Check your alignment before going to the track
12-03-2005, 01:43 PM
#1
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Check your alignment before going to the track
I just want to share my experience, so it might help to keep us safer.
I didn't realize that the GT3 was losing the alignment frequently until the beginning of this year. I found a shop with a brand new state of the art Hunter Computerized alignment equipment, and they were charging $75 to do my alignment. I always get a print out before and after. I was going to this place every 2 weeks, and I was really amazed that my before print was showing the rear toe consistently wrong. These are a few samples of my rear axle readings before alignment, I always set my rear axle to 0.25° Toe in per side:
LR / RR
0.10° Toe out / 0.50° Toe out
0.12° Toe in / 0.06° Toe out
1.14° Toe out / 1.00° Toe out
0.26° Toe in / 0.29° Toe in
0.15° Toe in / 0.22° Toe in
0.26° Toe in / 0.12° Toe in
0.40° Toe in / 0.21° Toe in
The few times I have hit the track with the alignment off (last year), my car didn't feel good at all. I couldn't justify it for a while, a $100k sport car that didn't give me the confidence of my old Boxster S on the turns. I could only go fast on straights, accelerating faster than others and braking later than others (muscle car road racer), but when turning the car didn't feel planted, and most of the cars on my run group were faster.
There was this one day at Pocono North, entering the bowl (NASCAR turn 3) and I spun the car. Few laps before I almost spun it at the same place. I went to the pits and checked my MPSC, tire pressures and wear were ok. This is the track configuration I've driven the most, because it's just 1 1/2 hours from my place, and a lot of times there are arrive and drive events with some clubs. I always squeeze the gas post apex at that turn. This episode took me to start the research on what is going on with this car. The car just went away with no signs, no feedback, no tire sound.
In another event at the same track last year, we had an autocross in the Pocono East Course and open track on the North course. I spun the car on the autocross, the car just went away without feedback, I was driving on 3rd gear with my stock R&P (probably over 80mph). By that time I suspected the alignment was off in just 3 weeks after a fresh alignment, but I couldn't confirm it. On the same event I hit the Pocono North Course, and I couldn't keep up with any car at the track at that moment. Typically, I'm capable to keep the car at full gas on the NASCAR turn, but that day I couldn't go over 110mph. A regular 996 and a 996 C4S were walking away from me at the bowl pretty easy.
I haven't hit a track event this year without a fresh alignment. The confidence this car gives when properly setup is pretty high. I beat my fastest lap ever on Pocono North course on light rain. Talking about rain, I couldn't go to a track session last year if it was raining, because the car felt scary. I don't skip track sessions on the rain anymore, because the car feels safe.
The rear toe links and control arm use eccentrics. This problem is not unique to the GT3/GT2. Every 986, 996, 987, 997 and the Cayman is using eccentrics to adjust rear toe and rear camber. The problem is more obvious on the GT3, because it has a stiffer suspension so it will move the eccentrics out of their setup more often, and the car goes to the track more frequently.
The solution to this problem is easy: Don't go to the track without checking your alignment. It takes 1/2 hour at a local shop to check the alignment, if the alignment is off then re-align the car and have fun at the track (safer fun).
If you want to correct the design problem, here are the options I've found so far:
Rear Camber:
A) Replace the rear control arm with the GT3RS control arm (2 pieces like the front one), and use shims to setup camber. Replace the control arm bushing that attach to the subframe with the bushing on the GT3Cup toe link.
B) Keep the stock control arm and replace the control arm bushing that attach to the subframe with the bushing on the GT3Cup toe link. Install the ERP upper link to adjust camber.
C) Keep the stock control arm and replace the control arm bushing that attach to the subframe with the bushing on the GT3Cup toe link. Install the CROSS arm link to adjust camber.
D) Replace the rear control arm with the ERP arm link. This require an additonal link to the subframe
Rear Toe (the critical one):
1) Install the GT3Cup toe links. Devek has the new version available. That kit contains new bushing for the toe link attachment to the subframe.
2) Replace the stock toe link bushing that attach to the subframe with the bushing on the GT3Cup. Install the Cross upper toe link to adjust Toe.
3) Replace the stock toe link bushing that attach to the subframe with the bushing on the GT3Cup. Install the ERP upper toe link to adjust Toe.
4) Replace the stock toe link with the ERP lower toe link.
I'm still trying to decide between B1, D1, B4 and D4. Leaning toward D1. There is the radical solution to replace the entire rear suspension setup with the ERP monoball links (5 per side), around $3k on parts plus labor.
Now, all we need is one of our sponsors with a group buy price for a solution package.
I didn't realize that the GT3 was losing the alignment frequently until the beginning of this year. I found a shop with a brand new state of the art Hunter Computerized alignment equipment, and they were charging $75 to do my alignment. I always get a print out before and after. I was going to this place every 2 weeks, and I was really amazed that my before print was showing the rear toe consistently wrong. These are a few samples of my rear axle readings before alignment, I always set my rear axle to 0.25° Toe in per side:
LR / RR
0.10° Toe out / 0.50° Toe out
0.12° Toe in / 0.06° Toe out
1.14° Toe out / 1.00° Toe out
0.26° Toe in / 0.29° Toe in
0.15° Toe in / 0.22° Toe in
0.26° Toe in / 0.12° Toe in
0.40° Toe in / 0.21° Toe in
The few times I have hit the track with the alignment off (last year), my car didn't feel good at all. I couldn't justify it for a while, a $100k sport car that didn't give me the confidence of my old Boxster S on the turns. I could only go fast on straights, accelerating faster than others and braking later than others (muscle car road racer), but when turning the car didn't feel planted, and most of the cars on my run group were faster.
