Rear tyre pressures versus front

[darkwolf 0]

The recommended pressures for my 1998 BMW 540i for my standard wheels (which are on the car now) 225/55/16 are:

While Loaded:

2.2 bar (31.9 PSI) front

2.7 bar (39.2 PSI) rear

Standard:

1.9 bar (27.6 PSI) front

2.2 bar (31.9 PSI) rear

My question is, theoretically I have more weight at the front wheels. So wouldn't I want higher pressures there?

I always thought that above normal (increased) pressure resulted in less grip, below normal (decreased) pressure resulted in more grip.

So where have I gone wrong that it seems to me that BMW wants me to do more burnouts.

Obviously I'm following the manufacturers specs in regards to pressures. But I just like to know why I do things as apposed to doing them because I read I should.

[pureboiracer 0]

not necicerily. you may find if you switched them round you would be understeering alot. bmw have come up with these figures for a reason. they didnt just pick them out of a tree. so evidently they must believe thehandling is better with those pressures.

i have 22psi in front and 48 in back on my e30. now that is skid happy. a couple of psi diference wont be the difference between burnouts and not

[darkwolf 0]

not necicerily. you may find if you switched them round you would be understeering alot. bmw have come up with these figures for a reason. they didnt just pick them out of a tree. so evidently they must believe thehandling is better with those pressures.

i have 22psi in front and 48 in back on my e30. now that is skid happy. a couple of psi diference wont be the difference between burnouts and not

Yeah I figured they would have a reason. Hence why I am still running factory set ups. I just like knowing why they have done something. Call it OCD or whatever but that's how I am.

[pureboiracer 0]

they probably have done it to prevent exessive understeer.

[Mike 1]

If you run the rears lower you will have more traction in the wet.

I've read the opposite, reason being the higher pressure opens the channels in the tread, allowing more water to escape. Does that have any validity to it?

[bravo 35]

Read this About halfway down the page is more info than you ever wanted to know on the subject.

[bravo 35]

lots of info and also the good old myths from 30 years ago including tyre rotation - like anything read it and then check it against a specific authorative source

But of course.