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What's the optimal tire width for maximum speed on roads?

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What's the optimal tire width for maximum speed on roads?

Old 11-11-18, 05:48 AM
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el forestero
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What's the optimal tire width for maximum speed on roads?

My very basic understanding of how tire size and speed are related has come from watching a few youtube videos and reading a few webpages. In a nutshell, a number of them say something like this:

Wider tires can have lower rolling resistance because the part of the tire that deforms in contact with the road is shorter than it is with a narrower tire.

Also, wider tires can be inflated to lower pressure than narrower tires. This in turn improves speed by smoothing the ride and reducing the slowing effect of the unevenness of road surfaces.

These points have been demonstrated in outdoor riding tests, which are said to be more useful than lab tests in which road surface unevenness isn't taken into account.

In the youtube videos and webpages on the topic, 23 or 25 mm-wide tires are typically referred to as narrow tires, and 28 mm-wide tires are mentioned as examples of wider ones. They don't deal much with sizes outside that range.

It isn't clear from these videos and webpages at what size the wider=faster generalization breaks down, or if it ever does. Assuming I stick with fairly smooth-surfaced tires, and rims designed for the size of tires I'm mounting on them, can I keep getting faster tires by going to larger and larger ones? At what size do wind resistance to the less-aerodynamic forms of wider tires (and rims), or other drawbacks, outweigh the factors that tend to make wider tires faster?

Am I going to complete 100 to 160 km rides in significantly less time and with less effort if I spring for some new 28 mm tires and rims, or will I do just as well, or better, if I stick with the 35 mm-wide tires I'm currently riding on? Or should I go even wider than 35 mm? Or narrower than 28 mm?

Is there research to back up an opinion on this, one way or another?

In case these details affect the answers, my riding environment is hilly and mountainous with moderately-smooth, paved roads.
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Old 11-11-18, 06:12 AM
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Like most things, the answer is, It depends. Under most conditions and on most road bikes, 28-mm tires will have less rolling resistance than 35-mm.

I think there's more debate in this forum between 25-mm and 28-mm.
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Old 11-11-18, 06:33 AM
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Unless you get into huge balloon tire size range, the width of the tire will have virtually no effect on your speed unless you're racing at the highest level of the sport. You'll feel a little difference in smoothness but it won't equate to a measurable higher average speed. And the guys at the highest level of the sport generally run 23-25, or 28's on cobblestone courses. And if you're road racing on a proper road racing frameset, it's doubtful you can fit anything bigger than a 28 anyways. Additionally, I'm not sure if anyone even makes a big tire like a 35 that is a high TPI road racing quality tire, not to mention road tubular. The reason bigger tires can have lower rolling resistance is because they can be run at lower pressures, not because they're simply a bigger physical size. But nobody is going to race on a tire with 50psi because it's too squishy.
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Old 11-11-18, 06:39 AM
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The more important consideration is to match the width of the tire to the external width of the rim to lessen drag caused by turbulence.

The answer to most Bike Forum questions: Stop worrying about it and ride your bike more..
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Old 11-11-18, 06:50 AM
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If you want to know what the fastest tire width is, just look at what the pros use. In the Tour de France, it's 23 or 25mm (23mm used to be the standard, but 25mm is becoming more and more popular). On rough terrain, such as Paris-Roubaix, it's 28mm (or 25mm with wide rims).

If you have a choice between 25 and 28, go with 28. You won't notice the speed difference, but you will notice the extra comfort. You'll appreciate that choice at the end of a long ride.
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Old 11-11-18, 07:25 AM
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23 mm tires

I ride 23 mm, but I am old fashioned. I would like to try 25 mm next time I am up for or in need of new tire purchase. I won't go to 28 mm because I don't think my frames will handle the clearance and if they do it will be a tight or borderline fit.
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Old 11-11-18, 07:55 AM
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It depends on you, your weight, the bike, the road condition, and how much, if anything, you are carrying. Because of my weight, some of the local road conditions I won't ride on anything narrower than a 35.
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Old 11-11-18, 09:12 AM
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Originally Posted by steve0257 View Post
It depends on you, your weight, the bike, the road condition, and how much, if anything, you are carrying.
What he said.

All-up bike and rider weight, road surface (smooth concrete, smooth asphalt, rough asphalt, sand, crushed stone, dirt, gravel), tire construction (depth of tread, flexibility of casing), tire inflation pressure, tread pattern (smooth vs knobby), weather conditions (i.e. dry, wet, snow, etc) and can your bike handle wider tires -- yours obviously does...

