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Discussion Starter #1
It would be great if we could get some experienced track guys and gals to share their wheel and tire setup (along with chassis settings), in order to learn from each other on what works well on the SS.
My experience with the staggered wheel/tire width setup has been very good. I see some places on this board where people claim they need a square setup to increase front grip. My experience is I can't use any more front grip - the car is neutral now and with more front grip I will be managing oversteer too much and it will be slower. I also understand that my tow hitch influences my cars dynamics, pushing it towards decreased understeer, or increased oversteer. Of course I could re-tune the suspension to compensate but that's not what I'm trying to discuss here.


So let's keep this discussion to firsthand experience with people who have been on track with their SS, what is your chassis setup, your wheel and tire, and how did your SS handle?





I'll start:
2014 SS, no roof, stock suspension, Holden tow hitch (an extra 50+ lbs on the back of the car).
Camber: -2.25* Front, -1.5* Rear
Toe: 0 Front and Rear
Front whl/tire: Apex 19x9" ET35 with 245/40/19 Michelin PSS
Rear whl/tire: Apex 19x9.5" ET43 with 265/35/19 Michelin PSS
Cold tire pressure: 33 lbs/in Front and Rear
Handling Balance on corners >60mph:
Corner entry: Neutral (allowed mild trail braking). Mid-Corner: Neutral (front tucks in with small lift of accelerator). Corner Exit: Mild Oversteer (power induced)
Stability while braking at >1g: Excellent




Jeremy
 

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Discussion Starter #2
As an experiment, I put a square tire/wheel setup on my car and ran the road course at NCM Motorsports Park for 2 track days. This course has a mix of low and high speed corners, and a good amount of elevation change. We ran the "West" course, which is 2 miles long, and my lap times were 1:35-1:36.

My alignment specs were the same as my first post above.

The only car changes I made compared to my first post above were:
I removed my Holden trailer hitch
Changed front wheels to: Enkei Ranjin 19x9.5 ET35
Changed tires (all 4): Bridgestone Potenza RE-71R, 265/35/19

As expected, the square setup exhibited more oversteer than the staggered setup. Tire temps also showed the rear tires much hotter than the front tires. With the square setup, I was forced to apply power later in the corner, and the car would tolerate less trail braking than the staggered setup. Also, esses (or quick transitions) required very, very gentle steering and throttle so as to not invoke oversteer (which ultimately made the car slower through the section).

After the first day, I added a 1.5" tall wicker bill to the rear spoiler. The wicker bill reduced the rear aero lift and changed the cars aero balance so that the rear end stuck better in higher speed corners, less oversteer (slightly reduced but not eliminated), and my lap times immediately dropped 0.5 seconds. I estimate that a change back to a staggered tire/wheel setup would have reduced lap times some more.

There is a reason that HSV uses a staggered setup in their special vehicles, it works better on a road course IMO.

Jeremy
 

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Thanks for posting this comparison. My stock front tires are hammered after just three days on track. Badly stepped outer tread and some chunking along the circumferential ridges. Still 6-7/32nds left but tread blocks are pretty worked. Rear tires still look great. They only have 3-4K of highway miles on them. I stuck with stock 36psi front & rear.

I'm only running .8* camber in front, slightly less in back (will have to look at the printout again).

I would get a mild push on turn in without trail braking, but felt pretty bananced mid corner. Very easy to steer with throttle on the way out.

Maybe I'll mess with front camber before going to wider tires in front. I think I can get one more track weekend out of these front tires. May not make it out until November, which likely means a wet track, so may not be a direct comparison.

I'll probably have to spring for those white line offset strut mounts or use wheel spacers to get much more camber with stock wheels. Tires were awfully close to the strut with my winter tires on (DWS06 in 245/40).
 

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Discussion Starter #4
Thanks for posting this comparison. My stock front tires are hammered after just three days on track. Badly stepped outer tread and some chunking along the circumferential ridges. Still 6-7/32nds left but tread blocks are pretty worked. Rear tires still look great. They only have 3-4K of highway miles on them. I stuck with stock 36psi front & rear.

