best 914/6 track car alignment specs
 

my car is a track-only 914/6, which developed excessive oversteer. I found the rear control arms had side-to-side movement, both right and left hand side. to remedy this unwanted rear-trailing arm movement, what is the best set up? poly bronze bushings, or perhaps Tarett trailing arm kits? i am using the Tarett sway bar & drop link kit in front. finally, what is best toe settings, front and rear?

sixes are notorious for oversteer. If this problem, however just developed and you did not change anything, then something happened that has to be checked.

The factory put a bit heavier springs in the rear of the stock sixes and a larger front and smaller rear sway bar. the 916 with its 2.4S engine has 16 up front and 15 sway in the rear just to give you an idea

You want a little toe in on the rear so that it doesn't try to become the front. For the track, you probably want a little front toe-in as well, because the front will tend to toe-out as speed increases. And the toe-out will make the nose feel very darty and will require you to actively manage the car's path through the whole turn.

Trailing arm movement can be caused by a number of things, from the bushings (which you evidently suspect) to the wallowing out of the inboard suspension mounting ear to the outboard suspension point sliding (loose bolts or other issues) to one or both mounting points for the trailing arm cracking (often due to rust inside the parts) to the trailing arm itself cracking and/or flexing.

You need to find the source of this issue first of all!

Your choice of bushings is likely to be limited by the rule set you run under. In a number of cases, replacing rubber bushings with metal parts will promote you into the cubic-dollar classes where you're likely to be a rolling chicane for all of the tube-frame monsters with full-on slicks and so forth. So make sure you read up on what you're allowed to do.

Once you fix your trailing arm movement issue, you'll want to do some testing to figure out the balance of the car in various situations.

Tires have a pretty large influence on what alignment settings work the best for a car. Some tires like more negative camber than others, for instance. Street tires usually like more, and full-on race tires usually like less. The tire manufacturer should have an idea of what their tire likes the most.

--DD

As suggested, look at trailing arm bushings and for ovaling of the trailing arm pivot holes.

As for toe settings, for track only I use 1/8" per side toe in for the rear. Yes this is a lot, but 914s flex and this prevents flexing to a toe out condition. In the front I use 1/8" total toe out. That's admittedly aggressive even for track, but it's in line with what other long-time 914 racers use.

Alignment
 

Agree with above comments…..
If ok and nothing was done ….something wore out.
Obviously shouldn’t move side to side.

Since this discussion is about handling what spring rates are you running? Does the car have any aero, spoilers or is it stock body? Too high rear spring rate will create oversteer.

the rear suspension points need to be braced for a track car.
"Toe" braces reduce the flex and the long term wear and damage that occurs

do you have inboard... or out board toe braces on the car?
I run zero toe on my rear end... this is not the common answer, but works for me.

brant