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Tyre Pressures 
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Part built GTM

Joined: Wed Apr 15, 2015 4:52 pm
Posts: 123
Location: Devon
GTM: Libra
Post Tyre Pressures
Hi Guys

What do you all run pressure wise
The lighter the car the more % the unsprung weight is
Does this tend to say run lower pressures?
Need to bear in mind the tyre deflection of the sidewall needs to be part of the suspension?

Pete


Wed Sep 11, 2019 5:57 pm
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Part built GTM

Joined: Wed Apr 15, 2015 4:52 pm
Posts: 123
Location: Devon
GTM: Libra
Post Re: Tyre Pressures
More data which may help

I'm running 18psi Front 22psi Rear

Weight is 900 kg with the 3.0v6

40% front - 180 kg per tyre 205 / 45 / 17

60% rear - 270 kg per tyre rear 225 /45 /17


Wed Sep 11, 2019 6:13 pm
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Part built GTM

Joined: Sat Oct 22, 2016 12:41 am
Posts: 69
Location: Brisbane Australia
GTM: Spyder
Post Re: Tyre Pressures
My Spyder has only done 700 km so don't have much feel for tyre pressures yet. My gut feel is that tyre pressures should relate to weight on the corner vs tyre width more so than to unsprung weight. eg 180 kg on a 205 (0.88 kg.mm) would need 17% less pressure than 270 kg on a 225 (1.2 kg/mm).

So assuming 22 psi rear as a starting point, you get 22 x 73/100 = 16 psi front.
Or assuming 18 psi front, the rear comes to 18 x 100/73 = 24.6 psi rear.

So yes, with your 60/40 weight bias and significantly less tyre bias , you probably do need a lot of pressure bias. 22 might be a bit low with your heavy engine??


Thu Sep 12, 2019 2:11 am
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