scottfsmith

There was a recent interesting video by NorCal cycling where they tried 28/32/34mm tire widths on the same course with the same power and measured times:


The conclusion was that on standard roads 32mm tires are the fastest, and 34mm were actually faster than 28mm tires. These results are at odds with a lot of other experiments but I think the reason why the larger tires did so well is they used the new Roval Rapide CLX II wheel set which has a 35mm (!) outside diameter in front. This wheel set is optimized for 26mm rubber (on smooth bike race roads) but seems to do very well with wider rubber on rougher roads.. they are around the 105% rule for 32/34mm tires so it makes sense. Oddly enough they don't talk at all about this in the video itself, they are oblivious to the rim width impact.

Anyway I like big tires for comfort/control, but I also like to go fast.. with this data I recently decided to switch to 34mm for my winter wheels. The rims are 32mm external diameter so not so far off these fat CLX IIs. I got the Vittoria Corsa Pro Control tires which are the only performance road tire I could find in 34mm. I'm curious if anyone else watched that video and what you thought of the even-fatter trend. Most road bikes won't take 34s which rules it out for many, but I happen to have an endurance bike which takes up to 35mm or so (and I happen to have some fatter aero rims, which I got for gravel originally). I'm going to ride these 34mm guys this winter and see if I like them enough to run them in the summer.

mstateglfr 

What's most impressive is that both guys managed to ride the course 3 times and ended all 3 rides with the exact same power output.

lasauge 

I think it's still too early to answer this question - there just aren't enough really fast 33-38mm road tires and appropriately wide road rims on the market yet for widespread adoption and experimentation.

But if I had to guess, I think most road riders will end up on 28-35mm tires and that what's best for each rider will depend on their weight - but we still don't really know if any wider could be practical with the right tire casing design. I've ridden my share of 38-50mm pavement tires and love them for practical everyday travel, but they definitely come with a weight and rolling resistance penalty. For pure speed, anything wider than 32mm slows me down. I run my 30mm Corsa Pros at 50psi and they're plush enough already that I don't feel any desire to go up to 32s except for the purpose of experiment.

choddo

And presumably identical at every point along the route too. I’d like to see those charts.

I see someone else asked this question in the comments and they did do a direct overlay in another video on cheap vs expensive tyres. Would like to have seen it for this one.

znomit

And identical wind?

choddo

and riding position

scottfsmith

I have also been on 30s for the last 3-4 years and have been quite happy with that really. The main motivation I had for thinking about bigger is in the winter the bike paths I ride on get a ton of debris and I have lots of sticks, leaves, rocks and gravel to deal with. So at least for winter I think it will be an advantage to have more comfort and control. For summer I'm sure the 34s will be a bit slower but maybe not by enough for me to care.

Re: the quality of the study, its clearly not serious science but the fact that in 6 rides the 2 rides with 28s were the two slowest at their speeds says to me there has to be something going on with the tires. (There is no wind I can see in the video, that would have skewed things I would agree.). The main weakness of the study in my mind is the complete ignorance of rim width. My wider rims are 32s and my guess is they would not do nearly as well as the super-fat 35s they used with the 34mm tires. If they used standard-width aero rims I am pretty sure the 28s would come out on top -- there have been other informal studies of that scenario.

PeteHski

I think this is the key point. Maybe you will notice the obvious benefits of a wider tyre more than any slight loss in speed. The fact that you can run considerably lower pressures is a big bonus if running tubeless with sealant.

I currently run 30 mm tyres on my road bike, but I’m very tempted to go wider next time. 32 is the max available in my preferred tyre.

jadmt

My schwalbe pro 1’s in 700x30 and my conti gp5000’s in 700x32 both measure exactly 31mm

choddo

I might get some 30s for my gravel bike when it’s on road. What tyres do you use?

PeteHski

I’m using Conti GP5000S TR in 30 mm. I think Conti have nailed it with these. They mount very easily on my DT Swiss carbon rims and hold up well on our rough, potholed roads. Grip and ride is excellent too in dry and wet conditions. I’m keen to try the 32c version for even lower pressures and comfort.

Previously I used Pirelli P Zero TLR 30 mm and they were harder to mount (required a few blasts with my boost track pump) and far more prone to cuts on my local roads. I thought it was just bad luck the first time, but the cuts kept on appearing on both tyres and I had to plug both of them. After just 500 km I gave up on these tyres. The Contis have been far more durable in this regard. Just a couple of very minor cuts and only one obvious puncture were the sealant did its magic. Not had to plug one yet.

scottfsmith

Same here, excellent tires! I have occasionally had difficulties getting them to seal tubeless, in particular I had to clean off the rims and tire edges of old sealant to get them to re-seat a few times. I was using a particle sealant I had to remove a bit of the tire to get in but I recently switched to Orange Seal so I could just inject more sealant into the stem which should make that less of an issue.

