classic 18" tyre pressures
08 December 2005, 12:00 AM
#5
Blimey thats low
I have about 34.5 front and 32.5 rear. I pump them to 35.5 front and 33.5 rear when I know I'm doing a bit of 'country road' driving. I reduce the pressures to about 33 front and 31 rear when its raining.
Yeah I'm a closet tyre pressure person
On my standard 99 sti5 16 inch alloys I run slightly lower pressures - about 33/31 all the time. Bit like a bike wheel - mountain bike tyres dont need to be pumped up as high as a racer - the lower the profile the higher the pressure should be really
On the track I put them up to about 36 all round but with 38 in the Front left (for Castle Coombe........)
I have about 34.5 front and 32.5 rear. I pump them to 35.5 front and 33.5 rear when I know I'm doing a bit of 'country road' driving. I reduce the pressures to about 33 front and 31 rear when its raining.
Yeah I'm a closet tyre pressure person
On my standard 99 sti5 16 inch alloys I run slightly lower pressures - about 33/31 all the time. Bit like a bike wheel - mountain bike tyres dont need to be pumped up as high as a racer - the lower the profile the higher the pressure should be really
On the track I put them up to about 36 all round but with 38 in the Front left (for Castle Coombe........)
14 December 2005, 10:44 PM
#6
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28 to 30 is about right i think mate. anymore than that and they can get a bit skatey on turn in. drop them to about 26 if you're going on track cos the pressures will raise with increased temperature
15 December 2005, 09:04 AM
#7
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The pressure you need depends on many things but the main one should be safety. Running very low profile tyres like a 215/35 on a relatively heavy car means you may need to run more pressure than you would expect as the load rating of the tyre may not be high enough to cope. The only way you can be sure is talk to the tyre manufacturers Technical Department, give them all the details for your car and let them tell you what they recommend as a minimum pressure.
The problem will come if you run the tyres at too low pressures so that it isn't oversensitive and twitchy as posted above. To make the car stable the pressure may be too low to cope with the weight leading to premature wear if your lucky, cracking of the sidewall and potentially tyre failure, if you're not.
We run a 225/35 tyre on our P1 18" wheels which has an 87 load index and even then the pressures are high at 38/35 to cope with the potential performance of the car.
Note that we only recommend 18" wheels and tyres on the early cars if the suspension is uprated, the standard dampers cannot cope and the car is borderline dangerous if the geometry is even slightly out.
Ref decreasing cold pressures for track use, DO NOT do that with a road tyre as you risk it falling apart. The increased pressure due to the heat balances out at some point so that the tyre doesn't deflect too much and get any warmer. Dropping the pressure back down makes it run warmer and unlike proper competition tyres, a road tyre is designed to work best at relatively low temperatures.
Mike
The problem will come if you run the tyres at too low pressures so that it isn't oversensitive and twitchy as posted above. To make the car stable the pressure may be too low to cope with the weight leading to premature wear if your lucky, cracking of the sidewall and potentially tyre failure, if you're not.
We run a 225/35 tyre on our P1 18" wheels which has an 87 load index and even then the pressures are high at 38/35 to cope with the potential performance of the car.
Note that we only recommend 18" wheels and tyres on the early cars if the suspension is uprated, the standard dampers cannot cope and the car is borderline dangerous if the geometry is even slightly out.
Ref decreasing cold pressures for track use, DO NOT do that with a road tyre as you risk it falling apart. The increased pressure due to the heat balances out at some point so that the tyre doesn't deflect too much and get any warmer. Dropping the pressure back down makes it run warmer and unlike proper competition tyres, a road tyre is designed to work best at relatively low temperatures.
Mike
Last edited by MikeWood; 15 December 2005 at 09:09 AM.
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