GMG 997 GT3 Sway Bars feedback
10-21-2008, 01:10 AM
#1
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GMG 997 GT3 Sway Bars feedback
After testing the RS at a local road with the stock sway bars, I was quite disappointed that even with the front at full soft and rear at full stiff, the car will still push.
I mounted a set of GMG sway bars last week, and ran them at an AutoX on Sunday with PCA.
The push is gone.
Initially I set the rear bar in the middle and the front bar in the middle as well. This is a conservative setting, as it would provide 5 sway bar settings towards oversteer, and 5 towards understeer.
The car with this setup was pushing, but that was expected. Then I move the front bar two holes towards soft (full soft). This made the car undriveable, due to excessive oversteer. I like a loose car for autoX, but not this loose.
The good news was that I got into an excessive oversteer car without using the rear bar at full stiff.
Finally, I set the rear bar at full stiff, and the front bar on the middle. I should have set the front bar one from soft, leaving the rear bar in the same place all day. However, I move the rear bar at full stiff to find out about power delivery on turn exit. The car was neutral with this setup, but the rear bar at full stiff made the car lift the inside rear wheel on tight turn exits (I was on Michelin Slicks at the time) and the LSD was working too hard.
Next time, I will set the rear bar on the middle, and front bar one from soft. This will reduce the problem on tight turn exits having the inside rear wheel with low grip. This setup will add just a little more oversteer, because moving both bars one hole each doesn't keep the balance, as the front bar is bigger.
I'm running on an unknown alignment, I know the car needs an alignment, but the previous owner doesn't know any better about last alignment date, and specs. I will obtain a pre-alignment print out, so I can determine the initial bar settings with my intended and proven alignment specs.
I mounted a set of GMG sway bars last week, and ran them at an AutoX on Sunday with PCA.
The push is gone.
Initially I set the rear bar in the middle and the front bar in the middle as well. This is a conservative setting, as it would provide 5 sway bar settings towards oversteer, and 5 towards understeer.
The car with this setup was pushing, but that was expected. Then I move the front bar two holes towards soft (full soft). This made the car undriveable, due to excessive oversteer. I like a loose car for autoX, but not this loose.
The good news was that I got into an excessive oversteer car without using the rear bar at full stiff.
Finally, I set the rear bar at full stiff, and the front bar on the middle. I should have set the front bar one from soft, leaving the rear bar in the same place all day. However, I move the rear bar at full stiff to find out about power delivery on turn exit. The car was neutral with this setup, but the rear bar at full stiff made the car lift the inside rear wheel on tight turn exits (I was on Michelin Slicks at the time) and the LSD was working too hard.
Next time, I will set the rear bar on the middle, and front bar one from soft. This will reduce the problem on tight turn exits having the inside rear wheel with low grip. This setup will add just a little more oversteer, because moving both bars one hole each doesn't keep the balance, as the front bar is bigger.
I'm running on an unknown alignment, I know the car needs an alignment, but the previous owner doesn't know any better about last alignment date, and specs. I will obtain a pre-alignment print out, so I can determine the initial bar settings with my intended and proven alignment specs.
10-21-2008, 02:21 AM
#3
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The RS is better compared to my 2004 GT3, where the only thing I liked (stock) was the engine. I did not like the transmission, brakes, style, interior, suspension and weight. I got to improve everything but the exterior, and fell in love with it.
I like everything in the RS, except transmission, suspension and weight. However, tranny and suspension are better than the 2004 GT3. Weight, is just wrong, this car weighed 3,320 lbs with a full tank of gas (I always take an initial weight reading before doing mods).
I like everything in the RS, except transmission, suspension and weight. However, tranny and suspension are better than the 2004 GT3. Weight, is just wrong, this car weighed 3,320 lbs with a full tank of gas (I always take an initial weight reading before doing mods).
10-21-2008, 02:43 AM
#4
Drifting
An alignment on these cars does wonders on its own. Most of the tracks I go to here are either very tight or very fast, but the car seems to be fine in all conditions. My lap times are up there so I know I'm pushing the car and myself hard enough to reach the limits (with a safety margin of course). Conversely, it could also be driving style as in the past, I've had to drive around car setup changes throughout race distances.
I wonder also if the GT3 is more neutral because of the narrower rear track and less rear downforce? I do agree through that it may be worth it to get aftermarket anti-roll bars, just so that you have the option of adjustment. My car is at the stock settings for the anti-roll bars which don't leave much, if any, room for balance adjustment.
For those that have never autocrossed, it may be worthwhile to note that a car that is neutral on an auto-x will most definitely be very biased towards oversteer on the track, something that would probably be a bit difficult to handle. If you're going to the track with the GMG anti-roll bars, start with a more conservative setting than what NJ-GT is running.
I wonder also if the GT3 is more neutral because of the narrower rear track and less rear downforce? I do agree through that it may be worth it to get aftermarket anti-roll bars, just so that you have the option of adjustment. My car is at the stock settings for the anti-roll bars which don't leave much, if any, room for balance adjustment.
For those that have never autocrossed, it may be worthwhile to note that a car that is neutral on an auto-x will most definitely be very biased towards oversteer on the track, something that would probably be a bit difficult to handle. If you're going to the track with the GMG anti-roll bars, start with a more conservative setting than what NJ-GT is running.
10-21-2008, 08:35 AM
#5
sway bars
Please give us feedback with the GMG bars on the track. Have you tried a full soft bar in back and stiffer setting up front? Also, what size Michellin slicks are you running?
