Tyre Pressures for Road and Track
Road pressures are set cold from the placard, track pressures are set from the hot figure, and confusing the two is why road tyres get destroyed on track days.
On the road, set the placard pressure cold and check monthly. On track, the number that matters is the hot pressure, so you start lower and bleed down between sessions.
Pressure changes the shape of the contact patch, and the contact patch is all the grip you have. It is also the cheapest adjustment on the car, which makes it the first one to get right.
Cold means cold
The pressures on the door shut placard or in the handbook are cold pressures, meaning the car has been parked for a few hours or driven less than a couple of miles. Driving to a garage and checking there gives you a warm reading that can be several psi high, so you end up setting the tyres too low. Check first thing instead, with your own gauge, because forecourt gauges take a beating. Ambient temperature also moves pressure by roughly 1 psi for every 10 degrees Celsius, which is why tyres read low on the first cold morning of autumn and nothing is actually wrong.
Why under and over inflation both cost grip
Under inflation lets the tyre roll onto its shoulder in corners, overheating the outer edge, blunting response and raising fuel consumption. It is also the condition behind most heat related tyre failures. Over inflation crowns the tread so the centre carries the load, which reduces the contact patch, wears a strip down the middle and makes the car skittish over bumps. The wear pattern across the tread is the honest record of what your pressures have been doing, and it is worth reading before you change anything else about the setup.
On track
Tyres gain pressure as they heat, often several psi in a session, so a road tyre set to placard pressure cold will be well above its best by the second lap. The method is to note the cold pressure, come in after a few hard laps and take a hot reading immediately, then bleed down to your hot target and record what cold pressure produced it. Do the same corner order every time. Tyre manufacturers publish hot targets for their track and semi slick ranges, and those figures beat any general rule of thumb. Remember to put road pressures back before driving home.
The conditions that matter
- ✓Set road pressures cold, with your own gauge, and check them monthly.
- !Pressure rises with heat, so a track session can push a tyre well past its best pressure.
- !Uneven wear across the tread is the clearest evidence that pressures are wrong.
Sources
These are the provisions the road-legality rules linked above rest on.
General guidance only. Details vary by exact vehicle and change over time; confirm with a reputable specialist before modifying.