yow

I have some 345s I want to run on the rear of my c5z (TT & HPDE). Right now I run 315s square on c5z 18x10.5's. What wheels should I run in the rear if I want to go up to 345s? I've searched and I know the easy answer is that I'll have to tub or get flared fenders. If I wanted flared fenders and no rub on the inner fender, I'm trying to determine what offset and backspacing I'll need.

Anyone run a 345 rear / 315 front setup on a c5z that may want to share info? I'm not opposed to buying fenders and a pair (or set) of rims. I just don't want to shell out the money and have to hope they fit when they arrive. Share the wealth of knowledge to a little guy like me?

Thank you so much!

brkntrxn

What car handling symptom are you attempting to resolve by going to 345s in the rear with 315s in the front?

yow

I've been using A7 315s square. I just came into a handful of 345s and I wanted to try them. I would expect them to be just a bit faster, assuming I can get on the gas harder at exit. It's neutrally balanced, but I still have power oversteer at exit of corners where the aero doesn't do much.

What are your thoughts? I'd hate for the 345s to go to waste.

brkntrxn

I agree you can get on the gas sooner on corner apex and exit, but with that much increased mechanical grip in the rear and nothing added to the front, you will create a push with the front end on corner entry and possible on corner exit.

If you are doing it to play around, no worries. If you were doing it to expect to go faster, I would expect differently. But it all depends on driving style and what works best for your right foot. I know for me and my car and my driving style, I would like more rear mechanical grip on corner exit, but I am very unwilling to give up a balanced setup.

brkntrxn

Let us know your results after trying them. I know a couple of people running 335s square and some running 345s in the rear with 335s in the front.

I also know of a couple of NASA TT1 and TTU cars running a 345/315 setup with aero. Although they have 600+hp, they aren't any faster than me in the corners and our lap times are almost identical. I have asked them to increase front grip OR drop hp in order to decrease rear tire width for more balance... but they like that dyno number and big power on the straights.


-Kevin

yow

I've got some 335s too. I wonder what it would take to run 345/335 setup? Talk about some meat! I need someone to tell me about wheel options and fender issues to sort out. I'm willing to try it and report back. Given that a 315 square setup is so good, do you think a 335 square or 345/335 setup would be even better? Seems like the trade-off is weight for a few mm of contact patch and track width.

My 315 square is pretty balanced, so I see what you're saying about possible push. I've got good aero up front. Last year I had the DIY abs splitter we're all too familiar with. Now it's aluminum, radiator laid forward, hood vents, etc. If it does push, maybe adjust with swaybars?

yow

brkntrxn

335/345 would be a great mechanical setup.

savage

if your 345's are hoosier A7's 345/35/18's i will trade you a pair of A7's 335/30/18's in very good shape( used once)from my c7 z51 that are too short to run on my new car. we both pay shipping to each other- thanks

yow

I've got quite a few race take-offs so I'm not really in need of tire swapping at the moment. If anything, I need to sell some tires. I listed a few in the classifieds, although I did not list any of the 315, 335, 345 A7s. I'm hoping to run some combinations to see what works best.

J.R.

I think you will find that the 335/345 combination will work quite well as long as you have the car set up properly. This is especially true if racing NASA as the benefit for DOT vs. slicks (.5 power to weight penalty).
If I was to build another C5 under current NASA rules this would be the trick combo.
I have seen data from a couple of C5's running this combo (one being ST1 and other being ST3) and I think the A7 is the best choice at present as they tend to perform better later in the event than the previous A6's. This is especially true if you get a full course yellow where you get the A7 to cool down part way throughout he event.
For TT's I don't think you can beat this combo as I bet the A7 is just as fast as slicks.

yow

Do you know anyone I can reach out to with that setup? I have questions about wheels and fenders.

J.R.

sending you a PM