eduskator

32mm isn't standard for race bike. May-be for endurance bikes.

TCR - 28mm
Propel - 25mm
Tarmac SL7 - 26mm
Teammachine - 25mm
Soloist - 28mm
Ultimate - 25mm

urbanknight

The OP doesn’t specify “racing” bikes, and posted it in the “road cycling” section and not the 33.

Chinghis

Hehe, my observation is that I have always had trouble getting my tires up to that last 100+ psi. Now I know I can just say screw it and live with 80 psi.

GhostRider62

Ok, Canyon Endurace, Cervelo Caledonia and Cannondale Synapse comes with 30mm tires. Three commonplace endurance bikes.

32mm is not standard and in fact, it is very, very rare to see either a road bike or endurance bike sporting 32 mm stock

merlinextraligh

you’re leaving out the aero part of the equation. Admittedly, that’s going vary with the rim and frame, but ceterus peribus the wider tire is going to have more aerodynamic drag. How much, and how much it matters is debatable, but it is a factor to consider in the equation.

scottfsmith

I saw a study which took into account all these factors, I wish I remembered where. The takeaway was if you have the right rim width for your tires and are on normal roads 28mm was optimal. My guess is pros are slowly moving to 28s due to this kind of data. That may be the stopping point of the size increase for the pros, there is no more juice to squeeze out of wider width due to the wind resistance.

For non-pros, 30-32mm is the natural leveling off due to the very small penalty. Or maybe we’ll all be on e-bikes with 4” tires soon. haha.

SoSmellyAir

28 mm tires on 25 mm IW hookless rims!? I recently bought Roval Terra CL II, a 25 mm IW hooked wheelset which also specifies a minimum tire width of 28 mm. I know the old ETRTO standard is way too conservative, but the 3 mm difference between tire width and wheel IW seems so small. But maybe I am chicken (or just outweigh you significantly).

Increasing tire clearance does have a downside: longer chain stays, and thus a longer wheelbase. But it is important for marketing to reference the big tire clearance number to imply a greater capability for everyone to follow the "all road" trend. It is somewhat analogous to how so many 11 speed bikes now come with the biggest range (11-34) cassette.

urbanknight

Wow! I was pumping my track tubulars to 140 or 150, which amused me because I weighed 125 at the time. I really had no need to run that high of pressure on the aging concrete velodromes back then.

SoSmellyAir

I am not sure that my floor pump is accurate enough for me to participate meaningfully in any discussions which reference specific tire pressures.

Troul 

30 or 32 for those of us not willing to close the donut box & want a supple ride with a road bicycle. This spare tire I call a gut may not address a flat, but it'll conceal the treats with the flab!

Troul 

your pump doesn't have a little icon on the gauge resembling a rock? Gotta pump them tires up so high that they get hard enough to cut thru the glass!

PeteHski

Trek Domane and Giant Defy both come stock on 32 mm these days. Other endurance bikes are 30 mm and pretty much any new road frame has clearance for at least 32 mm.

mstateglfr 

I left out the aero part because I don't know it. You also don't know it. We don't know the rim profile either.
It's an unknown variable and so I didn't address it because it isn't a factor in my post. My post focused on known factors- weight and rolling resistance.

mstateglfr 

A Domane chainstay is 420mm and a size 54 wheelbase is 1010mm long.
A Cannondale Super6evo chainstay is 408mm and a size 54 wheelbase is 1008mm long.
Why is a 420mm chainstay a downside? And the Domane wheelbase is basically the same as a full on race bike of the same size.

I'm also unsure why an 11-34 cassette is bad to spec on general road bikes. For years(decades), road bike were geared far too high for average users and even many enthusiasts. The last 6 years has pushed the needle towards more realistic and useful stock drivetrains. Why is that bad?
If you want an 11-28 or 11-25 cassette, just buy it. It's far simpler and cheaper to add a smaller cassette to a stock drivetrain with a GS RD and long chain that it is to add a larger cassette to a drivetrain with a short cage RD and short chain.

urbanknight

I'm sure my thumb can find the 72.6 psi that the online calculator recommends.

merlinextraligh

The point of your post certainly appeared to be there is no speed penalty to going to 32. To make that claim you have to consider all the factors, weight rolling resistance, and aerodynamic resistance, which becomes a bigger part of the equation the faster you go.

As I acknowledged in my post, the exact effect on aero is going to be affected by the rim design and the fork and frame. However, to say that you don’t know the precise effect, due to those confounders in no way means it’s not a real factor in the equation.

and it is an ascertainable number. The makers of deep sectioned wheels can give you the data for their rims, and which tire size is optimal for those rims based on their own wind tunnel data.

used to be Zipps were built to be optimal with 23mm tires. Newer wider rims today tend to be designed for 28mm. I’ve yet to hear of a deep sectioned rim optimized for 32mm tires, although it could be coming.

So the aero penalty is not only the shear frontal area of the tire, it’s that the interface of the rim and tire is not optimal for wind resistance.


All that said the aero effect may not matter to many, and may be trumped by other factors such as comfort for some, but it doesn’t mean it’s not a factor.

Bah Humbug

Or maybe roads are getting worse, at least some roads in some areas, and people riding them have different needs from you.