That said, speed is one thing, comfort is another! A potential increase in speed is meaningless if the 'ride' beats up the rider to the point of being unbearable for a given distance. My road bikes all wear 28s or 32s, but one (Miyata 710) just barely fits a 28 on the front due to fork crown clearance. I'll probably switch to a 25 front to gain more than the 1mm clearance I have with the 28s. My all-up weight is over 200 pounds, and ride the 28s at 85psi front, 90 rear.
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Old 11-11-18, 09:27 AM
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I have a road bike that I switched from 23 to 28 on. I also have a gravel bike with 38's.

Schwalbe Pro One's with 30ml of sealant weigh almost exactly what GP4000 + standard butyl tube. So the switch is easy to pin down as only a width change with no other variables. On the road bike, it didn't change my speed but gave me quite a bit of extra confidence on my rides. I sometimes get pebbles between the tire and fork making a racket now. Other than that, it's a great set up.

The gravel bike is noticably slower even on pavement. It is 4lb heavier and less aero though.

It seems that 28-32 is the point where you see diminished returns on upsizing tires. No sense in going larger for road riding
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Old 11-11-18, 10:23 AM
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I assume your question is actually: what is the optimum tire width for maximum sustained speed on the road? As rides over dozens to thousands of miles over good pavement.

The correct answer was already stated: it is what the pros ride in race conditions. And they ride 23 or 25mm tires. Tubulars exclusively - obviously.

At average sustained speeds of 20-30mph, aero dominates over the trivial differences between tire rolling resistances. Other major consideration: as low as possible wheel weights. Heavy but aero wheels are of no use if you get dropped on the first climb. And, too much aero is bad if the bike is uncontrollable in side winds.

Ultimate solution: 1,200 gram (or less) carbon wheelset running 200 gram tubular tires. Bring a support vehicle.

Anything heavier and wider is a compromise for increased flat resistance and rider comfort. And cost of course...
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Old 11-11-18, 01:41 PM
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Originally Posted by el forestero View Post
It isn't clear from these videos and webpages at what size the wider=faster generalization breaks down, or if it ever does.
Of course it does. Rolling resistance can only drop so much, while the weight and aerodynamic profile of a tire will just get bigger and bigger and bigger as the width is increased.

But...
At what size do wind resistance to the less-aerodynamic forms of wider tires (and rims), or other drawbacks, outweigh the factors that tend to make wider tires faster?
...This isn't very clear, because it's hard to characterize. On the road, the factors working against wider tires are pretty subtle. It's simply not easy to dig clear-cut answers from the noise, especially as it depends on so many things, from surface conditions to riding speeds to wind conditions to the particular wheels being used.

The widest set of tires I have for my gravel bike are 53mm, but they're otherwise constructed like a high-performance road tire. With those tires installed, I can take that bike to road rides and still ride with the same people as when I use a skinny-tired road bike. And on solo rides that I treat like time trials, I can't very clearly distinguish the difference between it and those road bikes*.
By contrast, the bike is currently wearing a cheap set of beefy urban tires that are about 45mm wide. They're heavier, and burdened with very thick and tough protection all around the sidewalls. These tires are causing the gravel bike to lose a huge ~2mph on the road versus my road bikes. The aspects of tire construction besides width matter a ton.

If your riding is on reasonable paved roads, then 35mm is probably overkill. But I don't think moving down to a 25 or a 28 is going to significantly speed the bike up either, so I wouldn't necessarily recommend switching down from 35s if there's some reason you like riding 35s.
If you're concerned about speed, then you should ensure that the 35s you're running are at least fast 35s. What particular tires do you have?
If you decide to run deep aero rims, I'd recommend erring toward tires that are no wider than what the rims were aerodynamically profiled for. You still get some benefit of aero rims when using a too-wide tire, but not as much.

*Excluding climbs, that is. My gravel bike is an extremely heavy build, resulting in a bike+rider weight about 7% higher than when I ride my Emonda. This tends to produce a 5-7% performance penalty while climbing the same hills at the same effort. (The fat tires are only a small portion of the weight penalty.)
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Old 11-11-18, 02:30 PM
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If you are asking this question, you are probably riding in a manner that width doesn't matter.

I'm quite happy with 32-35s on most my bikes. I don't feel that the 25s on my "fast" bike have much to do with the 1 mph or so more of speed I get out of it.
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Old 11-11-18, 03:06 PM
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Assuming you're a recreational rider, you'd do better to maximize comfort than speed with your tires. You can match or exceed any nominal speed gains from a narrower tire with a slight increase in conditioning/effort or minor weight decrease. Meanwhile the comfort offered by tires at 32mm+ will let you give your best, longer.

