I'm looking to get new wheels for my 2002 x-type. I recently had it lowered on H&R springs (1.3"R and 1.4"F) but it's still riding on the stock 16" wheels.

I'm looking at getting 18x7.5 BBS CV rims (or maybe 19x8 BBS CKs) but I'm worried about fitment issues. The offset on the CVs is 40mm (and 42mm on the CKs). I've seen a couple x-types on 18"s with similar offsets but I don't think they were lowered. I really don't want to have to roll my fenders, but I like the look of those BBS wheels.

Does anyone know what the offset is on the stock 16x6.5 wheels?

If I have that info I should be able to figure out how much further the BBS wheels will stick out and tell if they'll rub or not.

 

Knyach, keep in mind that offset is a function of rim width. So, a rim that is 6" wide and an offset of +40mm will look completely different than a rim that is 8" wide and an offset of +40mm. In the case of the 6" wide rim, the hub will sit 4.6" from the back of the rim, where the 8" wide rim will sit 5.6" from the back of the rim. The value that you want to really look at is the backspacing. This value lets you know how much of the tire is going to be between the hub and the back of the wheel well (important for not having your wheel rub the frame during turning. For the case of our jags, the backspacing value you want to look for is 5.6".

Offset is nice to know as this tells you how far from the center of the rim you are from the face of the hub. Where this is important is ensuring that the center of the tire is in line with the center of the bearing. You start getting too far away from this desired position and you start putting excessive forces on the bearings, leading to rapid bearing wear. In the case of our Jags, you are looking for +40mm. But, keep in mind that you go with a wider tire with the same offset and you are pushing more tire into the back part of the wheel well, therefore running into issues with the tire rubbing at full lock. Granted, the same can be true of just dealing with backspacing. You start pushing the tire too far out to the edge of the tire and then the outside edge of the tire will start rubbing on the front/back of the wheel wells.

So, it is a fine balance between allowable offset and desired backspacing.

 

Thermo, rim knowledge AND electrical expertise. Impressive.

 

Thanks for the reply Thermo.

I'm aware of the backspacing issue. I've been trying to work out the numbers for different wheel sizes to make sure that I had enough room on both sides. Backspacing shouldn't be a real issue. The 18x7.5 BBS CV rims on 225/40-18 tires have a backspacing of 5.8" and sit 2mm closer to the suspension/brakes which is a marginal difference.

I want the offset info to figure out if they'll rub on the outside when going over bumps. Assuming the stock 16" rims have an offset of 48mm, the BBS rims will stick out an additional 18mm (0.7"). I did a quick measurement of how much space I have between the current wheels and the edge of the fender and it's about 0.5-0.75". That's cutting it pretty close.

Tire rack has some O.Z. 18x8.5 inch rims with a 46mm that come out an additional 0.5" and they guarantee there won't be any fitment or rubbing issues when mounted on 225/40-18 tires.

 

To answer your original question, the offset on the stock 16 x 6.5 wheels is 52.5 mm. Yes, quite large.

 

MarkC, thanks for the info. That's some serious offset.