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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

#131

Post by bernulli »

dredmorbius wrote: post #30
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?

Static friction being constant regardless of contact surface presumes a uniform surface consistency (uniform frictional coefficient). Large (an knobby) tyres are a statistical bet that there will be sufficient friction somewhere on the contact patch. When riding over nonuniform surfaces (dust, loose pebbles, twigs, mud, leaves, and embedded rock), that's a gamble the large and contoured tyre is far more likely to win…

Is the static friction what is going on with wheels? Why do race cars (dragster, F1, etc) have wide, smooth (un-knobby) tires if it's so disadvantageous (no gain, but higher weight and moment of inertia)?

Re: Myths in cycling: wider tires are slower

#132

Post by PragmaticPulp »

bserge wrote: post #105
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…

Does it really matter? Unless 1 extra mile per hour will make or break your commute or you're racing, just go with the most comfortable choice. I've been planning an E-Bike conversion and it looks like wider tires would be a better choice, as would shock absorbers which everyone says are less efficient. I'll give up that efficiency in a second if it means my ass and legs aren't sore when I get to my destination.

If you’re going a short distance: No, it doesn’t matter.

For a longer ride or a trail ride, the loss from the tires adds up. One extra MPH means a lot when you’re doing a multiple hour ride at an average of 10-15MPH.

Tire pressure influences rolling resistance significantly on larger tires. I’ll some times increase pressure on longer rides or for uphill portions. Lower pressures have more traction, so I’ll let air out for the downhills.

It doesn’t seem like much, but everything adds up as you push into longer and higher effort rides. Non bikers roll their eyes when we talk about saving small amounts of weight, for example, but it makes a difference over time with less weight to throw around. Again, you won’t notice on short rides around town but when you’re spending tens of hours every week on the bike in increments of 1-3 hour rides, it’s worth optimizing these things.

Re: Myths in cycling: wider tires are slower

#133

Post by soperj »

fsckboy wrote: post #109
soperj wrote: post #90

Earlier quoted context omitted.

I use clip ins now, have for about 5-6 years. I don't think you actually pull up.

you should actively pull up your leg so the down leg is not working extra to lift it, and the pull up muscles are different muscles so your idle down muscles are still getting a rest. The pulling up of your leg results in easier pedaling overall, and it is relatively as if you are pulling up on the pedal. Should you actually then pull up? You should go for the most natural sustainable pedal motion for you. When I ped…

Honestly, go try biking by only pulling up. You don't pull up.

Re: Myths in cycling: wider tires are slower

#134

Post by quietbritishjim »

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…

In this article, "slower" clearly means "slower [when putting the same amount of power in]". Or, equivalently, "need less power to get the same speed". Of course any tires are the same speed if you adjust the power input to compensate.

Re: Myths in cycling: wider tires are slower

#135

Post by ultrarunner »

dharmab wrote: post #35
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.

I would argue that "designed for [off] road mix" is pretty charitable. A 500-pound dirt bike with a comfortable seating position wins the tough-aesthetics competition, but off road performance is meager at best. I built decent off-road skills on a DL1000, but the weight was always such a liability as to make it impracticable. I moved to a smaller and lighter bike and have more fun, but 99% of people I met in Arizona are happy with their big ADV bikes— with zero interest in going off road.

I think the most interesting take-away is that there is a segment of people who value being given an excuse for something rugged— I heard lots of "I just like the peace-of-mind that I could go anywhere if I needed to" whether they believe themselves or not.

Re: Myths in cycling: wider tires are slower

#136

Post by wiredfool »

bri3d wrote: post #110
marwatk wrote: post #98

Earlier quoted context omitted.

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.

No, because the tire has substantial structure and isn't a latex balloon, for lack of a simpler explanation. In the case of automotive tires, the carcass (structure) of the tire governs the contact patch much more than the inflation amount.

So, part of the point of the Rene Hearse tires is that they’re as supple as they can possibly make them. They are producing essentially the same best tire that they can in a huge range of sizes.

(Well, at least until they started doing endurance casing and knobbies, so now it’s more like 4 of the best tires they can, aimed at slightly different target users/races)

Re: Myths in cycling: wider tires are slower

#137

Post by jiscariot »

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…

My only complaint about the gravel trend is that at the entry (and mid) level they are often using pretty crappy disc brakes when rim brakes would have been a better choice in 90% of cases. When they are hydraulic, they are a dream to use, but with a cable you really lose the brake feel.

Re: Myths in cycling: wider tires are slower

#138

Post by dredmorbius »

bernulli wrote: post #131
dredmorbius wrote: post #30

Earlier quoted context omitted.

Static friction being constant regardless of contact surface presumes a uniform surface consistency (uniform frictional coefficient). Large (an knobby) tyres are a statistical bet that there will be sufficient friction somewhere on the contact patch. When riding over nonuniform surfaces (dust, loose pebbles, twigs, mud, leaves, and embedded rock), that's a gamble the large and contoured tyre is far more likely to win…

Is the static friction what is going on with wheels? Why do race cars (dragster, F1, etc) have wide, smooth (un-knobby) tires if it's so disadvantageous (no gain, but higher weight and moment of inertia)?

For your standard street-car tyres ... mostly, modulo variations in surface, rain, snow, mud, etc. On reasonably fresh dry clean tarmac though, yes.

For racing tyres ... you're getting into a differet set of circumstances and uncomfortably far from my knowledge and experience, though my understanding is that the rubbers are specifically engineered to be sticky, more so at high temperatures (hence why drag racers spin out, it warms the tyres). That's no longer the domain of static friction.

There's also the matter of thermal management, where tyres at high speeds generate a lot of heat. How much size affects and/or is determined by this, I don't know. I am aware that street-tyre speed ratings are based on thermal properties, however.

Knobby tyres are most effective on non-uniform surfaces: dirt/rock and mod most notably.

Re: Myths in cycling: wider tires are slower

#139

Post by kazinator »

carl_dr wrote: post #106
kazinator wrote: post #70

Earlier quoted context omitted.

I suspect that 42mm is already into diminishing returns for road cycling.

I am definitely slower - 4.5mph or so - on my 42mm gravel bike on road than I am on my 32mm road bike. But my road bike has slick tyres and the gravel bike’s tyres are more knobbly, and I run the gravel bike’s tyres at much lower pressure. (And there is the difference in geometry of each bike, too.) I’m not even sure you can buy 42mm slick tyres, so a like-for-like comparison is probably very hard.

Slick tires, by which I mean minimal treat pattern, do exist in 42mm or even wider widths.

(Source: I have seen them on bicycles.)

Re: Myths in cycling: wider tires are slower

#140

Post by alistairSH »

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…

Dont tell my wife. She’ll want me to sell 3-4 of my bikes! ;)
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