Myths in cycling: wider tires are slower • Hacker News Board

Re: Myths in cycling: wider tires are slower

#111

Post by carl_dr » Mon, Jun 14, 2021, 9:30 PM UTC

toxik wrote: post #97

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.

In particular their inertia is higher, and the tire is the worst place to put heavy things physically speaking.

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.

Re: Myths in cycling: wider tires are slower

#112

Post by KeplerBoy » Mon, Jun 14, 2021, 9:32 PM UTC

onethought wrote: post #28

How is this a test if they didn’t measure energy expenditure? Using a human rider feels like a flaw here.

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.

Re: Myths in cycling: wider tires are slower

#113

Post by TheAlchemist » Mon, Jun 14, 2021, 9:33 PM UTC

brianwawok wrote: post #66

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)

Does your gravel bike have road slicks? Is your geometry the same, i.e. your reach and drop is the same?

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).

Re: Myths in cycling: wider tires are slower

#114

Post by datameta » Mon, Jun 14, 2021, 9:34 PM UTC

Retric wrote: post #32

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…

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.

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.

Re: Myths in cycling: wider tires are slower

#115

Post by durkie » Mon, Jun 14, 2021, 9:34 PM UTC

wolverine876 wrote: post #50

durkie wrote: post #27

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.

I'm missing something: How do lower pressures lead to tubeless?

'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.

Re: Myths in cycling: wider tires are slower

#116

Post by fsckboy » Mon, Jun 14, 2021, 9:34 PM UTC

jcarpio wrote: post #104

soperj wrote: post #5

Another one is that clip in pedals make you faster.

An opinion piece on the matter of being clipped in vs street shoes: https://www.rivbike.com/pages/the-shoes-ruse

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.

Re: Myths in cycling: wider tires are slower

#117

Post by davisoneee » Mon, Jun 14, 2021, 9:34 PM UTC

wolverine876 wrote: post #108

davisoneee wrote: post #78

Earlier quoted context omitted.

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.

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.

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.

Re: Myths in cycling: wider tires are slower

#118

Post by matsemann » Mon, Jun 14, 2021, 9:36 PM UTC

wolverine876 wrote: post #108

davisoneee wrote: post #78

Earlier quoted context omitted.

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.

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.

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.

Re: Myths in cycling: wider tires are slower

#119

Post by Retric » Mon, Jun 14, 2021, 9:39 PM UTC

kazinator wrote: post #42

Retric wrote: post #32

Earlier quoted context omitted.

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.

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.

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.

Re: Myths in cycling: wider tires are slower

#120

Post by wiredfool » Mon, Jun 14, 2021, 9:39 PM UTC

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?

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.