Dave Ashurst
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 posted on 18/3/03 at 07:55 PM |
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Tyre pressures?
Title almost says it all...
1 What tyre pressures are people running?
2 How can I tell whether a tyre is over or under inflated without getting tyre wear first?
Any thoughts?
yours curiously
Dave
PS mine's a book locost on 185/60/13s
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auzziejim
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| posted on 18/3/03 at 09:12 PM |
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doesnt it usually say on the tyre?
James
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Findlay234
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| posted on 18/3/03 at 09:57 PM |
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well on my fiat tipo it mentions it in the car. as long as you get the recomended tyres. but sorry i dont know what to use on a locost. suck it and
see, youll see uneven wear if your wrong so you can change it.
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David Jenkins
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| posted on 18/3/03 at 10:25 PM |
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I'm using a West-field manual for a guide - they use 20psi as a starting point.
DJ
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Dave Ashurst
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| posted on 18/3/03 at 11:45 PM |
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thanks guys
James,
If it says anything on the tyre it's probably max safe pressure / load isn't it?
Findlay,
true, uneven wear would show it ultimately - I hoped there was a better way like shape of contact patch or some such
David,
That sounds encouraging. Is that manual available online somewhere I wonder? Does it suggest a process to optimise tyre pressures for handling for a
given car set up? Have you put it to the test on the road?
I'm running 22psi all round just now. Had 16psi at the front and stiffer damper settings all round until last month. Then I experimented with the
shock settings to help keep the tail under control in the damp. Got that sorted and then worried the tyres might suffer at such low pressure so
pumped them up to 22. Perhaps 16psi was ok after all. 30 was definitely too harsh and skiddy.
I found no guidance on setting optimum tyre pressures for handling, and safe limits, until now though. So any more advice would be welcome.
kind regards
Dave
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Jon Ison
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| posted on 19/3/03 at 06:25 PM |
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the best way to sort it is, (IMO) with a temp gauge, you need a constant temp across the tyre, if its cold on outside the press is too high, i run
16psi, front n rear, but thats in a BEC, a esier way maybe "dust" the tyres and drive the car in a straight line, see how much of the trye is
actually touching the road, if the press is too high the outer edges will still have the dust on them, i know wot i mean anyhow.......
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Dave Ashurst
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 posted on 19/3/03 at 07:08 PM |
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Cheers Jon, I know what you mean too. I'll give those a go. DA
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steve m
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| posted on 6/5/03 at 11:51 PM |
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I have done some expirements with tyrre pressure and have found for best comfort/handling I use 16 psi all round
my tyres are 13/205 (a bit to wide)
tyre wear so far has been zero on the front
and minimal on the back
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carnut
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| posted on 7/5/03 at 09:55 AM |
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It all depends where your driving it to what tyre pressures to put in for example on the track will be a little different.
Ill expand. Lets take Donnington for example. Its a clockwise circuit meaning more right-handers therefore the passengerside wheels will be more
under load than drivers-side so will need less pressure. I would run 1psi less. The distribution between the front and rear will be different
depending on the car. I find an easy way to set it all up is to take the car out on the track, bring it in and measure the temp of each tyre and
adjust pressures acordingly
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Spyderman
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| posted on 7/5/03 at 01:46 PM |
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quote:
Originally posted by carnut
It all depends where your driving it to what tyre pressures to put in for example on the track will be a little different.
Ill expand. Lets take Donnington for example. Its a clockwise circuit meaning more right-handers therefore the passengerside wheels will be more
under load than drivers-side so will need less pressure. I would run 1psi less. The distribution between the front and rear will be different
depending on the car. I find an easy way to set it all up is to take the car out on the track, bring it in and measure the temp of each tyre and
adjust pressures acordingly
I thought it was the other way round.
In every car owners manual I have seen it says to increase the pressure slightly for higher speed use.
As the tyre warms up it expands and so the pressure decreases.
I could be wrong tho'.
Terry
Spyderman
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andyd
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| posted on 7/5/03 at 08:28 PM |
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No. As air heats up it expands. The amount of air inside the tyre is constant (apart from leaks) so as the air heats up and expands the pressure
increases because the tyre doesn't increase it's volume at the same rate as the air inside. Ultimately the tyre does increase in volume
slightly but the rubber of the tyre is fairly think so there's not much of an increase.
Andy
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Viper
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| posted on 7/5/03 at 08:32 PM |
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On our 18" slicks the tyre pressure will go up by roughly 10 psi when hot, (i wouldn't expect road tyres to change anything like that
much)
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