CRex

Am putting on a set of GMG sway bars for my 997.2 GT3RS which gives me an opportunity to rethink my alignment. The car's used (almost) exclusively on track and my hometrack (Zhuhai) is similar to Watkins minus the loop/chute section (i.e. fast straights, sharp-ish turns, hard on brakes, limited camber effects). I'm planning to run the following geometry:

Intended Setup
Camber: -2.75 / -2.25 deg (F/R, per side)
Toe: -0.05 / 0.25 deg (F/R, per side)
Caster: 8.5 deg
Sway Bars: Middle / Middle (New, thicker GMG bars)

For reference, my Current Setup
Camber: -2.4 / -2.0 deg
Toe: 0.00 / 0.20 deg
Caster: 8.5 deg
Sway Bars: Full Soft / Middle (OEM bars)

Tires are Hoosier R6's at hot temps of 31/33. LSD is a cup 60/40 stack.

I found my old setup generally neutral with a slight amount of push. Prone to a bit of body roll at turn-in. Rear's almost too planted i.e. not easy to rotate. My thinking here is to nip that body roll with stiffer bars and compensate the duller turn-in with an extra bit of front camber. I'll start the sways in the middle and leave some room for trackside adjustments, perhaps a notch softer in the front eventually.

Would appreciate any thoughts on my setup. Is that too much camber in your educated opinion? Am I dancing with danger if I run the GMG rear bar at full stiff?

p.s. I'm less fixated with tire wear than maximizing handling. Red group.

Thanks in advance!!

TRAKCAR

Sorry, I think sometimes stiffer sway bars are going backwards.
Some very good drivers, lost laptime with stiffer bars.

Funny, yesterday at Orbit they told me that if I want to find a faster setup be prepared to go backwards 90% of the time while trying!

The rear bar I can see if your car now won't turn enough to your liking with the front bar on full soft and the rear bar on full stiff? I never found use for the stiffest setting of the rear bar as it is and running Hoosiers VS Toyo's only make it easier to rotate the car (to me)

The stiffer front bar will make things worse?

No dancing with danger, just build up speed slowly and feel the car move under load and off load before you go find the real limit.

Different drivers different likings. Even at top level pro driving in indurance racing one driver will hate a setup another will love it. Same laptimes.
Tracks also matter of course. Some drivers lose laptime, but love how the car feels and that is probably more important in the DE racing ;-)

Can't wait to read your posts
Waste a day playing with it, do 5 laps, come in, change setting to make it "better" until it gets worse and back up. do one end of the car at the time.

RSRanger

+1 on all Peter said.
In the past, in racing I've heard swaybars commented as "bandaids" to the suspension. There are many other more important components to suspension set up.

Ranger (Sua Sponte)

997gt3north

You 'may' be fighting your cup LSD - ie it may be giving you too much push.

I don't know the specs of it / who installed it / preload / etc - but Peter has mentioned this in the past about Orbit finding the correct Cup LSD setup to work with the street car.

For the guys with the Guard LSD (me), they ask you lots of questions about use, tracks, tires etc as it definitely affects the car - both positively but also negatively if it isn't quite right.

I'm not saying this is the issue, and even if it is, sways and alignment can make it 'better' so likely small tweaks will work.

I'm going to guess, if you are using a 19" Hoosier 325, that adding more rear camber is not going to help your desire to rotate the car - I would in fact reduce it to -1.8 (this seems to be a common number that many have found works with a very wide rear tire)

I think NJGT has some old post about the GMG bar settings as does MVEZ - I would pm MVEZ about his settings on those bars. I believe for a big track setup NJGT used (rear bar soft, front 1 from soft and said car was neutral)

If you are running after market rear toe links, then you might also try reducing your rear toe-in very slightly.

Nizer

Blue bushes too???

Mvez

+1 Peter. I have found that as speed builds, I've been softening the GMG bars. I currently run them at 1 hole from full soft front, full soft rear. Of course, I do have slightly uprated front and rear spring rates, and run on 305 RA1's, but the car is now great for my driving style, and perfectly neutral.

