Kevin Huntley Posted June 6, 2002 Share Posted June 6, 2002 I have a set of 19" Pirelli PZERO Rosso tyres 255/30's front and 275/30's rear and I was wondering what the correct tyre pressures should be? I have been told when you go for lower profile tyres you should increase the tyre pressure by 10% per inch increase in Diameter is this true? I am currently running 40psi and the car seems to handle well but is this optimum? Cheers Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted June 6, 2002 Share Posted June 6, 2002 I currently run my 18's (265 and 235) at 36psi all round, just like stock settings. However i think i will be dropping to 34psi at the front as the ride can be a bit hard sometimes. Quote Link to comment Share on other sites More sharing options...
paulrenn Posted June 6, 2002 Share Posted June 6, 2002 Isn't there a recommended pressure range detailed on the sidewall itself? I'd say, go for the softest setting, see how it handles, and keep increasing all four corners a little at a time if needs be. You need to maintain quite a reasonable amount of pressure to avoid your expensive alloys getting misshapen by road irregularities...I know from experience I've been recommended to run about 35 PSI or so. Quote Link to comment Share on other sites More sharing options...
Doughie Posted June 6, 2002 Share Posted June 6, 2002 sidewall i think will only show the *maximum* recommended pressure to run. From a physics point-of-view, for 4 tyres supporting the same total weight (of the car =1.5tonnes) then the larger the tyres are, then the pressures *should* decrease slightly I think. From the equation : Pressure = Force / Area you can see that with the same Force (weight of the car) the pressure *reduces* as you increase the area. Area = contact patchof the tyre with the road. So if the recommended tyre pressures are 36psi for stock tyres (17") then i would maybe run 34 or 35psi on 18" but in the end, it's really down to personal preference. There is the "protect the rims" issue to think about too. Generally i found for stock 17"'s that 36psi was a bit too high, and ran about 34psi rear and 34 -35psi fronts. Wet conditions i would tend to lower the pressures a little. A lot of high-speed running i would tend to increase the pressures a little. try kicking it off at 34psi and increase by 1 psi from there and go for little test drives. I think you'll find it a little jiggly and harsh ride above 35 or 36psi. Quote Link to comment Share on other sites More sharing options...
Ian C Posted June 6, 2002 Share Posted June 6, 2002 If you change the tyre pressures, you will need a running in period as the tyre 'wears' into the new profile it's got. The car will feel like it's tracking is out for about a hundred miles. Well, that's what I've found, anyway Don't be suprised if upping the pressure makes it feel horrible to drive at first. -Ian Quote Link to comment Share on other sites More sharing options...
Flavio Posted June 6, 2002 Share Posted June 6, 2002 I ran my 19" PZero's (275/30 and 245/35) at 2.8 bar (41psi) initially but found that too hard. I now run 2.5 bar (36psi). An added benefit is slightly more grip when launching hard. Make sure you check the tire thread depth regularly, especially on the inside. Supras literally eat tires! Flavio Quote Link to comment Share on other sites More sharing options...
Kevin Huntley Posted June 6, 2002 Author Share Posted June 6, 2002 Thanks for the info guys, I will go to the garage tonight and give 36 psi all round a go and see how it handles. Quote Link to comment Share on other sites More sharing options...
Terminator Posted June 6, 2002 Share Posted June 6, 2002 Kevin the only problem with that is your tyres may be warm so you will not get a true reading. I always set mine cold 35 front 34 rear on stock 17's Quote Link to comment Share on other sites More sharing options...
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