Car getting unsettled while driving
Thread Starter
Rennlist Member
Joined: Oct 2020
Posts: 161
Likes: 26
Car getting unsettled while driving
Should the last of my suspension chronicles I hope.
So the backend of my 987.2 gets a little wobbly while going over some parts of the road. But it's not too consist on what upsets it, it happens from a variety of speeds, from 35 mph to 70 mph. Horrible roads I think that would trigger this wiggle a lot barely do and the smoother paved roads a bit more leery, but it's not always the same every time. But no control lost and I keep heading straight regardless, some good chassis balance in play to keep me aligned.
It wasn't always like this. It manifested after I recently installed Cayman R suspension on my base 987.2. In addition to replacing the struts and springs, I also replaced the rear LCAs, rear toe links, rear trailing arms, rear and front droplinks, front caster control arm, and inner and outer tie rods. I managed to get that all completed on 8/21/21.
I then got it aligned at Firestone (taking advantage of the lifetime alignment) to Cayman R specs on 8/22/21 and then again on 8/23/21. I was still having some issues so I took it to the dealer on 8/25/21 to get aligned and they mentioned Firestone did a good job of aligning the previous two times. Still having issues as you can see from the video taken on 8/27/21. Even driving around today on 8/29/21 I can still feel the car get a little loose.
I can upload the alignment papers if need be. I'm unsure of what is causing this, whether it be the new suspension parts or the alignment itself, or the springs themselves still settling in. I believe tire pressure can be ruled out since at 40 psi warm and 32 psi warm for the rear wheels, the issue remains the same (I forgot what psi the fronts were at).
So the backend of my 987.2 gets a little wobbly while going over some parts of the road. But it's not too consist on what upsets it, it happens from a variety of speeds, from 35 mph to 70 mph. Horrible roads I think that would trigger this wiggle a lot barely do and the smoother paved roads a bit more leery, but it's not always the same every time. But no control lost and I keep heading straight regardless, some good chassis balance in play to keep me aligned.
It wasn't always like this. It manifested after I recently installed Cayman R suspension on my base 987.2. In addition to replacing the struts and springs, I also replaced the rear LCAs, rear toe links, rear trailing arms, rear and front droplinks, front caster control arm, and inner and outer tie rods. I managed to get that all completed on 8/21/21.
I then got it aligned at Firestone (taking advantage of the lifetime alignment) to Cayman R specs on 8/22/21 and then again on 8/23/21. I was still having some issues so I took it to the dealer on 8/25/21 to get aligned and they mentioned Firestone did a good job of aligning the previous two times. Still having issues as you can see from the video taken on 8/27/21. Even driving around today on 8/29/21 I can still feel the car get a little loose.
I can upload the alignment papers if need be. I'm unsure of what is causing this, whether it be the new suspension parts or the alignment itself, or the springs themselves still settling in. I believe tire pressure can be ruled out since at 40 psi warm and 32 psi warm for the rear wheels, the issue remains the same (I forgot what psi the fronts were at).
Racer
Joined: May 2018
Posts: 471
Likes: 122
From: Colorado
Have your wheels checked for bends and/or balancing. Had a similar experience after lowering my car and had 2 bent wheels (I’d bought from a fellow Rennlister) and 1 out of balance. I’m beyond sorted now. Car is fantastic.
Racer
Joined: May 2018
Posts: 332
Likes: 79
What is your current alignment and are the suspension replacements all OEM?
with a lower ride height, you’re operating in a different window of the bump steer curve. But it could just as well be an alignment issue.
with a lower ride height, you’re operating in a different window of the bump steer curve. But it could just as well be an alignment issue.
Last edited by Squeaky; Aug 30, 2021 at 02:03 PM.
Thread Starter
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Joined: Apr 2002
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From: Oklahoma
hm, weird scenario. your description sounds like an alignment issue (specifically I would think toe out) but your alignment specs look good.