If your are on 335 rear Hoosiers, the middle might be good, but you don't want a big oversteery car for a track similar to the Glen. The rear GMG bar makes pretty big swings in handling changes, so once you get the car to take the "set" you like, adjust the front bar instead, as the % of change is smaller and much better for fine tuning.

+1 997gt3north. I'd keep your rear toe the same as before to try and limit the amount of variables you change. Just add more front camber, keep the rear camber similar, but not higher.

CRex

Thanks everyone for the pointers. The idea behind this is really to eliminate body roll and make the car easier to rotate mid-corner. I think I have a fair idea of where to start for my next event...

Appreciate all the pointers, and yes, I reckon this is one of those trial-and-error things... some two years ago I swore I'd not tinker with the suspension on an RS again and here we are... got myself too thick a skull and not enough grey matter inside to learn from the past

As it is, OEM full soft and rear full stiff loosens the car just fine, but the front wallows like a yacht. Heck, makes DE Cup look like Stanley Cup...

Will surely post my thoughts on this setup post-event. Got a few cheater aspects going this time (lightweight battery, fresh Hooters, new alignment) so there are a couple ***** in the air... target is to shave meself 1 sec off a 1:49.5 lap...

I hear you Ranger. This whole thing started with me driving a cup car last month and getting fixated with how little body roll that thing had. And then these GMG bars had to present themselves in some basement sale right around then... it's a series of unintended consequences from then on...

How'd you know? They're blue and white here but equally unforgiving... the owners built it back in the early 90s with hopes of hosting the Chinese F1 race but never got safety-qualified. One wonders...

Aha, that's a new angle--wasn't quite thinking the LSD before but you got me connecting dots. I've had the pleasure of working with MattM for my .1RS and sad to say the grease monkey (oops I mean indy) doing my LSD here doesn't have half the racing experience of Matt's outfit... not saying that's the culprit either, but definitely something to think about.

Your suggestions make a lot of sense--I'll probably run rear camber at 1.8 or -2.0 and not add to it. The thinking around 0.25 (per side) of toe is to keep the rear planted under braking (0.2 as it is wiggles a little and I already run cup rear toe links).

Much appreciate the constructive ideas!!

NJ-GT

I would not use GMG bars in a 997.2 GT3/RS/4.0. They are good to solve some ill handling in the 997.1 GT3 caused by stock mismatch sway bars, and too soft front shocks valving.

The 997.2 has perfect sway bars, and good shocks. To make it faster, it requires removal of rubber bushings in the suspension. To make it even faster, stiffer tranny mount. Then it is custom shocks and new springs. Then it is new uprights. Choose your target and budget and go for it.

The only sway bars I would consider for a 997.2 GT3 are the blade style ones, as they don't bind while turning.

Nizer

How many have actually done this mod?

http://www.torquesolution.com/product-p/ts-por-006.htm

Mvez

Interesting. When my tranny comes out for a re-gear, I might look into this. Urethane tranny mounts on my M3 worked nicely.

TRAKCAR

Looks like it could be a better solution than the Cup car cable fix for the 2-3 shift issue some have..

joyride5

I have done this in my previous 996tt tranny mounts as they were all torn up.
Bought a shore a80 urethane kit and filled the mounts with it.
Definitely increased stiffness to the mounts.
The urethane kit was only 35-40 bucks if I remember correctly.

NJ-GT

If you want to have a fun moment. Place a GoPro under the car at a track day, and look at that tranny move a lot. 700 lbs of combined pendulum weight in between tranny and engine makes for unwanted loss of grip.

It helps even more in a GT3.

NJ-GT

No it won't fix it. I installed a Cup solid transmission mount (expensive all metal no bushings). It was horrible, so much noise, and it did not fix my problems shifting from 2nd to 3rd with lateral loads (996 GT3).

TRAKCAR

Thanks Rad!
So it is purely an engine moving issue?