Fritz Flynn

On Valentines day my 07 GT3 RS arrived and 4 days later I was at VIR with NASA and thoroughly enjoyed learning the handling charactertics of the car, being mesmerized by the rear brakes, grinning like a kid on a roller coaster when shifting into 5th and basically having the time of my life ......BUT

The rear tires were not up to the challenge and the drivers seat (GT 2 seat) was killing my neck with a helmet on so I couldn't wait to get it back on track with some better rubber and a seat that's suited for a helmet and HANS. I had a second set of decent kuhmo 710s (305 30 18s) to replace the bald/worn originals (315 35 18s) and lucky for me Kenny at Werkstatt was able to squeeze me in between his busy race schedule to install a better seat along with getting the Kuhmo tires mounted, changing the oil etc.... So thanks again to Kenny and Scott at Workstatt for taking such good care of me and allowing me to have a blast at the track.

So off I go to the BMW event with better tires and a better seat. The tires really made the driving experience less nerve racking and now I understand why some folks actually prefer the engine in the back. REALLY cool experience easing out the brakes a bit hot waiting for rotation and accelerating out of corners. Similar to my FD (rx7) but with much more grip when applying throttle and just a smoother over all vibe.

One thing I noticed right away was how hot the rears were getting VS the fronts. Started out at 24 PSI all the way around and determined after one session I was off on that guesstimate. The rears were blowing up to 39 and the fronts to 33 upon returning to the paddock. So I lowered the fronts to 23 and rears to 21 and that was better but ended up at 22 L front 20 L rear 23 R front and 21 R rear for starting pressures and the rears were still blowing up a bit and getting greasy. Basically 710s must be autocross tires or designed for a lighter car. I also think more tire in the rear would of really helped so I'll definitely be going back to the 315 35 18s which should shave some time especially if fresh.

Still setting shocks stiff, sport and TC off. Forgot to press the buttons during one session and thought the diff was misbehaving until just about pit in it dawned on me that I hadn't pushed in the 3 buttons (big sigh of releif that I didn't already break something). I learned the TC is actually fairly limited which is nice because you can still slide the car around a bit but it will rein you too much on those tight corners so you are better off driving with out it for sure.

Only took one vid from the last session on Sunday and it was sprinkling a little which kept me from getting too crazy. Also the vid is a waste because I just bought a go pro and had no idea how to use it. I'm happy with the camera position but the video outside is way to bright and you really can't see much of anything although the inside/cabin vid is nice. I'll post up a lap or two anyway as time permits. I think I remember reading about a setting that will help with the brightness issue so hopefully I'll get that resolved next time out.

Once again I'm really impressed with how well the brakes work, how easy it is to modulate and trail brake etc.... Worlds different than my RX7 but this car will take me some time before I'm running similar lap times that's for sure

Again vid to come shortly and I'll see you guys at the Zone 2 event in 3 weeks.

OH man this is worth mentioning. One of my students was in a ZR1 and the acceleration, corning, braking........BRUTAL I'd ride with him then go out in my car and feel like I was in an s2000.

PS another 996 GT3 lost coolant but it wasn't the usual pressed and glued fittings but a hose that degrades from heat which according to Thomas Hart needs to be replaced every two years or so if you track your car a lot. I'll be looking at my hoses carfully and making sure they are still soft.

JClark

Green GT3 RS? Wicked car, congrats on the purchase.

My D student this past weekend had the black Cayman S. Everytime we saw you guys in the ZR1 I kept thinking please God give that instructor strength! By the end of the back straight you were over the horizon already.

Fritz Flynn

Thanks man I'm lovin this car.

I never would of made it without those prayers along with the group of VIR corner workers having similar thoughts

ukrbmw

Cool - I wanted to attend but couldn't make it. Was going to be a great shakedown event before NASA in March. Oh well.

Sounds like a damn fun weekend!! Congrats on the new car.

Carrera51

Fritz:
Your new toy looks great. The more you drive it, the more you will like it and the less you will use the RX-7.

Fritz Flynn

Hi Mark,
Great seeing you at the track and thanks again for the gloves We need to get together about some shoes and driving gloves sometime. This narrow foot well in the P car is not working so well with my fat Adidas super models

I think you are right about the car thing but that FD is definitely an old shoe that's really fun to drive. Here's a vid from the last time trial at Summit Point. It'll be while until I'm driving the RS like this.

http://www.youtube.com/watch?v=K8jN3awDv8w

Fritz Flynn

Rockin weekend for sure

I hope Zone 2 is equally lucky on the weather.

docwyte

710's are definitely autocross tires. They'll give you a few hot laps and that's it. Not sure on your GT3, but I usually aim for 39psi hot front and rear on my tires (Toyo RA1's/Nitto NT01's).

Fritz Flynn

Yep that's what I'm gathering. 39 in a heavy car with a wide short radius tire seems a little high to me but hey if it's sticking then stick with it

mglobe

I'm surprised no one else has commented on the pressure increase. Nine PSI (24 to 33) in the front is a lot, but FIFTEEN PSI (24 to 39) is huge. Is this all due to the brand of tire??? Or could there be too much moister in the rears, or an alignment issue causing this?

Fritz Flynn

I agree that's the most I've ever blown up a tire typical for me in my RX7 is 10 to 12.

I think it's all of these:
Not enough tire both radial size and width
Soft tire
997 GT3 use some pretty high toe in #s in the rear
911s have lots of weight hanging over those tires
I generally keep the right foot planted the entire session (25 minutes)

I think the appropriate starting pressure with a 315 35 18 Hoosier R6 for me is going to be about 20 psi and I expect the tire to be at 34 on track and 32 when I get out of the car and check it in the pit.

mglobe

Granted my race car is lighter than your GT3, but FWIW pressures on my Spec996 consistently increase by 6 to 7 psi both front and rear. I of course drive flat out... I suspect that something is wrong on the back alignment of your car. Possibly toe, but that's a SWAG.

Fritz Flynn

Again I was also surprised but not in shock just interesting to see all those things I mentioned causing such an impact.

Weight is huge on tire wear but even more important is how much power the car is putting down etc.....

Back straight I'm at approx 160 (digital read out on the cluster which is likely high) and 150 on the front.

I always see at least 10 psi inflation in my RX7 that weighs 2650 and puts down approx 335 rwhp w/ 275 40 17 hoos. Typically start at 22 psi on a normal 70 degree day.

Likely we could add too much rear toe to the list but again these cars need some toe and this car has little push and I seriously doubt it's a toe out problem or braking would be more interesting.

onefastviking

Just an assumption on my part but ....... any chance you are sliding the tail around a little ? On the GT3's the rear brakes can be engaged as part of the TC/PSM to help keep you from sliding. If you are sliding it, or driving to the point where the rear is stepping out then the cars electronics may be trying to help you out, by adding rear brake they are causing a lot of extra heat to be generated into the tire thus the more increease in the tire pressure.
FYI - Braking generates heat in a tire more than anything else you can do.

If this is in fact what is happening then you will need to dial it back so you don't slide the car and then you should see the rear tire pressure increase at a more regular rate.

Hope it helps,

Fritz Flynn

In my book if I'm not throttle steering I'm not pushing hard enough so yep the rear end is sliding a lot. I also use trailing throttle over steer for just about all the small corners. Basically I over drive but hey it's fun and fast for a lap or two, I'm a time trial guy However TC is turned off so hopefully when it's turned off it's really OFF.

Yep braking is the best way to warm up your tires and at 160 back and 150 front those puppies are plenty warm.