Carl Byck

I am going to be aligning and corner weighting my 2nd gen RXy widebody. I have 16x12 w/24.5x13x16 R430 slicks rear, and 16x11 w/23.5x10.5x16 R430 fronts. I will be changing the fronts to 24.6x12x16, but I have two pair of the smaller tires to go through first.
I have never run slicks before, and I do not know what sort of camber and toe these tires like as compared to DOT tires. My starting spring rates are 600 front, and 400 rear(I am very open to suggestions here). The car has the interior removed, and a 6 point Kirk cage, so it probably weighs~2450+/- . I am using GC Advanced designs, and have all the AWR pieces except the front arms. I have two way adjustable sways front, and 3 way rear(Racing beat I think). I am looking for middle of the road suggestions, never having driven slicks, I have no idea of what to expect. my driving style is a little loose, and probably more aggresive than it ought to be.
The car is putting ~450rwhp to the ground, and I am concerned about camber gain on acceleration. that said, I suspect that with the 13" tires I should not have much trouble hooking up out of the corners once the tires are up to temperature.
I really cannot even ask the question in an intelligent fashion as i have no experience with the slicks. Also, moving forward, Hoosiers, or Goodyears, and what compounds for what track temps?
I also have one set of Radial slicks in essentially the same sizes, so what would I change when going to those. i realize these are guestimates, and averages, I just am looking for a starting point. i wll primarily be at ThunderHill, Infineon, and Laguna Seca. Thanks for the time, and consideration, Carl Byck 707-696-2705

tims

in basic terms you will need to run the bias ply tires upright and the radials will need to have alot of camber. All of these settings need to checked at the track by monitoring the tire temps and pressures. For Hoosier or Goodyear bias ply tires I ran 1.0* negative camber front and .5* negative camber on the rear. Tire wear and temps on the front were fine but rears wore the inside edge quickly. As far as toe I ran 1/16" toe out on the front and 1/18" toe in on the rear. I just ran a test of some Hankook radial slicks and they turned out to be great. much better than any bias ply I have tried. same toe settings but I ran 3* negative front and rear camber. All these settings need to be fine tuned for your driving style and HP setup. Make sure you have a good tire pressure gauge and a good pyrometer and of course keep good records. good luck

jgrewe

iTrader: (1)

Carl, on our FC 'vert EP car w/9" wide slicks all round we run about 1.9-2.1 neg in front and 1.6-1.8 neg in rear. "O" toe front and about 1/16" toe in in the rear. Since we are talking about two different beasts these # may get you started. Our car weight is similar but low to the ground and we have half the power. I'd have to look at spring rates but 450/275 rings a bell. Just expect the slicks to stick more and fall off faster passed the limit. We are running Hoosiers. Ride height and body roll will be much different than ours so have your pyrometer ready to get your settings perfected. You will have a huge grin on your face when those slicks get sticky the first time. Then you'll find out there is more in them when the temps are read and only half the tire is hot! Let us know.

Carl Byck

Thanks guys, a couple of questions for each of you,
Tim;
- any thoughts on the rear inside wear? I iamgine you were around ~250-275rwhp in a TII with an E6K proper tuning etc.
- did you experience signifigant camber gain on acceleration?
- whart sort of spring rates did you like?
- If I can get to ~0* in the rear would you start there?
- interesting the large camber differences between your two set-ups(vs jgrewe)
- what is a good source for hankook slicks?
- can Bias ply slicks be turned "inside out"?
- I imagine the front toe out yielded some nice turn in (something lacking in my previous set-up), what did it do in terms of wear?

jgrewe;
- radials, or bias ply?
- for both of you compound preferences? I imagine this is a function of ambient temps to a point.
- I have run 450/275, i found it to have a little much body roll even with my bar at full stiff, but the car was pretty neutral with 235-40-17 RA1 all around on 17x8 rims.
- R35/R45?
- same size wheels/tires front, and rear?
- for both, optimum operating temps? Is it better to run smaller tires to get the temps up, say I am only getting ~175-180*, should I try a smaller tire to get temps up in the 200-210 range?
- what is an acceptable temperature spread inside to outside
- should the suspension be setup differently left to right for a CW/CCW track?
- are bias ply more or less sensitive to toe and baer change vs a radial?

I really appreciate the input, obviously alot will depend on my car, and how I drive it. I will be on the track ~ 2nd week in July(latest), the car is being tuned July 7. Thoughts on stagger? I could go smaller in the rear to get the diameters closer, opininons? What sort of ride heights(measured where?) are your cars? In your experiences, more bar, or more spring given a choice? I have noticed that AWRs, and GC spring recomendations are very different, AWR being lower rates by nearly 100-150lbs, thoughts? Thanks again, Carl

tims

I imagine the wear was from camber gain on acceleration, but if it was at zero the handling was very loose. front toe settings have not had an affect on the tire wear. Also remember a typical EP car is only going to run sprint races usually 30-40 minutes, so you can be a little more aggresive with the camber settings. I am racing just enduros which are 3 plus hours each, and I don't have the budget to change tires at every stop. So my settings are a comprimise for wear and performance, but the Hankooks are light years faster and more consistant than the Hoosiers I usually run. I am using Frisby/Sierra Tires out of Las Vegas for my tires now. They were a great help and had very competitive prices. http://www.frisbyracetire.com/

jgrewe

iTrader: (1)

