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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

#121

Post by matsemann »

carl_dr wrote: post #7

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?

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.

Re: Myths in cycling: wider tires are slower

#122

Post by jeffbee »

Cockbrand wrote: post #100
dahart wrote: post #51

Earlier quoted context omitted.

> 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.…

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.

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.

Re: Myths in cycling: wider tires are slower

#123

Post by wiredfool »

geocrasher wrote: post #89

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.

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)

Re: Myths in cycling: wider tires are slower

#125

Post by haswell »

jaypeg25 wrote: post #86
haswell wrote: post #52

Earlier quoted context omitted.

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 n…

They came with 35mm "roadsport flak jacket" https://www.specialized.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!

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...

Re: Myths in cycling: wider tires are slower

#126

Post by mijamo »

outside1234 wrote: post #43
periheli0n wrote: post #17

Earlier quoted context omitted.

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.

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 power meter, bike computer etc.

Re: Myths in cycling: wider tires are slower

#127

Post by wiredfool »

chrismcb wrote: post #79
wolverine876 wrote: post #74

> 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 ar…

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.

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.

Re: Myths in cycling: wider tires are slower

#128

Post by wiredfool »

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)

Re: Myths in cycling: wider tires are slower

#129

Post by wiredfool »

MarkusWandel wrote: post #101

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 se…

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)

Re: Myths in cycling: wider tires are slower

#130

Post by adolph »

wolverine876 wrote: post #85

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 a…

https://sheldonbrown.com/
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