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Myths in cycling: wider tires are slower

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Re: Myths in cycling: wider tires are slower

#201

Post by Swizec »

auxym wrote: post #175
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…

In many ways, modern gravel bikes are a comeback of the "sport touring" road bikes that were popular from roughly the mid 70s to the mid 90s, then became mostly absent from market. Compared with "racing" bikes, they had wider tires, a more relaxed geometry, and various conveniences such as mounting points for fenders and racks. Thus, they were a much better option for the majority of riders who did not participate in…

In my neck of Europe those bikes reached peak popularity in the 90's and early 00's. We called them "city mountain bikes".

Their distinguishing feature was that a "mountain bike" comes with gears (normal bikes don't), which was very popular. The city edition came with fenders, luggage racks, a nice bell, stand, etc.

Big fat tyres, comfy geometry. The tires usually had a slick strip in the middle and grooves on the sides so you had slicks running on pavement and got massive grip turning on gravel.

As it got cheaper, they even started having front suspension.

Looked kinda like this:

https://www.bolha.com/image-bigger/gorska-kolesa/mosko-gorsk...

https://www.velo.si/modules/uploader/uploads/s_product/pics_...

https://www.bolha.com/image-w920x690/mestna-kolesa/mestno-in...

Re: Myths in cycling: wider tires are slower

#203

Post by londons_explore »

wiredfool wrote: post #129
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 ha…

The real test for a city is how many hypodermic needles and smashed bottles can you ride over before being stranded by a puncture in a not-so-nice area of town at night...

Re: Myths in cycling: wider tires are slower

#204

Post by dennisgorelik »

PragmaticPulp wrote: post #132
bserge wrote: post #105

Earlier quoted context omitted.

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 ou…

> One extra MPH means a lot when you’re doing a multiple hour ride at an average of 10-15MPH.

Why spend your effort on optimizing your bike performance by 8% if you can instead simply shorten the distance by 8%?

Re: Myths in cycling: wider tires are slower

#205

Post by mmmBacon »

taneq wrote: post #185
dharmab wrote: post #35

Earlier quoted context omitted.

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 see those dual sports all the time and I don't see the attraction other than image. They're less agile on-road which is where they spend their time. At least they're not as silly as the trend of sticking knobbly tyres on road bikes for that "scrambler" look. If anything the opposite trend makes more sense, the motard / supermotard style where a competent off-road bike is retrofitted with road tyres and suspension t…

This is only true if you keep the 21” front when and then only if you are trying to keep up with skilled riders (disclaimer I’m not the average rider). Had a dual sport that I made into a super moto with ultra stick rubber. Would blow away a GSXR/Ducati/R1/R6 on HWY 9 all the windy sections. Those bikes could out accelerate me on straights but they all held me up in corners.

Re: Myths in cycling: wider tires are slower

#206

Post by efraim »

kazinator wrote: post #6
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?

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…

Rubber tires does not generate grip through simple static friction. They stick to the road in two different ways, adhesion and deformation. The adhesion is weak molecular forces that stick the rubber to the road like sticky tape, a larger area will have more adhesion. The deformation deforms the tire to follow the surface and dig into it. Because rubber is viscoelastic, the force is greater on the lagging side of a bumb when the tire is slipping.

The adhesion is greatest in the front of the contact patch where there is less slip and a wide tire has a wider but shorter contact patch, so it has more grip from adhesion.

If you keep the pressure in two tires the same, a wider tire will have the same contact patch area as a narrow tire since they will carry the same force and force is pressure multiplied with the area.

Re: Myths in cycling: wider tires are slower

#207

Post by photojosh »

krono wrote: post #31
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…

Yeah, my roady friends are jealous because I get to use my gravelbike off-road, and my mountainbike friends are jealous at me for being able to keep up with roadies. And all that for the price of one bike and an extra set of wheels with slicks! Canyon Grail here, yes the one with the weird cockpit :)

How off-road do you go? I have a gravel bike too, but I much prefer the MTB for rocky descents.

Re: Myths in cycling: wider tires are slower

#208

Post by vecinu »

usrusr wrote: post #186
jiscariot wrote: post #137

Earlier quoted context omitted.

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.

Rim brakes on roadbikes are awesome, but they are awesome because the calipers don't have to go far around the tire. If you try to build them for wider tires you suffer far more flex and flex means that you can't pull a high lever transmission ratio before running out of lever movement. Remember "brake boosters" on cantilever brakes? Same problem, the requirement to transfer the counterforce far around the tire. I'm…

The only caveat is carbon wheels. I hate rim brakes on carbon wheels,they legitimately suck and disc is way better for that application.

I actually just sold my carbon wheels and downgraded back to aluminium until I buy a disc bike for the long term.

Re: Myths in cycling: wider tires are slower

#209

Post by efraim »

marwatk wrote: post #98
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.

Yes, with pneumatic tires the contact patch area is the load force divided by the pressure.

Re: Myths in cycling: wider tires are slower

#210

Post by efraim »

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…

The contact patch is only larger if the pressure is lower, and with a wide tire the contact patch is shorter and wider. Because of that there is less deformation of a wider tire along the rolling direction which is what creates rolling resistance.
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