bentree

I am running breyton 20s with 255/35 side walls on front and 295/25 on the rears - could anyone recommend tire pressure for my set up?

fyi- wheels bent twice already within 2 weeks and i am trying to figure out if this has to do something if I am not inflating the tire enough..

BMWRINO

I run 40psi on my 20 inchers... 245/30/20 front and 285/25/20 rear..

virgil

I've got the 19" run flats that come standard with the M pack.

I run on 36psi front because any more than that and I begin to notice a little understeer.

I run 32psi rear. My local tyre shop has a small glass floor (about 2' square) where they can show you how much rubber is in contact with the road. 32psi gave me max rubber with the run flats. They showed me this because I complained about wheel spin after they fitted new rubber and set the pressure at 40psi as I had requested. I like a shop that provides the driver with a little education.

Two little pieces of advice:

1. Use your own tyre guage ... never rely on the guage at your local garage ... customers drop them, knock them around ... they're not accurate.

2. BMW ALWAYS resets my tyre pressure to around 20-22psi to give a softer ride. It sh*ts me, but the keep doing it. So always check your tyre pressure (cold) before leaving the dealership after a service.

Cheers'

v

luigi524td

Yikes ... that's waaaayyyyy tooooo low for any tires fitted to our cars UNLESS you're trying to ride on a sandy beach!

jadatis

I have been busy wiht calculating tire-pressure since 2007.
Got hold of the Formula of the ETRTO ( European Tire and Rimm Technical Organisation) .
Learned myself Excell to make spreadsheets for tire-pressure.
Last one is for re-calculating tire-pressure when non standard Tires are placed on the car.
Translated this form from Dutch to Englisch .
http://cid-a526e0eee092e6dc.skydrive.live....20tyre-pressure
In this map always take the newest spreadsheet, and there are examples placed.
Got reaction from american that the TRA uses a diferent formula so for american cars you can not use the first part for recalculating back the loads that were used for normal use advice pressure.
But nowadays those ar often not given. Also made a spreadsheet for determinating the axle-loads for normal use yourselves, but have not yet translated that, it is a lot of work because of the amount of Dutch text, but if someone wants to use it, navigate to it on my sky drive of hotmail, from the link I placed, and if more say that it is usefull,I will do it.

I read in this topic that advice of BMW was much lower than what seems to be riding good ( Virgil point 2).
Probably this is because the RTA calculation comes to lower advice pressures then the ETRTO calculation.
So if you can find the right data of the car and tires, and fill them in the spreadsheet, thenyou can see what the ETRTO would advice.
I would like to read that from you, especialy the differences for heavy use and vacation use wich are to be trusted and mostly higher then the TRA . I think better advice.

needed from car
1 maximum Axle loads front and rear ( on metalish plate under motorhood or one of the door styles)
2 maximum speed of car ( in manual or estimated)
3 The advice pressures on the plackard somewhere on the car or manual , that are meant for the specific car. ( can do without)
4 If more then 2 degrees , the camber-angle ( When tires are placed on the axle so/-\) mostly not above 2 so not needed.

from tires example 195/65 R15 91T
1 maximum load in KG ,LBS or the Load index ( in example loadindex 91 stands for max. 615kg )
2 reference pressure or kind of tire. When there is on the tire-side-wall "At 240 kPa" or "at35 psi"then that always is the reference pressure, but for normal car tires in america that is almost always 35 psi. reinforced XL 280 kPa . so not the maximum pressure of tire.
3 Letter that stands for the maximum speed of tire ( in example T stands for up to 190km/h)

succes and if there are questions or you find some bugs , tell me here.