seanmcr6

So I'm on the fence about the wheel/tire combo I want for the track setup for my C4S. (which currently has stock suspension)

I've read many posts on her in the racing and 996 pages about going to 12 inch in the rear (staying with 18s) and moving to 9 inches up front.

So I was wondering if this could/would produce any issues with my 04's PSM? running 245s in the front and 315s in the rear?

Since I'm staying at 18s and pretty darn close to stock circumference, I would assume my bigger problem would be the stock suspension...yes?

Anyone running big fat R6s for track days on wide rims that can add some feedback?

cheers
sean

brad@tirerack.com

As long as you stay inside of a few percent difference in OD, you'll be fine with 245/315. It may take a bit more camber than stock up front to keep them from rubbing. Sway bars are a good thing to add as well.

996_C4S

I also have an '03 C4S and I run Hoosier R6's at the track on the stock turbo twist wheels. Rear: P295/30Z R18. Front: P225/40Z R18. My ride height is lower due to H&R spring kit. I've had no clearance issues at all. Performance-wise, this setup has been just fantastic for me the past few seasons. The Hoosiers last only about 5 days but oh, what a 5 days you'll have.

jumper5836

You can run the same as the the 996 GT2 on 12's
Just keep to recommended ratio and on 12's your could get away with more then 315, though on a C4S you don't any more. 295 is great.

ivangene

315 OMG !!

I am on 245's!! (rear)
Hate it when I pass you guys and those heavy tires - would you mind keeping the rubber off my windshield

jordanturbo

You can definitely go bigger, You can change the overall outside diameter as long as the difference in outside diameter between front and back is less than 4% (I believe that is Porsches recommendation)

the OD of a 315/30R18 is 25.44" and the 245/40R18 is 25.71". So the difference is less than 1%. The 315/30R18 will fit rim widths between 11 and 12" so they should fit on your factory turbo twists. The actual section width is only going up 0.8" so with stock suspension you should have no clearance issues. If you add spacers or drop it with lowering springs, you may have issues with clearance a little bit, but before you go and buy crazy suspension I would get a custom alignment, You would be surprised at how much adjustability the factory chasis components have

PS: where are you planning on tracking it? I know Fort Mac doesnt have a road course ha ha. Planning on coming down and trying Castrol's new course? I have taken my C4s to Namao and Greisbach for auto-x and strato, but found my civic was more suitable for that style of course. Race City was fun with the P-car, but its closed now. I went and saw the Drift West demo on the new Castrol road course and it looks really nice, but havent had a chance to drive any of my vehicles there.

jyoteen

I run 245/315; adjustable suspension

Hardback

I run 315 and 235 NT-01 on my hollow spokes. I have a lot of camber up front -2.8 & -2.3 rear. No rubbing front or rear. Car is lowered the maximum up front with 20mm rake on H&R coilovers.

Sean, the purple crack will no doubt give you tons of grip but with stock suspension & sways your car's body will lean and dive a lot. Any plans to upgrade these items too?

seanmcr6

SoCal is where I plan to track the most...Been there twice and love the tracks. Otherwise, if I ever move back to the center of the universe (ontario) I'll have 5 tracks to pick from.

I thought the stock twist was only 10"? no? I thought it was 18x8 and 18x10? I was planning to buy some new OZ rims from Damon...18x8.5 and 18x12.

Yes, for susupension, I was going to upgrade to GT3 sways and LCAs and upgrade the suspension to either PSS10s or moton. (big difference, I know) That all comes down to $$$.

I played on the track with some Pilot sport cup tires...liked them a lot. Tried a friends car with R6s and it's a different game altogether!! I plan to slowly convert my car to a strict track beast, so every "major" upgrade I do, I want to make it towards that goal. I figure the wheels are a good place to start, then suspension, then brakes, than body, and finally engine.

jrgordonsenior

IMHO you don't need those big tires out back, they'll only create drag add contribute to your understeer issues. The 295's are a good match with 245 fronts assuming your OD's are within parameters. If you were a TT I could see the 315's but they'll just cause more push....

KrazyK

Speaking of tires,,, would you guys change the stagger for street use only? Mine is 225 40 18's / 295 30 18's. I dont want to put anything on that makes the car look goofy on the street. I think the C4S OEM stagger looks good but wondered about a little wider.

jumper5836

Spacers will make the stance wider.

Stock rears are 11", hollow or solid. Only the GT2 was 12"

without a proper race suspension hoosiers are overkill. PS cups are good enough with the standard 225/295 combo. It's not a turbo there is no more grip needed cause the car is under powered.

Also with the increased grip. Make sure your engine can handle it. X51 pan and add probably need extra oil pickups as well as do a low temp thermostat. Even then good luck. These engines are crap.

This is interesting reading. Specially if your planning on running tires that increase the g-forces the engine will see.

part 4 and part 5
http://www.hartech.org/buyers.html

btw I am sadly running suffed up even having done the x51 pan and running on tracks that don't have high g corners.

KrazyK

WTF? Did you just say our beloved 3.6's are crap????????

996_C4S

Re: suspension -- I disagree. I first ran Hoosiers w/ stock suspension and then upgraded my springs & lower control arms. They made a huge, huge difference with the stock setup, and they just got better with my improved setup. If you're tracking one of these cars stock, it's just a fact that the first/best improvement to be made is stickier tires, and if you have an extra set of wheels, dedicated track tires are the way to go (there are many options, Hoosiers being a favorite).

Re: add'l G forces -- I've had no issues (knock on wood) in 4 years of tracking my C4S w/ Hoosiers (about 12 days/yr).

jumper5836

That's very little track time and it also depends on the track and lap times being done. Give it time.