Correct Offset for 18x12?
 

I'm thinking of having a set of 18" wheels made. 17" looks fine on the car, but if I've spending the money I want to go a tad little bigger while still maintaining some sidewall. I know tire selection isn't the best for 18's and will need to run a 335/30 in the rear. This requires a 12" wide wheel. I do not want any "poke" with the extra width. I want it all on the inside. If my math is right this means I need a +48 or +49 offset. Is anyone running this setup? Any clearance issues I need to consider?


Thanks

Re: Correct Offset for 18x12?
 

OEM 11" rear wheels are positive 36 mm offset. If you keep the same offset, additional 1" will grow out board. Increase by 1/2 of 1" (about 1.3 mm) will grow the wheel 1/2" inboard and outboard. At least, that's my understanding.

For reference, I have 11", 57 mm offset Fikses on the rear and 18 mm spacer.

Re: Correct Offset for 18x12?
 

You description seems to match my understanding. Here's the math I used:


11" = 279.4 mm
center line = 139.7 mm
center line +36 = 175.7 mm (inside) 103.7 mm (outside)


12" = 304.8 mm
center line = 152.4 mm
center line +48 = 200.4 mm (inside) 104.4 mm (outside)


The +48 would "poke" out just 0.7 mm, or 0.03 inches.

Re: Correct Offset for 18x12?
 

Take the stock offset and as an inch, No need to make it difficult with all the different numbers. I've been having custom wheels made for years,made to my specs and I always take a stock wheel,find out how much room I have on the inside of the wheel well and go from there. I've never had a wheel made that added anything to the outside of the wheel. I know the language here is as basic as it gets but it doesn't need to be complicated. One small area on the inside of the rear we'll wheel liner will need to be trimmed.

Re: Correct Offset for 18x12?
 

This may help you check your math: https://www.willtheyfit.com/

Re: Correct Offset for 18x12?
 

That is an awesome website, many thanks for posting it!

Re: Correct Offset for 18x12?
 

decimal is in the wrong place

13mm ~= 1/2" not 1.3mm

:thumbsup:

Re: Correct Offset for 18x12?
 

You are correct. I was thinking cm.

Re: Correct Offset for 18x12?
 

Glad you find it useful! :cheers:

Re: Correct Offset for 18x12?
 

Another part of putting together a wheel setup is matching the tires. TIRE RACK has the specs on all of the tires they sale. When I put the wheels on my Z I originally had a 275-35-18 on the front but felt the side wall was too short. I did some digging and found a 265-40 was a hair taller and only a 1/10 narrower than the 275-35 so that's what I went with.