I havn't been to the shop to get our setup sheet but I remembered that we got 9.5" wide last set. Bias ply R45's. Same all around and we are limited to 7" wide rims. The set up was from the last event at Sebring on the short course. I'll double check but I think the ride height is around 4.5" measured at the rocker right behind the wheel(fr & not including the welded seam) and 4.75" in front of the rear wheel at the rocker. We've been playing with ride hieght a lot lately. We've had the same problem in th rear as tims, can't get the outside of the rears evenly heated with out standing them straight up and then the car is loose. Thats why were are playing with ride height, to see what the rear will do for us. With our other car thats under construction, I've been mapping the suspension movement to see what is happening at different ride heights. The front has the usual strut problem of lateral roll center movement and the rear I'm just starting on modeling. I think the trick is going to be getting them to play nice together at a similar ride height.
We are going to try R35's next time at Sebring, the car is pretty friendly to tires and the wear is even.
I've never used radials so I can't help there.
As for temps, its so hard to know how hot the tires are really getting unless you can come to a stop right after a HOT lap. The tires will difuse the difference in temps pretty quickly after you stop. If you wait to long your temps will be low but they will look nice and even. Try to get them as close as you can across the tread. I've dealt with cars that you can make all kinds of changes and the temps never change. It was because the chassis was flexing so much. I usually test a different tire first each time I come in so its hottest.
We don't change the setup(CW/CCW) unless there is something particular about a track that would really give an advantage to set up for. Ex. mostly long right hand sweepers with one left turn. Its personal preference and the tracks we mainly run on are pretty balanced.
I'll get some more info off the setup sheet tomorrow if you have more questions.

speedturn

iTrader: (1)

I run a 1st gen chassis w/ 10" wide rims all around in vintage IMSA GTU; very similar to GT-2. I like Goodyear R430 slicks the best. I could get my front tire temps even all across the tread if I ran 1 deg negative camber, but then the car would push bad. By going to 2 degree neg camber up front, the tire temps always showed a little hotter on the inner edge, but the front tires stuck better in the turns.

The point I am trying to make is that getting even temps all the way across the tire with a pyrometer is not more important than fast lap times. If the car turns a faster lap with a little more neg camber, then by all means do it. The pyrometer is very good to help you see if you are under inflated or overinflated, but the pyrometer is not the last word on camber settings.

Try for hot tire pressure of around 29 to 30 psi. The hardest thing is picking a cold pressure that will end up just right hot at the end of a race. I usually start with around 21 or 22 psi on the left side, and 22 to 24 psi on the right side, so that I will end up hot in the 29 to 30 psi range.

Old slicks, anything older than the 2004 season, is probably too hard to be any good.
Slicks with less than 1/2 tread showing, and less than 1/3 showing on any one wear hole, is probably worn out and has lost it's stick.
Some pros say that trying to tune a chassis with old tires is a waste of time.
Nothing beats a new set of slicks; it is like bolting on a two second reduction on your lap times

tims

I would agree all setup and testing should be done on new tires. Used or old tires will only frustrate you.

Carl Byck

Sounds like I need a new set, mine are ''03-04 with ~80% tread, kept inside, no temp extremes, but advice well taken. Votes an the tire to start with? I would like a tire that is consistent as possible beginning to end, need not be the fastest thing built, just consistent, with reasonable wear. Thanks all, Carl

speedturn

iTrader: (1)

If they are '04 models, they will be good enough to get you rolling. You will probably have a lot of de-bugging to do. Plan to buy new tires shortly after you get the car past it's first track weekend.

I like the Goodyear 430 compound - it is the best compromise of all the good things you are asking a race tire to do.

The front running GT-2 competitors are running the Goodyear radial slicks, but at $2000 a set they are too expensive for me. They claim much longer wear than the bias tires, but I just can't afford that much money. http://www.bobwoodmantires.com/goodyear/gysprtrad.htm

tims

I would say for consistant performance and good wear radials are the only way. There are a few new manufacturers out there with quality tires. Avon, Hankook, Kumho, as well as Hossier and Goodyear all make radials at various price points. I found the bias ply's all faded quickly and never recovered and after a few heat cycles were undriveable. I forgot what rims size you have, but try your tire supplier and see what other makes he has. good luck and have fun. The old set of tires are probably good to shake down the car, but I wouldn't try to dial in a perfect setup with them.

speedturn

iTrader: (1)

tims - are you talking about true racing slicks or are you talking about DOT racing tires ?

Carl Byck

I checked the Hankooks, nothing close to my sizes. I am relegated to Hoosier, Goodyear, and Avon bias plys, and Goodyear radials. Goodyear does not make a front tire wide enough, and short enough. That said, I wonder if a 10.5" radial will perform better than a 12" Bias ply in the front??? I can get radials scrubs for ~75.00 in season, but they are not really the right size, the rear is too tall, and the front is too narrow.

tims

Speedturn I was refering to full race slicks. I have not run DOT's in a few years.

tims

Carl,
With the new radials I am running a slightly narrower tire comparer to the Hossier bias ply and the grip is much better.

Carl Byck

Thanks, I may try the Goodyear Radial, as they are readily available as take-offs, I may need to modify my rear fender a bit to be able to get the ride back down where I want it though. I think Yokohama, Dunlop, and a couple others make some 18" radials that are short enough, I have test fit an 18x11.5 with a 335-30-18, and it fit, we shall see.