ERND IT

Right now I run 315x18's on all four corners - and the car feels/handles very well for me...I am mostly an autocrosser, but do some HPDE's as well.

I'm thinking I will need some new tires for our Roebling Road event in November and thought I would try the 335x18's in the rear.

what, if anything, might adding the larger tire in the rear do for me - besides the obvious, more rubber on the road?

Are any of you running a 315F 335R set up??

Positive? Negative? Could I assume that it might be better for HPDE than autox or vice versa? I have 2 sets of wheels so I could swap as needed...

I did notice from on course photos that the recent SCCA ASP & ASPL national champs seemed to be running a very large rear tire...hmmm....

Any input welcomed !

Aardwolf

For my car I keep the tire size the same so as not to get more understeer. It's also nice to rotate them. When increasing size the amount of contact patch would stay the same but it's shape would change. The biggest gain is the type of tire used, sticky vs less sticky. Also keep an eye on the weight of the tire.

AU N EGL

I think 335s for autox are too wide. Too hard to get heat into and too hard to rotate the rear end on those tight corners.

If you want to turn in quicker, go down on the front size, 275 or 285 and the car will pivot much quicker

Yes it could be better for HPDEs for more high speed corners.

davidfarmer

you've got to realize that the actual contact patch is very similar between two tires of this size. Changing overall diameter changes contact patch much more than width. However, a larger contact patch does help spread out the load, and can increase grip some.

That being said, if your rims are wide enough and your fenders deep enough, there really isn't any reason not to try them. But overall tire design is more important than size, so a Hoosier A in a 305 would still grip better than a Toyo RA1 in a 335.

for the record, I'm running 315x18's all around on my NASA car....good grip, plus I can rotate at will to equilize tire wear on C5Z06 18x10.5 rims

John Shiels

will be trying it soon 315x18 & 335x18 Hoosiers

autoxn

Keep in mind that we use 12.5 inch wide rear wheels. More rubber equals better grip, but only if you get it all to the ground. You aren't going to be able to do this with a small rear wheel.
Hope this helps,
Mike "Junior" Johnson
That ASP guy your were talking about.

RAFTRACER

Any C5 Corvette that has won a national championship in ASP has run a 335 rear tire, for a long, long time.............

Congratulations Mike, well deserved win......Weren't you and Di the only two Corvettes this year to win Nationals ???? Even beat SS and BSP ....Good Job !!!!

autoxn

I do believe that there has only been two C5 corvettes that have one ASP, and they have both been RAFT built rides. Thanks Danny for putting together our "land missle." Everytime I drive this car I love it even more. I've had it for a little over two years now, and it still makes me smile every time I push the "loud pedal."
Mike "Junior" Johnson

ERND IT

thanks for all the replies - you bring up some excellent points.

I DO have a wide wheel - 18x12, so there will not be a fit problem -
and I don't mind if the wheels stick out past the fenders a bit either... although I already run spacers to help reduce rubbing...

I assumed - bigger tire = more rubber on the ground = more grip = potentially faster time...

Aardwolf - didn't consider the weight of the tire in the mix... good point

Tom - I understand rotating the car correctly thru turns, but don't necessarily like the feel of driving a "loose" car - although I am learning to take advantage of situations where a little of that can be used to my advantage.

John - I'd be interested in your comments after you've had a chance to try the 305/335 set up...

David - as for the contact patch and utilizing all possible grip - well that's kinda what I was thinking a 335 would provide-more patch on the ground. I wasn't thinking about tire size/type/brand comparison - as in one being stickier or higher profile than another...

Mike - I thought I saw you running those big tires at the Sanford event you and Diane came to last year to test... at the time you weren't sure if you were going to go with that setup... evidently it works pretty well Many congrats to you and Diane on your wins!!

RAFTRACER

Dude,
I can't take credit for your excellent showing last week at all.....It is nice to be involved with Di, yourself and the Evo school.......

Your win was defineatly a result of your immence preparations and skill ....

RAFT on , my friend.

97C5inSD

I run 315/35/17 front and 335/35/17 rear tires on my car spacers on the front and back they stick out some yeah but the car seems to hold really well and i very seldom have an issue with understeer unless i don't have the right tire inflation. Granted as has been stated it is harder to get the tires warmer on shorter courses to optimize grip but nothing alittle more air pressure dosen't take.

Granted i can see the aspect of being able to rotate tires but of the 2 sets of tires i have gone through with me car if they was the same size rotating woulda made no diffrent they have all weared pretty evenly i have flipped wheels before and thats about it.

John Shiels

Probably run Oct 9th PDA

Bink

Not to hijack -but, is Evo school on for the spring in Cincy?? Anything earlier??

Sorry, Donna


joel

autoxn

We hope to start putting our 2008 schedule together within the next month or so. I'm pretty sure that we'll be back in Cincy in the spring though. We look forward to running in RAFT country every year. Donna was there last year, making black marks all over the lot. Maybe next year we'll make some 335 marks. By the way, we missed ya' in Kansas.
Look forward to seeing you there,
Mike "Junior" Johnson
Evolution Performance Driving School

ERND IT

no problem
thanks for the info - I'll be watching your Evo calendar and will plan to come again - it was one of the best weekends of learning I've ever spent!

RAFTeRACER

More rubber on the road! My car loves 335 rear/315 front. I really liked 335's all the way around, however my P.S. pump did not!

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see5

I run 315s and 335s alternately and if you have the power to oversteer you will like the 335s. The problem is "centering" the rim. I have rubbed away the lower lip of my fender and often rub away the fender liners. No combination of offsets and spacers seems to work if the car is low.

I would run 395s if I thought it would help:

vms4evr

On my 02 Z06 I've tried the following.

Stock setup and tires, a few sets worth. Nitto R2s in 275/305 combo on stock rims. Square setup with 295 Hoosier Rolex slicks on 4 18x10.5 rears. 315/335 Hoosier Rs on CCWs. The CCWs are 18x11 and 18x12.

I thought the 295 square or a 315 square would be nice. You can rotate your wheels around to balance wear. Big cost savings. Problem I had was the oversteer was a bit annoying. Braking is fine.

All the staggered sizes mean you'll buy pairs of tires based on how hard you are wearing the fronts or rears. The 315/335 stagger with the Hoosier Rs is my favorite to date. You can put the power down sooner and harder mid turn. Braking is also improved. More rubber to the pavement. I haven't figured out how to rotate the car on track yet with that setup since the rear end sticks so well. There is a small amount of understeer. This is all on track.

I just tried that setup for an AX last month. 1st time I AX'd the Vette this year. You can't spin the rear tires unless you side step the clutch. Launches are good. No more spinning the tires while you slalom. The tires do stick out on the front and rear. So you need to offset yourself by about an inch more off the cones. If you can actually do that. It took me a couple of runs to stop tripping a cone with the rear tires. Fronts I wasn't doing it. Surprisingly the Rs had grip after the 1st run. Not track level but they weren't sliding around. Would have been nice to have the As instead of Rs though. Btw, the 335s in the rear will rub on your inner fender and slowly chew them up. Luckily those inner fenders are cheap. Mine is lowered on stock adjusters and I'm running the smallest spacer in the rear. No spacer in the front. They hit my DRM brake ducts in the front on turnarounds but the rest of the course they seem to clear.

Anyway take it fwiw. I'm just a hack and you've got good feedback from national level drivers.

Timz06

I don't think they will help you at Roebling. Roebling has a carousel and some long sweepers, you car is just going to push in those turns with that setup. I would stick with the 315 setup.