Another thread for tyre pressures

[sdio]

Hi all,


Can you guide me on following principles please.
The car is on same 185/60/13 048s tyres and pressures 16psi all around.
What will happen if i raise the pressure by +3psi on one of the two axles?
How can I improve initial turn in and grip until the apex only by adjusting pressures ? Do not mention driving style or geo settings please.
What combination would you say will give best results?

I am talking 16psi cold but mountain road driving no track.

Thanks

[DCL]

Within normal limits, increasing tyre pressure will tend to reduce grip . So increasing on the front will induce under-steer and increasing on the rear, over-steer.

The car has three states in a corner: The initial turn-in when weight transfer has yet to take effect, the steady state when weight transfer has fully happened, and the transition between the two.

The relationship between them is almost entirely set up by the ******** and controlled by the shocks. With a good quality 3-way shock you can adjust the slow speed damping to alter the speed at which the transition takes place.

Edited by DCL on Tuesday 4th April 13:53

[battered]

You want to talk about turn in on a 7 but without talking about suspension ge****ry? Why? Something as simple as a turn on each track rod end will dramatically change it, in 5 minutes flat, minimal tools, no cost, easily reversible.

[sdio]

battered said:

You want to talk about turn in on a 7 but without talking about suspension ge****ry? Why? Something as simple as a turn on each track rod end will dramatically change it, in 5 minutes flat, minimal tools, no cost, easily reversible.

I dont want to open another topic this is why i dont want to talk about geometry.

So max front grip is with less pressure than rear.
My guess and understanding from other threads is min pressure giving positive results is 0.9bar or 13psi +1psi to be on the safe side?

[battered]

Most people play tunes between 15 and 20 psi, then see how it feels. It's subjective, really. Then once sorted, remember a bit of toe either way will turn it from a twitchy racer that dives into corners to a stable, easy driver that's very pleasant on country lanes. You choose.

[sdio]

Thanks i will
I am now at 0 toe and 70mm below the sump.

[battered]

I think that's the standard place to start, with standard springs and dampers and roll bars, for road use. Yokos are nice and predictable once warm too. Just watch them on cold days, and watch out for the possibility that when they do eventually let go you might discover that you ran out of talent 20 mph ago.

[framerateuk]

Try it and see what happens.

I usually run 18psi on my CR500 and ZZS. I went up to 22psi on one trackday after reading some advice on here and the car was horrible! Understeer followed by snap oversteer! I couldn't work out what it was until someone in the paddock asked what pressure I was running. It was unnoticeable on the road, but on the limit on a trackday it made a huge difference. Put it back to 18 and the problem was sorted. These cars are very sensitive to pressure changes!

[pikeyboy]

framerateuk said:

Try it and see what happens.

I usually run 18psi on my CR500 and ZZS. I went up to 22psi on one trackday after reading some advice on here and the car was horrible! Understeer followed by snap oversteer! I couldn't work out what it was until someone in the paddock asked what pressure I was running. It was unnoticeable on the road, but on the limit on a trackday it made a huge difference. Put it back to 18 and the problem was sorted. These cars are very sensitive to pressure changes!

I try and run my CR500 and ZZR's at 22 hot. so go out do a few laps warm tyres, then come in check pressures adjust (usually drop down) to 22. most days I start at 18psi cold and work from there as the ambient/track temperature obviously plays a part. Also for any geometry work I up the pressures to 22psi.