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Myths in cycling: wider tires are slower

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Re: Myths in cycling: wider tires are slower

#31

Post by krono »

haswell wrote: post #12

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…

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 :)

Re: Myths in cycling: wider tires are slower

#32

Post by Retric »

kazinator wrote: post #6
louthy wrote: post #2

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?

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 exce…

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.

Re: Myths in cycling: wider tires are slower

#33

Post by carl_dr »

at-fates-hands wrote: post #24
aeharding wrote: post #14

Earlier quoted context omitted.

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...

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.

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.

Re: Myths in cycling: wider tires are slower

#34

Post by taude »

louthy wrote: post #2

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?

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...

Re: Myths in cycling: wider tires are slower

#35

Post by dharmab »

haswell wrote: post #12

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…

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.

Re: Myths in cycling: wider tires are slower

#36

Post by plorkyeran »

haswell wrote: post #12

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…

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.

Re: Myths in cycling: wider tires are slower

#37

Post by wizzwizz4 »

kazinator wrote: post #6
louthy wrote: post #2

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?

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 exce…

> 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.

Re: Myths in cycling: wider tires are slower

#38

Post by mantas »

at-fates-hands wrote: post #29
scoofy wrote: post #9

Earlier quoted context omitted.

Yes. Much, much wider. I nearly passed by this comments section because i assumed everyone already knew this was true.

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.

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 :(

Re: Myths in cycling: wider tires are slower

#39

Post by kazinator »

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.

Re: Myths in cycling: wider tires are slower

#40

Post by [deleted] »

wizzwizz4 wrote: post #37
kazinator wrote: post #6

Earlier quoted context omitted.

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 exce…

> 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]
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