There was this one day at Pocono North, entering the bowl (NASCAR turn 3) and I spun the car. Few laps before I almost spun it at the same place. I went to the pits and checked my MPSC, tire pressures and wear were ok. This is the track configuration I've driven the most, because it's just 1 1/2 hours from my place, and a lot of times there are arrive and drive events with some clubs. I always squeeze the gas post apex at that turn. This episode took me to start the research on what is going on with this car. The car just went away with no signs, no feedback, no tire sound.
In another event at the same track last year, we had an autocross in the Pocono East Course and open track on the North course. I spun the car on the autocross, the car just went away without feedback, I was driving on 3rd gear with my stock R&P (probably over 80mph). By that time I suspected the alignment was off in just 3 weeks after a fresh alignment, but I couldn't confirm it. On the same event I hit the Pocono North Course, and I couldn't keep up with any car at the track at that moment. Typically, I'm capable to keep the car at full gas on the NASCAR turn, but that day I couldn't go over 110mph. A regular 996 and a 996 C4S were walking away from me at the bowl pretty easy.
I haven't hit a track event this year without a fresh alignment. The confidence this car gives when properly setup is pretty high. I beat my fastest lap ever on Pocono North course on light rain. Talking about rain, I couldn't go to a track session last year if it was raining, because the car felt scary. I don't skip track sessions on the rain anymore, because the car feels safe.
The rear toe links and control arm use eccentrics. This problem is not unique to the GT3/GT2. Every 986, 996, 987, 997 and the Cayman is using eccentrics to adjust rear toe and rear camber. The problem is more obvious on the GT3, because it has a stiffer suspension so it will move the eccentrics out of their setup more often, and the car goes to the track more frequently.
The solution to this problem is easy: Don't go to the track without checking your alignment. It takes 1/2 hour at a local shop to check the alignment, if the alignment is off then re-align the car and have fun at the track (safer fun).
If you want to correct the design problem, here are the options I've found so far:
Rear Camber:
A) Replace the rear control arm with the GT3RS control arm (2 pieces like the front one), and use shims to setup camber. Replace the control arm bushing that attach to the subframe with the bushing on the GT3Cup toe link.
B) Keep the stock control arm and replace the control arm bushing that attach to the subframe with the bushing on the GT3Cup toe link. Install the ERP upper link to adjust camber.
C) Keep the stock control arm and replace the control arm bushing that attach to the subframe with the bushing on the GT3Cup toe link. Install the CROSS arm link to adjust camber.
D) Replace the rear control arm with the ERP arm link. This require an additonal link to the subframe
Rear Toe (the critical one):
1) Install the GT3Cup toe links. Devek has the new version available. That kit contains new bushing for the toe link attachment to the subframe.
2) Replace the stock toe link bushing that attach to the subframe with the bushing on the GT3Cup. Install the Cross upper toe link to adjust Toe.
3) Replace the stock toe link bushing that attach to the subframe with the bushing on the GT3Cup. Install the ERP upper toe link to adjust Toe.
4) Replace the stock toe link with the ERP lower toe link.
I'm still trying to decide between B1, D1, B4 and D4. Leaning toward D1. There is the radical solution to replace the entire rear suspension setup with the ERP monoball links (5 per side), around $3k on parts plus labor.
Now, all we need is one of our sponsors with a group buy price for a solution package.
Last edited by NJ-GT; 12-03-2005 at 04:01 PM.
12-03-2005, 03:58 PM
#3
Rennlist Member
Yup, the toe in the rear seems to go off pretty fast. Last time I checked the alignment was because of really bad tire wear inside rear left. At first I thought it was because I was running very low pressures to start but after I saw the alignment specs I knew better. I believe the right rear was toed out pretty bad and this is the left rear after three track days. Guess I better call Devek.
Last edited by Mike K.; 03-28-2013 at 08:21 PM.
12-03-2005, 07:39 PM
#4
Burning Brakes
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NJ-GT, another great detailed post. Yes, I've also found the rear alignment on my 986S to go out frequently and agree the eccentrics suck but they are a common setup. Mine went 1/2" (1º) toe out once. Luckily, I noticed it right away and turned around and went home. Didn't even want to take it on the freeway it was so unstable. What I've found, unfortunately, is that the more you adjust it, the more it goes out. There apparently is enough of a texture on the eccentrics and bolts to help hold them in place. The play in adjusting them is easily enough to throw the alignment off by the numbers (typical) you are seeing. What I found helped a lot was to put in fresh bolts and eccentrics. The slight texture on the new parts seems to help hold them in place longer. The clamping/eccentric doesn't do much to hold anything. I don't think I'll ever see any trick threaded control arms for my 986, so that's what I've learned to live with. Post any pics/links of any cool parts you find so I can drool.
12-04-2005, 10:25 AM
#5
Former Vendor
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It is amazing how fast the toe / camber changes in these cars. We replaced the eccentrics all the time in cars doing track events. Replacing these components is the way to go. Here is a partial ERP listing that I thought some of you might like to see what is available..
Last edited by viperbob; 05-21-2009 at 09:20 PM.
12-04-2005, 12:00 PM
#6
Burning Brakes
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Maybe this is a contributing factor to my crash at WGI?? I'd love to think it wasn't all my fault!!
Can't check now as the car is in pieces and the insurance company totaled it!!
Can't check now as the car is in pieces and the insurance company totaled it!!
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12-04-2005, 08:38 PM
#9
Burning Brakes
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USAA, however I don't know yet whether they will continue to insure me. I think the only reason I got this far was I have never, ever raced, practiced for a race, nor intended to ever do so. I have never even auto crossed, as that is a competion event. I only do DEs and I had a classroom schedule to go with my track time. Still, a large claim for a totaled car will not make me any friends with USAA. I would suspect that I am on borrowed time.