10-21-2008, 12:44 PM
#6
Interesting in that it sounds like you are going to end up in a similar setup that i have
- gt2 rear bar in the middle hole (same thickness as gmg bar)
- front bar one from soft (front gmg bar slightly stiffer than stock)
I have suspected the front bar difference is a balance of you running a larger front tire that has better grip - I plan on trying Pirelli slicks and Hoosiers next season and this was going to be the one change I was going to do - that is stiffen the front bar to the middle hole to compensate for the added front grip versus the r888 that I'm now running
Clearly there are so many factors that come into play for each of us picking where we like the sways set:
- driving style
- loose or tight car preference
- type of track (long fast, slow with turns)
- tires and pressures
- track temps
- track smooth or ruff
- etc
But at least there is now enough growing information about the setup of this car to make it work.
Concerning the alignment, from what I know so far, I think the 997gt3 prefers slightly less rear camber than the 996gt3 all else being equal for similar results - thus I have ended up in the -2.25 versus what I believe the more standard rear -2.5 for the 996
Please keep us posted
Paul
- gt2 rear bar in the middle hole (same thickness as gmg bar)
- front bar one from soft (front gmg bar slightly stiffer than stock)
I have suspected the front bar difference is a balance of you running a larger front tire that has better grip - I plan on trying Pirelli slicks and Hoosiers next season and this was going to be the one change I was going to do - that is stiffen the front bar to the middle hole to compensate for the added front grip versus the r888 that I'm now running
Clearly there are so many factors that come into play for each of us picking where we like the sways set:
- driving style
- loose or tight car preference
- type of track (long fast, slow with turns)
- tires and pressures
- track temps
- track smooth or ruff
- etc
But at least there is now enough growing information about the setup of this car to make it work.
Concerning the alignment, from what I know so far, I think the 997gt3 prefers slightly less rear camber than the 996gt3 all else being equal for similar results - thus I have ended up in the -2.25 versus what I believe the more standard rear -2.5 for the 996
Please keep us posted
Paul
10-21-2008, 03:17 PM
#7
sway
Hey Paul,
I agree with your alignment suggestions.
I have actually experimented, along with a lot of the others on Rennlist, with various wheel/tire combos and alignments.
Summary:
More camber up front than rear
Even tire pressures if not slightly less in the rear
Anything more than -2.4 camber in the rear gets very loose and gives up a lot in braking abilities.
Anything from -2.5 to -3.5 camber upfront is well tolerated. Benefits include very even tire wear and elimination of any push. I have experimented with multiple different degree's of camber with both sport cups / toyo's and Hoosier R6's. In my hands and driving style - I prefer a setting of approximately -2.8 up front. I have run up to -3.5 without a lot of added benefit. The car is very benign on the street with increased camber upfront.
Like others on the board, I will try real slicks next season which will probably put all our alignment settings out of sync with everything we have done so far.
I agree with your alignment suggestions.
I have actually experimented, along with a lot of the others on Rennlist, with various wheel/tire combos and alignments.
Summary:
More camber up front than rear
Even tire pressures if not slightly less in the rear
Anything more than -2.4 camber in the rear gets very loose and gives up a lot in braking abilities.
Anything from -2.5 to -3.5 camber upfront is well tolerated. Benefits include very even tire wear and elimination of any push. I have experimented with multiple different degree's of camber with both sport cups / toyo's and Hoosier R6's. In my hands and driving style - I prefer a setting of approximately -2.8 up front. I have run up to -3.5 without a lot of added benefit. The car is very benign on the street with increased camber upfront.
Like others on the board, I will try real slicks next season which will probably put all our alignment settings out of sync with everything we have done so far.
Last edited by sasportas; 10-21-2008 at 03:19 PM. Reason: typo
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10-21-2008, 04:24 PM
#8
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The diameters are 2.8% within the tolerance on the stock ABS, so no ABS error.
These skinny tires are a temporary thing.
Funny thing is that I dropped 2.8 seconds on a 77 secs AutoX course by switching from 265/325 MPSC to 24/27 MPSX. My best run on hot MPSC was 76.9 secs, my first run on cold MPSX was 74.8 secs, and my 3rd run on them a 74.09 secs. I still left time on the slicks, easily another second, I just under drove them and they did not get to operating temperatures (I measured 105 degrees front and 140 degrees rear, they require 140/195 minimum)
10-21-2008, 10:53 PM
#9
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More 10s and 12s, or 10/12.5, bigger? What's your plan for the front fenders?
Also right now I have 9s and 11s on my 930. I've heard that you can stuff 10s and 12s under the same fenders which makes me want to sell my fikses and maybe someday get some CCWs in that size. However, I've also seen mild flares for my car to give it more track. In your opinion how much of a difference do you think the track makes given equal wheels and tires? The 930 is the same width as a 996 GT3 (about) at 70 inches. While the 997 RS as well as the flares I'm looking at are 73 inches wide.
Also right now I have 9s and 11s on my 930. I've heard that you can stuff 10s and 12s under the same fenders which makes me want to sell my fikses and maybe someday get some CCWs in that size. However, I've also seen mild flares for my car to give it more track. In your opinion how much of a difference do you think the track makes given equal wheels and tires? The 930 is the same width as a 996 GT3 (about) at 70 inches. While the 997 RS as well as the flares I'm looking at are 73 inches wide.
