I dont understand the backspacing when in MMs

[WELTERRACER]

Im looking at as set of 20" BMW aftermarket wheels for my camaro.. they say they have a 15mm back spacing on the front and a 18MM backspacing on the rear..

Is the MM measured from what?? doesnt make sense to me..

Right now i have 17x9.5 wheels and they have a 5.5 inch backspacing..

[dipren443]

Pretty certain those numbers are referring to offset and not backspacing... Backspacing is measured from the rear lip to the back of the hub mating surface.

Offset is the distance of the hub mating surface from the wheel centerline. Positive offset translates to less dish on the wheel. Negative to more dish. Link below has some good diagrams.

Good link right here:
http://usacomp.com/terms.htm

[WELTERRACER]

Thanks.. THat makes sense.. i wish everyone would just use backspacing in inches... would make it alot easier..

[Boesch]

This site has some good information:
https://www.rsracing.com/tech-wheel.html

[gonein67bird]

Dude check this site out. When I got my BMW wheels not to many people had them, this convinced me I could do it.http://www.rims-n-tires.com/info_spe...20/%20Comparer