How Wide Is Too Wide For Road Bike Tyres?

Over the last few years we have seen a trend towards increasingly wide tyres on road bikes. At the Tour de France, most teams were riding 28mm tyres but we have also seen riders on tyres as wide as 32mm. In our latest episode of GCN Does Science, Si and Alex test the new Vittoria Corsa N.EXT tyres to see which size road bike tyres are faster at different speeds.

Chapters:
0:00 Intro
1:20 Our Hypothesis
2:14 The Tyres
2:49 28mm Test
6:36 32mm Test
9:31 Results

Corrections:
6:18 331W for 28mm at 40 km/h
10:15 Should say 331W for 28mm at 40 km/h!

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What size tyres do you use? Let us know in the comments below! 💬

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[sebastianhoger]

My Trek came with 32mm from the factory. I was also biased, that I "need" narrower tires. I have ridden the 32 Mill for ~2000km, switched to 28 mm for 6000km now and decided to go back to 32mm. I haven't seen any improvement in speed or anything like that with the 28mm but the comfort of the 32mm is so much superior that I prefer that. My usual rides are somewhere between 80-100km with 28-30 kph avg. And yes I am way too heavy to consider myself a "real road bike rider" :D

[Larsie]

My allround bike came with 32mm tubeless and I fell in love with them. The differences with my previous 25mm clinchers is massive:
- way more comfortable to ride on
- Can be easily inflated by a small hand pump because of the lower pressure needed.
- Can handle light gravel comfortably meaning you can add extra gravel tracks to your route.
- Can also handle rougher gravel without risking a flat, but it wont be very comfortable.
- feels more stable when turning

All in all I'm very happy with it. So far I've ridden more than 3k km with it without any flat.

[gregvassilakos]

Back in the 1990s, I was running 23 mm and 25 mm tires on my road bikes, and my racer friends were telling me I should be running 18 mm tires. Now, I'm still running 23 mm and 25 mm tires on my road bikes, and I'm being told I should be running 28 mm or 32 mm tires. Of course, back then I was being told I should have triple chain rings on my road bikes. Now, I'm being told a single chain ring is just fine.

[moshesror]

For the past 3 years I was riding 25, and last week I changed to a 30mm. I am so happy I watched your video, it’s much more comfortable, not affecting the speed, acceleration is amazing. Just more fun. Thanks Simon and GCN

[michaeltaylor]

I just changed my 28mm to 32mm and found no difference in speed but, ride comfort was absolutely superb! I accidentally climbed a 16% to 18% and took the climb much better than expected. Hills were no bother, speed consistent and being a 110kg belly buster I thoroughly enjoyed the ride. Sticking to my 32mm tyres - Schwalbe Pro One TLE Addix-Race Evolution, awesome! At 62, I gets me thrills where’s I can! 🤪

[jamesobrien]

My endurace came with a 30 up front and a 32 in the rear. It’s 95% used for tarmac but the roads aren’t the best and I’ll soon be running 35mm front and rear. For me the comfort and confidence a few mm’s bring are the difference. Im also aware that I’m never winning the tour or going pro so I don’t need to lie to myself and run 25’s just to suffer.

[colinfisher]

I was happy with 28mm until I accidentally ordered 32mm tyres by mistake, best mistake I've ever made for biking. The performance is the same for me but the comfort is so much more on long and quiet back country roads. I'm converted.

[chrisburn]

45psi! Wow, I remember people routinely pumping up to 120psi with 23mm tyres a few years ago. I never thought there was much point in that as it was just uncomfortable and skittish, and I felt so vindicated when Schwalbe did some research in perhaps 2010 and concluded that lower pressures (up to a point) were more efficient because they allowed the the carcass to absorb micro-bumps without vibrating the whole bike (which of course takes energy) - the point that everyone seems suddenly so aware of.

