How much of a difference does tire width make on road bike performance?
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F1 tires are spec, they run the tires that are supplied to them. The tires are actually very specifically not ideal- this was done in a weird attempt to make race strategy involving tire degradation more complicated.
e) misread a post
e) misread a post
Last edited by sheddle; 10-01-19 at 08:53 AM.
#52
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Once more: friction is not related to contact area. Simply put, larger contact area means also less normal force (pressure from weight), thus it cancels itself out of the equation.
See here the explanation for wide tires on racecars (spoiler - aclinjury has it right): https://www.physlink.com/education/askexperts/ae200.cfm
See here the explanation for wide tires on racecars (spoiler - aclinjury has it right): https://www.physlink.com/education/askexperts/ae200.cfm
#53
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I'm afraid you really don't know what you're talking about. You don't understand traction, grip, and rubber.
Please go here for a simple explanation of grip:
Friction Formula
"contact patch size" doesn't come into the equation of grip, it's in fact all dependent on the frictional coefficient of the rubber.
Somtimes, intuitions can get you into trouble. Here's something to think about friction and grip.
Let us suppose that we're sliding a square block of ice across the floor. The block of ice has certain contact-patch area with the floor.
Now, suppose we cut the block of ice into 2 halves so now that each half has 1/2 the contact-patch area of the original block.
Question: so do the 2 smaller blocks have less friction grip than the original larger block? The answer is no. All three blocks have exactly the same frictional grip. In other words, grip does not depend on the size of the contact-patch at all.
Now, there are reason why you'd want to use a larger tire (for traction, longevity, etc), but "larger contact patch gives better grip" is not one of them. I'm merely pointing out your false fact that you seem to hell bent on embracing, and doing the community a disservice. I hope you get this.
Please go here for a simple explanation of grip:
Friction Formula
"contact patch size" doesn't come into the equation of grip, it's in fact all dependent on the frictional coefficient of the rubber.
Somtimes, intuitions can get you into trouble. Here's something to think about friction and grip.
Let us suppose that we're sliding a square block of ice across the floor. The block of ice has certain contact-patch area with the floor.
Now, suppose we cut the block of ice into 2 halves so now that each half has 1/2 the contact-patch area of the original block.
Question: so do the 2 smaller blocks have less friction grip than the original larger block? The answer is no. All three blocks have exactly the same frictional grip. In other words, grip does not depend on the size of the contact-patch at all.
Now, there are reason why you'd want to use a larger tire (for traction, longevity, etc), but "larger contact patch gives better grip" is not one of them. I'm merely pointing out your false fact that you seem to hell bent on embracing, and doing the community a disservice. I hope you get this.
Three tires, with 80 pounds of weight on the wheel. Sane rubber compound on the tire.
The contact patch would be ( 80 lbs / psi ) square inches.
38mm at 48 psi. 1.6 sq inch contact patch
23mm at 100 psi 0.8 sq inch
20mm at 125 psi (I'm guessing) 0.64 sq inch
Are you saying that all these would have the same cornering grip?
Because there is the same cornering force on all of these? Up to the limits of the rubber material? What about real world rough surfaces?
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#54
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My old Cannondale CAAD 4 can't fit anything larger than 25's due to brake clearance issues. With most rim brake bikes 25's are going to be about the max you can fit. IMO, one of the biggest advantages of disc bikes is the ability to run wide tires.
#55
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Sorry, I'm not following your physics arguments. Maybe you can elaborate?
Three tires, with 80 pounds of weight on the wheel. Sane rubber compound on the tire.
The contact patch would be ( 80 lbs / psi ) square inches.
38mm at 48 psi. 1.6 sq inch contact patch
23mm at 100 psi 0.8 sq inch
20mm at 125 psi (I'm guessing) 0.64 sq inch
Are you saying that all these would have the same cornering grip?
Three tires, with 80 pounds of weight on the wheel. Sane rubber compound on the tire.
The contact patch would be ( 80 lbs / psi ) square inches.
