A few years ago, the trend was to run tyres that were 23mm wide or narrower and pump them up to pressures above 100psi. But more recent research has shown that this generates more rolling resistance than wider tyres run at lower pressures – as well as giving a less comfortable ride and less grip.
This is because at higher pressures the tyre skips over road imperfections, bouncing the entire bike and its rider up and down and leading to wasted energy, rather than smoothing out bumps and producing a more linear trajectory.
So now the trend is to run tyres of 25mm or wider at much lower pressures. And increasingly tubeless rims and tyres are being used to allow that pressure to be dropped even further, since there’s no risk of pinch flats.
A 28mm tyre will contain around 50% more air than a 23mm, so the pressure can be reduced significantly and you get a larger contact patch with the road for increased grip.
Rim widths on newer wheels have also increased to provide better support for these wider tyres, a more aerodynamic interface between the rim and the tyre and even greater air volume in the tyre to further increase comfort.
New bikes are usually built to take these wider rims and tyres. But some older frames do not have the clearance for them, so check that you have enough room before going wide.
Cyclocross and gravel bikes are designed to take really wide tyres – often up to 40mm. These tyres have very large air volumes and so can be run at really low pressures. Cyclocross racers often run tubular cyclocross tyres at below 30psi.
About tyre types
Most road bikes come with clincher tyres with inner tubes. The tyre has beads which attach it to the rim and the air is contained in the inner tube.
Tubeless clincher tyres work in a similar way, but there’s no inner tube. The wheel rim is airtight and has a special profile to help the tyre seat against its edges. The valve screws into the rim’s valve hole. A small volume of cycle tyre sealant is put inside the tyre to make the tyre airtight on the rim. The sealant can usually seal small punctures as well, without too much air loss.
Racing cyclists still tend to use tubular tyres that are glued to the rim, rather than clincher tyres, as the rim can be made lighter and there’s no risk of pinch flats. But if you have a puncture, the tyre cannot usually be repaired.
There are also a few makes of solid clincher tyre available – which of course means that tyre pressures and punctures are a thing of the past!