Other possible reasons:
1. tire pressures different (drastically) side to side
2. tire brand/size/model different side to side
3. something loose as mentioned above, or possibly installed incorrectly
4. shocks/struts worn or not able to appropriately control stiffer springs
5. sway bars preloading one side excessively
6. worn wheel bearings or binding brake rotors (not likely)
an out of balance wheel won't cause what you're describing but rather a vibration in the chassis/steering wheel
Other possible reasons:
1. tire pressures different (drastically) side to side
2. tire brand/size/model different side to side
3. something loose as mentioned above, or possibly installed incorrectly
4. shocks/struts worn or not able to appropriately control stiffer springs
5. sway bars preloading one side excessively
6. worn wheel bearings or binding brake rotors (not likely)
an out of balance wheel won't cause what you're describing but rather a vibration in the chassis/steering wheel
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Rennlist Member
Joined: May 2001
Posts: 3,006
Likes: 381
From: Chicago Area
Would a bad or defective strut or strut mount result in a lack of spacial positioning under dynamic loads? Static settings are just that, static. Sure looks like something is moving in a direction that is not intended.
Just a thought, as the issue appears to have presented post installation of parts...
Just a thought, as the issue appears to have presented post installation of parts...
Thread Starter
Rennlist Member
Joined: Oct 2020
Posts: 161
Likes: 26
hm, weird scenario. your description sounds like an alignment issue (specifically I would think toe out) but your alignment specs look good.
Other possible reasons:
1. tire pressures different (drastically) side to side
2. tire brand/size/model different side to side
3. something loose as mentioned above, or possibly installed incorrectly
4. shocks/struts worn or not able to appropriately control stiffer springs
5. sway bars preloading one side excessively
6. worn wheel bearings or binding brake rotors (not likely)
an out of balance wheel won't cause what you're describing but rather a vibration in the chassis/steering wheel
Other possible reasons:
1. tire pressures different (drastically) side to side
2. tire brand/size/model different side to side
3. something loose as mentioned above, or possibly installed incorrectly
4. shocks/struts worn or not able to appropriately control stiffer springs
5. sway bars preloading one side excessively
6. worn wheel bearings or binding brake rotors (not likely)
an out of balance wheel won't cause what you're describing but rather a vibration in the chassis/steering wheel
2. All DWS 06 for all tires and all factory sizes
3. Possibly, I'll probably go and retorque everything. Attached is the list of torque values (in ft-lbs) I could find across forums and videos, hopefully they are pretty close to spec.
4. Cayman R springs with Bilstein B6 struts
5. Maybe
6. Doesn't sound too likely
Instructor
Joined: Mar 2021
Posts: 226
Likes: 108
To confirm, you are torqueing the suspension components while the suspension is under load? The bushings don't like to be torqued while the suspension is uncompressed. My initial thought is a damping issue. Check the shocks for any leaks indicating a blown strut.
Edit: More thoughts. Do you drift to one side when you take your hands off the wheel? Does the car feel fine when braking?
Edit: More thoughts. Do you drift to one side when you take your hands off the wheel? Does the car feel fine when braking?
Last edited by plafondles; Aug 31, 2021 at 04:17 PM.
Thread Starter
Rennlist Member
Joined: Oct 2020
Posts: 161
Likes: 26
To confirm, you are torqueing the suspension components while the suspension is under load? The bushings don't like to be torqued while the suspension is uncompressed. My initial thought is a damping issue. Check the shocks for any leaks indicating a blown strut.
Edit: More thoughts. Do you drift to one side when you take your hands off the wheel? Does the car feel fine when braking?
Edit: More thoughts. Do you drift to one side when you take your hands off the wheel? Does the car feel fine when braking?
I did prior to the third alignment. The car feels completely normal under braking.
Instructor
Joined: Mar 2021
Posts: 226
Likes: 108
I only torqued the top strut mounts under load, not the LCAs or any other parts (would the toe link bushing count, I can't possibly see how that can be reached under load?). That would suck if there was a blown strut considering these are brand new parts.
I did prior to the third alignment. The car feels completely normal under braking.
I did prior to the third alignment. The car feels completely normal under braking.
Toe Link will be fine, but any rubber bushing should be torqued to spec with the car's suspension under load. This means control arm bolts, lower shock bolt, sway bar, ect, otherwise binding can occur affecting performance and premature wear of the bushing. Hub stands help a lot here, since as you mentioned, it is a royal PITA or impossible to tighten suspension with wheels on the car.