View Single Post
      01-11-2008, 06:04 AM   #28
330cdsport
Right Responsible
330cdsport's Avatar
United Kingdom
58
Rep
1,646
Posts

Drives: AW F21 M135i
Join Date: Mar 2007
Location: N. Ireland

iTrader: (0)

Garage List
Quote:
Originally Posted by E92Fan View Post
The offset, or ET measurement in millimetres, determines the position of the mounting point of the wheel in relation to the centreline of the wheel (see diagram below)

Attachment 121637

Looking at the picture above, note that the left hand side is the brake side, and the right hand side is the outer edge of the wheel.

In the left image, you can clearly see that the mounting point is positively offset to the right of the centreline of the wheel - so for instance an ET37 wheel will have the mounting point 37mm to the right of the centreline.

The middle image shows no offset at all, so the mounting point is in the same position as the centreline of the wheel.

The right image shows negative offset.

The higher the positive offset value, the more the wheels sits IN towards the hubs. The lower the offset value the closer to the wheelarch. In both cases, the width of the wheel is constant, the only thing that changes is the mounting position relative to the centreline of the wheel.

Great description. Thanks for that.

Also - going back to the Tyre pressure sensors..... My valve stems are rubber and not metal, does that mean my coupe uses the older 'wheel diameter' method to detect pressure.
I also found that when i recently got a slow puncture, the warning light did not come on until the pressure went below 20psi (from about 38psi). This seemed a very slow reaction to me.
__________________
Last: 330cd Sport - Silver Grey, 335d M Sport Coupe, F10 535d M Sport.
Current: AW F21 M135i, Coral Red, Pro Nav, Vis, HK, & Clunky Adaptive Suspension
Current: F15 X5 XDrive 40d M Sport - Space Grey, lots of toys.
Appreciate 0