RedLS1GTO

OK experts... time for the new guy to ask some dumb questions!

Little bit of background; I've been posting on here that I recently purchased a fully race-prepped 96 affectionately known to some a Frankenvette. At this point I KNOW the car is way ahead of the driver. I'm in the Navy so I am on a tight budget and an EXTREMELY tight schedule unfortunately. My plan is to start with some local AutoX to get some bugs worked out of the car and more importantly to get some seat time and get myself used to the car. My goal for this season is to hit the permanent road courses as soon (and often) as possible with plans on Summit Point and VIR as part of HPDE with an instructor to fix the dumb stuff I am certainly going to do. Whew, tired of reading yet?

With that background info I get to my actual question. The car has a set of Hoosier R6 315x17s on all 4 corners right now. The rears are about worn out and the fronts aren't going to last too much longer. I just bought a pair of 335x17 Kuhmo V710s that I am told were actually on all 4 corners at one time. I got a great deal on them and figured at worst I would have to buy another pair for the front. If I were to run these in the rear and the Hoosiers in the front for the meantime how bad should I expect the car to react? Keep in mind, the reason for the background was to give my goals. I'm not going for lap records, just trying to get used to my car and more importantly trying to get acquainted with racing the right way. Thanks as always. You guys with experience have been awesome at helping to make the racing dream a reality.

waktasz

I wouldn't do it. I know just using worn tires on one end and new on the other made for some "interesting" driving conditions, and this was in autocross in a low powered CSP Miata.

sothpaw2

I don't understand what you mean by that the Kumhos had been on "all four corners"? So what if the previous guy rotated them.

With respect to the Kumhos, find out how old they are (year made) plus how many heat cycles were they put through. If you bought from the original purchaser, he should know. It would be good if you could find out the same info. on the Hoosiers in the front.

Now, as long as the Kumhos are not soooooo old or heat cycled (unlikely if they still have a lot of rubber) that they are WORSE (less sticky in dry pavement condition) then a 2 year old street tire, you should be ok because you are new and just starting out and won't be driving to win a race.

Your main issue with the above is that the LT4 car has been modded to make more than stock power so it would overwhelm streeet tires even more than a stocker. So you have to be very, very, very respectful of this situation. This means smooth, easy, EASY on the gas coming out of corners and smooth application of your brakes.

I would pick warm dry days for your HPDE events. The tires will stick best on a sunny day, preferably above 70F.

And BTW, no driving those in the any kind of rain because of the lack of tread. Hope you have a tow set-up to get to the track.

AU N EGL

the grip difference between the Kumhos and Hoosiers is to great. you will not be happy with the cars performance.

and southpaw is correct, those tires wont like the street at all.

You will think you are driving on ice covered glass.

RedLS1GTO

I don't think I made myself clear which is no surprise. The car isn't going to be driven on the street and I wouldn't expect a set of slicks to work on the street in the first place. I'm new to sanctioned events, but not just a complete moron that went and bought the fastest car he could find. The Z06 that I drive to work every day is only about 20h.p. less than the race car.
I think I'm confused as to where the street tire thing came in. The Kuhmos are a V710 slick and the Hoosiers are an R6 slick. When I said that at one time the Kuhmos were on all 4 I meant that at one point in time, the car had a set of 4 335 Kuhmo V710s on it. The 2 that I purchased are brand new.

I guess the simple question is this. What is the difference in grip between a NEW Kuhmo 335 V710 slick and a 315 Hoosier R6 with one full HPDE weekend on them? I know it isn't the PERFECT solution but is it drivable?

waktasz

The wider Kumhos will be much stickier than a used R6.

sothpaw2

You're fine, the Kuhmo is new and should be stickier. The street tire thing came into it because decent street tires are all you need to learn "the line" as a newbie and handle the car safely as long as you are a little careful. Your slicks are overkill and you are going to have a lot more car than the others in your run group.

Enjoy

RedLS1GTO

Thanks for the replies. I know that I didn't go about things in the normal progression but with the price of the 96 I couldn't pass it up. To think, I was looking for a relatively stock C4/C5 that I wouldn't mind beating up a little on a track

I bought the car with the R6 slicks on it and from what I can tell I can get all sorts of sets of used slicks WAY cheaper than I can get street/track tires. I don't have any plans on driving it around town so I figured I'd just keep the slicks on it.

I can't wait to be that guy that shows up at the track with the pure bread race car... only to get in and drive it like a granny until I have a better handle on things.

VetteDrmr

Let me go after your original question a different way. I've run mismatched tires in the past, and the only real way you're going to know how they work together is when you get on the course.

You said you'll be autocrossing first. Running 335 R6s in back with 315 710s in front at an autocross is going to be interesting seeing which ones get up to temp first. Assuming they've got relatively the same amount of grip (rubber-wise), you should either have a neutral or understeering setup. Of course, if one or the other warms up first, that end will have more grip.

The great thing about trying this out at an autocross is that your speeds are slower and much lesss risk to the car.

Now, as far as DEs are concerned, most of the organizations in my area are now requiring novices (which I was even with 7 years of autocrossing) to run on street tires with a minimum 100 treadwear rating. So, Toyo RA-1/R-888s and Kumho V700s squeak in over the line, but the R6/V710s won't.

HTH, and have a good one (and thanks for serving! ),
Mike

Pylons

I've autocrossed (in a Chrysler Crossfire) on a mixed set...Kumho fronts and Hoosier rears...without issue

as others have said, as long as one pair is not worn/heat cycled out, I think you'll be fine