Questions about what offset means

[mikejungle]

Hey guys, please don't filet me, because I have googled and searched around, so i know the definition of offset, but I don't really know how to figure out how it really works.

For example, I have BBS RA mesh wheels that are 15" diameter and 6.5" wide with et30 offset. I need longer bolts for these wheels than the standard bottlecaps, and I'm pretty sure that it's because of the [increased?] offset.

I'm now trying to figure out whether 15" 6.5" (maybe 7") wide wheels with et40 offset will stick out more or less.

I thought more, but after reading a couple of threads, I'm confused as to whether that's right.

Thanks.

[FunfGan]

The only reason you would need longer bolts is if you're running spacers, offset has nothing to do with that. Perhaps you don't really know what offset is?

[LJ851]

Offset is the distance from the center of the wheel (width wise) that the wheel mounting surface is located.

Positive offset is everything from the center of the wheel to the outside (face) of the wheel.
Negative offset is everything from the center of the wheel to the inside (towards the center of the car) of the wheel.

Almost all OEM offsets are positve so your et 30 wheel has it's wheel mounting surface 30mm from the center of the wheel towards its face.

Offset has nothing to do with the length of studs/bolts you need.

[Vivek]

Less offset=sticks out more.

http://www.tirerack.com/wheels/tech/techpage.jsp?techid=101

[mikejungle]

ok...sorta getting it...do you guys think an et35 wheel with a 6" width would be noticeably recessed when compared to the et30 6" i'm running now?

should i get spacers? and what width?

thanks...

[AndrewBird]

Well, the difference is 5mm (35-30=5), so it will sit into the wheel well 5mm more, which is about 3/16".