Suspension vs I-85 & I-95, Observations, Options
04-14-2016, 11:48 AM
#16
Pro
Thread Starter
So, I decided to go with the GT3 front lower control arms with factory rubber bushings and remove the Ground Control front camber plates. Just placed my order with Tarret for the GT3 LCA kit.
I'll report once I have everything in and get the guys over at GMP Performance to make the hardware changes.
As an aside, I took the car out for a drive yesterday, and the only thing that bothered me at all was the low-speed creaking of the sway bar bushings driving in and out of the neighborhood. The car is nice and tight now, well-sorted, but comfortable for most of my driving. It's those expansion joints, bridge transitions, and bad interstate roads at 75 mph that wear me out. We'll see how far I can go toward more comfort without sacrificing too much handling.
I'll report once I have everything in and get the guys over at GMP Performance to make the hardware changes.
As an aside, I took the car out for a drive yesterday, and the only thing that bothered me at all was the low-speed creaking of the sway bar bushings driving in and out of the neighborhood. The car is nice and tight now, well-sorted, but comfortable for most of my driving. It's those expansion joints, bridge transitions, and bad interstate roads at 75 mph that wear me out. We'll see how far I can go toward more comfort without sacrificing too much handling.
04-16-2016, 09:08 PM
#17
Race Director
Join Date: Oct 2004
Location: KC ex pat marooned in NY
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Think about installing GT3 lower control arms instead of the camber plates. You can dial in a fair amount of neg camber with less nvh. My set up is pretty similar to yours now -- stock front bar, GT2 rear bar, Tarret rear toe links and locking plate, stock springs and struts, front GT3 LCA's, TPC DSC and an aggressive alignment. It handles really well and won't shake out your molars. If I don't complain on the twisties and my wife doesn't complain going over bumps I know I got it right 
04-17-2016, 01:26 AM
#18
Pro
Thread Starter
Yes. I'm grateful for the suggestion. I wasn't aware of the GT3 control arm option, but when it was mentioned, it became a pretty obvious change I needed to make. Get the camber options I want in the front while keeping some factory rubber in there--rubber that is good enough for the GT3.
My only metal joints will now be with the rear dog bones and toe links. And the polyurethane sway bushings will be gone.
The RSS dog bones seem necessary to get back to the camber I want, given I'm lowered some on the COs. I'm not sure I need the toe links in, and I'm also not sure how much they'll affect ride comfort, versus noise. When I removed the dog bones and rear toe links, road noise transmission from the rear wheels into the cabin improved, but I don't recall thinking that bump harshness changed much in the rear. I'm sure there is some effect, but I'm thinking the rear toe links are worth putting in. Don't they help maintain proper toe over bumps?
Has anyone ever felt the need for, or actually used, front toe links? The guys at GMP recommended against them when I originally made all the changes.
Are toe changes over bumps not something that needs to be addressed for street use? Maybe I should just leave all (front and rear) toe links out--assuming I can achieve proper toe and camber in the rear with just dog bones.
Still sorting this out...
My only metal joints will now be with the rear dog bones and toe links. And the polyurethane sway bushings will be gone.
The RSS dog bones seem necessary to get back to the camber I want, given I'm lowered some on the COs. I'm not sure I need the toe links in, and I'm also not sure how much they'll affect ride comfort, versus noise. When I removed the dog bones and rear toe links, road noise transmission from the rear wheels into the cabin improved, but I don't recall thinking that bump harshness changed much in the rear. I'm sure there is some effect, but I'm thinking the rear toe links are worth putting in. Don't they help maintain proper toe over bumps?
Has anyone ever felt the need for, or actually used, front toe links? The guys at GMP recommended against them when I originally made all the changes.
Are toe changes over bumps not something that needs to be addressed for street use? Maybe I should just leave all (front and rear) toe links out--assuming I can achieve proper toe and camber in the rear with just dog bones.
Still sorting this out...
04-17-2016, 08:35 AM
#19
The toe settings in the rear can get knocked out of spec pretty easily if you track the car or drive it aggressively. Then you get premature tire wear in the rear. The Tarett toe links and locking plate for the most part eliminate the problem. I didn't notice any additional ride harshness when I installed them.
04-19-2016, 05:27 PM
#20
Pro
Thread Starter
Thanks again for all the help. I'm going to put the rear toe links back in, lock out the eccentric, and not pick up any front toe links for now. Waiting for parts at this point...
Louis
Louis
04-20-2016, 08:48 PM
#21
Rennlist Member
Ever driven an old patch of interstate at 75 mph and wondered how your car, your wheels, and your back are still in one piece afterwards?
I don't know what to do about my suspension.
