964 / 993 Control Arm Bushings
05-18-2010, 01:06 PM
#301
That much I tend to agree with
For a while now I thought you just didnt care for me --
I guess I look at the issue with the cavity bushings as found on the front lower control arm, forward point, a little differently. Yes, they are made this way for comfort (NVH) but the nature of how the inner and outer portion of the rubber itself distorts and flexes isnt at all appealing to me.
What sent me off this road to develop a reasonably priced solution is what I saw 9 years ago when I had my first 993 on the alignment rack. With the lasers on their targets, I pulled down on the car while under the front mainly to check out the bumpsteer that so many folks talked about. Sure enough, just a small amount of suspension displacement, the lasers showed this nasty geometry. And this was as just ROW height on a 40k mile car!!!
Then I dove further into other potential causes and immediately it was obvious the forward pick up point of the lower control arm was indeed 'rubber' -- its how things in racing are described when not up to the task. In other words way too compliant laterally speaking. Just by hand forcing a control arm in and out sent the toe wacky on the laser targets -- I thought this is NO good for maintaining front end geometry. Imagine what is happening while on the brakes with larger forces at work!!
I thought the rubber cavity bushings (durometer 65-70) were just too compliant and of course spherical bearings over the top for predominantly a street car -- what is inbetween?
Just my thoughts on things. I will say I may be too critical given the time I spend with racecars where suspension installation stiffness needs to be as infinite as possible
For a while now I thought you just didnt care for me -- I guess I look at the issue with the cavity bushings as found on the front lower control arm, forward point, a little differently. Yes, they are made this way for comfort (NVH) but the nature of how the inner and outer portion of the rubber itself distorts and flexes isnt at all appealing to me.
What sent me off this road to develop a reasonably priced solution is what I saw 9 years ago when I had my first 993 on the alignment rack. With the lasers on their targets, I pulled down on the car while under the front mainly to check out the bumpsteer that so many folks talked about. Sure enough, just a small amount of suspension displacement, the lasers showed this nasty geometry. And this was as just ROW height on a 40k mile car!!!
Then I dove further into other potential causes and immediately it was obvious the forward pick up point of the lower control arm was indeed 'rubber' -- its how things in racing are described when not up to the task. In other words way too compliant laterally speaking. Just by hand forcing a control arm in and out sent the toe wacky on the laser targets -- I thought this is NO good for maintaining front end geometry. Imagine what is happening while on the brakes with larger forces at work!!
I thought the rubber cavity bushings (durometer 65-70) were just too compliant and of course spherical bearings over the top for predominantly a street car -- what is inbetween?
Just my thoughts on things. I will say I may be too critical given the time I spend with racecars where suspension installation stiffness needs to be as infinite as possible
ERP sport rubber bushes at both ends of the front A arm help immeasurably, will p/u be stiffer? absolutly will monooballs be stiffer yet again, yes and w/ less stiction. So for a pure track car what do you want? For a pure street car what do you want, For in between what do you want?
read what I am saying and think through what you want
race car what is best? monoball
street car what is best? rubber
something in between? sport rubber or p/u. Of theses 2 which compromises do you want to live w/? If you want p/u and are willing to live w/ the maintannace and wear potential as well as the NVH then great. But an alternative that performs very nearly as well w/o the maintainance, wear, noise & NVH drawbacks of p/u or monoballs is mighty attractive.
and lastly if you use p/u in front what are you going to use in back where the real issues are?
05-25-2010, 05:35 PM
#302
Rennlist Member
Hey guys, I pulled my A-arms off a couple of days ago and the first one I did (drivers side) I was having trouble getting the arm to separate from the concentric adjustment portion of the assembly. I decided to detach from the rear of the wheel but the bolt (red arrow) only loosened to a point. Long story short I got the a-arm off but I need to re-tighten and torque that bolt. Any tips/advice? My first time doing anything with the steering/suspension like this.
05-25-2010, 05:55 PM
#303
As far as the durability of Chris's bushings goes, I was an early adopter. I've had these on my car for over two years and 20,000 miles. No squeaks and no wear that I can detect, either with physical inspection or by how the car drives.
05-25-2010, 05:55 PM
#304
Rennlist Member
I haven't been following this thread, but I'll just add that I installed Powerflex front bushings 4 years ago and I haven't had any squeaking or any bad affects. Zero maintenance. Several thousand miles, and many track days.
Would I do it again? Heck, I dunno; I can't tell a difference.
Would I do it again? Heck, I dunno; I can't tell a difference.
05-25-2010, 11:07 PM
#305
Drifting
Hey guys, I pulled my A-arms off a couple of days ago and the first one I did (drivers side) I was having trouble getting the arm to separate from the concentric adjustment portion of the assembly. I decided to detach from the rear of the wheel but the bolt (red arrow) only loosened to a point. Long story short I got the a-arm off but I need to re-tighten and torque that bolt. Any tips/advice? My first time doing anything with the steering/suspension like this.
05-25-2010, 11:35 PM
#306
Rennlist Member
05-26-2010, 12:26 AM
#307
Drifting
My pleasure. Tip: when you take off the other side, if you haven't already, when you take out the eccentric bolt, before moving anything, take sharp object, like an icepick and scribe the inside of the opening, then you can put it exactly where it was upon re-assembly.
05-29-2010, 02:49 PM
#308
Rennlist Member
Ahh, nice Saturday afternoon here in Cincinnati. Low 80's and sunny, I've got the garage opened up and some tunes cranking. Just popped my 3rd Heineken as I wait for the bushing inserts to soak in some lacquer thinner so I can get the rest of the rubber off. Hope to have these done later this afternoon.
06-08-2010, 07:40 PM
#310
Rennlist Member
Thanks Roger!
After driving my car quite a bit over the last couple of days I've got to say, this mod is well worth the time and effort. My front end shimmy during light braking is gone. The "hunting" or "tramlining" or whatever it's called when cruising along in a straight line (most noticeable on the highway) is gone. The car all around feels more stable and corners better. Very happy with this. Now it's got me wondering what other rubber bushings or suspension pieces should be replaced. Anyone have any suggestions? Rear bushing? Engine mounts? Transmission mounts?
After driving my car quite a bit over the last couple of days I've got to say, this mod is well worth the time and effort. My front end shimmy during light braking is gone. The "hunting" or "tramlining" or whatever it's called when cruising along in a straight line (most noticeable on the highway) is gone. The car all around feels more stable and corners better. Very happy with this. Now it's got me wondering what other rubber bushings or suspension pieces should be replaced. Anyone have any suggestions? Rear bushing? Engine mounts? Transmission mounts?
06-25-2010, 03:24 PM
#311
Addict
Rennlist Member
Rennlist Member
Thank you Chris!
I had mine installed on Wednesday morning and then drove 350 miles to get home. I too had the 55 mph shimmy that balance couldn't adress and the shimmy under braking. Both gone but not missed.
As the technician who did the work and then test drove the car said, "it feels planted". I couldn't say it better.
I had mine installed on Wednesday morning and then drove 350 miles to get home. I too had the 55 mph shimmy that balance couldn't adress and the shimmy under braking. Both gone but not missed.
As the technician who did the work and then test drove the car said, "it feels planted". I couldn't say it better.
06-25-2010, 06:13 PM
#312
I replaced mine a few weeks ago with the ERP sport hardness ones and it was a revelation... but I also changed to EVO uprights GT2 Tie rods. Nevertheless, the fact is that the car never felt this good in the five years I've owned it.
Mine looked completely fine. But, 15 or so years are not kind to these parts so I'm now of the opinion that everyone should change these bushings regardless of mileage.
Mine looked completely fine. But, 15 or so years are not kind to these parts so I'm now of the opinion that everyone should change these bushings regardless of mileage.