My tire sizes range from 25 to 32mm. My speed is not noticeably impacted by those 7mm.
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Old 11-11-18, 05:43 PM
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Old 11-11-18, 05:57 PM
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Comfort and handling is more important to me then setting speed records. I find 28mm-32mm perfect for majority of riding situations.
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Old 11-11-18, 06:09 PM
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Buy wide rims, then your 25s will mount to 28, and you'll have it both ways.
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Old 11-11-18, 07:05 PM
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Id say go with 23 mm they are the fastest aero tires and most modern rims will have them buldge out to 24 25 mm . if you need cpmfort then go bigger , bit non of my road bikes can fit a 25mm becuase it usualy measures 27 .
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Old 11-11-18, 10:38 PM
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Some one else mentioned comfort, as well, and the OP talks about 50-60 mile rides; Maximum speed is great, and all, but if you're talking about rides lasting 3-4 hours or longer, then comfort will play a factor in how much you've got left at the end of the day.
Being able to run 5-10 PSI less pressure, (or more) depending on rider weight can make a noticeable difference in rider comfort without taking a hit on average speed which is more important than max speed on long rides.

I'm not fast enough to worry about aero, so 28's it is for me.
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Old 11-12-18, 01:06 AM
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Let’s sum this up clearly, removing the outdated myths.
1. The length of the contact patch is determined almost exclusively by the tire pressure and the diameter of the wheel. The wheel diameter is huge compared to the tire width, so it dominates the equation. Wider tires do not have less deflection at all, lower pressures have more. It simply isn’t what accounts for any gains.
2. You don’t need wide tires to run lower pressures, you need wider tires to reduce pinch flats at lower pressures. If you run a narrow tire on a wide rim, you still have to run high pressures to avoid pinch flats. You can always drop a few PSI on any tire.
3. The benifit if lower pressures is in reducing suspension losses. If vibration is uncomfortable, this is because your forward momentum is being diverted into vibrating your bum. Your bum doesn’t give that energy back. A tire does.
4. At least between tires of identical construction between 25-55mm, there is no difference in speed on a smooth surface at speeds under about 22mph. It is only on rougher surfaces, and most surfaces are rougher, that a wider tire may, may, offer more speed, maybe less. At racing speed, wind resistance starts to dominate. Your aero wheels must be designed to match the tire width or you loose almost all benifit by having them.
5. You can get top quality race ready road tires in all sizes up to 55mm in width. But mostly such widths are chosen for off pavement.

I did a century ride recently where I passed almost the entire field, and I am not that strong. I was riding an allroad bike with 44mm tires, while everyone else was riding typical road tires between 23-28mm, many with aero rims. The roads were rough, everyone was complaining bitterly, and I was grinning ear to ear.

Ride on. If you are not racing, it isn’t worth swapping tires for every event, and there is no magic width.
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Old 11-12-18, 10:34 AM
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Originally Posted by el forestero View Post

Am I going to complete 100 to 160 km rides in significantly less time and with less effort if I spring for some new 28 mm tires and rims, or will I do just as well, or better, if I stick with the 35 mm-wide tires I'm currently riding on? Or should I go even wider than 35 mm? Or narrower than 28 mm?
It depends what 35mm tires you are currenly running. Some 35s are very fast. Some are very slow.

Personally, Iíll probably never run anything smaller than 35s again, regardless of ride length. 35mm Compass Bon Jon Pass tires gave up basically nothing in overall speed for me over any narrow tire Iíve run. If I am ever in a situation where it is utterly imperative that I finish a 100 km ride on good pavement 5 minutes faster, I might look at narrower tire.

I think one needs to be very cautious when looking at what pros use to determine what is best for them.

Yes, right now, 25ish mm seems to be what pros are running on pavement. But consider the following:

First, as pointed out elsewhere in this thread one of the main reasons narrow tires are faster is aerodynamics. But the thing to remember about aero drag is that it increases exponentially with speed (as opposed to linearly, as with rolling resistance), so the faster you go, the more it becomes a factor. So if you (lIke me) donít ride anywhere near as fast as pros do, it is less of a factor.

Second, what are your priorities? For a pro, the top (and only) priority is to finish as fast as possible. No speed will be sacrificed for comfort. What about you? Will you sacrifice comfort over a 5 hour ride to knock 5 minutes off your time? Or sacrifice the versatility of the bike?

For years I drank the narrow tire flavored Coolade because that is what all the ďseriousĒ riders were riding. Then in 2010 I got a road bike that could clear bigger tires, and I tried them. At first, it was slower, because I was using slow tires (35mm Continental Contacts and Schwalbe Marathon Supremes), but then I tried a set of fast 33mm Jack Browns, and my times over long paved rides was indistinguishable from when I was running 23s. I was just a lot more comfortable when the road got rough, and this is when my rides began incorporating dirt and gravel roads. Then I switched to Compass tires, and I am not sure if they are faster (I suspect they are), but they are definitely smoother.

