F1 tyre pressure ?

[nztrev]

Have just had Good year F1,s tyres fitted to my chim 500.My tyre dealer had them at around 30psi at fitting which seems far to high from previous so3's fitted.Have found after about 500km's (300 miles approx)23 psi fr 25 rear to be ok,but my tyre guy is cr*pping himself they may de beed.Sizes are 235x40x17x8rim fr 265x35x18x9rim rear. Advice appreciated

>>> Edited by nztrev on Monday 30th August 07:49

[ian8542]

They are extremely wide tyres. My advice would be to get some nearer standard and take it from there.

[Steve_T]

Pressures sound about right depending on how stiff the sidewall of the tyre is. From the sizes I take it you have after market wheels - as Ian says those certainly aren't standard

Steve.

[GreenV8S]

I assume the profile is what causes the problem; with less sidewall height and therefore area, the same pressure exerts less force pushing the sidewalls outwards against the rim. Any time the loads from the road exceed the preload on the rim, the bead is in danger of pulling off.

Obviously the forces from the road depend on the weight of the car; is your tyre fitter used to working with much heavier cars?

Were the S03s on the same rims? I don't see why the F1s would be any more or less likely to come off the rims than the S03s at the same pressure? I would guess that if you have to run at 30 psi, you would compromise ride quality and grip quite significantly.

Mind you, with those profiles I suspect you might as well put a thick layer of black paint on the rims and forget the tyres altogether!

[nztrev]

The so3's were on the standard rims,while the fronts are wider than i would of liked f1s don't come in 225/17 ,plus the wheels were made to order with offsets just sqeezing everything in.

[K4TRV]

FWIW on std F1s on my Chim I use 23/21 R/F.

Track Days, I up them to 27/25 (cold) - they get to 30/30 hot !!

Enjoy!

Trev McM


>> Edited by K4TRV on Tuesday 31st August 09:03

[Esprit]

Hi Paul.... Old thread I know, but I was told in the past that my Goodyear F1s (GD-D2s, not the newer GS-D3s you have) should be running at about 33psi all round on my TR7.... the sizes are 215/40/16 at each corner..... tyre wear seems to be very even and the grip is never in doubt..... I'd be dubious about running them that low as you'll indeed be at risk of de-beading them in extreme cornering.... general rule of thumb is that the smaller your sidewalls are, the more pressure you need.... some applications even recommend 44+psi!
I'd run at about 30 all round (cold) in yours as a starting point..... I'd be reluctant to go any lower if it was my car.

[IPAddis]

TVR's running on standard tyres 245/45/16 rear should be either 22 or 24psi. 30psi would put you in a hedge very quickly.

This could be because of the weight difference between a TVR and a TR7?

Ian A.