Tyre Sizes!
Friday 26th February 2021
Every fourth Friday, we'll take a curve ball and look at something not usually on the radar... although this month it most certainly is...
For a long time the perception was that narrow hard tyres are faster. This has since been turned upside down and now it's common knowledge that wider and softer tyres (with supple casings) are faster, especially on uneven off-road terrain.
The reason hard narrow tyres feel fast is vibrations. Our brains are wired to perceive high-frequency vibrations as meaning more speed. So much in fact that you will feel slower on wider/softer tyres but you will actually be quicker. That might not be your thing to feel slow, but there are more benefits to the wide/soft setup...
Benefits
Firstly, you'll have less punctures/sidewall tears. Soft wide tyres are harder to penetrate by sharp objects, and less stiff sidewalls are harder to cut. Also in light of more recent research (some anecdotal), more vibrations equals more fatigue as it's your body absorbing the energy of bumps rather than your tyres. This can make a huge difference on a long off-road ride. Next, you'll have more grip. A wider contact patch will give you more confidence on uneven or loose terrain. Lastly they'll last longer. The wear rate will be much less (depending on the rubber compound), but it should be noticeably different to narrow tyres.
With these in mind, off-road riding is much more enjoyable with wider tyres.
Which Tyres
Unfortunately there's no industry standard for tyre suppleness and this is a huge factor in the performance of the tyre. The more supple it is the more efficient it is at deforming over bumps and springing back again, with little or no vibration into the bike and you, and therefore no energy loss. At the moment all you can go on is reviews and manufacturer information (like TPI, threads per inch, but even that's complicated!).
What do we recommend? Basically a 650b (27.5") wheels with around 2" (50mm) tyres is perfect [taller riders can run 700c/29" wheels]. Quick enough on tarmac and more than capable off-road with all the benefits outlined above. For the tread, you can run slicks if almost all your off-road riding is in dry conditions. If you know you'll be encountering mud then some form or knobbly tread is recommended. Even then only the most widely spaced chunky knobbed tyres will slide in deep sloppy mud, so cut a balance with how much road riding you'll do. Ideally you'd have two sets of wheels but that's not always an option.
So why are all gravel bikes sold with 700c wheels and 35-45mm tyres. Because that's what the industry thinks you'll want and need, and it's in fashion. I wouldn't be surprised if in a few years if they're selling new versions of their bikes with 50mm+ tyres, telling you it's the next big thing for off-road riding!
A great video by Path Less Pedaled on why wider and supple is better:
