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Discussion Starter #1
K guys, I've been doing a lot of searching and reading about rear fitments with widened stock wheels and learned what I could get away with... I only need help on one more thing--spacer width!
Here's the break down:
- I just sent off my stock 17's to Weldcraft to be widened 1.5" to 17x9.5".
- I already have two Nitto 555's in 285/40/17 to squeeze in back there.
- While the body shop installed the SAP kit, they rolled my quarters.

I've read the following section on ls1tech's sticky page about wheel fitment:
8.0" ............ +36 to +65 ........ 245, 255
8.5" ............ +42 to +65 ......... 245, 255
9.0" ............ +48 to +65 ........ 255, 265, 275
9.5" ............ +55 to +64 ........ 265, 275 (body mods are required)

After adding the 1.5" (38.1mm) to the back of my wheels--the new offset will be +67.05 [48+(38.1mm/2)].

According to the chart (on 275's), it seems like the maximum spacer for my new offset would be 12mm (67.05-55) and the minimum spacer would be 3mm (67.05-64).

My tire is a 285 rather than 275--so, would it be ok if I pick a spacer in the middle of that range? Say 6mm-8mm or so? I have read that many people run 6mm spacers on 275's. I ask because 6mm spacers are available locally for me--but anything larger than 10, would be something that I would want to special order from Motorsport Tech.

The only reason I'm posting this is because there are a lot of posts asking about Weldcraft widening--but barely any of people who have done it. And the few that I did find, only widened to 9". If anyone could give me some insight, I would really appreciate it!
 

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You're on the right track. I run 285/40/17s on one inch wider 9"x17" stock wheels. The 4 main things are studs, fenders, spacers and bushings.

The stock studs are soft and a little short to start with. ARP rear wheels studs (Camaro/Corvette) are cheap.

The fenders on mine are moderately rolled. Trimming can be done if you want to prep and paint the edges afterward.

I run 5mm spacers to give me an effective ~55mm offset. You can easily and safely pound the inner fender in a bit in a couple of spots with a BFH to give more inner room. With 1 1/2" wider wheels a 10mm spacer would give you roughly the same inner space as mine but bring it out 5mm more to the outside. If you get it close to 60mm (the 6mm will get you at 61.5mm) you should be able to make it work. Much higher offset and you start running into maybe grinding the control arm edge or using sideways shock extensions to get clearance.

Even if you get a clear path of travel you may get slight rubbing on hard corners due to the control arms flexing. The inner bushing in particular has voids and flexes quite a lot. I found replacing both with fixed poly inner and outer control arm bushings really tighten things up and well as helping camber issues.
 

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Discussion Starter #3
Perfect... I've been playing with so many numbers, that I wasn't sure if I was even thinking straight anymore! Thanks for the reassurance!!

Few questions...

- Even though the bolt pattern is different for GTO's and other GM's--I gather that the actual stud threads are the same (pitch, etc)?
- Did you just reuse the stock lug nuts?
- What types of bushings did you go with? I saw a few different types out there...

Lastly, can you post a few different angled pics of your widened wheels? I've never actually seen a pic of one!
 

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You need the ARP Camaro/Corvette studs as they not only have the correct pitch (12 x 1.5) but also the knurl size that holds them in. Others will not work in the rear. They are ARP-100-7708 and about $25 for both wheels. They are longer than stock (the rear stock ones are shorter then the fronts to start with) and I cut a little off. I hated the stock plastic covers so I got Gorilla Nuts "tuner" black, closed end nuts. I used the old nuts to tighten and draw the new studs in.

I used Super Pro bushings for the control arms but Lovells or Energy work just as well. I'll have to do some searching for pictures but I'll try to find some.
 
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