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 Post subject: Hoosier Radial Settings
PostPosted: Tue May 29, 2018 4:43 am 
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Joined: Fri Oct 14, 2016 5:08 am
Posts: 65
Location: Dubuque, Iowa
What is the general setup/starting point for these? I can't find any literature for their slicks, only the DOT-R's.

We were given feedback to run them similar to the DOT-R's, (camber, cold/hot pressure, etc.) but it doesn't seem to be working.

Cold/Hot pressures
Working temp range

I was planning on giving Hoosier a call as well, but figured the posted information might be of help.

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PostPosted: Tue May 29, 2018 5:03 am 
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My setup is indeed similar to that of the R7. I run 3-4deg neg camber on the front, about -0.5deg rear (solid axle car), roughly 23-24psi cold for 28-30 hot.
that's on my 1st gen RX7, 2200lbs, Mcstrut front, solid axle rear.

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PostPosted: Tue May 29, 2018 5:27 am 
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Matt93SE wrote:
My setup is indeed similar to that of the R7. I run 3-4deg neg camber on the front, about -0.5deg rear (solid axle car), roughly 23-24psi cold for 28-30 hot.
that's on my 1st gen RX7, 2200lbs, Mcstrut front, solid axle rear.
+1 for all of that on a solid axle rear-drive Spridget.

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PostPosted: Tue May 29, 2018 5:33 am 
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Location: Dubuque, Iowa
I'm thinking we're way overinflated - as a result of ditching weight over the years when converting from ITS to EP.

We used to run around 29-30 cold/39-40 hot with a 2750lbs car on the R7. We are now down to ~2290

As we ditched weight and changed to the slicks, we never lowered our tire pressures.

Our most worked tire is only seeing about 180 degrees. Car has very little grip.

Does this make sense? over inflated? not able to build the heat? It seems like the tire is getting overworked and gets slippery as the session goes on, but no matter when we check the temp we can't break 180 degrees.

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PostPosted: Tue May 29, 2018 5:58 am 
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I'd agree with that philosophy. My problem has always been underinflation.. I would run my STU car at ~20psi cold and build up to about 26 hot.. they have more grip with lower pressures, but the sidewalls flex and car gets squirrely mid turn. Same thing on the slicks. I went from ~20cold to ~24cold and the behavior got a LOT better.
However, after 10-12 heat cycles on the tires, they're done. I know the track was much hotter and greasier last time I ran at MSRH, but best I could do last weekend was a 1.48 whereas I was running 1.44- 45 at the last race here on new tires. (in October weather)

When I was running higher pressures, the car would feel like I was on ice until the tires got hot, but they were still low on grip. lower pressures increase grip, but also increase sidewall flex. I've never done any work with temps as I don't have a pyrometer (and I'd rather pay thousands for tires and go slow than to spend a test day actually tuning tire pressures and setups).

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PostPosted: Tue May 29, 2018 6:16 am 
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What does the profile of the tire temperatures show you (inner, middle, outer)?

When I was experimenting with pressures, it was very clear when I was over and/or under inflated. Plotting the data in Excel was the key in "seeing" the magnitude of the problem - it did not seem so bad until then.

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PostPosted: Tue May 29, 2018 6:52 am 
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Which compound are you using? 180 is about right for S80s.

The S80/100 radial slicks have a dramatically stiffer sidewall than the DOT A7/R7 tires.

Because of that, you'll probably need less spring/bar and probably less camber/caster.

As someone suggested, the pyrometer should be your best friend. And don't tool around back to the paddock and check them. Come off the track hot and stop as fast as you can in the hot pits, and take the temps right away.


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PostPosted: Tue May 29, 2018 6:54 am 
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Location: Dubuque, Iowa
planet6racing wrote:
What does the profile of the tire temperatures show you (inner, middle, outer)?

When I was experimenting with pressures, it was very clear when I was over and/or under inflated. Plotting the data in Excel was the key in "seeing" the magnitude of the problem - it did not seem so bad until then.


It was a rather consistent gradient from inside to outside. Usually around 20 degrees from I to O.

I'll plot in excel to see if anything jumps out at me. Good tip.

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PostPosted: Tue May 29, 2018 6:56 am 
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blamkin86 wrote:
Which compound are you using? 180 is about right for S80s.

The S80/100 radial slicks have a dramatically stiffer sidewall than the DOT A7/R7 tires.

Because of that, you'll probably need less spring/bar and probably less camber/caster.

As someone suggested, the pyrometer should be your best friend. And don't tool around back to the paddock and check them. Come off the track hot and stop as fast as you can in the hot pits, and take the temps right away.


S80.

We did all of our stops after a hot lap directly to the pit stall.

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PostPosted: Tue May 29, 2018 7:09 am 
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Location: Spring Hill, FL.
The rim width makes ahuge difference in footprint also. 1/2 in might need a 5 # air adjustment up or down.
Running too low allows the tire to get on the edge and instant loose. Try to run just above the tire edge on pressure. Use the old school method of crayon.
A target of 38# for the DOT works for most cars and about 36 for FWD on slicks.
The RWD has a lot less outer front tire dynamic loading and can use a target near 28-30 often. Keep in mind that more pressure rolls easier ..
Also you may have the best grip with the temps showing a little cool outer edge. About 15* less is my target.

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