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Setup - Hoosiers - Advice

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Old 03-14-2017, 06:41 PM   #1
AGO
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Default Setup - Hoosiers - Advice

As I run for the first time with R7, I wanted to share impressions and ask for opinion/experiences to you all.

Car: 2010 GT3, no mods just alignment, rollbar, GT2 seats and harness, and Sharky bypass.
Tires: since '15, I run quite a few sets of MPSC2. Now learning R7.
Track: COTA

1. Car balance changed on R7's vs MPSC2. More front end grip, balance shifted towards oversteer which is ok on slower corners but not a great feeling on the fast stuff... it required more delicate steering inputs and judicious use of throttle (all good, fun)

2. Pressures: overinflated on the first run due to combination of delay of session and increased ambient temps. I dialed it down and my last run was with 25 front and 23 rears, ended with 34 front and 36 rear, consistent through the session (about 72-75F ambient).

3. R7 felt more stiff on the sidewalls, I'd say higher total equivalent spring rate. It felt nice to drive.

4. Good consistent behavior (once initial pressures were dropped), getting looser at the end of the stint but no big drama.

5. Alignment for reference:
Front: Camber: -2.6 F, Toe out: 0.07deg, Caster: 9 deg, swaybar 2nd from full soft
Rear: Camber: -2.6 R, Toe in: 0.11 deg, swaybar in middle position

6. Shoulders after 4 sessions: outside ok, some roundness and wear, not "extreme" when compared to inside more square shoulder.

7. To complete the weekend view... after the 4 sessions with R7, rest of the weekend was wet/dump and switched back to MPSC2, balance was back to normal (just a bit understeery). I know them better and can lean on SC2 more, still a lot to learn on R7's.

8. May need to raise 5 to 10 mm the front ride height as the R7 are wider and just rubbing the front fenders when loaded. Nothing big but you can tell from fenders and fronts.

So the question what to do to get a better balance - suggestions?
Here are some ideas:
A. More rear wing? It's a regular 997.2 GT3. Goal, more planted, reduced oversteer on fast corners (like T10)
B. Full soft on rear swaybar? (Alternative: 3 hole from full soft on front swaybar) Pros-cons? Suggestions?
C. A bit more toe-in on rear?
D. Just play more with tire pressures?

Goal is to keep having the car with good balance on MPSC2... and have a nice platform to learn the R7's.

Comments and suggestions much appreciated!

Thanks !!!
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Old 03-14-2017, 07:01 PM   #2
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get your tire temps. I'll bet you need quite a bit more camber. I run NT01 and am at over -3 in front and have pretty even temps, and generally even tire wear, although I could use a bit more in front still. At some point its a balance as braking gets affected as you lose straight line contact patch.
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Old 03-15-2017, 12:55 PM   #3
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Thanks Spyrex.

Any advice from you and all on preferred settings for swaybars? Of course this is track and setup oriented but good to know if those are noted in the settings...
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Old 03-16-2017, 12:58 AM   #4
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1. Use tire pressures and camber to achieve consistent temps across the width of the tire (not for handling).
2. Use sway bar adjustments to achieve desired handling through the turn.
3. Put as much rubber in the rear as you can (315's).
4. Turn off traction control and use your right foot to learn how to take T10 more aggressively. (oversteer is not necessarily something to try to avoid; learn how to exploit it).
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Old 03-16-2017, 02:41 AM   #5
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^ 315 if you are talking ntO1 is not the right profile for the 997. It's too low and screws with the rake.
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Old 03-16-2017, 06:43 AM   #6
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JC asked about Hoosier R7's.

Your best R7 set up is 18" wheels, 245 in front and 315 in back. The bigger the contact patch in the rear, the more it will address oversteer in high speed turns like COTA T10, the carousel, etc.
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Old 03-16-2017, 09:28 PM   #7
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Based on my experience, -2.6 camber in the rear is too much. I use -2.0 and most others also seem to be in the -1.8 to -2.0 range. Inner edge wear improved from R6 to R7, but still seems to be the highest wear area on mine. Keep an eye on it.

I am currently at -2.9 in front. Temps were a little more even with less camber, and some recommend keeping to about .5 delta from front to back, but I was getting outer edge wear.

Regarding R7 sizes, I would love to get more tire in the front - and I've seen others with 245's mounted, but I've tried both profiles of 245s and neither works for me. The 245/35 was too wide and rubbed the front main springs while the outside edge was already proud of the fender, and the 245/40 was tall enough to be cut by the front edge of the fender. I opted to go with the 225's that have nearly the exact dimensions the the R6 245/35. Since I can't run anything wider than that in the front, I've never tried anything wider than a 315 in the rear.

Front setup specs:

Stock top strut mount position
Ride height - 90mm (when using the R7 225 or R6 245)
Camber -2.9
Total Toe 17' Out (2.4mm)
Caster 8 degrees 40'
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Old 03-17-2017, 09:57 AM   #8
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Now I only used to autox my 2010 GT3, but the car was incredible on 235/19 and 315/19 Hoosier A6's
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Old 03-17-2017, 10:01 PM   #9
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Quote:
Originally Posted by RedRSA View Post
Based on my experience, -2.6 camber in the rear is too much. I use -2.0 and most others also seem to be in the -1.8 to -2.0 range. Inner edge wear improved from R6 to R7, but still seems to be the highest wear area on mine. Keep an eye on it.

I am currently at -2.9 in front. Temps were a little more even with less camber, and some recommend keeping to about .5 delta from front to back, but I was getting outer edge wear.

Regarding R7 sizes, I would love to get more tire in the front - and I've seen others with 245's mounted, but I've tried both profiles of 245s and neither works for me. The 245/35 was too wide and rubbed the front main springs while the outside edge was already proud of the fender, and the 245/40 was tall enough to be cut by the front edge of the fender. I opted to go with the 225's that have nearly the exact dimensions the the R6 245/35. Since I can't run anything wider than that in the front, I've never tried anything wider than a 315 in the rear.

Front setup specs:

Stock top strut mount position
Ride height - 90mm (when using the R7 225 or R6 245)
Camber -2.9
Total Toe 17' Out (2.4mm)
Caster 8 degrees 40'
I don't think -2.6 is enough that's what I ran for a while and my car was still chewing the outside shoulder pretty bad on track. I went to -3.2 rear and wear is now even. Best bet is to get a pyrometer and measure temps across the outer, center and inner edges and try and get even temps then look at wear patterns.
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