38mm at 48 psi. 1.6 sq inch contact patch
23mm at 100 psi 0.8 sq inch
20mm at 125 psi (I'm guessing) 0.64 sq inch
Are you saying that all these would have the same cornering grip?
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I think I expressed this wrong but iirc contact patch is sort of an indirect effect of rolling friction - i.e. at lower air pressures, you lose more energy to tire deformation than if you run rock hard 120psi 700c23s. i.e. "stiffness".
"rolling resistance" is a better term than "rolling friction" since it's really more a case of mechanical efficiency than actual "friction". to put it another way, tire grip is an enormously complicated process with a huge number of variables, not just coefficient of friction.
"rolling resistance" is a better term than "rolling friction" since it's really more a case of mechanical efficiency than actual "friction". to put it another way, tire grip is an enormously complicated process with a huge number of variables, not just coefficient of friction.
Last edited by sheddle; 10-01-19 at 09:04 AM.
#57
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When I bought my '86 Miyata 710 a few years ago, it had a 23 front and 25 rear. Too skinny for the rough roads I ride on, so I went with 28s front and rear.
The rear fits fine, but...
BUT the front tire barely clears the fork bridge!
That's only about one millimeter clearance. I'll probably have to knock the front size down to 25, and keep the 28 rear.
.
The rear fits fine, but...
BUT the front tire barely clears the fork bridge!
That's only about one millimeter clearance. I'll probably have to knock the front size down to 25, and keep the 28 rear.
.
Last edited by Cougrrcj; 10-01-19 at 09:01 AM.
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That's why it's better to not pretend to be Isaac Newton, put down the text books and look at what works 99% of the time and also eliminates efficiency losses due to vibrations from the road making their way up to the rider's body.
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You're absolutely correct, also with cantis but disc brakes are a quantum leap in this area of focus!
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When I bought my '86 Miyata 710 a few years ago, it had a 23 front and 25 rear. Too skinny for the rough roads I ride on, so I went with 28s front and rear.
The rear fits fine, but...
BUT the front tire barely clears the fork bridge!
That's only about one millimeter clearance. I'll probably have to knock the front size down to 25, and keep the 28 rear.
.
The rear fits fine, but...
BUT the front tire barely clears the fork bridge!
That's only about one millimeter clearance. I'll probably have to knock the front size down to 25, and keep the 28 rear.
.
I'm fine with 23-23s run under the limit. Don't plan to go on dirt any time soon.
Last edited by sheddle; 10-01-19 at 09:15 AM.
#61
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I think I expressed this wrong but iirc contact patch is sort of an indirect effect of rolling friction - i.e. at lower air pressures, you lose more energy to tire deformation than if you run rock hard 120psi 700c23s. i.e. "stiffness".
"rolling resistance" is a better term than "rolling friction" since it's really more a case of mechanical efficiency than actual "friction". to put it another way, tire grip is an enormously complicated process with a huge number of variables, not just coefficient of friction.
"rolling resistance" is a better term than "rolling friction" since it's really more a case of mechanical efficiency than actual "friction". to put it another way, tire grip is an enormously complicated process with a huge number of variables, not just coefficient of friction.
Wide tires at lower pressures have better dampening abilities; they ride OVER small imperfections (and some big ones) without having to "lift" the bike and rider over them and without transferring vibrations to the rider.
A very hard tire is much better on a glass-smooth surface but a wider tire is better on everything else.
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You could switch over to 650b rims with long-reach calipers - you may be able to get up to the 42-47mm range in the front/rear, respectively. That would make a HUGE difference
#63
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No arguing with that; however, it is wrong to assume that this advantage continues infinitely with ever larger tire volumes and lower pressures (like you did before in this thread). At some point the contact patch becomes long enough for the rolling ressistance that comes from deforming the tire to outweigh the gains in efficiency from dampening small surface irregularities. A certain sweet spot exists for any given combination of rider+bike weight, riding surface, tire, and tire pressure. Decreasing pressure below that point results in more rolling resistance, even if pinch flats/rim damage are of no concern. Not to mention the greater weight of larger tires and the clearance issues.
