Who's done the wider tyre road experiment?

Thanks for the follow up. Out of curiosity, what do you like about the N.EXT over the Roubaix?

My 34s are great. Been putting in a good amount of miles on these with no complaints. Rolls great. Recently had a piece of glass embedded into the tread but didn’t puncture through. There are a bunch of gashes particularly on my rear tire (akin to more racey tires), but it’s been holding up just fine.

I also got them for a great price. With that said, I think I’d have a hard time deciding to go with these again if the price was at/near retail. I’m strongly considering the Conti GP5k All Season TR to replace these, but still a ton of life left on the N.EXT.

Road feel. The Roubaix were like floating over the road. I prefer a little more road feel. That’s the one thing I don’t like about the 4000, 5000 and 5000 TL.

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Got a little too ambitious on a short gravel path while on my 34mm N.EXT. Still holds air just fine but the sidewall bulge is iffy. Trying to decide whether to replace it with another 34mm N.EXT or to try something else. Might be a good time to try out the Roubaix or to splurge on the new Specialized Mondo.


There’s a new NorCal cycling video which seems to imply 32’s are fastest (and I have 2 sets of 28mm tires in the mail :grimacing:).

32 for the win! That’s my preference too. My bike has the same wheels as in the video.


Jeff’s videos are fun to watch but he doesn’t do careful experiments and analysis.


After spending a week in CA riding close to 400 miles, I can see why the bigger tires are faster. Had to be the worst quality roads I’ve ever ridden. I was thankful to be on 32s.


I ride gravel tires here in California. Between the potholes and the sand (I’m on the coast) the gravel is probably smoother. :rofl:


A few caveats to his testing…

  • small sample size
  • same rim profile was used for each tire size (wider rim might make the 34 faster?)
  • NorCal and his friend are both elite athletes - for those of us that can’t maintain 225W or 300W (~20 and ~24mph here, IIRC) for long rides, the 34 might be faster (assuming rolling resistance is relatively more impactful than aero at slower speeds)

Regardless, NorCal’s videos are usually interesting and this is no exception. And I’m not surprised wider was faster - all the recent testing I’ve read about shows the same pattern - wider, lower pressure, go faster. See also the “should we use MTB tires for gravel racing?” thread on this forum (the answer is yes, sometimes a 2.3" XC tire is faster than a 40mm gravel tire).


If the test protocol and analysis are done well, neither sample size nor the speed/wattage are problems. Same rim profile could be.


I thought wind resistance increased exponentially with speed where rolling resistance increases linearly? Wouldn’t that mean that different test speeds could at least theoretically favour different tyres? E.g. If the 28mm was the most aerodynamic but also had the highest rolling resistance, then the higher the speed the more the aerodynamic advantage would come into play. So it might be the slowest tyre at lower speeds/wattage but the fastest tyre at higher speeds/watts

Which might explain why the Worldtour with very high speeds seem to still prefer 28mm (and I’m assuming the Worldtour is fairly optimised on tyres these days given that guys like Josh Poertner and Dan Bigham are advising the teams). Though could also be explained by wheel sponsors - the Rovals in the video are pretty wide at 35mm external width on the front (I think), that’s wider than a lot of the teams are using. And/or Worldtour races are generally on good tarmac (other than the cobbled races obviously).

Yup, which is why if you vary speed and power you can estimate both CdA and Crr, and thereby determine how much difference you’d see at low speeds vs. high.

(Also, if you do the protocol and analysis well, the “sample size” increases so you can calculate the variability in your estimates of CdA and Crr).

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The main issue with all of it is that you don’t need to run a 34c on the front and he didn’t test 28/34 or 28/32 (which is how these wider tyres are oft-used in the pro tour).

The majority of your RR gains are made on the back wheel. Next to all of your cda tyre gains are made on the front.


Hi Professor, nice to have you here.

In your experience, have you observed a pattern where at some width tires become too wide for a given average speed (assuming the rule of 105 is followed). Or is this something that can’t be generalized?

Well, first of all, I can only test with my bike, and on my bike the widest tire I can fit is a 28. But more generally, yes, there should be a width where the Crr decrease is offset by an increase in CdA if you ride fast enough. We see that on the velodrome where the speeds are high and the surface is very smooth, and that’s well-predicted by the physics, which is reassuring. So although I can’t test beyond 28 on my bike, I’d expect a similar thing on the road. Obviously, the road surface comes into play, but for a given Crr and CdA, you can calculate the “cross-over” point. Note that Crr scales just like road gradient, so you get a different cross-over on a flat road than you would on a hilly or rolling route.


I had my first puncture on my last outdoor ride of the 2023 season, so id ballpark about 8000km’s without issue. It did seal with a plug (eventually, half hour of pfaffing about) to get me home, but I’ll probably replace it in the spring. They are an absolute bastard to seat on my rims, so I would switch to something else, but I have another Pirelli new in box.

Have just taken delivery of Conti GP 5000 all season in 32s, Will be fitting them tomorrow and christening them this weekend; will report back with initial impressions. Based on the BRR data, they tick just about every box for me. I’d have liked the ability to run a 30 at the front, but (for some reason) Conti don’t offer them in that size!

Tarmac SL7 installed 32c All Season TRs on September 4th. About 1010 miles so far. Rode them thru the end of October and then switched to my gravel bike. Only rode 5000 AS TRs twice in December, twice in January, and then had Tarmac serviced last week and started riding the Tarmac again last night. Compared to my Checkpoint with 42c S-Works Pathfinders, the 5000 AS TRs at 60psi (I’m 91+kg) have some nice “float” over rough roads (the Pathfinders are even better). Really happy with them given they have better protection versus more supple tires.

Plus with all our crap roads I think the rolling resistance is likely lower than running a 28c tire - an opinion that is apparently backed up with non-scientific testing by NorCal Cycling recent video

(same wheels as mine)

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Recently got my new do it all bike, the Canyon Grail which comes with DTSwiss GRC 1400 carbon rims 42mm deep and Schwalbe g one rs evo gravel tires. Did a few rides and they felt slower than my 60mm deep rims with gp5000 28mm tires. Checked out byciclerollingresistence, but their test only showed less than 5 watts difference between the tyres.

So today I did a little test. A 16km continuous loop without stops at my z2 pace on both wheelsets sitting upright with hands on the hoods. Tests done back to back.

GRC 1400 with Schwalbe: 27.5km/h at 171W
60mm rims with gp5000 28mm: 28.7km/h at 171W

That’s a huge difference I did not expect. Must have been a combo of rolling resistance, less aero rim/tyre combo and larger tyres making me less aero by raising the bike and rider. This was only at z2. The difference will be even bigger at race pace. The 28mm was faster across all segments headwind, tailwind and crosswind. I expect the roads would have to be pretty rough for the wider tyre to be faster.

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Not surprised by your results. What width are your Schwalbe G-One RS Evos? 40mm?

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