[ColinBroderickMaths]

I'm currently riding 28 mm which is the thinnest I've ever ridden. Before that I was riding a hybrid bike with 35 mm. I was expecting the 28 mm to be a really rough ride, but actually have no problem with it at all. Find them perfectly comfortable. That's probably because even when I was riding the 35 mm, I was doing so almost exclusively on the road, so they were always held at relatively high pressure, and so I'm already used to that feel.

[buster.keaton]

After decades of riding 700x23c tires at over 100 psi, I figured the wide rim and wide tire setup (700x32c) on my 2020 Trek Domane SL7 was a marketing gimmick. However, I'm now a believer in the wide rim / wide tire package and can't imagine going back to narrow tires for endurance and training rides. I feel so much less fatigued at the end of a ride and I've been able to ride over the nastiest of roads and gravel w/o flatting (partially due to a tubeless setup as well.)

[Kobe]

Very interesting video. I ride long distance, sometimes into ultra-endurance (circa 200km) and I opted for a 32mm. Reason being that I wasn't trying to go as fast as possible, I wanted to go as far as possible and the argument was that comfort over an 18 hour ride would be better than an extra 1 or 2 kph over the same distance. The beauty about this of course, everyone can choose what works for them!

[simDIY]

A few months ago I changed from a 25 mm to a 28 mm Continental Grand Prix clincher tire mounted on a Vision Team 35 wheel. Beter cornering, less pressures, a bit more comfort, better on those small gravel roads when 'necessary', and much better looks. Love it. Go for that wider tire when possible is what I think.

[lesliegoa]

My Scott Addict comes with 32 mm Schwalbe One tube tyre and I run 53/58 psi F/R. Far more comfortable than my older bike's 28 mm at 70/80 psi with no significant loss of speed.

[shanedickenson]

I remember fitting 26" x 4.00 to my bike, and all I can say is that the difference was incredible, it completely smooths out bumps in road, and gave me a little bit more confidence on the occasional gravel track.

[solovinojuntoseva]

I replaced my aluminum wheels with carbon wheels and went with the recommended tire size which were thin. It vastly improved my ride, but I recently purchased a look with thicker tires and was astounded at how much more comfortable the ride was. Given that I am a casual rider, I prefer the comfort.

[tommoritz]

At 10:32 Si says, "28s at 40k/h were statistically better....10W more efficient". The table at 10:16 regarding average power required on 28s at 40k/h was 343.0W and at 10:21 the table shows the average power required on 32s at 40k/h was 343.5W. I only see a 0.5W power difference. Can Si show his math? Or was this a typo on the tables?

[benjaminc.franke]

Interesting video, thanks! Currently using my gravel bike as a do-it-all bike with two wheel sets. On the road wheels I run a 32mm Conti GP5000 tubeless, works brilliantly, super comfortable and extremely forgiving when riding gravelly cycling paths. Not concerned about speed too much, came to accept I am very slow ;-)

[JeremyLawrence-imajez]

I used to switch from my 28mm road tyres to my 32 CX tyres when roads got slippery in Autumn each year. Then several years I realised I didn't go any slower. Not used the narrower road tyres since. Plus as I tend to go off road a lot even with the 28mms, I was even faster with the fatter, grippier and more comfy tyres there too. Less rim smacking too.
I switched to lower pressure even earlier after doing bike comparisons and discovering the lower pressure tyres and as a result way comfier bikes were faster.
Wider tyres also need wider rims to prevent a lightbulb shape which is not good for aero benefits. The difference in this test could be simply down to that rim width aspect.

[MrAnon-]

I moved from 28 to 32 but kept the same tyre pressure in the 32 that I was running in the 28. The research that I carried out suggested lowering the pressures in a wider tyre if you want better comfort, or keep a higher pressure in the wider tyre for lower rolling resistance/faster speed.

[Mr.Bas..U]

My Merida Reacto 6000 came with 25mm tyres, upgraded to 28mm tubeless tyres on carbon rims 3weeks after and absolutely love it!