Tyre pressure?

[Percent]

I have a E36 328i which is stripped out for track but used on the road too.

The tyres are all Falkens with a max PSI of 50. Both front and rear are 35 profile so quite low.

The rims are 18 inch BBS reps.

What would be the best PSI to run day to day on the roads and also tracks days?

I checked the pressures last night and both fronts were at 25psi and the rears are 40psi.

The suspension is are on very stiff springs and sits fairly low [one finger gap at rear].

[GreenV8S]

For road use, if those tyre sizes were a standard fit on the car I'd go for the manufacturers recommended tyre pressures.

Optimising tyre pressures for grip and handling is a huge topic because it interacts with suspension setup too. If you're interested in that I suggest you start reading up on the theory. The optimum pressure is going to vary depending on lots of factors (brand/size of the tyre, tread depth, heating history of the tyre, track conditions, track design etc, spring/damper and geometry settings) and you will need to find what works best by comparing small changes. I suggest starting at the same pressure you use on the road. It is commonly advised to raise tyre pressures on the track, and there may be valid reasoning behind this, but I've heard it from many people who are just repeating it without understanding what the effects are. My experience is that it may have other benefits - maybe stopping soft road tyres rolling onto the sidewall - but it's not a general way to improve grip or handling.

[Percent]

Thanks for the reply.

If I look here

http://www.falkentire.com/tires/care-safety-warran...

My tyres have a load index of 90 does that mean it can take 1,323 of pressure at 36PSI. Though I don't know how much weigh each corner is bearing.

Their chart doesnt go past 36PSI but the tyre sidewall states 'Max inflate 50 PSI'

hmm.

[AW111]

40 PSI sounds a lot for street use.

[GreenV8S]

Percent said:

both fronts were at 25psi and the rears are 40psi.

I agree. I don't know anything about that car or what pressures are normal for it, but that does seem like a very big difference between front and rear. If the tyres are similar to ones specified for this car, I'd use the manufacturers recommended pressure for those tyres as a starting point.

Just be be clear - you should expect to be well within the maximum pressure/load figures for the tyre and should not be planning to go anywhere near these limits.

[peterg1955]

a quick Google of a BMW forum (link below) suggests around 32psi all round for an E36 328 on 18" wheels/tyres

http://www.bavarian-board.co.uk/forum_posts.asp?TI...

[HustleRussell]

I wouldn't exceed 40 but it's probably not far wrong. Maybe something like 36 front 38 rear. You're going to need to trim them down for track use.