I've got a 92 SC 300 and I'm getting a set of 18 ' HD MSR rims The front are 7.5 wife with +42 offset. N rear are 9' wide with a + 40 offset.
The tires are either 235 or 245 40 18's front
265 35 18 in rear.
My car is lowered on springs n shocks n have no rubbing issues now
I just want to make sure my bbk will clear with those offset s

 

They won't, you'll need a minimum of around 30-35 to clear ls400 bbk, unless you're talking about rotora or brembos, stoptech etc..., that's a different story

 

Thanks. So basically I need a plus 30 on the front to be sure with that rim.

 

What matters is your hub to spoke clearance since wheels are different. You could have high disk which will clear BBK or low disk which will only clear stock brakes. Best way to be sure is to measure it.

 

Thanks for the info. I'm not sure how to measure for the Clarence without having the new wheel I called the place that has the wheel / tire combo I want Nd they basically said they couldn't honor any return etc if I had upgraded brakes . I just want to make sure they will fit before I buy them.

 

Not true every rim is different so offset is not the issue. It's all about disk clearance like said earlier. ..then once that's determined then offset plays a role in whether or not the spoke design will clear your brakes. For my wheels I needed a +11 to clear supra BBK

 

look on the spoke of the wheel...some say hi, med, lo for the disk face.

 

With a 7.5" wide wheel in the front and such a high offset, you're going to need a huge spacer anyway to make it not look like a hovercraft.