grrrmonster

Nice weekend at MidOhio. What had been a nicely neutral setup turned into an understeer issue- car just didn't want to turn in, not getting grip up front.

First adjustment: adjusted tire pressure. Some help, but still persistant. MAde 3 adjustments, helped a bit with the feel, but unable to generate desired grip.

Suspected front tires to be maybe heat cycled out (continental slicks)

Next step taken: stiffened front bar (shortened by one hole to the 2nd hole front the front of the car). Result: understeer reduced much more noticeably,
but turn-in still not what I expected (based on previous visit to MidOhio).

Getting new alignment next week before next event (MidO). Will make sure we are at least -2.5 degrees camber (feedback gleaned from looking at other posts).

The tech is suggesting trying a 7mm spacer up front.

Any feedback on effect of running a spacer up front on understeer & turn in feel?

Stock shocks and springs, all suspension bits are monoballs.

(Yes I know I should get a nice set of Motion Control dampers but WAAAAYY too much $$$$$$$ for a short term fix. Someday...)

RamVA

What tire sizes are you using?

In general running a stiffer front bar will make the car push more, not less. You are better off going stiffer in the rear (and probably softer in the front, but that might create other issues if turn in isn't good).

If you can use a 7mm spacer you can probably just run a 10mm wider tire. If you can it would make a bigger difference.

It's hard to guess without knowing tire sizes, but I suspect it's either cycled tires or front toe. If you are running stock-ish sizes/stagger then it has to be tires or a setup problem.

996FLT6

Stiffen up front swaybar only adds more understeer. What's the swaybar setting on rear? Bigger fronts ie wider always a good thing plus add shims for more caster. 8+
caster is always a good thing. You're LSD is kosher? Mike

ShakeNBake

How stable does the rear feel?

grrrmonster

Rear is great.
New Gard LSD differential
245/40-18's in front.


One other change we tried-- swapped out to another set of wheels with new BFG tires-- same results, so put the slicks back on.

GT2 rear bar, at full soft setting.

My tech says the .1 inherently have more grip at rear than front, hence the suggestion to widen front track.

suggestions on alignment settings?

chub2000

call Tom @ TPC

RamVA

I suggest your tech doesn't know these cars. 7.1 non-RS cars generally shouldn't push much on track, and if he's the guy that set it up in the first place then that's maybe the problem.

Stiffen the rear bar and soften the front bar. A click or two on each.
Run -2.5 camber all around (as you suggested).
Just a minute or two of toe in in front.
Between 25-30 total toe in the rear. And get locking plates so it holds.

I wouldn't bother with spacers until you do the above, fiddle with the bars, and check it out. The bars alone will make a much bigger difference in their adjustment range than 14mm more of track, as will 10mm of tire width. Honestly, I doubt 7mm spacers make meaningful difference and if you have to go there you have a bigger problem.

When you get it aligned post up your "before" specs and we can be more helpful.

996FLT6

Wow. Just let u know for 911's in general if u want to dial out understeer it's opposite of what your shop suggest. U want tail happy oversteer it's the opposite setting. Total front soft total rear stiff- nice oversteer. Rear soft full stuff front- its total understeer- trailbrake well!!! Mike ps- if u felt understeer got better with stiffer front I recommend a few autocross's for u- constructive critisism. Mike

BBMGT3

yeah, stiffening front bar makes understeer worse, not sure why you felt it was better. Not only does your tech not seem to know what he's doing, but perhaps you don't know what you're feeling either.

Get someone who knows the car to do a lap or two and tell you whats up.

grrrmonster

Thanks. After nearly 30 years of track driving and 15+ years of racing, maybe I don't know what I'm feeling when the front end is washing out and pushing, and the car not wanting to turn down to the apex and generate grip like it was at previous events. The adjustment on the front bar helped.

I suspect the alignment is not at all where it needs to be (hard to tell at the track). Also suspect that tieing the car down on the trailer with straps around the wheels may be pulling the wheels (and alignment) out. Have a set of Rennline tie downs that will be going on this week.

Still learning the GT3- so beg some patience as I still have a lot to learn about it.

My primary interest was around what effect running a front spacer would have.

How much wider is the front track of the RS?

Will post up the "as is" setting when we get it on the rack-- I suspect it is way out from where it should be.
Where should the caster be set?

Thanks for the input.

tcsracing1

i find that by stiffening the front bar it makes understeer worse especially in hard corners. The car will just plow as to opposed to getting that "bite" and turning in.

Tom@TPC Racing

It has been my experience that the only times by adding more front bar helps with corner entry is when the increased front roll stiffness is masking another issue(i.e. weak front shocks or shocks close to bottoming or braking too late/hard for shock/spring package or too much front toe out. etc). Too many unknown variables. Working with a good shop to set ride height and alignment is definitely a good place to start. IMHO, I would not even consider wheel spacers at this stage of the game. Good luck and enjoy the experience from the progress.

997gt3north

Since you have:
- a Guard LSD (as do I)
- a GT2 rear bar (as do I)

Let me give you the setting that work on my car:

-2.3 front with zero toe
front OE bar one stiffer than as delivered setting (thus not full soft but 1 from full soft)
-1.75 rear camber with 2mm per side toe in
GT2 bar in middle for Hoosers

I have rotated the front struts, shimmed the LCAs to get the camber numbers (plus it widens the track and increases caster back to OE 'type' numbers around 8) - and I run 7mm front spacers to further widen the front track


my guess is that you have too much rear camber and not enough front AND you have to switch the sway bar settings by one hole on each end

I also have the LSD on the higher lockup settings (which further promotes understeer) and my setup is neutral.

Furthermore, I have lowered the rear ride height more than the front (further increasing rear grip) which should further increase understeer and yet the car is neutral. You need more camber front than rear (about .5) and with slicks you need slightly more rear bar.

sin911

The problem I had with my .1 was that the car's body rolled a lot due to the soft suspension and sway bar settings, so I had the shop tighten the rear bar (I had GT2 bar at the rear as well) to the middle setting. This made a significant change to the cars handling.

I concur with 997gt3north. Around -2.5 Front camber, zero toe & -2.2 to -2.0 rear camber with slight toe in. The front felt very planted to me with the front bar one from softest and rear in the middle.

BTW on the .1 GT3 and RS have the same track on the front.

chardonet

Anyone have the part number for the GT-2 sway bar? Thanks in advance!