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Discussion Starter · #1 ·
I should know this but still confused, search function is a bit too broad.

09 CS with stock 18 OE wheels & rubber. What is the offset on these?

Just bought some track wheels & NT01 rubber:

Front 18x8 45 245/40
Rear 18x9.5 49 275/40

Only 1 track day with the new wheels but I am rubbing some in the rear (inside) - any help with calculating spacer size much appreciated. And just rear or do I need front ones as well to stay balanced?

Will I need a new alignment after using spacers?

Thanks in advance!
 

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I don't know for sure if the '09s are the same, but the '06 through '08 OEM 18" rims have 57 mm front and 43 mm rear offsets.

Without knowing exactly how much rubbing you're getting inside, your wording makes it sound like the optional 5 mm spacer kit (fronts too) may be the right move. I have the same size R-comp tires on OEM rims with no rubbing.

Alignment should be the same after adding spacers.
 

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Discussion Starter · #3 ·
Thanks Jim.

The NT01's have a barely noticeable rub ring on the inside - will keep it simple and order nominal spacers all around.
 

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Your fronts are already out pretty wide and should not need any more spacing. The extra width of your rears is completely on the inside. The outside is at the same place as stock (except for your wider tires). You could easily put a 15mm spacer on the rears since many people do that with the stock wheels.
 

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I should know this but still confused, search function is a bit too broad.

09 CS with stock 18 OE wheels & rubber. What is the offset on these?

Just bought some track wheels & NT01 rubber:

Front 18x8 45 245/40
Rear 18x9.5 49 275/40

Only 1 track day with the new wheels but I am rubbing some in the rear (inside) - any help with calculating spacer size much appreciated. And just rear or do I need front ones as well to stay balanced?

Will I need a new alignment after using spacers?

Thanks in advance!
For factory wheels, the offset and width are stamped on either side of the valve stem (single digit is width, double digit is offset).

When (3/4 turn, full lock, etc.) & where (f or r) do you hear the rub? I have heard from others that if you run 245s in front (with factory offset) the fronts will rub at full lock. I don't have direct experience with this, but just what what I've read on the internet FWIW.

If your spacers aren't too wide, you shouldn't need to realign. I added a pair of 15mm to the rear wheels and the alignment guy said I don't need to realign again.
 

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Discussion Starter · #6 ·
The rub marks are only in the rear by the suspension, and using one of the calculators looks like the front has plenty of room with the 45 offset but the rear is 11mm tighter than OE, so I just ordered the 7mm spacers from GMP that should give me clearance without upsetting anything.
 

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Discussion Starter · #7 · (Edited)
For factory wheels, the offset and width are stamped on either side of the valve stem (single digit is width, double digit is offset).
I thought so too but they are not printed anywhere on the outside of the wheel. I checked twice. Maybe it is on the inside but don't have a chance to pop a wheel off at this time.

These are the OE 18" CS ones.

So going with the assumption they are 57f and 43r. Would be great if someone can confirm.

EDIT: just confirmed the above by reading the manual (duh!) Guess wasn't expecting that level of detail to be there. Thanks for everyone's help,

Ralph
 
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