Topic: Solstice Performance Book or Don Knowles T2 - What wheel and tire size?

[kennysabarese]

I've been looking through the Solstice Performance book a lot as you can tell... The book references 19" wheels that are used, but I don't see anymore info on specs of the wheels and tires.

There is an autox section but that is not how they prep the T2 racecar.

Does anyone know the wheel and tire specs? and the types that were used in the T2 cars?

[Graywolf]

Hi kenny, The pontiac Solstice performance book can be ordered at any Gm dealer for $18.95 part #88958697 isbn#0-9790602-1-4      The wheel size 18x8 oz ultraleggra, tire hoosier 295/30zr18 a {autocross]  Each tire and wheel is 10lbs lighter than the Gm chromed wheel. Tire rack states this tire is to big for the rim 1.5 inches wider than stock.  Well I did what Gm did and it works great.  This set up works great on road racing courses/hi speed autocross/time attack.  Drive fast,drive safe  Graywolf

[snaponbob]

In looking through the book, on page 16 there is reference to 18" tires. On page 94 there is ONE reference to 19" wheels. Either the page 94 reference was a mis-print or they were using a 19" wheel to make the math on page 95 work out. I am betting on a mis-print. There is ZERO benefit to 19's for racing. Actually all specs for 19" create negatives in competition. As for 295 A6s "fitting" on an 18x8 wheel, ONLY Hoosiers will do this due to their soft carcass construction. AAMF, I have 315s on 18x9s. NEITHER set up is optimum, but in Stock class only 18x8s are legal, so the A6 295s are a must in A/S and 285s for C/S. Some have had luck with 245 V710s in C/S, but that is rare.

[kennysabarese]

Wolf I do have the book and that is what started the confusion

The only reference to 18" I saw was in the autocross section, which is what Bob is pointing out, not the actual racecar build.

Actually I just got the book open and I see that in the alignment section there are two different wheels in the photos!

On page 95 they are measuring vertically and the measurement is 19 inches. And they refer to that 19 many times. But that may not be the wheel size.

Maybe I'll have to call Phoenix to find out.

I just want to know what setup they have to determine if they used a larger contact patch then stock. This will help me make my tire choice.

[Graywolf]

Well they are measuring from the outer ring of the wheel I just went out and measured my 18x8 oz ultraleggra race wheel and they measured 19 3/8ths inches and trust me they work great I have 8 wheels and race tires mounted ready for action. Graywolf

[Graywolf]

 you will have a larger contact patch The tires are a 1 1/2 inches wider than stock Follow the book set your camber etc. like they say I have seen no increase or abnormal tire wear. Expect your times to improve Remember tire rack will say you can't put those tires on that rim  GM did and so did I with great results Graywolf

[kennysabarese]

I'm not getting slicks. Planning on dunlop direzza star specs for track and street. So I dunno what tire size to choose. I was even thinking of getting 17" wheels to save weight, and the tires are a bit cheaper.

Also what are those other wheels in the book, they look like normal solstice 5 spoke wheels painted black.

[Graywolf]

Saving money is great, but wasting money%^#^#%^. Make sure you research the tires, Tire diameter must be the same or ratio/speedo etc will be different which could make your car slower.  Gm placed alot of research in this, I suggest being patient/save money and buy wisely Gray Wolf

[kennysabarese]

Yes I am not planning on changing diameter, Discount Tire Direct has 17" packages that will work for our cars.

But I'm pretty sure the racing guys have a different contact patch then stock, maybe even a diameter. That's what I'm trying to find out. I couldn't find even in the book the size Hoosiers they put on it. Just what is in the AutoX section. Maybe it's the same

[kennysabarese]

Actually on the page 10 in the book there is a caption that says:

"The T2 class allows some more changes to the production package in the form of bigger wheels and tires, and aftermarket radiator and diff cooler"

So maybe 19's or maybe just 18x9

[snaponbob]

Actually on the page 10 in the book there is a caption that says:

"The T2 class allows some more changes to the production package in the form of bigger wheels and tires, and aftermarket radiator and diff cooler"

So maybe 19's or maybe just 18x9

SCCA allowed the T2 GXP's to run WIDER rims than stock. Diameters in T2 must be stock. These "adjustments" are how SCCA fools around with the "competitiveness" of cars in the "T" classes.

[kennysabarese]

Sounds good. So if they are on 18x9 do you think they run the same size Hoosiers as you?

[snaponbob]

Sounds good. So if they are on 18x9 do you think they run the same size Hoosiers as you?

I am pretty sure that they ran 295/30X18 A6s. Although a 295 WILL mount up well on 18x8's, the 9" width will help with side wall support and thus handle better. I ran into the similar situation with my 315's on 18x9's (could budget CCW 18x11's for the 09 season), where they WILL mount up okay, but the 11's allow so much more sidewall support that than can be run at lower pressures - two key factors (low pressures require better support) in better grip on Solo pads.

[kennysabarese]

Cool. Slowly putting the pieces of the puzzle together in my dumb brain.

Yeah usually on racecars you see the wheel being wider than the tire and the tire angles in. Though that's not good for protecting your wheels from curbs!

So I guess the question is would a 295/30x18 in another tire be good for street driving.

[snaponbob]

Cool. Slowly putting the pieces of the puzzle together in my dumb brain.

Yeah usually on racecars you see the wheel being wider than the tire and the tire angles in. Though that's not good for protecting your wheels from curbs!

So I guess the question is would a 295/30x18 in another tire be good for street driving.

If you are talking about 295s on 18x8's if they are not Hoosiers - than absolutely NOT !!!!!!!!!!!!!!!!!!!! If you have 18x9 wheels than 285s might be the limit. Keep in mind that 245s are recommended fitment on 8's, 295s are 1.6" wider than 245s, so that really spells 285s on 9's for STREET.

[kennysabarese]

I'm getting Dunlop Direzza Star Spec. Definitely not hoosiers

[Ben L]

Then, practically speaking, 275s  on a 9 inch on the rear are your limit.  They are pretty damned wide.  Take a look at the photos of my set up.

[kennysabarese]

Ok good news. I just called Phoenix Performance, the guys who built Don's car.

They used CCW 18x9.5 wheels with Hoosier 275/35 tires

That's a really wide wheel. They had to use spacers in the back.

He said if I wanted more details to call John @ CCW

I asked what he recommends for street tires, and he didn't have an answer. So I might call CCW and ask them.

[Ben L]

They are good guys down at CCW. 

They built my FFR coupe wheels, which are big, indeed.  11x17 up front, and 12x17 in the rear, with custom backsets.  They called twice before building the wheels to get additional measurements.

Don't know that they will have tire recommendations.  In fact, they asked me what tires I wanted to run on the wheels they built for me.

They will supply the tires you spec., and touchless mount, balance and deliver them on your spanky new rims for the Tire Rack price.

Best deal in serious custom three piece race wheels on the planet.

[kennysabarese]

Those are massive!

The only problem with CCW wheels is the are crazy $$$$$$

Maybe the OZ 18x9 are the best bet. Also the SSR's are under 200 a pop now on tire rack