Ideal tire size for road

TL:DR
Best tire width for road.

Here’s my scenario. I’m in the market for a new road/gravel bike so need to learn new info. I know that, assuming all the right conditions (tire pressure, internal diameter, propel wheel, etc) what is the fastest road tire size? 28 is faster than 25 but assuming correction conditions, is 32 faster than 28? Is the fastest tire size higher? Also, is there an ideal tire for size for gravel (naturally conditions will make choices different) but same basic question. Then-is there a “best” internal diameter now as well? Figure knowing this will help me figure out which bikes to start looking at. Thanks all.

I’d lean towards 23-25mm internal width and 30-32mm tires for road in 2024. Great in a straight line, absorbs road vibration better, and significantly more grip and confidence in corners than narrower options.

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The “truth” is not yet known. This is an area where things are changing and there are lots of conflicting opinions.

Wider tires at lower pressures provide greater comfort, greater shock absorption, and better traction when cornering. Many people say they are as fast, or faster because by absorbing some of the bumps and reducing bouncing plus reducing fatigue, they will make the overall bike+rider faster. Note that, to get the best aero performance from wider tires, you need wider wheels.

Many other people will hang their hat on rolling resistance and use slimmer tires, arguing vehemently that those are faster.

There is NO way to tell what’s actually, fully, scientifically true yet. People are trying to find out. I’ve spent the last couple of years reading everything I can find (and understand) on this topic, and the above is the best I can give you.

My personal conclusion was that wider tires, at lower pressures, on wider wheels, ARE faster and more comfortable and corner better, and I’m not racing or winning so traction and comfort are more important anyway. I’m also 70 lbs overweight. I chose to ride (for my gravel bike on the road) supple 700x44 slicks at 40psi on wheels that are 29mm wide internally and 40mm wide externally, and I’m in heaven.

As I lose weight, I’ll eventually switch to 700x38 slicks on those same wheels, which will almost perfectly fit that magic 105% ratio for aero gains. I think that’s the ideal wheel/tire for me.

Most road frames won’t handle a tire that wide… if so, use the widest tire that’ll fit, on an appropriate wheel.

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Really depends on the roads where you live.

Smooth as glass? 25s (or 23’s, gasp) will still be fastest.
Road chatter, 28-32 will help you out a bunch.
Blasting potholes on the reg? 40+ would suit you well.

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26
28
30
Or :32

Maybe something else. It depends.

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Its unclear if anything between 23 and 32 is faster but I know I’m more comfortable on the higher end of that. There might be some drop off at 30 and higher due to wind resistance.

for me personally the ideal wheel is something like the roval clx ii. It’s been introduced in 2020 and hasn’t been updated. That speaks for itself imho. Wide (35mm) front wheel with hooks, tubeless ready and reliable DT internals. You can mount tires from 28 to 34 - I‘d go 30 in the front 32 in the back. Is 23mm on a 19mm IW wheel more aero? Probably. But it’s not comfortable out on the road. So if you don‘t ride in a velodrome or track I‘d go at the very least with 28mm tires today.

Rolling resistance says that all the tires are practically a dead heat once air pressure is adjusted normally for each tire:

Look for the section: Rolling Resistance at Recommended Air Pressures (15% tire drop)

Pros seem to still ride 28mm tires though roads in France are pretty smooth. They do seem to go up to 32-34 for bumpier events.

If speed is the absolute criteria then one wants to start with a wider rim (like the Rovals mentioned) and then fit a width appropriate tire such that the tire does not bulge beyond the width of the rim.

Jan Heine was telling us years ago that hysteresis was sucking up our watts and that supple wide tires with lower pressures were the way to go.

It seems though that nobody has scientifically measured this yet. Rumble strip tests are interesting but not very real world. And 15 second roll down tests aren’t long enough to really show differences. Norcal cycling’s test was less than scientific though and an entertaining effort.

I suspect that on smooth roads, the conclusion is that wider tires aren’t a penalty assuming a properly sized rim (width) other than in the weight department.

And don’t fit Gatorskins to your expensive aero optimized wheels. :slight_smile:

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For both, road and gravel the current trend is to go wider. On the road 28 mm is the bare minimum these days with 32 mm on track to becoming the new normal. I wouldn’t be surprised if 35 mm slicks will be a standard option in a few years.

Most roadies seem to be more conservative than mountain bikers or triathletes, though. Not sure why.

