325ti Tyre Pressure?

[volvoforlife]

I have a 325ti and in the handbook it says tyre pressure for All Summer Tyres (Except R17 Extra Load) should be 32psi front and 38psi rear.

These numbers seem very high and my wheels are 16" not 17". The ride also feels quite skippy over rough surfaces.

Have I misread my manual or are the figures given correct?

Thanks in advance for any suggestions.

[MartinQ]

I've got an E46 318i saloon with 16" wheels. From what I've read I use 29psi front and 33psi rear and this seems good to me.

[Patrick Bateman]

The manual must state it for a reason so I'd go with what it says. And no you haven't misread it, I've got the same manual.

[Jadatis]

The exeption for reinforced/XL/Extra load is because XL tyres have their maximum load at a higher pressure.
This is called the reference pressure.
I kept myself busy with re-calculating tyre-pressure-advice, with use of the System the European car- and Tyre- manufacturers also use. Got hold of copy of page 14 of standards manual ETRTO 2007 and worked it out.
But already found an American article with a new better suggestion of calculating, the European power though gives save advice.
For 16 inch tyres, you can recalculate, with spreadsheet I made, take the newest one in next map and open it in Excell or open-office Calc, but not directly in the browser, wich wont work.
http://cid-a526e0eee092e6dc.office.live.com/browse...
In the first sheet the needed data are mentioned, but if you cant work it out ( learned excell myself, and presentation is not my strongest point), give me the details here, and I will do it for you as an example.

If you give more details like empty weight and build of car ( motor in front, frontwheel drive, wheelbase, number of persons and luggage) I can determine the aproximate weigt on the axles for "your own imput".
Then I can give an advice for your specific use. For the advice-pressure, the actual weight on the tyre and the speed you maximaly drive with is important( als camberangle, alignment, but seldomly needed).
Mostly this will give for only driver in the car, a lower pressure back then front.
The Equation calculates the minimum pressure for the weight and speed ( and camber-angle), at wich the tyre wont get damaged, no less no more. By using a weight and speed in the equation, that is always higher then that is used for the condition you calculate for, gives advice-pressure with some reserve.
Greatings from Holland
Peter

Edited by Jadatis on Monday 13th December 10:06

[volvoforlife]

thanks for that Jadatis, but it is a bit too complicated for my needs.

i have put 32psi front and 38psi rear and the ride is unbearably hard. i think i will go down to 29psi front and 33psi like MartinQ has.

[taznuv]

Agree the ride is terrible on the recommended setting and it gives traction problems on bumpy roads. Haven't got the figures to hand but I find it best with the fronts as recommended and the rears dropped a bit, unless of course you are carrying a lot of load.