Advice: what tyre pressures should you run

Tyre pressures... Just what should you run?

Scrutineering at a number of riding schools includes tyre pressures. The reason is twofold. Firstly, you'd be amazed at what's been observed. The record high was on a Honda CBR600RR with 52psi in the front and an amazing 58psi in the rear. The record low was on a 916 Ducati with 13 and 15psi!

If either had been let out it may have given the rider an interesting result. Secondly, we know that most tyres are designed to run at a set cold pressure for racetrack use. By setting the tyre to that cold pressure it will give the best possible grip and handling for that day.

Each tyre is manufactured with several considerations: how it will be used; to what type of bike it will be fitted; what loads and forces will be placed upon it.

The manufacturer responds by setting the combination of construction, profile, compound and tread pattern. For that tyre to work as it is designed, it must be used in the correct tyre pressure range. So important is this subject that Dunlop has issued a warning to riders: "It is strongly emphasised that the incorrect mixing of tyres and incorrect inflation pressures can result in undesirable and dangerous handling characteristics, particularly on high performance motorcycles."

What's the most important thing to obtain from a tyre? Grip and traction, the stability or handling of the tyre and the tyre life. In short, you need to follow the recommendations of the tyre and motorcycle manufacturers!

So what are the best pressures?. Well, the lower the tyre pressure the more the tyre deforms. The more the tyre deforms, the more friction there is between the tyre and the road surface. The more friction, the more heat. The more heat, the greater the opportunity the tyre has to regenerate itself by shedding the 'used' layers of rubber (to a point). This deformation of the tyre also creates a bigger contact patch at the cost of a little stability.

This is desirable at a racetrack. You want grip. Tyres that are used purely on the track wear the edges first because on a racetrack you generate much more force on the edge of the tyre. You want the tyre to deform, heat and literally 'shed' the used layers of rubber.

On the road you have other considerations. The stability or handling of the tyre is extremely important, as you don't have the controlled conditions of a racetrack. There are other road users and emergency situations that you just don't have on the track. You spend more time with the bike upright on the road, no matter how 'sick' a rider you are!

This means that tyre deformation actually works against you. Now it's deforming when the bike is upright. This means it's wearing quicker in the centre and will 'square off'. This changes the profile and the handling and grip of the tyre. The higher the pressure, the less it will deform giving you the best possible tyre life and handling.

Tyres of 20 years ago aren't a patch on today. A tyre that is designed to be run in a pressure range has a compound that will grip if set in that range.

This means that not only would you run a higher pressure on the road, if you are carrying bigger loads than normal, you would probably increase the pressure.

If you can keep the tyre in the shape it is meant to be in, then it will give you grip, handling and life.