|08-14-2016, 11:01 AM||#1|
Avid TSL User
Join Date: Apr 2011
Location: Mountain View, CA
Rear suspension upgrades.
In parallel with the composites project from the other thread, earlier this year I updated the rear suspension.
The car had a tendency to understeer. No big surprise. At the limits of grip it skipped over the pavement for lack of a better description, and jerked the wheel pretty violently in my hands. Imagine a feeling like a stone skipping on water being communicated through the steering wheel. Not fast, exhausting to drive.
That could have been any number of things, so why choose rear suspension?
- Rear swaybar is a classic fix for FWD understeer that I should have done long ago.
- The front already had homemade coilovers and sellholm arms, search my earlier threads for those. The car had these symptoms before and after the fancy front suspension.
- The rear had been totally neglected other than stiff/low coil springs and needed to be done anyways.
I was hoping that the skipping was a symptom of the tires plowing over sideways and would be addressed by getting the rear to rotate. Another possibility was underdamped/oversprung oscillation, which would be harder to prove and fix.
1. Replaced stock rear sway bar with Taliaferro 1"
This install is super easy. I've done it to other saabs before. Hardest part is extracting the rusty factory hardware. The heads on my factory bolts all broke off, which is common. Balance the bar on a jack (in this case a tall jack underneath the lift) and rotate to fit, so you're not trying to hold the entire weight of the bar while you work on it.
The thumb looks funny because I lost the thumbnail and nail bed in a karting accident back in January. These pictures were taken when it was still all scabbed over.
2. Replaced rubber axle bushings with Taliaferro polyurethane.
This was my first time replacing rear axle bushings on one of these cars. I did it by removing the bolts and lowering the torsion beam slowly supported on a jack, until the bushing was visible. The torsion beam is still held to the car by the dampers and won't fall off, but you do have to watch for tension on the brake lines.
The factory bushing is rubber inside of a hard plastic sleeve, which I'm guessing was a press fit. I drilled a hole through the rubber for clearance and then used a small chisel to shatter the plastic sleeve all the way through from right to left, causing the tension of the rest of the sleeve on the metal bore to release. Then it was easy to tap the rest of the bushing out. Greased new bushing was easy to tap in. Repeat on other side.
3. Added Taliaferro adjustable perches.
Because the rear suspension has never been adjustable, I've never even tried to set ride height and corner balance on this car. I still haven't had time, but at least it's now possible.
I couldn't figure out how to make the included nut welded to a stick work, so I ended up putting m8 rivet nuts in the lower spring perches instead. I couldn't get the rivet nut flaring tool into that confined space without taking the torsion beam all the way off, which would have meant taking off the brake lines, so I used the same technique Taliaferro recommend in the front subframe brace installation instructions: flare the rivet nut just enough that it needs to be hammered in to fit snugly, then finish flaring with a bored-out nut and stack of washers.
(Sorry, no good pictures of this install. Will update with one later if I remember.)
4. Melty rear brake line.
That sweet new exhaust installed last winter melted the drivers' side rear brake line a little. This is slight physical abrasion, not just radiant heat. I'm glad these were stainless and not rubber.
I replaced it with another of the same kind, double bagged in spark plug wire sleeve (DEI or thermotec, I forget) with some aluminum tape to keep it in place. That too will eventually abrade, but it should buy a lot of time to figure out how to move the exhaust pipe a centimeter or so further away. Stiffer hangers would do it, or just bending/lengthening one of the hanger brackets to keep the rubber hangers under more tension so they have less off-center travel.
Getting back on track after doing these things, I'm pleased to say it was a night and day difference. The car wants to rotate and the nasty feedback through the wheel has only happened when the tires got overheated/overinflated. Impossible to say which of these changes did what since I didn't test them individually, but their combined effect was exactly what I was hoping for.
Everyone including me already could have told me that rear sway and some fresh bushings are a lot more bang for the buck than most of the tempting upgrades out there. I have no idea why I procrastinated so long before getting to these.
|08-14-2016, 04:38 PM||#2|
Live, eat, and sleep by TSL
Join Date: Mar 2005
I loved the rear roll bar upgrades I did on my car. I first started with a double stacked sway bar (it was cheap) then moved on to the gs unit.