| comes to "slick-ness", it looks like you're already
| starting from a slicker baseline than I was.
|
| - [0] https://www.wtb.com/products/nano-40c
|
| - [1] https://www.panaracerusa.com/products/gravelking-
| slick-foldi...
| plorkyeran wrote:
| The Pathfinder tires that come stock on recent Diverges are
| pretty widely regarded as not just the worst part of the
| bike, but a sort of bafflingly bad choice because they aren't
| even cheap. If you're looking to spend some money upgrading
| your bike, they're a good place to start.
| house9-2 wrote:
| I've got about 500 miles on my Diverge (and the
| Pathfinders) the tires ride great.
|
| - Good on the road, even cornering is decent which was
| unexpected with light tread.
|
| - Great on gravel: flat, uphill, downhill, and cornering
|
| - Decent on single track
|
| I think maybe they get a bad rap because they are on the
| heavy side for the price? When the time comes for new tires
| not sure if I will get another pair or try out something
| different.
| acdha wrote:
| If they're causing you problems, consider replacing them.
| Otherwise I'd just wait until you get a flat -- no point in
| spending money on something which isn't a problem. You're
| commuting so you're reliably putting on mileage without
| [presumably] getting in to dodgy situations or trying to
| shave every second or gram off.
| pmontra wrote:
| Anecdotally my gravel bike is faster with 28 mm slick tires
| than with 42 mm sawtooth tires. Of course sawtooth vs slick
| makes a difference in friction. The hubs in the wheels could
| make a difference too. I use the 28 mm wheels when I go on
| asphalt roads in the mountains because I don't want the extra
| weight and friction. 42 mm for everything else.
| shrimpx wrote:
| I used to ride thin-tire road bikes but a year ago I bought a
| Mercier Kilo WT (WT is for "wide tire") which is a light road
| frame with a fork that allows beefy gravel tires. I don't think
| I'll go back to thin-tire road bikes.
| thisisnico wrote:
| My bike is the best for the city.. got a Specialized Tri-Cross
| with 32mm tires.. can do everything and handle our horrible
| roads.
| jiscariot wrote:
| My only complaint about the gravel trend is that at the entry
| (and mid) level they are often using pretty crappy disc brakes
| when rim brakes would have been a better choice in 90% of
| cases. When they are hydraulic, they are a dream to use, but
| with a cable you really lose the brake feel.
| sam_lowry_ wrote:
| Ha! I only figured it out after buying Kona Rove NRB, which
| is not even an entry-level bike, but it turned out to have
| disk brakes and extremely fragile paintwork.
|
| It served me well, but I am still somewhat cautious when
| descending since then.
| wolverine876 wrote:
| > _in theory_ , wider tires are faster due to their shorter
| contact patch, which deforms less as they roll
|
| What is meant by "contact patch"? If it means 'portion of tire in
| contact with the ground': Assuming the tires are the same
| circumference, I'd expect the front-to-back dimension of the
| contact area to be the same, and being a wider tire, the side-to-
| side contact dimension to be larger, creating a larger contact
| area.
|
| And given equal force on the tires, wouldn't the same force
| deform a smaller contact area more, not less? What am I
| misunderstanding?
|
| > Laboratory tests on steel drums eliminate the rider and thus
| the _suspension losses_. If you look at _hysteretic losses_
| alone, narrow tires run at higher pressures and thus flex less,
| meaning they absorb less energy.
|
| > We tested on real roads, with a rider on the bike, and found
| that the increased vibrations of the narrower tires caused energy
| losses that canceled out the gains from the reduced flex. These
| _suspension losses_ are mostly absorbed in the rider's body.
|
| How do _hysteretic losses_ apply here?
|
| And, why does the increased vibration cause energy losses (which
| I take to mean reduced efficiency of energy used for movement)?
| If the energy is absorbed by the tire or is transferred via other
| bicycle components to the rider, what's the difference in energy
| loss/efficiency?
| davisoneee wrote:
| If you're going OVER imperfections (i.e. high pressure tyres),
| you lose some energy going 'up'.