I'm only running .8* camber in front, slightly less in back (will have to look at the printout again).

I would get a mild push on turn in without trail braking, but felt pretty bananced mid corner. Very easy to steer with throttle on the way out.

Maybe I'll mess with front camber before going to wider tires in front. I think I can get one more track weekend out of these front tires. May not make it out until November, which likely means a wet track, so may not be a direct comparison.

I'll probably have to spring for those white line offset strut mounts or use wheel spacers to get much more camber with stock wheels. Tires were awfully close to the strut with my winter tires on (DWS06 in 245/40).

Thanks for sharing!


I'm nearly max'd out with camber too, my tire is 6mm from the strut, which is about as low as I will go.


A little camber will help slightly with the outside tire wear, you will have to go -3+ to get even wear. This is a picture of a front Bridgestone RE71R with only 2 (20 minute) sessions on it. -2.25* camber and 41psi hot. (these tires grip better at lower pressures but also have more edge wear, so its a balance)


The Bridgestone RE71R have great grip but wear too quickly to be cost effective.


I think the Whiteline upper mount will get you an additional -.5* camber.
 

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Thanks for sharing!


I'm nearly max'd out with camber too, my tire is 6mm from the strut, which is about as low as I will go.


A little camber will help slightly with the outside tire wear, you will have to go -3+ to get even wear. This is a picture of a front Bridgestone RE71R with only 2 (20 minute) sessions on it. -2.25* camber and 41psi hot. (these tires grip better at lower pressures but also have more edge wear, so its a balance)


The Bridgestone RE71R have great grip but wear too quickly to be cost effective.


I think the Whiteline upper mount will get you an additional -.5* camber.
Yeah, 0.5* is what whiteline advertises. Will probably need both the strut mounts and spacers to get over 2*. I'd prefer not to run spacers, but they're cheap enough that I can take them to the shop, see what the limit is with bushings only, and throw the spacers on if needed.

Really torn on tires; the re050 actually did okay for me, but pricey for such a short life. 200tw replacements in the correct sizes and weight ratings don't seem to exist. Probably would wear too fast on a 2 ton car anyhow. I have 6 more months to research...

I don't want to go too far into track territory with this car. It's my daily and I have another car for track days that is much cheaper to run with 195/50r15 tires and $50 brake pads that each last a dozen or more track days. The SS will probably see a couple track days per year though, particularly if I decide to road trip to new tracks since it's a far more comfortable road car.

I hope more folks jump in on this thread to contribute. Would love to see what's working for other SS owners.
 

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Very interested in further results.

I do have a question though, why are you running a skinnier tire than stock in the rear?
 

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I wouldn't change from the square setup. I would change the alignment if you are getting corner exit oversteer. Try 1/8th total toe in rear.
 

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As an experiment, I put a square tire/wheel setup on my car and ran the road course at NCM Motorsports Park for 2 track days. This course has a mix of low and high speed corners, and a good amount of elevation change. We ran the "West" course, which is 2 miles long, and my lap times were 1:35-1:36...
Hello Jeremy. Was the track strict on noise violators? I'm going there in a few weeks and have debated replacing my Solo exhaust with the factory setup. I have cats, but no resonators. I think there's a 105db limit, so I'd hate to get booted for excessive noise.
 

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Discussion Starter #9 (Edited)
I wouldn't change from the square setup. I would change the alignment if you are getting corner exit oversteer. Try 1/8th total toe in rear.

Its not corner exit oversteer, its oversteer all over, read post #2.


Would you share your track setup and experiences?

to clarify, my experience may only apply to the 2014 models, as the springs, rear bar, and shocks were all changed for 2015+
 

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Its not corner exit oversteer, its oversteer all over, read post #2.


