jason89i

After completing a full suspension refresh, self corner weight, self alignment, reputable shop aligned, etc. There were still some odd vehicle dynamics. Car would sporatically trammel and sometimes shift under large throttle transitions (from on to off in upper rpm range.)

I just rescaled and reset KT. Oddley enough, the rear link was 1/8" off and now causing a 25# difference (preload) on each side.
I also noticed that the sway bar did not rotate freely. Took maybe 15# to move.

How sensitive is the 993 to preload?
What are the effects of preload?

I just made some adjustable links, but haven't driven it yet.

Should my links be shorter?

Thanks, Jason

OverBoosted28

From what I have seen, the RS sway requires the curved drop links. Your drop link perch should be centered in the space and the curved drop link is necessary to achieve that.

jason89i

I took the curved rs drop links off. Was much easier to build adjustable links I cannot imagine removing the shock to adjust link tab height.

with the pss10 / rs sway bars......
Link tab is flush with sway tab.
Sway link is on axis with shock. (not canted to front or rear.)
Still have 1" clearance between link and toe arm.
Geometry for links is good. I don't see where the curve is advantageous.

EDIT: Just noticed your picture was with the suspension unloaded. Good catch. I need to jack up the car and see if there is interference when unloaded.

OverBoosted28

Yeah, not sure, but when the suspension droops, it may have a problem. I have the H&Rs, which mount over toe link. Just think the curved link is for a reason. Most likely to keep geometry symmetrical.

jason89i

yep. at full drop, there is interference.

rs curved link for reference.


at rs ride height, lots of room for strait links.


when the car is jacked up, there is interference.

jscott82

Shorter links would help.. My biggest concern is those long links start getting awful close to the ground.

jason89i

Preload gone. Suspension is fixed! Car feels so much better. I am shocked with the implications of preload.

Corner weighed with sways disconnected
F= 560 / 540 R= 894 / 869 = 50.4 cross
Corner weighed with rear rs sway links (which introduced preload.)
F= 587 / 521 R= 872 / 890
My understanding is that the preload was compressing one spring (stealing spring resistance) and decompressing the other side (applying that negative resistance to the opposite wheel.) I would assume that this odd transfer of resistance could freely travel from one side to the other while driving. Could someone please explain the physics behind this. I am shocked that it made that amount of difference. ~25# of corner weight (freely shifting between corners) doesn't sound like enough to cause a high speed twitch or trammel. Would be very interested to hear your thoughts.

Anyways, on to pictures.

I ended up bending the links.



suspension compressed (as wheels sit on ground.)


suspension fully unloaded.... no more interference....


suspension fully unloaded....




Checked them against the rs ones. roughly 1/2" longer.

jcochran1

The underside of your car is beautiful and I love your link bender.

jason89i

thanks. the underside project can be seen here.... https://rennlist.com/forums/993-foru...-and-rear.html

too much wrenching, not enough driving.

Bill Verburg

If there is preload it is pulling on one side, which at the same time relieves the load on the other

Bent is definitely the way to go at lowered ride heights, you do not want any contact even at full droop.

Tarrett sells bent links w/ mono-ball ends. The ones I have seen are too long and need to be shortened
Here's an original and shortened one

jason89i

Thanks Bill. Just bent my links (see post 7 above). No interference even at full unload. Considering shortening them an inch or so. j

V

Timely post. I bought RS sways like three years ago and now I will install them as a winter project along with a suspension refresh. I am missing the RS rear drop links as these were NLA already three years ago from Porsche.

Are the RS rear drop links still the preferred solution? My car is lowered around RS height, maybe a bit lower.

If yes, how do I source a pair of these?

Or is it better to just buy the Tarrett links with mono-ball ends as in the picture above?

I also read on Jackals Forge that the RS rear drop links doesn't work with KWV3 coilovers since these have fixed locking collars so the RS links are too short in this case. Is it safe to assume that the RS and Tarrett links work with most coilovers that have adjustable locking collars?

KNS

I love your drop link bender but just curious - if the suspension were to take a serious abnormal load might there not be a failure in the weakest "link"? Haven't you created a point of failure?

jason89i

How did I create a point of failure?

Having a hard time thinking of a situation where the sway link would experience abnormal loading. Sway / links only transfer spring resistance from one side to the other.

OverBoosted28

You're correct in their function. The weakest part of the link would appear to be the bolt, that mounts into the wheel carrier. That's what broke on mine.