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

Re: Myths in cycling: wider tires are slower

#91

Post by falcolas » Mon, Jun 14, 2021, 9:03 PM UTC

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.

Re: Myths in cycling: wider tires are slower

#92

Post by soperj » Mon, Jun 14, 2021, 9:03 PM UTC

matthewowen wrote: post #18

soperj wrote: post #5

Another one is that clip in pedals make you faster.

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.

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.

Re: Myths in cycling: wider tires are slower

#93

Post by Cockbrand » Mon, Jun 14, 2021, 9:05 PM UTC

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.

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.

Re: Myths in cycling: wider tires are slower

#94

Post by carl_dr » Mon, Jun 14, 2021, 9:07 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.

> 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...

Re: Myths in cycling: wider tires are slower

#95

Post by fsckboy » Mon, Jun 14, 2021, 9:07 PM UTC

kazinator wrote: post #39

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 o…

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?

Re: Myths in cycling: wider tires are slower

#96

Post by [deleted] » Mon, Jun 14, 2021, 9:08 PM UTC

CalChris wrote: post #49

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?

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]

Re: Myths in cycling: wider tires are slower

#97

Post by toxik » Mon, Jun 14, 2021, 9:08 PM UTC

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.

Re: Myths in cycling: wider tires are slower

#98

Post by marwatk » Mon, Jun 14, 2021, 9:09 PM UTC

falcolas wrote: post #91

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 milea…

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.

Re: Myths in cycling: wider tires are slower

#99

Post by sam » Mon, Jun 14, 2021, 9:09 PM UTC

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…

If you're interested in wheels, check out The Bicycle Wheel by Jobst Brandt. If you're building wheels it's a must have.

Re: Myths in cycling: wider tires are slower

#100

Post by Cockbrand » Mon, Jun 14, 2021, 9:10 PM UTC

dahart wrote: post #51

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?

> 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.