Was I actually faster with 23mm tires? Maybe (on pavement), but the difference was so small that it was completely overshadowed by normal ride-to-ride variation. Finishing a 5hr ride 5 minutes faster is just meaningless to me.

Last edited by Kapusta; 11-12-18 at 11:06 AM.
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Old 11-12-18, 09:43 PM
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Originally Posted by rumrunn6 View Post
+1 and more
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Old 11-12-18, 10:40 PM
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Super helpful and informative posts, all. Thank you! Given the kind of riding I do, long-distance recreational, and not at pro race speeds, sounds like any speed gains I might get from going with narrower tires aren't going to be great enough to merit giving up the increased comfort of riding on wider tires inflated to relatively lower pressures. I'm currently riding on Bontrager H2 Hard-Case Lite tires and AT-750 alloy rims. Very interested to hear more on what folks have found to be high-quality, fast 32 or 35 mm tires and rims, and will post a new thread on that.
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Old 11-13-18, 10:23 AM
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Originally Posted by el forestero View Post
Super helpful and informative posts, all. Thank you! Given the kind of riding I do, long-distance recreational, and not at pro race speeds, sounds like any speed gains I might get from going with narrower tires aren't going to be great enough to merit giving up the increased comfort of riding on wider tires inflated to relatively lower pressures. I'm currently riding on Bontrager H2 Hard-Case Lite tires and AT-750 alloy rims. Very interested to hear more on what folks have found to be high-quality, fast 32 or 35 mm tires and rims, and will post a new thread on that.
Compass.

There ya go. Saved you an entire thread.
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Old 03-09-19, 07:03 PM
  #24  
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Originally Posted by catgita View Post
Letís sum this up clearly, removing the outdated myths.
1. The length of the contact patch is determined almost exclusively by the tire pressure and the diameter of the wheel. The wheel diameter is huge compared to the tire width, so it dominates the equation. Wider tires do not have less deflection at all, lower pressures have more. It simply isnít what accounts for any gains.
2. You donít need wide tires to run lower pressures, you need wider tires to reduce pinch flats at lower pressures. If you run a narrow tire on a wide rim, you still have to run high pressures to avoid pinch flats. You can always drop a few PSI on any tire.
3. The benifit if lower pressures is in reducing suspension losses. If vibration is uncomfortable, this is because your forward momentum is being diverted into vibrating your bum. Your bum doesnít give that energy back. A tire does.
4. At least between tires of identical construction between 25-55mm, there is no difference in speed on a smooth surface at speeds under about 22mph. It is only on rougher surfaces, and most surfaces are rougher, that a wider tire may, may, offer more speed, maybe less. At racing speed, wind resistance starts to dominate. Your aero wheels must be designed to match the tire width or you loose almost all benifit by having them.
5. You can get top quality race ready road tires in all sizes up to 55mm in width. But mostly such widths are chosen for off pavement.

I did a century ride recently where I passed almost the entire field, and I am not that strong. I was riding an allroad bike with 44mm tires, while everyone else was riding typical road tires between 23-28mm, many with aero rims. The roads were rough, everyone was complaining bitterly, and I was grinning ear to ear.

Ride on. If you are not racing, it isnít worth swapping tires for every event, and there is no magic width.
at the end of the day, comfort is probably the answer.

i have been experimenting a bit with tires, from 25 to 35 so far, to see what they offer. my rides are both racing and touring; for a short ride it makes no difference. the touring bike came with 32, switched it to 25 and no real speed increase. now it has 35 front and 32 rear, for use on our rural gravel roads. haven't tested much yet but prolly better than 25's.

failing that, then the mtb's will take over for rural gravel. sometimes our roads here are more dangerous during evening rush, so the less travelled rural gravel roads will make more sense. i even thought to change the touring bike out to wider maybe 40 or 45 to see if that can better cope.

generally 25's do fine on the racing bikes for street use and may try wider on them if they fit. my thinking is that the front needs the widest for steering and comfort, and may try a 32 up front to see what happens on a Trek 1000 and Trek 1500. these bikes get the most use as they are fun to ride, but a bit more comfort up front is desired.

since i ride below 22 mph, these wider tires should not affect speed in any significant way. for me it is about getting out there daily and pounding pavement. any encouragement from equipment will go a long way.

comments?

thanks great thread to help with decisions.
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Old 03-09-19, 08:39 PM
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my prevous roadbike had 28.
now i have 25.
i feel noticeably faster on 25 and less fatique.
and 25 feels just as cimfortable as 28.

just came back from group ride. i was just barely able to keep up. if i still have 28,... i would have been dropped fir sure. for sure.

difference in speed may not be much...but its diff btn winner and loser.

Last edited by mtb_addict; 03-09-19 at 10:37 PM.
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