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Myths in cycling: wider tires are slower

renehersecycles.com

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Re: Myths in cycling: wider tires are slower

#151

Post by pmontra »

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…

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.

Re: Myths in cycling: wider tires are slower

#152

Post by dnhz »

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.

Re: Myths in cycling: wider tires are slower

#153

Post by loeg »

mantas wrote: post #38
at-fates-hands wrote: post #29

Earlier quoted context omitted.

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"…

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.

Re: Myths in cycling: wider tires are slower

#154

Post by msandford »

dnhz wrote: post #152

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.

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.

Re: Myths in cycling: wider tires are slower

#155

Post by discreteevent »

dnhz wrote: post #152

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.

Mountain bike has knobbly tread. This article is taking about wide smooth tires.

Re: Myths in cycling: wider tires are slower

#156

Post by loeg »

bretthopper wrote: post #3
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?

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.

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.

Re: Myths in cycling: wider tires are slower

#157

Post by localhost »

mijamo wrote: post #126
outside1234 wrote: post #43

Earlier quoted context omitted.

Also, they have higher raw weight, so thinner is better uphill.

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…

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.

Re: Myths in cycling: wider tires are slower

#158

Post by et-al »

wiredfool wrote: post #128
TheAlchemist wrote: post #58

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)

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)

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 by swapping out wheels on the slower-on-paper Firefly and 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.

Re: Myths in cycling: wider tires are slower

#159

Post by jasonvorhe »

germinalphrase wrote: post #146
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…

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.

Who is that rider?

Re: Myths in cycling: wider tires are slower

#160

Post by wolverine876 »

davidgould wrote: post #141
wolverine876 wrote: post #108

Earlier quoted context omitted.

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.

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.

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 ...

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