Andy (Portland, OR)

What I learned in my new (to me) is that an "out-of -the-box" GT3 is a racey looking snow plow. I'll explain.

While waiting for my alignment, seats, roll bar, harnesses, R compound tires, etc. -- and first local track day, which is still a couple of weeks off -- I figured I'd take my completely show room stock car (original tires and everything) for an autocross, something I haven't done in several years since I've come to prefer the track. Nice day, and nothing better to do. Moreover, I felt it would be an opportunity to learn about the car in a risk-free environment.

Well, what I learned, mainly, is that the car pushes like crazy in it's current configuration -- in the one real sweeper, it plowed so wide that the spectators started backing up! Sure, I could have backed off the throttle, and it would have tucked back in, but that's not the point. So, next run, I give it even more gas, thinking I'll rotate the car with power. Problem is, it took so much power to overcome the understeer that when it finally roke loose I couldn't catch it -- cloud of smoke and cheers from the crowd. Really a fun day and learned alot, since my whole purpose was to explore the car, not elapsed times. (In fact, I figured going out there that if I didn't spin the car I wouldn't have acheived my objectives for the day.)

So, I have a question or two. I'm told that a proper alignment (which I have a reservation for) and sway bar settings, can make the car neutral. Is this true? Given the inherent rear weight bias, size of the tire stagger and severity of the current understeer, I'm somewhat skeptical. It seems to me that reducing the tire stagger might also be necessary and desireable -- wider in front or wider in front and narrower in rear. What sayeth those who know much more about these cars than I?

Thanks in advance for your advice, Andy.

bora

What are the sway bars set at?

Bob Rouleau

Andy - what you have been told is true. With a proper alignment (negative camber) your car will steer correctly. Note, all 911's tend to understeer in slow corners. That's why God invented trail braking. Your alignment is definitely off, that's been the case for the majority of GT3s as delivered.

Rgds,

Andy (Portland, OR)

Wherever the factory set them -- nothing's been done to the car, other than oil changes, since delivery. I haven't bothered to look because I'll adjust them at the same time as the alignment and corner weighting.

brucegre

Andy, it might be the point - Bob mentioned the trail braking, basically you need to do something at initiation to get the car to start rotating, and then catch it with the throttle. If you want to power it into rotation, it won't happen, even with a good alignment. At least, not at any kind of speed. But you can swing the tail all over the place with a quick breathe out, feel it start to go and then plant the rear with your foot. In a high speed sweeper, we can enter under part throttle acceleration, and go to the floor very early (T6 at Tremblant, T8 at Mosport), but if the entry is fairly low speed, as I imagine yours was at an auto-x, too much throttle too soon will just wash out the front.

What was your entry speed/gear when this was happening?

Bruce

mooty

andy, GT3 does need some trail braking in certain type of turns. but be very very careful, this is NOT a car to learn how to trail brake in. if you trail braked just a tad too much, you be chasing your tail.

Andy (Portland, OR)

2d gear. Speed hard to say (35-45 mph?), at entry at the lower end of the power band for second gear. It was a fairly large sweeper, the fastest 180º turn of the course.

So, if I'm understanding you correctly, with this car my rotation bag of tricks does not include power-on oversteer -- it will just push. No tail out driving?

Andy

DavidNR

Andy,

Set the front bar on full soft, the rear one from full stiff. You will get a nice controllable rotation into oversteer that is correctable with the throttle, just don't add too much!
The car is really set up for the track and autocross requires a different setup. The car is actually a lot of fun on an autocross course as long as its not too slow or tight.
Oh and be sure to change the front bar back right away.

mooty

modern 911's dont respond well to tail out driving. you can do it, but it's slow.
you can use pwr on oversteer to do soem correction AFTER some careful lifting, but like i said, mostly for CORRECTION.

NJ-GT

Expend 15 minutes and set the front sway bar at full soft, and the rear one at one from soft. For track days, move the front one to one from stiff, and leave the rear one at one from soft. This works on the stock suspension for both Sports.

Andy (Portland, OR)

Thanks, David, but I'm a bit confused. Which set up are you giving me -- track or autocross, and when you say to "change it back" which setting are you referring to? I'm interested in both setups, track and autocross, although my primary focus is track.

Is there a general consensus as to the starting point for each setup, recognizing, of course, that each track is different and that some minor deviations from the "general rule" might be appropriate.

Thanks, Andy

Andy (Portland, OR)

So, I'm not hearing anyone say anything about relative F/R tire sizes in the context of car balance.

The reason I bring this up, is when I switched the fronts on my Boxster S from the stock 205s to 225s, the understeer was significantly reduced. I still had to play with the sway bars to make it completely neutral, but it was a very good place to start.

The stock tire stagger is even greater on the GT3 than on the Boxster S (235/295 vs. 205/255). Has anyone gone to 245s or 255s on front (assuming such tire sizes even exist)? Results?

I have always figured that the reason Porsche puts (relatively) skinny tires on the front of its cars is to promote understeer for safety reasons on the street and that reducing the stagger for the track would be beneficial. This certainly worked on the Boxster -- does it work on the GT3?

Thanks for helping this newbie.

mooty

i woudn't touch tires size unless you want a specific result and know what you are doing (NJGT certainly play with tire sizes a lot).

fongster's car on stock suspension and my on motons both use stock size rubbers and they do not understeer. maybe a mild high speed mid corner push, which if i tuned it out, i may be twtiching even in low speed corners. you need the stackered tires to stablize the rear end. work with it first, then play with sizing if you like. the sway bar adj as mentioned does wonders.

also, it drivers very very differently than mid engined box you are used to. you can't "throw" a GT3 around, you are either committed or you spin in a GT3. is a more delicate car, and fun at that. you will enjoy it, just keep putting on the miles.

NJ-GT

For autocross, I'm currently running 285 Front and 315 Rear Kumho V710 (10"/12" custom offset wheels). The results have been the best so far compared to every other tire brand/model/size combination I've used for this Sport. The other National competitive GT3 I know so far are running 245/285 Kumho V710 or 245/305 Hoosier A3S05. The 245/315 Hoosier A6 will be tested on one of those cars pretty soon.

For the Track the setup is radically different. Too many variables to mention. I will stick to my 240/270 Pilot SX (can't go wrong with GT3Cup sizes for track days).

brucegre

Hey Andy, back to the first question you asked me, about not being able to drive with the tail out on power. I was kind of expecting you to tell me you were in second gear - with the rear grip that this car has at low speed, when you stomp it you're almost pulling a wheelie, so the car just plows, as you found out. If you breathe out of it and get the rear going around, then the power application will either plant the rear and carve the turn, or you can keep the swing going because the tires are sliding just enough to let you do what you want.

Tire stagger, I did run 255/295 f/r for an event last year, no huge difference in front end grip. I think all of us in Rennsport are running the stock size 235/295 combo (MPSC for the most part). I do run a 250 slick on the front of the race car, but mostly because that's the easy size to get in a Dunlop.

Don't forget that your Boxster was mid-engine, so neutral handling is the order of the day for that car. The 911 is just a big hammer running backwards down the track.

Enjoy it!