MB wheel offset and wheel spacer questions

[cam69ss]

Hi,
I am a little confused with regards to wheel offsets. Is wheel offset measured from the outside of the rim to the inside flat surface of the mounting hub?
My car came with 21.5 mm offset and I want see if I can use 37 mm offset? If I buy 15mm spacers for the 37mm wheels would the combined offset now me 42 mm or 22 mm? I am assuming that the 37mm offset will push the wheel towards the outside of the car, if that is the case I wouldn't think .600" more sticking out will cause rubbing problems. Any thoughts?
THanks,
Dan

Offset is the distance from the mounting surface of the wheel to the wheel's centerline, so to determine offset of an unmarked rim, you need to first measure how wide the wheel is over the outside of the rims, divide that dimension in half, and then lay a straightedge over the inside flanges of the rim and measure to the mounting face. On almost all foreign cars, and most American stock equipment, the mounting surface is set farther OUT than the centerline of the rim: this is positive offset. If you add spacers, you REDUCE a positive offset (move the rim farther from the hub), so putting a 15mm spacer into an ET 25 (25mm positive offset) rim leaves you with only 10mm offset.

The combination you propose would indeed produce a 22mm offset.

[yhliem]

Offset is actually the distance from the ceterline of the rim to the mounting surface. You are sort of confusing offset with backspacing which is actually the distance from the inside wheel rim to the mounting surface.

for a great explanation with pictures, go to

Tire Rack's page on offset

Mercedes uses negative offset steering geometry because impacts to the front wheels are less likely to force the steering to try to turn. It's simply a matter of reducing the mechanical advantage applied to the front wheels via leverage.

[cam69ss]

Thanks for the helpful information guys.
Dan

[benjylafond]

Dan,

How did the CLK rims work out on your 300SE? Did you have to use spacers? I want to know b/c I bought SLK rims for my 560SEC and the fronts have 37 offset and the rears have 30. The rears are also 8 in. wide.

[cam69ss]

The 30MM offset will probably work for your fronts. the back 37MM will work for your rears too but it would be tight and look funny. I did have to use spacers.
Dan