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#65
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I'm afraid you really don't know what you're talking about. You don't understand traction, grip, and rubber.
Please go here for a simple explanation of grip:
Friction Formula
"contact patch size" doesn't come into the equation of grip, it's in fact all dependent on the frictional coefficient of the rubber.
Please go here for a simple explanation of grip:
Friction Formula
"contact patch size" doesn't come into the equation of grip, it's in fact all dependent on the frictional coefficient of the rubber.
Once more: friction is not related to contact area. Simply put, larger contact area means also less normal force (pressure from weight), thus it cancels itself out of the equation.
See here the explanation for wide tires on racecars (spoiler - aclinjury has it right): https://www.physlink.com/education/askexperts/ae200.cfm
See here the explanation for wide tires on racecars (spoiler - aclinjury has it right): https://www.physlink.com/education/askexperts/ae200.cfm
Sorry, there is more to tires than physics 101. The simple friction equation is all well and good when you have fairly rigid smooth bodies in contact with each other. Rubber and tires are not this however, they are very dynamic and flexible. If contact patch didn't matter, drag racers wouldn't drop their tire pressures. But, lower pressures on the same sticky tire DO result in more grip because of the larger contact area. More rubber interfacing with the road means that there are more points of mechanical interface where the rubber is physically interlocking with the pavement surface and to make the tire slide, those pieces of rubber must be physically sheared off (the source of skidmarks)
Width, even at the same tire pressure also influences lateral traction on because of tire slip angle while cornering and the contact patch shape, it all has to do with how the contact patch deforms due to lateral forces. Simply, a long/skinny contact patch cannot support the same slip angle because the tire sidewall must deflect more and at some point cannot. I'm not sure how much this carries over to bikes due to the different tire shapes vs cars, but in cars wider tires of the same compound do most certainly increase cornering grip.
#66
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Sorry, there is more to tires than physics 101. The simple friction equation is all well and good when you have fairly rigid smooth bodies in contact with each other. Rubber and tires are not this however, they are very dynamic and flexible. If contact patch didn't matter, drag racers wouldn't drop their tire pressures. But, lower pressures on the same sticky tire DO result in more grip because of the larger contact area. More rubber interfacing with the road means that there are more points of mechanical interface where the rubber is physically interlocking with the pavement surface and to make the tire slide, those pieces of rubber must be physically sheared off (the source of skidmarks)
Width, even at the same tire pressure also influences lateral traction on because of tire slip angle while cornering and the contact patch shape, it all has to do with how the contact patch deforms due to lateral forces. Simply, a long/skinny contact patch cannot support the same slip angle because the tire sidewall must deflect more and at some point cannot. I'm not sure how much this carries over to bikes due to the different tire shapes vs cars, but in cars wider tires of the same compound do most certainly increase cornering grip.
Width, even at the same tire pressure also influences lateral traction on because of tire slip angle while cornering and the contact patch shape, it all has to do with how the contact patch deforms due to lateral forces. Simply, a long/skinny contact patch cannot support the same slip angle because the tire sidewall must deflect more and at some point cannot. I'm not sure how much this carries over to bikes due to the different tire shapes vs cars, but in cars wider tires of the same compound do most certainly increase cornering grip.
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No arguing with that; however, it is wrong to assume that this advantage continues infinitely with ever larger tire volumes and lower pressures (like you did before in this thread). At some point the contact patch becomes long enough for the rolling ressistance that comes from deforming the tire to outweigh the gains in efficiency from dampening small surface irregularities. A certain sweet spot exists for any given combination of rider+bike weight, riding surface, tire, and tire pressure. Decreasing pressure below that point results in more rolling resistance, even if pinch flats/rim damage are of no concern. Not to mention the greater weight of larger tires and the clearance issues.
