The effects of dodgy tyre pressures

[Nicholas]

Hello everyone,

A few months ago I noticed that my tyres looked unusually deflated and checked them, and it turned out they were about 6 or 7psi lower than they were supposed to be.

Since then I've been regularly checking them (at least once a week, when cold of course) and they tend to be about 2 or 3psi, sometimes even 4 or 5psi lower than the ideal value, which to me does not sound like good news!

First of all - is this normal? I know one is supposed to check every fortnight but they seem to be fluctuating rather more than one might expect. Since I first noticed I've had a change of car and the pressures are still changing quite a bit. I'm not throwing the car about or anything like that either, just the usual 15 minute commute each day, that sort of thing.

Secondly, I'd be interested to know what are the dangers of having very low (or high) tyre pressures. I'm vaguely aware that steering and braking can be affected...:confused:

Any advice will be greatly appreciated!

Nicholas

[Vicki]

The danger is that when you get a puncture, too high a pressure means they tyre will burst, giving you a blowout. If the pressures are too low, grip levels might suffer.

[Tim Falce]

If they are not the correct pressure they will wear unevenly. If they are too high your steering will become light and you may only be riding on the centre section of the tyre which will lose grip and steering and braking will suffer. Too low and they could overheat and the side walls will be damaged and same problems with steering and brakes.
Make sure you check the pressures when the tyres are cold, if you are using the car regularly they would always be the same other wise you probably have a puncture, faulty valve or damaged wheel. If the car is standing for weeks on end they may deflate slightly.

[Nicholas]

Okay then, that's cleared up a few things for me. Thanks very much both of you

[Morris 1100]

Get yourself a good tyre pressure guage.
So that you can check what is in the tyre and not check how bad the gauge at the service station is

[Tim Falce]

Originally posted by Morris 1100
Get yourself a good tyre pressure guage.
So that you can check what is in the tyre and not check how bad the gauge at the service station is

Good point Morris 1100, use the same guage every time

[Mattracer]

That's a good starting point- you don't know how many times the service station gauge has been dropped and/or driven over in the driveway.

Over-inflated means the tyres wear out more quickly in the middle since the middle of the tread will be the contact patch and an excessively hard ride. Under-inflated means most noticebly, sloppy or heavy handling/steering response, increased fuel consumption and excessive tyre wear.
As a general rule, it can be better to go for the maximum recommended pressure, that is, for high speed/heavy load operation, for sharper handling, better road feel and less fuel consumption but no more than that.

[Dave Brand]

An important point here, which everybody has overlooked, is why are the tyres losing pressure? If everything's in good condition it should only rarely be necessary to add air - I generally find that I let a couple of pounds out in the spring when ambient temperature starts to rise, put a couple of pounds back in autumn when temperatures drop.

If it were me, I'd get a tyre specialist to check for leaks. Are the valves in good condition & fitted with caps, have you got alloy wheels which are showing signs of decay which could lead to their being porous, etc. The tyres should also be checked for condition - prolonged running at too low a pressure may have damaged the sidewalls.

[Tim Falce]

Originally posted by Dave Brand
An important point here, which everybody has overlooked, is why are the tyres losing pressure?

Originally posted by falcemob
if you are using the car regularly they would always be the same other wise you probably have a puncture, faulty valve or damaged wheel. If the car is standing for weeks on end they may deflate slightly.

[Dave Brand]

Oops.....but that was two days ago.....I've got a short memory span!

[Mackmot]

remember that pressure is affected by the atmosphearic pressure and by ambient temperature. Even on a day racing you can drag the car out first thing in the morning and check the pressures and an hour later when it goes on track it can change pressures can be 2 or 3 psi higher