Tyre pressure

All of what you are saying is theoretically correct. The Construction and Use regulations do indeed require you to have your tyres correctly inflated to the maker's specification.

This is where my traffic cop's 10% tolerance comes from I guess.

Chris

Yeah, but at 35psi, that's only 3.5psi change either way. Some changes between loaded/unloaded highspeed/low speed are in excess of 3-4psi (not to mention how shockingly out of calibration many pumps seem to be).

I use the Halfords battery operated compressor, the one that plugs into the car battery socket. Reasons: -

There's usually a queue at the garage for the tyre hose; and someone is usually breathing down your neck, I don't like to be under pressure doing this task.. I don't trust the garage pressure indicators. You can calibrate the Halford battery compressor periodically, by testing your tyre pressure at the garage, after you have used the Halfords unit). I carry the Halfords unit in the car, (useful if I have a flat and the spare is also flat). Tyres should be filled with air when the tyre is cold, (better to do this outside the house, before you drive anywhere).

Tyre pressures are dependent on: - The vehicle and tyre manufacturer's recommendations. The routine road speed, (about town or motorways). The mass of the vehicle, (whether it's a car or van). Whether it's front wheel or rear drive. Whether it's a Lada, in which case the pressures on each axle may be totally different.

Jaymack

When buying these sort of things, be careful about some with crap guages. I don't especially care if it claims to go to 180PSI. But an (analogue) guage that can read to that pressure is much less easy to read and tell between 35 and 32PSI than one that goes to 60PSI.

I run my escort estate at 42 front 48 rear on Falkens, since at the Ford pressures they wear as if under-inflated.

do the police have calibrated pressure test equipment if so to what standard and what if they let some air out whilst trying to test the tyre ? Also do they have a calibrated thermometer and compensation tables ?

Afaik the police do not routinely get involved in checking tyre pressures, unless they're having one of their drives where they pull people in for checks. If a vehicle is involved in a serious accident, it is possible that a technical examination will be carried out, and in this case tyre pressures would be checked in case they were a factor in the crash. Other than that, they might have a word if they spot a tyre visibly underinflated. In fact I know they will, because my next door neighbour got stopped by a trafplod car which was following him as he had a slow puncture. But all they did was tell him to put the spare on, and buggered off.

Steve

I'm guessing VOSA might ;-)

Chris

The message from snipped-for-privacy@spam.vlaad.co.uk (Paul Cummins) contains these words:

I'm glad I'm not the only one who's noticed that.

I reckon the car firms specify lower pressures than ideal to reduce the harshness a bit and keep the whining car reviewers quiet.

I'm glad someone more sensible than me has noticed this too.

Falkens are good to 5ipsi, and I'm sorely tempted to run the rears that high sometimes...

Where have you been for the last 20yrs? This used to be true with rear drive crossply narrow rubbered leaf spung battle cans, but definately not anything semi recent with widish front drive half handling tack.

Rear- 44psi for fully loaded and or high speed yes, (fronts should be around

Monitor tyre wear and handling and then re-adjust to suit...

Tim..

I had similar problems until recently on my celica - wore the shoulders of the fronts like mad despite being 2psi over recommended. Had slight play in the front wheel bearings and worn bushes - arbs and tie bar, so replaced them and then took my car in for a full 4 wheel laser alignment (castor/camber and toe). After they fixed both the fronts and rears (wasnt aware there was a problem with the rears) and since have had no issues at the correct tyre pressures. 48 at the rear is very high, not far off the max rated pressure for normal tyres IIRC, get those warm and you're right up at the max which isnt ideal, plus you're gonna have a massively reduced contact patch for the rears over what you should have. I suggest that if you have tyre wear issues you should fix the cause rather then cover it by crowbar methods!

The tracking is laser-perfect, and the wishbones and suspension were new for the MOT 11,000 miles ago.

I don't need the rears higher than the fronts, but I prefer understeer in a Ford, thanks...

On Sun, 28 May 2006 15:57 +0100 (BST), I waved a wand and this message magically appeared:

Time you changed that. Elections been and gone.

Tracking, i.e. toe. isnt the only suspension measurement that has a vast effect on tyre wear and handling - your average kwik-fit wont do camber/castor checks.

As for rears high giving understeer - never had that, only ever had oversteer from high rears - escrots must be different to any of mine.

: I have to agree, the vehicle manufacturer states precise values for : loading conditions and so any deviation could be considered to be : making the car un-roadworthy.

Only if one, or the law, believed that 32psi was safe and that both

Ian

The message from snipped-for-privacy@spam.vlaad.co.uk (Paul Cummins) contains these words:

They'd have had a giggle at the trailer I saw at the dump this afternoon. Tiny trailer behind a Disco - so it was already tilted up by about a foot at the ball. The wheels were a good three inches out at the front and in at the top. Looked like a duck. You could hear the tyres scrubbing as he pulled in. And see them steaming after crossing a puddle.

Ah, no there's no problem on the rears, at all.

The rears don't wear at all. After 30,000 miles, I still have 7mm of tread, and moulding sprues :-)

Time to fix your handbrake :-)

Chris