Would you share your track setup and experiences?

to clarify, my experience may only apply to the 2014 models, as the springs, rear bar, and shocks were all changed for 2015+
Front Wheels:
Size: 19x9.5
Offset: et33
Weight: 23lbs

Rear Wheels:
Size: 19x9.5
Offset: et33
Weight: 23lbs

Rear Tires:
Make: Bridgestone PS04 Pole Position
Size: 275/35/19

Suspension: Factory
Ride height:
Front: Factory
Rear: Factory

Alignment:
Front Camber: -1.5
Rear Camber: -1.0
Toe:0 F/R

Modifications to body:
Front Fenders: Factory
Rear Fenders: Factory

I don't track my SS, but I've set up numerous other cars over the years. In all that time, I've found I was faster switching to wider tires and adjusting my alignment, damper settings, spring rates, or driving to accommodate the extra grip.

I would still add a little rear toe-in.
 

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Discussion Starter #11
I don't track my SS, but I've set up numerous other cars over the years. In all that time, I've found I was faster switching to wider tires and adjusting my alignment, damper settings, spring rates, or driving to accommodate the extra grip.

I would still add a little rear toe-in.

Thanks for contributing,


I agree that I'll take all the front grip I can get, and then tune the rest of the car, or my driving, to compensate for the extra front grip. Front grip is the hardest to get in front-engined cars.


Where I think we disagree, and this is based on my experience with the SS so far, is that I believe the car will be faster with a 9.5" front wheel and 10" rear wheel (note I don't have this setup but would like to try it) than 9.5" all around.


Rationale: The 19x9.5" is a reasonable size wheel to have on the front, no clearance issues. I gained front grip going from a 9.0" front wheel to a 9.5" front wheel, so I would NOT want to put on anything less than a 9.5" wide wheel on the front. I WOULD argue that a 10" wide rear wheel (combined with the 9.5" wide front) will increase rear traction and the car will handle better, and be faster, than the 9.5" square setup I currently have. The handling balance should be better, more like the 9.0" front / 9.5" rear setup I had initially (post #1).


I also understand your idea of adding some rear toe in, and I will try it (maybe next weekend). But, rear toe could also be a Band-Aid, testing will tell.


Jeremy
 

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I ran my first HPDE last Saturday at Thunderhill, with the stock RE050's and wheels but the tires were almost done so grip was minimal at best. My alignment: -1.5 front camber, -1.2 rear camber, 0 toe all around, and I have the Caster bolts installed so another .5 front caster:


I've been doing everything with this car this year... Canyon carving, Autocross (almost a full season), HPDE, and even went to a drag strip this last week. I have a custom set of wheels coming for "stock" class Autocross, but I just replaced my re060's with 255/35/19, 275/35/19 Firehawk Indy 500's. They are a much better tire than stock right out of the gate with almost zero tendency to snap oversteer when stabbing the throttle and a much more progressive feel. At $600 for the set, I do recommend them for anyone who wants to do light track driving and doesn't care about super fast lap times.

If I were to do a set of wheels just for HPDE, and I am actually contemplating this as my 3rd set of wheels/tires, I would go with 265's or 275's up front with a 9.5" wheel and around +35 offset, and between 285 and 305's in the rear depending on cost with a ~10.5" wheel with a about a +50 offset to tuck the wheel without rubbing. I think the staggered setup is probably quicker on the track especially if you go with R-compounds. A good idea is to look at what Gen5 camaros are doing for track tires and go from there.
 

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...If I were to do a set of wheels just for HPDE, and I am actually contemplating this as my 3rd set of wheels/tires, I would go with 265's or 275's up front with a 9.5" wheel and around +35 offset, and between 285 and 305's in the rear depending on cost with a ~10.5" wheel with a about a +50 offset to tuck the wheel without rubbing. I think the staggered setup is probably quicker on the track especially if you go with R-compounds. A good idea is to look at what Gen5 camaros are doing for track tires and go from there.
This is quite close to what I settled on. Toyo R888R 265 front 285 rear. Front camber -1.7 rear camber -1.2. The car neural steers quite well and wears the tires very consistently for a heavy sedan.
 
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