Non-RFT pressures

[Phoenixboy]

I am currently running about 30PSI all the way around on my 2006 2.5si. It has conventional non-RF Goodyear Eagle 3s on the back and Bridgestone Potenzas on the front. I found that reducing the pressures from 35PSI has improved the ride, reduced bump steer and tramlining significantly.

Let's remember that it's a combination of tyres, springs, shocks and other suspension components that all need to work together to give an acceptable ride and grip level. Really high tyre pressures and stiff suspension might improve turn in, but it does nothing for high speed stability and general road holding on typical British roads!

I am sure with RFs, the extra pressure is required to ensure the tyre does not deform, but with conventional tyres a little more flex is quite desirable. Race cars use relatively low pressures 20 - 25 PSI - and they run on generally excellent tarmac. Dropping the tyre pressures has not adversely affected the handling in any perceptible way with my car and I do drive quite energetically

correct, but dropping pressures on track as I am sure you know is because of heat generated on track, hence you then check pressures after a session when tyres are hot

 

[Phoenixboy]

I am currently running about 30PSI all the way around on my 2006 2.5si. It has conventional non-RF Goodyear Eagle 3s on the back and Bridgestone Potenzas on the front. I found that reducing the pressures from 35PSI has improved the ride, reduced bump steer and tramlining significantly.

Let's remember that it's a combination of tyres, springs, shocks and other suspension components that all need to work together to give an acceptable ride and grip level. Really high tyre pressures and stiff suspension might improve turn in, but it does nothing for high speed stability and general road holding on typical British roads!

I am sure with RFs, the extra pressure is required to ensure the tyre does not deform, but with conventional tyres a little more flex is quite desirable. Race cars use relatively low pressures 20 - 25 PSI - and they run on generally excellent tarmac. Dropping the tyre pressures has not adversely affected the handling in any perceptible way with my car and I do drive quite energetically

correct, but dropping pressures on track as I am sure you know is because of heat generated on track, hence you then check pressures after a session when tyres are hot

You also get into issues were
People fit slick tyres, but aren’t able to ride hard enough to generate the heat required to make them work.
Also then need tyre warmers to avoid the heat cycle issues.
It’s an interesting subject that I learnt through talking to tyre and suspension gurus on track days.

 

[noiseboy72]

From what I gather, tyre pressures will go up about 4-6 PSI for a 20 degree rise in carcass temperature - which is all you will get outside of F1 and the like. F1 need to control the ride height very precisely for the aero to work correctly, hence why 0.5PSI could be 1/10 second at some tracks. Not an issue with a road car and on mine the ride height did not change at all with the difference in pressures.

The lower pressures allow more flex and better bump absorption with the main loser being fuel economy. I do wonder whether this is why quite high pressures do get specified...

 

[ihadablackdog]

Just had new non-rft Eagle F1 asymmetric 3 all round on 225/40/18 and 255/35/18

And set pressures to 2.6bar in front and 2.7 in rear (always thought it was better to go slightly over the pressures on the sticker).

This works out almost 38psi on front and just over 39psi on the rear.

Reading this thread now makes me think they are going to pop!

Being the thicko that I am, was any “average” agreed? I.e 34/36 etc? Don’t want them to wear unevenly and quickly.

 

[patriot66]

Just had new non-rft Eagle F1 asymmetric 3 all round on 225/40/18 and 255/35/18

And set pressures to 2.6bar in front and 2.7 in rear (always thought it was better to go slightly over the pressures on the sticker).

This works out almost 38psi on front and just over 39psi on the rear.

Reading this thread now makes me think they are going to pop!

Being the thicko that I am, was any “average” agreed? I.e 34/36 etc? Don’t want them to wear unevenly and quickly.

That's very high in my opinion. I have the same size non-rft tyres and run them at 2.1 bar front and 2.3 bar rear. The car rides well, grip is excellent and they wear evenly across the tread.

 

[Lazza]

I have settled on front 36 rear 38 and that feels about right to me. That’s on 19s but the size shouldn’t make a difference to pressure.