Tyre pressures

So what? Why is always-a-bit-high (or always-a-bit-low) better than sometimes-a-bit-high-and-sometimes-a-bit-low?

I'm assuming, of course, that any sensible person will always make sure that left and right pressures match, regardless of the gauge in use.

Ian

OK, so using the same gauge repeatedly helps you spot leaks.

But you haven't "established the optimum pressure" with your gauge - all you are doing is ensuring that you always have the same pressure, which might be wrong.

Ian

Cite, please?

Ian

This has been discussed in the uk.rec.cars.* hierarchy so many times that it would be easy to Google for. However, here it is again:

s41A(b) Road Traffic Act 1988, Road Vehicles (Construction and Use) Regulations 1986, reg 27, as amended

HTH

Chris

Because , if you've adjusted the pressure to compensate for different tyres, you don't care about the absolute pressure, just that it's the pressure you've discovered to work.

In news:Z4UKh.11116$ snipped-for-privacy@newsfe5-win.ntli.net, berksposter wittered on forthwith;

Tyre pressures are dictated by both the car and the tyres.

No, you're correct in what you say.

Tyre pressures should ideally be set to what the tyre manufacturers recommend for the car, however, not many people actually bother to check the tyre pressure difference between say Bridgestones and Pirellis. The sticker the vehicle manufacturer fits is normally well within tolerances and therefore good enough for most people.

Ye Olde Firestone S660s were my least favourite tyre of all time. If you put the car manufacturers recommended pressures in the middle of the tyre would be bald within weeks, whereas if you put Firestone's recommended pressures in it'd make everything feel as mushy and 'orrible as a Mk3 Golf diesel.

Nope, that says "inflated as to make it fit for the use to which the motor vehicle or trailer is put".

Thank you. I presume you cut and pasted that from the yahoo legal advice page. Unfortunately, despite lots of searching on the Statutory Instrument website, I can't find the one in question (there were 2399 SI's in 1988) and so cannot confirm that it is the manufacturer's recommendation which defines over and under inflation.

Ian

Ah. See your point. Thanks.

Ian

It does that certainly, but again you are missing the main point.

You're losing me. What do you mean by wrong? Wrong because it differs from that recommended by the cars maker? Recommended tyre pressures are exactly that, recommended. They are not cast in stone. Variations, eiither way within reason, are perfectly acceptable and safe.

IME a variation of a few pounds either way doesn't usually affect the wear pattern of a tyre. If it does, the variation is too great, and the pressure should be adjusted accordingly.

Not all tyres behave in the same way. Different makes, even with the same construction, can give a different feel to a cars steering, cornering and braking. The optimum pressures are those which give the best compromise between all of those factors, which may or may not be the same as those recommended.

Of course if 'tailoring' tyre pressures to suit yourself is too much bother, by all means just stick to the makers pressures, and use garage guages. They probably aren't innaccurate enough to for the average motorist to notice the difference. Mike.

Of course when you lose said guage you're buggered as you have no idea what the pressure actually was...

That also makes me wonder about compulsory skid pan training...

I had a car pick up a nail and get a slow puncture in a rear tyre on a long straight dual carriageway. I got to the next small roundabout and tried to just flick-flick around it as usual (no other cars, very very good visibility).

When I tried to straighten up, putting all the pressure on the soft tyre, it gave completely and left the car slewing at quite an angle across the road. Having had several fast RWD cars and having plenty of mucking about in snowy carparks, I just caught it, straightened up, pulled over and investigated.

With no experience of going suddenly sideways, I would have been into a tree, or another car. But IME it doesn't take *much* practice oversteering to get the basic idea of steering into a skid and easing off the throttle. But most poeple never even get that vital ten minutes.

You presume incorrectly then.

I searched using Google Groups for an earlier thread on this subject.

Chris

Probably someone else cut and pasted then, as the layout and punctuation is a) exactly the same as the Yahoo version and b) not the same as anyone else's (that I could find).

Ian

Er.. OK.

Chris

berksposter mumbled incoherently to the rest of uk.rec.cars.maintenance:

Having gone from 15s to 17s of similar width (slightly wider actually) I found the stock pressures too low by 4psi. Start at standard pressures then monitor the grip and wear. Coat your tyre tread in chalk and drive a couple of meters on it, then look - it wipes off the main pressure areas first. If thats the outside edges throw a few more psi in, if its the middle, lose a couple.

So what happens if a manufacturer provides a car with 16" wheels but one upgrades to 17". Is that also a construction & use offence?

The requirement is that they be fit for use. Ditto their inflation pressure.

I dunno. And what about using radials when the manufacturer specified crossplies?

Ian