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Hello everyone. I've been looking through the thread "C3s with 18" Wheels" and a few other posts. I need a little help. As I was looking through, there are a lot of great pics with specs but overall it's somewhat "discombobulated". Several of the posts only have part of the specs and others only posted the pics.
Here's my situation, after reviewing the posts, I came up with what I thought would work for a staggered set: 18 x 8 with 4" back spacing and 245/45 for the front and 18 x 9 with 5" back spacing and 275/40 for the rear. After talking to a wheel shop, they told me I'd need 1" wheel spacers for the rear for them to fit. The car has been lowered front and rear about 1.5" with stock trailing arms. So, this has me a bit confused.
If you have 18" wheels, would you please post a pic along with all of the following specs.
1. Wheel size and back spacing
2. Tire sizes
3. Suspension modifications needed for the wheels
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
I have posted in the C3 18" wheels as noted by you. I have 18" 8.5" BS 4.5" front and 9.5" BS 5.25" rear on stock suspension with tire sizes you mentioned. You do not need 1" spacers if you want to keep the tires flush with the top of the fender opening in the rear. The fronts fit mine without modification and the tires sit inboard of the fenders. Back to the rears. I also used an 1/8" spacer. I relocated the parking brake bracket. This is easy to do for those that have a welder or take to a shop. My rear spring was interfering with the inside of the rim only when the rear was jacked up but I have 8" spring bolts. I doubt stock 6" bolts would be a problem. When the weight is on the wheels, the spring ends are above the inside of the rim but only barely inside the rim. I also used slightly smaller diameter washers under the rubber spring cushion which further reduced spring interference. I'm just finishing up my setup so I haven't had a chance to road test but I don't anticipate any problems that can't be easily adjusted. I think your making a good decision going 18" wheels.
18x9 rear,18x8 front. 5"BS. michelins 235/50 255/45
Rebuilt rear and front suspension to original specs with the exception of the rear composite spring. will need to relocate parking brake bracket. Really happy with the turn out.
18 x 8 4" BS 245/45 -front
18 x 9.5 5.25 BS 275 x 40 -Rear
Potenza RE-11's
When I went through this, I found most people have gotten away with 5.5" BS without a spacer and I recall seeing somebody with a 5.75 BS with no spacer. After a lot of measuring, I concluded that 5.25 was the max I could go, and that turned out to be right. It is very close to the fender lip and I would have preferred 5.5" BS if it wouldn't have rubbed. I have ~5/16" between the frame and the sidewall. Although I have offset trailing arms they don't do anything for clearance unless you have small diameter tires because the frame (at the TA pocket) is the limiting factor...and possibly the spring. I have coilovers so I didn't need to worry about that.
The Tire Rack website lists both the tread width and the section width, which was very helpful. I assume you know that a 9" wheel is 10" measured from the outer edge of the lip.
Here's my measuring set-up. I'm sure there are other ways to do this, but this proved to be spot on.
You will need to lower the car to ride height because of the arc in the IRS movement. In this picture I don't have it all the way down because my half shaft isn't quite level.
18" Wheel Options
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