ScoobyDoo69

iTrader: (17)

Hey all,

Just wondering, on track what tyre pressures would you use for 225/45/17s on a Blobeye STi?

On the road I run
34psi Front
36psi Rear

When on a small circuit recently I found that my sidewall was well flexing like mad, and I'm wondering if the tyres were at fault as I was using an old set, or the pressures had much to do with it?

Thanks

Toffee

iTrader: (3)

for on the road your not too far away, your rears seem a bit high you should be looking for around 35 psi when your tyres are hot at the track. Try setting them around 27psi when cold and then go from there, take your time warming em up

ScoobyDoo69

iTrader: (17)

So would the sidewall flex have come from them being too high in pressure after they heated up? I can imagine that the pressures went very high after a few laps..

But Target wise am I right in saying that I should have the pressures lower, so they reach the optimum pressures when warm?

Toffee

iTrader: (3)

The taller the sidewall the more flex you will have, but saying that different tyres have different strength side walls. I went from Dunlop Sport Maxx to Ultrac Sessantas and I think that the Sessantas have a softer sidewall, so I increased the pressures by 2psi when running the Ultracs to compensate.

I have just taken delivery of some Pirelli P Zero's and they feel like they have a very stiff carcass so we will have to have a play around to see what makes these feel happy.

Basically your right the harder you driver the more heat you will generate in the tyre and so the psi will increase, obviously the harder the car is being driven the higher the increase so the starting point may need to be lower, without knowing where your driving, the tyres you have or how hard/fast you are driving it is impossible to state what is "perfect"

If you aim to have your tyres around 34psi when hot they will be in the right ball park, I would say though that your rears are too high, your front tyres are supporting the weight of an engine, your rears have less weight to carry but are having to cope with more drive, I usually run 34fr & 32rr on the road, I will start with 27psi fr & rr on the track and take my time getting up to speed while the tyres are warming up, once the tyres are hot I will more than likely have to lower them another couple of psi