Tyre Pressure Is a Trade-Off, Not a Race to the Top

What follows is the working version of tyre pressure: the decisions in the order you actually meet them, with the reasoning attached.

What pressure is actually holding up

A pneumatic tyre does not carry load through its rubber, it carries load through the air inside, and the casing simply contains that air. The contact patch area is roughly the load on the wheel divided by the pressure, which is why a heavier rider needs more pressure for the same footprint. That relationship is the single most useful thing to understand, because it means the right pressure depends on load and width rather than on a universal number.

A wide tyre at low pressure and a narrow tyre at high pressure can support the same weight with a similar sized contact patch. The number printed on the sidewall is the maximum the casing is rated to hold safely, and it is not a recommendation for how to ride.

Where the energy goes

Rolling resistance comes mostly from hysteresis, the energy lost as the tyre casing and tube flex on entering the contact patch and spring back on leaving it. Raising pressure reduces that flex, so on a genuinely smooth surface such as a velodrome or fresh asphalt, higher pressure does roll faster.

The bit that actually matters: on a real road the surface has texture, and a hard tyre stops absorbing that texture and starts throwing the bike and rider upwards instead. Lifting a rider vertically several times a second costs energy, and that suspension loss rises with pressure while hysteresis loss falls with it. The two curves cross, which is why measured rolling resistance on rough surfaces gets worse above a certain pressure rather than continuing to improve.

Why the same tyre needs different pressures

Adding panniers, a child seat or a heavy bag shifts load onto the wheels and flattens the tyre further at any given pressure. Front and rear wheels rarely carry equal weight, so running identical pressures front and rear is a convention rather than a technical requirement.

Most riders carry more weight on the rear, which is an argument for a few units more pressure behind than in front. Road surface matters as much as load, and a route over cobbles or broken asphalt wants noticeably less pressure than smooth tarmac. Temperature moves pressure too, since air pressure falls as it cools, so a tyre inflated in a warm hallway reads lower outside in winter.

The failure modes at each end

Run far too low and the casing folds under cornering load, the tyre feels vague, and you risk a pinch flat where the tube is crushed against the rim. Pinch flats leave two small parallel holes, which is a useful diagnostic because it tells you the pressure was the cause rather than a thorn. Run far too high and grip drops, because a smaller contact patch has less rubber engaged with the road when you brake or turn.

With a loaded rack, very high pressure also transmits every road defect through the frame into your hands, which produces fatigue long before it produces speed.

Neither failure is dramatic on a transport bike, but the low-pressure one is more likely to leave you at the roadside with a puncture.

Finding your own number

Start from any tyre manufacturer's own load and pressure guidance for the width you are running, since those charts are based on measured casing behaviour. Then adjust downwards until the ride feels harsh only on the worst sections of your route rather than on all of it.

If you start feeling the rim on square-edged bumps, you have gone slightly too far and should add a small amount back. Write the number down, because tyres lose pressure steadily through the tube and the valve, and butyl tubes lose it slowly while latex tubes lose it fast. A floor pump with a gauge is worth more to a commuter than almost any other workshop purchase, since guessing by thumb has a very wide error band.

How often to check

Every tyre leaks, so the question is not whether pressure drops but how far it has dropped since you last looked. Weekly is a reasonable habit for a bike ridden daily, and before any long ride regardless of when you last checked.

Mid-traffic, squeezing the tyre tells you whether it is catastrophically flat and almost nothing else, because the human hand is poor at distinguishing moderate pressures. Checking is also the moment you notice a cut in the tread or a piece of glass working its way through the casing. Thirty seconds a week prevents more roadside repairs than any other single habit in cycling.

The takeaway

Inflate for the surface you ride on and the weight you carry, not for the number on the sidewall.

Most of riding well is being boring and predictable to everyone else on the road.