|
| If you go THROUGH imperfections (lower pressure) you don't lose
| so much energy going 'up' as the tyre absorbs rather than
| bounces you.
| wolverine876 wrote:
| Thank you, but maybe I'm being dense:
|
| Tire hits bump, causing energy B to impact tire. The whole
| bike and rider go 'up' or just the tire goes 'up'. How is the
| former causing more energy loss? The amount of energy is B
| either way.
|
| I can see how one is more comfortable, because the tire takes
| the hit and not me, but I don't grasp the difference in
| energy.
| davidgould wrote:
| The human body is not perfectly elastic, as it is made out
| of meat. When the bike goes up and down, it makes the meat
| jiggle or flap which dissipates energy in the flesh as
| heat. So taking the hit at the tire which is much more
| elastic instead of in the heavily damped rider is more
| efficient.
|
| Take a look a slow motion video of riders on a rough road,
| say some Paris-Roubaix footage and you can see this.
| wolverine876 wrote:
| Ah, thank you; that makes sense to me. I didn't
| anticipate a big difference between a tire and a person
| in that regard. FWIW, from the article:
|
| > Studies by the U.S. Army found that the more discomfort
| vibrations cause, the more energy is being absorbed. And
| the amount of energy that a vibrating human body can
| absorb is significant - the U.S. Army's study measured up
| to 2000 Watt!
|
| Let's not imagine how that study was conducted ...
| davisoneee wrote:
| When the pressure is lower, less energy is deflected
| upwards. The tyre flexes over the hit.
| _ \________/ \___/x\___/ versus
| x
|
| Less energy is transferred to the 'up' meaning the energy
| is still going forward. You still have upward motion, but
| that's less energy taken away from forward motion.
| matsemann wrote:
| There is no fixed energy B. If the bump only deforms a
| small part of the tire, that's little energy. If the bump
| makes the whole rider jump, thats lots of energy.
|
| The bump is basically static.
| chrismcb wrote:
| The contact patch is the portion of tire that is touching the
| road. A wider tire should have a smaller contact patch...
| Maybe. A wider tire means the force can be spread out more and
| should deform the tire less. So the front to back dimension
| will differ.
| wiredfool wrote:
| The contact patch should be a constant area for a given
| pressure and load.
|
| A wider tire will have a wider, but shorter, contact patch at
| the same pressure.
| analog31 wrote:
| I suffered with this myth for decades. Now, it didn't affect me
| too much because the narrower tires that I got, also took a lot
| higher pressure, and I usually inflated them to the max. And as a
| result of only caring about skinny tires, I neglected tire
| clearance on my frames.
|
| Then a few years ago I got a bike that could take wider tires,
| and was good enough quality to really try out for real. Today I'm
| one more anecdotal data point in support of wider tires. Now, I
| don't necessarily opt for the lowest possible rolling resistance.
| Instead, lowering the pressure allows me to ride in greater
| comfort but without the tires feeling slow.
|
| And of course other things affect rolling resistance too, such as
| (from what I've read) the suppleness of the sidewalls and other
| aspects of tire construction. And I'm not prepared to spend $$$$
| to find the holy grail of tires.
| CalChris wrote:
| Narrow tires also require higher pressure with a less comfortable
| ride. Bigger riders, Clydesdales, require more pressure. These
| rock hard tire inflations are then more prone to snake bite
| flats. As the discussion section in the article points out, wider
| tires used to be common. I think we're rediscovering why.
| kazinator wrote:
| Snake bite flats are precisely from low pressure. The term
| comes from two punctures that come from the rim pinching the
| tire, which is due to inadequate pressure to absorb an impact.
|
| Rock hard tire inflations are prone to failure from the
| pressure itself.
| CalChris wrote:
| I short handed it a bit. My point was that this 'low
| pressure' for heavier riders is higher than it is for lighter
| riders. If you don't increase your tire pressure, the same
| pressure will cause more snake bites for a heavier rider than
| it would for a lighter rider.
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(page generated 2021-06-14 23:01 UTC)