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Tyre pressures
- Thread starter vipergts
- Start date
Try 25 cold.
Ok - I wonder why? Perhaps it ballooned the tyre so the middle of the tread was touching the road more that the edges, i.e. it's acting like a narrower tyre. 
See pic.
My old track car gripped well on 195/55/15 tyres at 25 cold (30 hot). At 30 cold it slid more.
Your tyres hold a lot of air for a lightweight car so I reckon 25 cold is plenty. My 370Z runs at 33 cold on the front but the tyres are low profile and the car a lot heavier than an S30.
Others might disagree.
See pic.
My old track car gripped well on 195/55/15 tyres at 25 cold (30 hot). At 30 cold it slid more.
Your tyres hold a lot of air for a lightweight car so I reckon 25 cold is plenty. My 370Z runs at 33 cold on the front but the tyres are low profile and the car a lot heavier than an S30.
Others might disagree.
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Ok - I wonder why? Perhaps it ballooned the tyre so the middle of the tread was touching the road more that the edges
My old track car gripped well on 195/55/15 tyres at 25 cold (30 hot). At 30 cold it slid more.
Your tyres hold a lot of air for a lightweight car so I reckon 25 cold is plenty. My 370Z runs at 35 cold but the tyres are low profile and the car a lot heavier that an S30.
Others might disagree.
Yes
Different cars
Different weight splits
Different tyres sizes
Different tyre types !!!!!!!
Apart from that its a perfectly valid comparison
Yes, that's what I said! I was making the point that my 370Z needs higher pressures because of those things. Lee was running a pressure closer to my 370 which I doubt is appropriate. I gave a pressure I had found to work well on an S30.
What do you use in your front tyres, that might be a more helpful reply for Lee. If you are going to say that that's of no use to Lee whatsoever then fair enough but he's got to start somewhere.
Here's something I've thought about:
Apart from the requirements regarding tyre wear, tread depth, damaged sidewalls, etc, the tyres must be correctly inflated. Regulation 27 section b states “the tyre is not so inflated as to make it fit for the use to which the motor vehicle or trailer is put”. This definition is not very helpful, but correct tyre pressures are vital for safe handling and optimum braking, grip and tyre life.
Low tyre pressures
Cause increased fuel consumption, more air pollution, shorter tyre life and greater risk of tyre failure.
High tyre pressures
Cause reduced comfort, less grip, greater risk of impact tyre damage and reduced stability in braking and cornering.
So how can that be enforced when wheel/tyre sizes are drastically outside the manufacturers specification? By just by a visual inspection (and then measurement) for a soft tyre I suppose. Also if Lee had an accident could the police take into consideration that Lee's wheels are twice the width of the ones originally fitted?
Pete I'll try and bring some humour into this now - if I fitted wheels to my 370 that were twice the width they would be 18" wide at the front and 20" at the rear.
Rob said:
Once again my setup is of little use as the tyres are 16 inch, 225 width and 50 profile, plus they are on a different car with possibly a wildly different weight distribution all I can do is indicate what I use and which works for me
Generally (hmm) something like this
Rears, 225/50/16 on an 8.5 inch rim R888's cold 28 hot 38
Fronts, 225/50/16 on an 8.5 inch rim Kumho V70A cold 26 hot 35
These will be changing shortly for Trofeo R's which will need a whole new set of dialing in
If I was running down the 1/4 mile the fronts would be 40 and the rears about 11
There is a guideline for R888's here
http://www.adamsandpage.co.uk/tyres/racing-tyres/toyo-tyres/