I like to drive long distances, and I often travel from Charlotte to DC and back. When I can, I go VA back roads, but that doesn't always work with my schedule.
I have driven that route (I-85 to I-95) with the car bone stock. I've driven it with: Ohlins R&T coilovers (14 clicks out), Ground Control camber plates in front, RSS toe links, RSS dog bones, GMG sways, and Tarret drop links. I then softened the coilovers to 18-clicks out and drove the route. I then softened them all the way (about 22 clicks out) and removed everything else but the sways and drove the route. (The coilovers have always been set to minimum drop, which amounts to about a half inch.)
I still can't relax and drive because I have to brace myself for the next road-to-bridge expansion joint that slams me around as if I'm in a wooden wagon!
Is there no way to make the 997.1 Turbo not bounce like a boat (stock) without sacrificing your back???
Observations:
- I loved the effect of putting everything on until I took a long trip up the interstate--more noise, tiring over the filled potholes and road imperfections, and the big road transitions WILL hurt you if you are not seated correctly.
- Taking the links out reduced the NVH-type noise, but I'm thinking of putting them back, because the handling is noticeably degraded without the links, even with the coilovers and sways still on.
- The sways are either coming off, or the bushings will be changed to rubber, because the urethane bushings are noisy--creak, creeaak, creak, creak...
- My rears will not go less than -1.4* camber with the eccentric. It was with the dog bones and toe links that I had the rears set at -1.0* camber, and the car felt better through a curve then than it has since. (I had -1.4* in the front then, and still do.)
- To me, the stock PASM setup was too soft (bouncy) in "Normal" mode and way too stiff for use on any public road I know of in "Sport" mode.
Options?
- Do I go softer on the Ohlins coilover springs? Can it be done without causing a shock/spring mis-match?
- Is there an OE-style strut/spring alternative that is better than stock? Or, do I only have lowering springs or coilovers to choose from? (My experience looking at just springs was that all of them were meant to lower the car and were stiffer than I really need them to be.) There is seemingly no alternative that is meant to improve upon the stock setup without the track in mind--no in-between.
- I know of the TPC PASM Module, but is it meant to help with interstate expansion joints, so to speak? I can't tell from the chatter whether they make a significant improvement on the stock "Normal" PASM mode. It seems meant to improve track performance, and I don't know how that translates to my issues.
LP
I don't know what to do about my suspension.
I like to drive long distances, and I often travel from Charlotte to DC and back. When I can, I go VA back roads, but that doesn't always work with my schedule.
I have driven that route (I-85 to I-95) with the car bone stock. I've driven it with: Ohlins R&T coilovers (14 clicks out), Ground Control camber plates in front, RSS toe links, RSS dog bones, GMG sways, and Tarret drop links. I then softened the coilovers to 18-clicks out and drove the route. I then softened them all the way (about 22 clicks out) and removed everything else but the sways and drove the route. (The coilovers have always been set to minimum drop, which amounts to about a half inch.)
I still can't relax and drive because I have to brace myself for the next road-to-bridge expansion joint that slams me around as if I'm in a wooden wagon!
Is there no way to make the 997.1 Turbo not bounce like a boat (stock) without sacrificing your back???
Observations:
- I loved the effect of putting everything on until I took a long trip up the interstate--more noise, tiring over the filled potholes and road imperfections, and the big road transitions WILL hurt you if you are not seated correctly.
- Taking the links out reduced the NVH-type noise, but I'm thinking of putting them back, because the handling is noticeably degraded without the links, even with the coilovers and sways still on.
- The sways are either coming off, or the bushings will be changed to rubber, because the urethane bushings are noisy--creak, creeaak, creak, creak...
- My rears will not go less than -1.4* camber with the eccentric. It was with the dog bones and toe links that I had the rears set at -1.0* camber, and the car felt better through a curve then than it has since. (I had -1.4* in the front then, and still do.)
- To me, the stock PASM setup was too soft (bouncy) in "Normal" mode and way too stiff for use on any public road I know of in "Sport" mode.
Options?
- Do I go softer on the Ohlins coilover springs? Can it be done without causing a shock/spring mis-match?
- Is there an OE-style strut/spring alternative that is better than stock? Or, do I only have lowering springs or coilovers to choose from? (My experience looking at just springs was that all of them were meant to lower the car and were stiffer than I really need them to be.) There is seemingly no alternative that is meant to improve upon the stock setup without the track in mind--no in-between.
- I know of the TPC PASM Module, but is it meant to help with interstate expansion joints, so to speak? I can't tell from the chatter whether they make a significant improvement on the stock "Normal" PASM mode. It seems meant to improve track performance, and I don't know how that translates to my issues.
LP
i don't know how well this setup would work over fwy expansion joints.