tyre pressures chimaera

[gascon]

just been reading all the advice regarding pressures for trackdays you guys really take it seriously ,but who to believe, i recently took my chimaera to our local track here in the sw france for the first time, warm day, toyo T1S, i increased to 28 rear 24 front, i experienced tyre squeal and a srubbed look to outside edges ( although i didn't check this until home) well i realise i'm a novice but just about everything half serious seemed to corner faster than me, never once experienced oversteer and yes i have before in a variety of rwd cars, ok so maybe i was just rubbish! or can someone suggest what i can do

[grahamn]

On my Cerbera I run 26 all round for normal road use. For track days I start of by rducing this to 20 all round and then check after a couple of hot laps and reduce if more than 26. It seems to run well at these pressures.

[NTEL]

On a clock wise track try 21psi front nearside, 24 psi rear offside, 23psi front offside, 23psi rear nearside. Do three steady laps to get a little heat in them and then see how you go. You could also put a little more negative camber on the front.

At the end of the session check the pressures. You are aiming for about 26psi in each tyre when hot. Adjust the pressures to achieve this by either adding air or taking it out on each tyre, again when hot.

Edited by NTEL on Friday 31st July 15:04

[Mark (UB)]

gascon said:

just been reading all the advice regarding pressures for trackdays you guys really take it seriously ,but who to believe, i recently took my chimaera to our local track here in the sw france for the first time, warm day, toyo T1S, i increased to 28 rear 24 front, i experienced tyre squeal and a srubbed look to outside edges ( although i didn't check this until home) well i realise i'm a novice but just about everything half serious seemed to corner faster than me, never once experienced oversteer and yes i have before in a variety of rwd cars, ok so maybe i was just rubbish! or can someone suggest what i can do

(cold tyres)
warm day/track 20 front 22 rear, cold day/track 22 front 24 rear.

I wouldn't go any lower than that if you are just starting out. Get your car set up by someone who knows their stuff, camber, toe etc

are you on original dampers/springs?

Edited by Mark (UB) on Friday 31st July 16:45

[gascon]

thanks for replies, very helpful and after 4 sessions 22 rear 20 front worked well- different car!

[chris7676]

Bit surprising - how can you run it so low? Even light Elises need a bit more.

[gascon]

driven hard the tyres heat up, after starting with 22/20 and after 4 laps pressures rose to 25/23 so i guess thats the answer, when i started wth higher pressures i can only guess what the pressures rose to and lke that the car was a handfull

[jonamacg83]

By reducing tyre pressures you are allowing more flex in the sidewall, which eases the forces on the tread, hence they do not overheat as much. To understand this its best to think of the tyre sidewall and the tread as two separate entities; if your pressures are high, and the sidewall is stiffer as a result, more of the 'flex' of the tyre is put through the tread, so it heats up more and eventually overheats. So - if a tyre overheats - reduce pressures.

See the bottom couple of paragraphs:

http://www.macgracing.co.uk/trackdays_setup1.html

Jonny

[chris7676]

I heard the opposite and it seems totally wrong to reduce the pressures in order to effectively drive on your sidewalls - you think they don't overheat or are more suitable for that that the tread? But who knows, maybe there lies the TVR handling "magic"