I ride 33mm very high TPI (120, ish?) tubular CX race tires on my everyday bike (very long story how that came to be). I just put flat bars on it (also different thread) which shifts my weight back, so I am now running about 21 psi in the front and about 38 in the rear (I am about 173 [sheesh!] and my computer bag weighs another 19 lbs). I have ridden 29+ bikes and they ride WAY better than my current setup, even with wider-than-average tires at very low pressure. My next bike will be a 29+ platform for sure.
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My 28's are definitely faster than my 38's on pavement.
on gravel my 40's are faster, but on pavement the 40's are draggy. Both the 38's and the 40's push wind, and have a weight penalty.
As for my road bike, I probably can't tell any difference in speeds/power/watts, but the comfort of the 28's is noticeable over the 25. Just because I can, I'll probably go tubeless on the road bike and go back to a 25. or leave it at a 28. A 28 in a paceline is effortless!!
on gravel my 40's are faster, but on pavement the 40's are draggy. Both the 38's and the 40's push wind, and have a weight penalty.
As for my road bike, I probably can't tell any difference in speeds/power/watts, but the comfort of the 28's is noticeable over the 25. Just because I can, I'll probably go tubeless on the road bike and go back to a 25. or leave it at a 28. A 28 in a paceline is effortless!!
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one of the funnier things I've heard is that 23s/high tire pressure have a psychological speed effect over lower air pressure tires specifically because of the road vibration, which is why racers took a while to use wider tires
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I also heard most grand tour teams have gone to 25mm tires and some Specialized-sponsored teams with 26s, again, WAY too narrow for everyday riding but efficiency doesn't always win races. They're made for a sprint-finish not for pedaling efficiency or comfort.
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I mean, yeah, at this point if I showed up at an A group ride with 23s people would probably think I'm wacky and out of date for using narrow tires when everyone knows that the pros are using wider tires these days.
I really don't care because I have fairly heavy bomb-proof wheels, and also you can just ride around potholes. If I cared that about "plush", I'd be a downhill MTB racer, instead of a doofus riding a 40 year old bicycle.
I really don't care because I have fairly heavy bomb-proof wheels, and also you can just ride around potholes. If I cared that about "plush", I'd be a downhill MTB racer, instead of a doofus riding a 40 year old bicycle.
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I mean, yeah, at this point if I showed up at an A group ride with 23s people would probably think I'm wacky and out of date for using narrow tires when everyone knows that the pros are using wider tires these days.
I really don't care because I have fairly heavy bomb-proof wheels, and also you can just ride around potholes. If I cared that about "plush", I'd be a downhill MTB racer, instead of a doofus riding a 40 year old bicycle.
I really don't care because I have fairly heavy bomb-proof wheels, and also you can just ride around potholes. If I cared that about "plush", I'd be a downhill MTB racer, instead of a doofus riding a 40 year old bicycle.
#73
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Thanks for showing you are as clueless about racecars as you are about bikes. They run wide tires for CORNERING TRACTION. Not longevity (they change tires frequently).
And don't worry, you obviously lack the chops to debate with me! The friction equation doesn't control for NUMEROUS variables at work in a tire's interaction with the road in real-life conditions.
And don't worry, you obviously lack the chops to debate with me! The friction equation doesn't control for NUMEROUS variables at work in a tire's interaction with the road in real-life conditions.
But hey like you said, it's a free country, so you're free to babble on without any evidence.
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That makes no sense at all. I ride with men and women who are in the 120-160 weight range and use 32-35mm tires on their drop bar bikes, which are wide sizes for drop bar road bikes. All are quality tires that are light and roll well- the riders love em.
None are wide riders though.
And I see countless healthy/fit cyclists riding pavement on gravel tires all the time.
...perhaps you mean 2+ inch tires when you claim that wide tires are for wide riders? Even then I wouldnt agree, but at least that would eliminate all the stated and examples of wide tires being used by fit cyclists.
None are wide riders though.
And I see countless healthy/fit cyclists riding pavement on gravel tires all the time.
...perhaps you mean 2+ inch tires when you claim that wide tires are for wide riders? Even then I wouldnt agree, but at least that would eliminate all the stated and examples of wide tires being used by fit cyclists.
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