tyre pressures in the wet

the recommended pressure is the same wet or dry, it keeps the profile of the tyre correct, so giving the best contact area too much pressure pushes out the middle of the tyre and reduces pressure on the outer contact area. too little lets the outer edges take all the grip, the centre takes little, in addition the low pressure lets the tyre slew sideways in relation to the rim.

mrcheerful

Like most things mechanical the settings are trade-offs between one benefit and another. Often, by altering something to better suit one set of circumstances you make it worse for another. By reducing the tyre pressures - which would give you better grip - you increase the rolling resistance and the tyre will heat up more and increase your fuel consumption. Also, the handling will alter, probably for the worse. And if you have an accident that's serious enough to warrant an investigation the police will check the tyre pressures against the manufacturer's recommendations. If they are out then you may get slaughtered for it and your insurance company may have something to say about it.

If you increase the pressures, you will get less grip (because there's less tyre on the road), the handling will again alter and the above will apply. Usually the only reason to change the pressures is if you carry more weight. The handbook will tell you about this. I'd leave well alone if I were you.

Rob Graham

I think you need to look at your driving before your tyres if you're spinning off at roundabouts.

Still though many disagree, lots of companies recommend that your grippiest tyres should always be on the back

the current michelin advice is to always fit new tyres to the rear.

mrcheerful

Why not try driving sensibly and responsibly? Public road are not racetracks. Why not invest in a Fiat Uno 750 - it may just save your life!

Terry D

The message from "mrcheerful ." contains these words:

It's the current advice from the UK tyre trade body - whatever that is. Saw a notice about it in a tyre shop.

The message from "klf" contains these words:

Yes, that's right. They should (and have with me) offer to put the part worns on the front and put the new boots on the back.

That's excellent advice. So I go in with a front wheel drive car and ask for two new tyres for the front. Are you seriously suggesting they would prefer to fit them on the back! Don't be silly. They would say anything to sell 4 tyres and depending on where you go they now offer rip-off insurance policies ! Either that or you get told you need shock absorbers. Women with baby seats in the car are always told about brakes. Most garages will lie as they're put under pressure to sell.

Ignoring the question of grip front to back, it actually makes sense to rotate the rear tyres onto the front in a FWD car as, if left there, it's possible for them to perish due to age rather than being worn out. Far better to actually wear them out.

recommendations say for towing, the rears wheel pressures in particular are increased. I had a scooter many years ago and I had a faulty tyre I went the Michelin HQ ( an Artdeco building ) the manager told me they could tell how old or how abused a tyre was by the amount it had expanded (rubber expands when heated)that's another story( they changed tyre for free). But he told me how to make sure the tyre pressures where correct. This is what he told me. Put a sheet of paper in front of tyre and drive over it if the tread mark is blurred in the centre its under inflated, if the middle well defined and the edge blurred then the tyre is over inflated. The message is manufactures sometime recommend pressures to overcome deficiencies in design of steering geometry in the past. As with the early Renault 12's the front tyres where so under-inflated that the steering was very heavy when I complained to their technical people. the only person I could talk to, a chap with the brain of an automaton, who recited the hand book from memory and did not have any technical know-how. Needles to say Renault increased the tyre pressures on the 12 the next year by quite substantial amount .

MikeS

well that was my first spin in 3 years of owning that car (alfa) , i just pushed a little too hard to see what the front frip was like in the wet, my fault m lud !

i normally do , just pushed a little too hard seeing how well the fronts grip in the wet, was only doing about 25!

i know, tell the local boy racers around here, one was clocked at 85 in a 30 zone a few months ago!

but i'd die of embarrassment!

Scott M (smorris_12@delete_this.yahoo.com) gurgled happily, sounding much like they were saying :

If a particular car is SO nose-heavy that the rear tyres are going to perish rather than wear out, it's a fairly good indication that the rear tyres are so under-used and over-specced that it's a complete waste to put new ones on the back.

Well perhaps you should inform all the tyre trade of your superior knowledge on their specialist subject.

If you logically think about it then unless the tyre sizes are unequal front and rear (Mercedes and Smart for instance) then it actually makes very good sense.

some of The reasoning is that punctures are most likely to happen on the rear, but are least likely on a new tyre, rear wheel punctures or baldness or hardness may lead to a spin. Rear tyres may not wear out on a front wheel drive car but do perish.

Go into most tyre shops and get the explanatory leaflet.

Also if you are saying that your existing rear tyres are too poor in condition to go on the front then perhaps you do need four tyres!.

mrcheerful

The message from "mrcheerful ." contains these words:

We get this response every time this subject is discussed - some people just won't listen to what they're told, either by us or by trade bodies.

Unless your front and rear wheel/tyre sizes are different ;-) ..but in general I agree.

I thought you were going to say "waste of time putting tyres on the back at all" and had a vision of cars with nothing but a set of castors behind. :-)

Personally, I go for putting tyres where their needed rather than getting them swapped back and forth. Perishing is only a problem for v. low mileage cars anyway, but that does tend to be the nose-heavy FWD super-minis. And I suppose, if the annual mileage is low enough, you're be getting problems of this sort at both ends.