PeteHski

The difference in aero hardly matters to pro racers, never mind an average club racer or recreational rider. A lot of teams were racing on 30 and 32 mm tyres at Paris Roubaix this year. While you can say that’s only because of the cobbles, there is still 200 km of 50 kph road to cover. If there was a significant loss of speed on those wider tyres, they wouldn’t be racing them. Simple as that.

Back in the real world the pros of wider tyres greatly outweigh the cons for almost any rider on mixed quality roads, especially on longer rides when fatigue from vibration becomes a significant factor.

The only reason to run 25 mm tyres is if your frame can’t fit anything wider or your roads are super smooth and you want to save a few Watts at most IF your rims are optimised for narrower tyres.

I’m happy using 30 mm tyres on my endurance race bike, whatever the road quality. I don’t feel I’m losing out significantly in speed, but I certainly appreciate the ride quality on a long hard ride. It might look more “pro” to run a 25 mm front and 28 mm rear, but it’s not going to give me any meaningful advantage.

One other advantage of wider tyres and rims is when using sealant in a tubeless setup. The much lower pressure gives a better chance of the sealant coping with a puncture. 60 psi is a lot easier to seal than 100 psi and you lose a lot less pressure if it leaks for a second or two before sealing. I usually just see a few spatters of sealant on the seat tube with barely any loss in pressure. I only notice there was a puncture when I check my bike at the end.

GhostRider62

All well and good but a few exceptions is not the same as saying 32mm is standard. For those who think a 32mm tire has equal aerodynamics to a 25mm tire, I have a bridge to sell you. Or, may I ask have you measured? Or are you just regurgitating Jan Heine's dogma.

PeteHski

The OP was referring to Trek and Giant endurance bikes, which both come with 32 mm tyres. These are hardly very, very rare bikes as you stated.

Not sure anyone said it was a standard thing across the entire industry, but 30-32 mm certainly is standard for endurance road bikes in 2023.

When I bought my Defy in 2019 they were on 28 mm and had narrower 17 mm rims. I think they made the change to 32 mm and wider rims in 2020 or 2021. My 2022 Endurace came with 30 mm tyres on 22 mm rims and I find that combination a significant improvement in ride quality.

I believe my rims are optimised around 28 mm tyres and any slight loss of aero over a 25 mm tyre optimised on narrower rims is of no concern. I look at the overall pros and cons rather than focusing on a single factor, especially when that factor is very marginal. For me the benefits of extra tyre width and volume is worth a lot more than a few aero Watts.

seypat

I'm lucky I guess. I have enough bikes/wheelsets that I had the same brand of tire from 23's to 32s on different wheelsets. I could swap them out on the same bike, use different pressures, side by side. For me, there's not much of a difference. Maybe some between the 23s and 32s. The 32s feel sluggish. I also realize that at 5'8' and 200lbish, a typical frame is going to ride less stiff to me than to the typical 5'8" 120-160lbish rider. Heck, the tire size might not even matter that much to me on gravel, if I rode gravel. Come to think of it, I did have to cut though a section of gravel one time on a route I was riding. I was on the 32s at full pressure. Plush enough. I usually buy the cheapest size within a particular brand.

SoSmellyAir

A shorter wheelbase handles slightly better? A Trek Emonda in size 54 has a 981 mm wheelbase. Even my old Cannondale Synapse (not a race bike) in size 54 has a 990 mm wheelbase.

An 11-speed 11-34 cassette has 2T gaps on the small end in exchange for more cogs on the big end. This is good for steep hills and gravel riding but not so ideal for riding along at a just right cadence.

GhostRider62

Roubaix comes in 28 mm tires.

mstateglfr 

The wonderful thing about bikes and components is there is no shortage to allow each of us the opportunity to make our bikes perfect for what we want or how we ride.
With that said, bikes have to come stocked with something, so it makes more sense to stock endurance bikes with wider range gearing since as already mentioned, it is easier and cheaper to make gearing tighter with a smaller range cassette than it is to make gearing wider with a larger cassette, new chain, and new rear derailleur.
If you dont want or need a 34-34 bailout option on an endurance road bike, cool- just change the cassette. I dont need that gearing option and therefore I have 11-28 cassettes. Frankly, I dont need an 11-28 either, but the jumps are small enough that I dont care to change anything out.
But while I dont need an 11-34 cassette, I recognize that others may benefit from one. And I also recognize that its easier and cheaper for those who want a smaller cassette to make that change than it is for those who want a wider cassette to make that change.

As for the Emonda having a tighter wheelbase than the Domane, well yeah that makes sense due to it being designed for a different style of riding. I cited a race bike too, and it happened to have a wheelbase that really isnt noticably shorter than the Domane. This was done because you brought up how longer chainstays and wheelbases are a downside. If we were talking 480mm chainstays, sure I would agree. But 420mm? Come on now- you really think you can tell the handling difference between a bike with 410mm and a bike with 420mm chainstays if they both have the same tires and setup? And even if you could tell the difference, would that difference be a downside? Are you going to not turn a corner on the 420mm stays that you could turn on 410mm stays? This is road biking we are talking about- its like the least technical type of riding there is.

PeteHski

It's about the only mainstream endurance bike that still does and the frame clearance is relatively tight for a modern endurance bike. With wider tyres, the need for a front shock is also becoming more questionable. I would put money on it that the next gen Roubaix is on 30 or 32 mm tyres and possibly ditches the Future-shock, which has always been divisive.