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Pontiac Fanboy
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1,021 Posts
Discussion Starter #1 (Edited)
Nothing I've done is new, I just read what others have said and applied it to my car. Folks like flink, Stoopalani, REBinc, Miker (even him), and many others have my thanks for their posts here on LS1GTO.

I look forward to other GTO owners copying, adapting, or improving on what I've done. Currently, I HAVE NOT installed my offset strut mounts. I have 275 width tires on identical wheels with maximum front negative camber. An initial hard test drive on the street resulted in very minor rubbing on the outer tread blocks of the passenger-side rear tire. I expect more rolling of the passenger-side rear fender will clear this up easily.

I do not believe my current setup is ready for autocross or the track. Slamming on the brakes with the wheels turned will probably eat into a tire. Right now, I'd say this works on the street, but offset mounts will be needed for decent camber up front and ideal fender to tire clearance.


Necessary Modifications
Coilovers
Rolled Fenders
Appropriate Wheels and Tires
Hub Rings
Negative Front Camber
Wheel Spacers (for CTS-V Brakes)

Specifications
Suspension: Pedders XA Supercar Coilovers
Common knowledge is that these are private label BC Racing coilovers with different default spring offerings and allegedly customized valving for Pedders. The strut body dimensions are likely identical and the only clearance consideration is where the spring collars are located based on your ride height.

Suspension: Whiteline Poly Strut Mounts
Nothing special here. I thought the test fit would show my Whiteline Offset Strut Mounts would be required, but the tire clears the coilover body in the stock location.

Wheels: Apex ARC-8
18x9" ET42 wheels that Apex normally sells. These are made for BMWs so hub rings (69.5 to 72.62mm) are a good idea. I had an old set laying around that I cleaned up and they work perfectly. Hub rings are all over Amazon and Ebay.

Tires: Continental ExtremeContact Sport
275/35ZR18 have a lot of overlap with the 18x9 wheels. I would guess these "run big" as people like to say. I've been a fan of Continental's bang for the buck for a while and am happy these fit. I was worried I should have gone with a 265, but these fat 275s actually fit.

Wheel Spacers: Motorsport-Tech
6mm spacers were necessary to clear my 4 piston CTS-V FRONT brakes. THAT SAID, I've read that 5mm should clear, but I already had 6mm from a previous setup. Overall, I was able to downsize from the 12mm spacers that were necessary for my G8 wheels to clear the V brakes.
On the rear, I was able to remove the 6mm spacers and only run the hub rings.

Fender Rolling
Front and rear my fenders were rolled when I got the car due to the aftermarket wheels that were originally on there. More recently, after an autocross hiccup, I've rolled the front fenders as flat as I could get them. In the rear, I worked them the best I could. I used the standard knock-off fender roller that is all over Amazon or Ebay that costs around $60. There is no need to buy the brand-name Made-In-China roller for over $100 when the no-name is the same tool.

Alignment
Out back, it's been a while since it was on an alignment rack. /shrug
Up front, the knuckles are pushed in as far as they can go into the strut clevis. Offset mounts will restore a margin of error and adjustability that is likely needed for track driving.


I hope this helps someone else out. Please let me know if anyone has questions.


Pictures
 

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Pontiac Fanboy
Joined
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1,021 Posts
Discussion Starter #2 (Edited)
More pictures.

Car is a mess, daily driver grade with 160k+ miles and no garage.
New Headlight Armor is waiting to go on...
 

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Driven from ɹǝpun uʍop
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594 Posts
nice work
 

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Pontiac Fanboy
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1,021 Posts
Discussion Starter #6 (Edited)
Guessing without the spacer up front youd rub the coilover? Clearance looks tight at least. Nice work glynn.
Probably, but without the spacer the wheel definitely contacts the brake caliper.

With OEM brakes, a spacer would not be needed at this offset to clear the caliper. A 255 or 265 tire may even clear the coilovers at that point (becuz maths).
 

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Chickun maka lousy houspet
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372 Posts
OMG! THIS IS EXACTLY the post I needed to read!!!

I'm putting CTS-V rims on my '06. I had them narrowed to fit the standard rims size, but I wanted to go bigger than the 235's I was running. Great post and I'll be trying some of these tips!
 

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Pontiac Fanboy
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1,021 Posts
Discussion Starter #8
Update:
I've put about 600 miles on the car since the install. Most of that was my commute to work, but also some rough suburb roads and back roads in the hills of northern Baltimoron-land.
Front tires still don't rub.
As for the rear, I haven't been able to get to that fender yet but it's still just a gentle rub on the passenger rear tire.

Battled the common steering wheel shake, but finally fixed it with a few cycles of indexing the front wheels and pedantic torquing of lug nuts.

I have noticed the front end grip is excellent, but the rear has felt more loose in the turns. This was after an at home front toe adjustment using plates up to about 1/8" toe in. Adjusting the front sway bar had dialed most of that out. Previously, my Hotchkis bars were 2-front, 2-rear. Now they're 3-front, 2-rear and it's more stable at high speed. Honestly, it feels great now.
 

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wHaT a LoVeLy DaY!
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935 Posts
Now we new to get you some re71rs and some arc 8 wheels ! :-D


Sent from my Modem using V92 Technology
 

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Pontiac Fanboy
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1,021 Posts
Discussion Starter #10
Another update since this was bumped; I've adjusted things a bit more and the GTO is fantastic on the back roads.
Adjusting the rear sway bar to 3 out of 4 stiff and setting the cold tire pressures to 35 front, 32 rear did the trick. Swaybar setting even jives with that old High Performance Pontiac article Kollar was a part of. :)

I'm very happy with the Continentals on the street. Lots of grip and the sidewalls don't feel mushy when they're warmed up like my old Conti DW tires did. I don't know if they're better than the old Conti DW on the track and I won't have time to find out until next year, unfortunately.

All this work improved things a ton. I'm really loving the GTO setup like this.
 
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