Red5

When I'm on slicks I run koni double adjustable shocks and 17x11 running 315's up front with 17x12 running 335's in the rear. And it works well.


Now I want to run a street tire class. Specifically the CAM (Classic American Muscle) for teh SCCA as well as an LS Fest.

The new rules state you have to have a completely street legal, licensed and insured car on 200 UTG tires and above.

The current tire to run is the BFG Rival. It is a 200 UTG tire and beats pretty much everything else out there. (But they tent to come apart when pushed too hard)

I would buy rivals and call it a day but they don't make them in a 315/35/17.


So now I'm wondering about running a square set up vs a staggered set up. The Corvette (Mine is a 98) comes staggered. THat is to say that we have 17x6.5 up front on 245's and 18x9.5 on the rear on 275's.

Are these cars designed to function better on a staggered set up?

autoxer6

For autocross, my experience is that maximizing width is more important than balance. I would go to 18" up front to get a wider size Rival, and then the largest rear that fits.

An unbalanced car may be harder to drive, and maybe less fun, but its always been faster for me. You may just have to turn the car with the pedals more.

LateBreak

It's a shame that Dunlop discontinued the Direzza Z1, they were a great tire. The Direzza ZII's aren't as good as the Z1 from most reports, but they're still a great tire and a solid alternative to the Rival without the reported delamination issues.

Dunlop's tires run to run wide for their size, so you may be able to find a suitable size even if the sidewall reads something other than you're used to. I prefer to shop the 'specs' tab on tirerack as it gives you all of the information in an easier reading format.

troyguitar

I don't know about autox but many road course time trial guys run non-staggered setups. In NASA the most common I have seen is 275's all around, it works fine. Some guys even ran 245's all around and went fast.

hklvette

In my experience and observation, you won't need as much camber to make the tires work. Depending on your spring & bar choices, around two degrees at both ends is enough.

Matt Feeney

My plan so far is run the Dunlop Z2's in this years Scca B street class, the tire rack test showed the z2's heat up faster and are quicker than the z1's but might overheat on track or with 2 drivers. Tough call though because BFG pays contingency...

Red5

I've always thought that wider is better. But for me to re-purchase another set of CCW's just to have 18's seriously effects the amount of fuel I can burn in my boat this summer. And this is a ll for fun. No offense guys but every now and then I get some real talent on board.



Even if they run wide for their size the largest they make in the D II's is a 255/17. This would only work if I raced with my stock ZO6 (c5) wheels.

Not sure if we are comparing apples to oranges here or not. For me I need some meat to grab traction when I am rolling out of a turn. From my limited experience it appears that (the way I) autocross is much more aggressive than the way that most people do track events.
Limiting myself to 200 UTG or higher is punishment enough. But I can see how road race set ups may reward thinner tires.



BFG neds to offer the 315/35/17's

OR

Kuhmo needs to give their XS a 200 UTG rating.

69autoXr

I'd probably start with C5Z rear wheels all the way around, then you'd have tire size options to play with in the Rival (275, 295, 315). You could stagger or go square.

Ramo7769

That's the dilemma with street tires is that they just don't make good ones (200 UTQG+) in 17" anymore. I had a similar dilemma as you. That's why I decided to run Z06 rears, 18x10.5s square on my FRC. I'll be running 285/30-18 Dunlop Direzza ZIIs. However, I have stock power and will be running STU (285 is the largest tire allowed in the class). How much power do you have?

I also plan to run track days and I know from personal experience that the ZIIs do very well with heat lap after lap. I run a Chevy S10 in the 24 Hours of Lemons with ZIIs and they did great through track days and endurance races and I'm going to be buying a third set of them in spring. I have concerns about Rivals holding up to hot lapping.

I haven't heard/seen any reports that the ZIIs are inferior to the ZIs in any way. I've only seen the opposite, in fact. Here is one example: http://www.tirerack.com/tires/tests/...y.jsp?ttid=168

Matt Feeney

STU looks so much fun, just putting a good seat in the car will be amazing, thats next years plan for me as well.

Red5

Racing a vette on 200 and above can be a bit of a chore. But look at the bright side, you are much less likely to break anything. The lack of traction means that the bottle neck happens at the tires instead of transmissions etc. And you get to look like a ricer kid doing some sideways drifting action.

Course you will be doing well to keep up with a Miata in CS that runs slicks. But what the heck, it's all about having fun. And that Miata will have to leave the parking lot sooner or later.

Guess I may look into buying a pair of rear ZO6 wheels. I just hate all that additional weight as compared to my CCW's. Rotational mass matters.

Ramo7769

Z06 rear wheels aren't that heavy at 21lbs a piece. Sure, CCWs might have an edge in weight and more sizes available of course. Getting much lighter than 21 lbs has diminishing returns since tires have far more rotational inertia than the wheels at that point.

troyguitar

How are your rules set up? In my class I get to run more power or less weight if I run the skinnier tires, that's why we do it (that and they're cheaper and more available).

Ideal setup is going to change a lot depending on your rule set.

Ramo7769

The class being discussed is CAM in SCCA Solo and is open in terms of tire size. The only restriction is DOT approved 200 UTQG treadwear limit.

troyguitar

Yikes, open sucks. Sounds like if you want to win you need to buy $$ 18x12 wheels and run 335 Rivals all the way around. I'd skip the 18x10.5's

69autoXr

I've seen it reported on this forum that an 18x12 CCW weighs about 22lbs, with a 17x11 about a pound or two less. The 18x10.5 C5Z wheel is right there as well. The BFG Rivals probably add more weight compared to a 315 A6, a google search comes up with 29lbs for a 315-18 Rival vs. 24lbs for a 315/30-18 A6.

Red5

I agree, now for the money part.





But the A6 is not 200 UTG or above.

theseal

For what it's worth c5's hate it when you push the fronts out wide for autocross. Track the benefits are worth it.

Unfortunately for street tire classes the tire make itself is critical. A rival will be solid. Most of the best 200 track tires don't come in better sizes. Wish they'd make a 345 or 355 rival though.

Bottom line for that class you are probably looking at 335 all the way around.

Ramo7769

Would you mind explaining your thoughts on that a bit further? Have you run square for autocross and track? I would think you would want the car more loose, with more front grip, for autocross than for the track.

I have seen Super Stock C5 Z06s running 315 A6s square with a big front bar successfully in SCCA Solo Nationals.

69autoXr

Unfortunately you missed the point, but it sounds like you've already decided which direction you're going to go, so I'll move on.