BTW there was a commentary on the above NorCal video on Chris Millers YouTube:


Not much new, but interesting to see how excited these guys seem to be about this.

eduskator

Overbeaten road bicycle topic.

Theoretically, wider = more air volume = lower pressure required = less RR = faster. If you consider the ''real world'' factor, it may not be. *Mic Drop*

choddo

"lower pressure required = less RR"

Does that follow? My primitive simian brain always associated higher pressure with less rr but maybe less speed thanks to worse effects from imperfect surfaces.

choddo

Ordered

genejockey 

I imagine years of training with power meters and having to hit and maintain specific power outputs helps A LOT.

Any time I try to do a structured workout on the smart trainer without engaging Erg Mode, my power is all over the map and I end up mentally exhausted from constantly thinking "More power! More power! NO! Less power! NO! Not that much less! More! No, less! No, more!!"

I have to give kudos to Jeff for trying so hard to eliminate variables, while still doing a real world test. It may not be perfect, but at minimum it indicates you won't lose speed going from 28s to 32s, and might gain some, and at the same time improve comfort. I think I'll pick up a pair of 32s for the Canyon, if I find some good tires on sale at a good price!

terrymorse 

Your brain is onto something. There are two types of RR: 1) from the deflection of the tire casing, and 2) from road vibration that's transmitted to the bike+rider.

High pressure will always reduce #1, but it may increase #2. It depends on the roughness of the road surface. The "ideal" pressure is just low enough to allow the tire to absorb the road roughness, but not lower.

Iride01 

If we only knew BITD how right we were on our 27" x 1¼" tires (32mm wide). Even the sportier cyclists were only touting 27' x 1-1/8" tires (28mm wide). And maybe a rare 27" x 1". All on a rim that is only 8 mm larger in diameter than the 622 of a 700C rim. I've long missed my 27" tires that road so well compared to the 700C's of their day that were really narrow.

And why we popularized 700C as a name for a wheel size is really a big question, since in the French tire sizing the tire would be about 39mm wide to give you the required 700mm outside diameter height on a 622mm rim that the 700 represents.

Though back then the tire technology wasn't what it is today. So weight as well as aerodynamics of wheels back then may have made rough riding narrower tires better for the long haul distances saving more overall watts than their very short ride suggests.

All that said, I'm still on 25mm tires. Might go to 28mm when my last spare 25mm is used up.

JohnDThompson 

The premise is that for any given pressure, a wide tire will deform less under load than a narrower tire with the same construction, and thus have less rolling resistance. Lower pressure comes into play by improving comfort and road handling with as good or better rolling resistance than a narrow tire on the same surface.

Sierra_rider

I use the same tires/size on my Endurace and am also considering the 32 next time...they work great for a tubeless set up, these don't get the sidewall seep that some tires do and are easy to seat on the rim.

I'm running non-TR 28s with TPU tubes on my Ultimate right now, I'll probably switch that to tubeless once I wear the current tires out. I'm a bit more limited with frame clearance and brake clearance(rim) with that bike, so I think 30 is going to be about max.

Fredo76

I trained on 27 1/4" and 27 1/8" tires for awhile in the '70s, racing on sew-ups and later training on them too. The sew-ups were a lot faster, and nobody can tell me different. Now I'm liking 28mms in both clinchers and sew-ups. Fredo is maxed at 28mm in the rear, but I've used 30mm sew-ups on the front, too.

My brother put 48mm RH Barlow Pass tires on his new wheels for the bike he keeps here. His new wheels are nice, but I prefer the 35mm Continental Terra-Speeds on the wheels I was using before.

And his new freehub is definitely too loud (White Industries).

Good thing the Ricky Racers still resent the Chumps, and vice versa. I'll be gone by the time that changes!

Maelochs

In my understanding, "worse effects from imperfect surfaces" is ... rolling resistance.

Though sometimes it can be bouncing resistance, I suppose.

Jrasero

28mm IMO in 2024 should be the standard especially if you are on a 21mm internal since aero wise it's the most flush. However, I am starting to see more and more 23mm-25mm internal width wheels and in that case 30mm and 32mm make more sense.

I personally run 30mm GP5000 clinchers on a 21mm internal w/ TPU tubes on my Aethos and the thing is very comfortable. For my aero race bike I have 28mm GP5000 clinchers with TPU tubes and combined with stiffer wheels, stiffer frame, and the slightly narrower tires run at higher pressures it's a more sporty but less forgiving ride

This is all to say I truly think in less than 5 years that the new standard for new modern race bikes will be 30mm tires

phrantic09

The Zipp 303S is 23mm and optimized for 28- though they cite total system efficiency.

I would imagine there’s some sweet spot between 28-34 where aero loss is minimized and RR is maximized, it seems it’s 32.

What wheels were they using, Reserve? Those have 25 internal width so the 32 being faster makes sense.

choddo

Interestingly we are both right it seems

https://x-engineer.org/rolling-resistance/