Modern rims have an internal width of 23–25 mm. I have 3T Discus 45|32, and they are 25 mm wide internal. Ditto for Zipp 303Ses.

In terms of speed, it depends on the roads you are on, but I’d personally opt for 32ish mm and try 35 mm in the off season. (My road bike frame doesn’t have enough clearance for that, so I am stuck with 28–30 mm tires.)

The discussion around gravel is a lot more complicated, because gravel ≠ gravel. Although also here I can see a clear trend towards wider tires. Many pros who did Unbound this year went with ~2.1" mountain bike tires and deep wheels.

Yes, and this is IMHO a strong argument in favor of erring on the wide side when it comes to tires. Where I live now we have cobbles in some areas and I can tell the difference adjusting the tire pressure by a few psi.

Yup.
More aero ≠ always faster.

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I decided to test tires. I was on two sets of Schwalbe Pro One TLE, now that I needed to replace them I went for the Conti GP 5000 S TR ones, all of them 28mm. However, the next tires will be Vittoria Corsa Pro at 30mm, both front and rear. Initially I wanted 28mm front and 30mm rear, because my wheelset is optimized for 25-28mm, but at the back it is negligible so wanted to try 30 there but the 30 turns out to be available for me much cheaper than 28 so I am going for 30 on both front and rear.

May be a while until I ride those, but long story short, try out and see what you like.

Personally, the Conti feel better so far, but importantly I am riding them new and coming of tires that are 1000s of km old. So the comparison isn’t fair and it’s been a while since I rode the Schwalbe new so it’s hard to remember what they felt like new.

The advantage of wider: more comfort but what isn’t talked about as much - more grip.

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Pogacar has tires that measure to 33mm on his tour bike. I think 25mm internal. So I’d say pretty confidently that they are the fastest for road. And their road surfaces are pretty nice and 100x nicer than my local roads. I’d be getting 32’s if I had a bike that could take them.

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Dang you beat me to it lol. Just saw Poga’s bike review measuring 33.

I switched to 30s last year and there’s absolutely no way I’d go smaller. Even if there’s a .5w difference (there isn’t), the way the bike rides and fatigue reduction is immediately noticeable. It’s just fun! Riding a bike that doesn’t beat you up is awesome.

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The trend is definitely wider tires. I would say 28 is the absolute minimum and with a modern rim I would go 30s or even 32. The so penalty is miniscule with those wide rims and the added comfort and grip is worth alot. Currently on 28s but as soon as the rest tyre is done it will be a 30 and the front Will change to especially If I get new wheels with 30mm or more external width.

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Casing also makes a huge difference. I’m a huge fan of Vittoria’s tires, because they are so supple. My Pirellis finally wore out and the Corsas I got for them have a sublime ride.

I always mean to try out GP5000s, but never get to it. I don’t want to shell out €€€ only to find out I prefer something else.

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I’ve recently moved from 25s to 30s. The shop set them up with TPU inner tubes and I switched to latex after a few weeks. The TPU on 30s was more comfy than 25s and latex but didn’t feel faster. Now with the latex they feel fantastic — more alive.

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The lower pressure needed for wider tyres has another benefit, sealant can do it’s job better and it’s also easier to get them up to a correct pressure range with a small pump

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Interesting. I’ll have to try them once my current tires wear out. I just have Maxxis high road 32s which is what came with my bike. I doubt I’ll go any smaller than 32s in the future

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I love gp5000s. Just bought a new 30mm pair for £110 and set them up tubeless (first tubeless setup). Can’t wait to get out in them tomorrow.

In my experience gp5000s feel so fast and grippy. I’m sure you’ve had similar experience though, so is agree - don’t change if you’re happy. I’m the same, now I’ve had these (on previous bikes at 25mm) I don’t want anything else

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Have you ever tried veloflex? At least as supple or even more supple depending on the tyre, better puncture protection, better grip (according to bicycle rolling resistance at keast)only a fraction of the price and less than 1-2W difference in rolling resistance

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Recently switched to 32mm (measuring 35mm) Conti gp5000 S TR on Reserve 52/63 wheels (25 int, 35ext) and I’m never switching back to a lower tyre width. The amount of comfort, grip and confidence I get from this setup is just amazing. Even though our roads in the Netherlands are pretty smooth the difference between 28 and 32 is very noticeable.

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