set up for 13" radials on vw rabbit

I just ran my Rental rabbit on R75 Hoosiers this past weekend. We ran 30 psi cold in the front and about 26 cold in the rear. -3.0 front camber and -2.0 (would like 2.5 or more) in the rear. This seamed to be where the car was happy. I am running the same tire on my GTL car and really love them.
 
Ran Watkins Glen last week and talked with the Hoosier rep. He said that 2 1/2 neg was the maximun camber for the R series tire. I ran with 2 1/2 front and rear. 215 R80 on 7" wheels at 27 hot at the front and R75 190 on 6" at the rear at 25 hot. This is a 1600 H prod Scirocco at 1830#. Front springs are 650# and rear 350#. I have two rear bars one 1" and another 1 1/8". I ran only with the 1" and disconnected the 1 1/8 bar as the rear was to lose with both. The car handled well. At Lime Rock and Pocono both bars worked well. I hope this helps.

Johannes Krauss
 
There is no blanket "max camber" for any tire. It will be defined by a lot of factors, including suspension camber curve, roll stiffness, desired speed/tire life ratio, driving style, track conditions... to name a few.

What is posted here is enough to get you in the ballpark. Test from there to figure out what gives you the pace/wear combo that you want.
 
I contacted Hoosier to get the scoop and I was told that my 3 1/2 degrees in front was fine. I have had 5 failures this year. All were inside tirewall failures. I know of two others that have had the same issues. I was told that it was a West Coast issue. Anyone else had problems this year?
 
The "R" tire is being replaced by the "S" this tire is designed for more camber. I never had a failure a larger camber but I know others have. The compound is the same but the tire in stiffer. It is supposed to be faster.

The key factor in set up is alway tire temps. pressure and tire wear. And will be different for each drive, car combination.

Johannes Krauss
Racing since 1979
 
I hate to say it, because now I'll probably have one.... But we've never had a tire failure running -4degrees on the front of our CRX's.

One thing I can tell you for certain.... Aim for 35psi hot. I'm starting at higher pressures cold that what I'm reading people are getting hot. Running low tire psi of course will put a lot of strain on the tire. I haven't experienced any reduction in lap time or wear running all the way to 37-38psi hot. Most durable slicks I've ever ran on. Not to mention, wow what a difference the first few laps... The slide and grab is eliminated and more a nice rotation/slide when you exceed the limit. Its a radial tire and despite what I was told, this is what we run. I highly recommend guys you at least just start with your hot pressures.

Now, wet set up. First and foremost.... Read the book going faster. Especially about racing in the rain. Racing in the rain isn't a setup, its a different driving style and a completely different line. Sure a set up can help, nut nothing will help you as much as the proper technique. It amazes me how man drivers I've talked to about it, explain it, they say yeah, yeah, I know. And then they throw on rain tires and drive right on the traditional line as I pass the around the outside of the carousel where all the grip is. Don't want to read? Let me just say this. The grip is where you never drive in the dry. Where the rubber isn't in the track. Where the line isn't polished smooth. Or maybe easier to say.... Where the marbles are. Because no tire or set up will help you slow down when you're breaking on the slick normal driving line.

As for set up, real simple to think of it this way. You have less grip therefore less weight transfer. Soften the car up IF you have time, mind it if you don't while driving. Cold tires psi should be 5psi off your hot temps in dry... A great starting point.

With that said, I LOVE RACING IN THE RAIN. And chuckle every time when I hear, man, you were driving quite an interesting line out there! 8)

Above all, be patient, be cautious, be extra smooth and be ready to slide and lock up. And when you do, don't push harder on the brake pedal, reduce pedal psi, wait and look where you want to go. And constantly, look for grip. Don't enter the corner the same way as you did the previous lap when you almost slid off the track, the solution isn't just slowing down, the solution is staying off the slick stuff.

Hope this helps.

Now sign up for the Cat national and Gratten and support your regions!!!!!!!
 
SPEEDSHAK":1nayfmdw said:
Now, wet set up. First and foremost.......
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.......switch to front wheel drive.

Thanks for the info Lawrence. As another data point on a rear-drive car, I ran 3 1/2 degrees camber on the front and the front end stuck real good. Since I can't run rear camber I backed off the front to 2 3/4 degrees and the car is very well balanced at this point. That is above the so-called 2 1/2 degree max but it works and the radials are doing well for me at the moment.
 
SPEEDSHAK":2zgw0jz6 said:
Now sign up for the Cat national and Gratten and support your regions!!!!!!!
Click to expand...

If it wasn't a 24 hr tow I'd seriously consider being there. Would you believe I actually looked at my calendar this week and thought about it?

As for the radials, I've also never had any problems or failures with them to date. But I also have yet to get my car to handle as well as it did with the old bias plys. As was obvious to anyone that may have had to follow me through the kink. I still can't seem to get any temp in the rear tires. Getting closer though.

Your hot pressure numbers are a bit surprising though, having said that, I will admit to having tried up to around 35 psi hot once and didn't notice any loss of grip... in the front. :roll:
 
Jay Griffin":1shb6rno said:
SPEEDSHAK":1shb6rno said:
Now sign up for the Cat national and Gratten and support your regions!!!!!!!
Click to expand...

If it wasn't a 24 hr tow I'd seriously consider being there. Would you believe I actually looked at my calendar this week and thought about it?
Click to expand...

Jay,
Grattan is a few hours closer (20 hours to Cocoa Beach) and is in August (8/23, 8/24).....the week before Labor Day weekend. So store your trailer at my place, build in a few days of vacation in the cool of west Michigan (wineries, museums, etc.) and then go racing at an awesome track. It'll challenge you like no other. Just sayin'.......

Dayle
 
Jay Griffin":13p5vd55 said:
SPEEDSHAK":13p5vd55 said:
Your hot pressure numbers are a bit surprising though, having said that, I will admit to having tried up to around 35 psi hot once and didn't notice any loss of grip... in the front. :roll:
Click to expand...
Click to expand...

That is one of the things that is hard for people to understand about the radials. Their grip is not related to tire pressure like the bias ply tires. Tire pressure affects the spring rate of the tire, and if you like the tires at the higher inflation numbers then you have the added bonus of reduced rolling resistance.

The other thing that I have found that people new to radials miss is that you need a special probe for your tire pyrometer. It needs to be longer so that it hits the steel belt (I am told). There seems to be a standard offset to the old pyrometer tip, and if you can calibrate it to the proper tip you can get real numbers. Otherwise get used to the feeling that you aren't getting any heat in your tires, or you could go crazy trying to find the right pressure to get the heat that you expected. That won't happen because you will always get low readings with the wrong tip.
 
Ron Bartell":6wq7ul42 said:
The other thing that I have found that people new to radials miss is that you need a special probe for your tire pyrometer. It needs to be longer so that it hits the steel belt (I am told).
Click to expand...

:think: Hmm, this is something new. Not to dispute what you're saying but I'm guessing you got this info from a Hoosier engineer? This could possibly explain some things.
 
HMMMM-FB and all those P cars do drive with those wheels don't they!! Just wondered if anybody was paying attention. Does it make a difference if the engine is in front of the driver? :)
 
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