Discussion question , rear trailing arms
 

I have read where you should torque these down while the car is sitting on the ground. I just installed new ones on my 01S and it was lifted on jack stands while I did this..I do not understand why it would matter ?

I removed the bolts and pulled these out by hand, installation was the same requiring no real pressure anywhere, and there is no adjustment for these...so why would it matter ??

I am about to have a 4 wheel alignment so I did not really care about it getting slightly off, but I would like to understand.

PS a tip for anyone about to do this, a 3/8 extension is very handy to align or orient the ball joint before you insert the new part !

You must torque them at ride height, or the ball joints will be stressed, and quickly fail.

How is one supposed to do this in a regular garage? There's no way to get a torque wrench in there with it on the ground.

The best way would be to jack the car up, then lower it onto ramps that are reversed (meaning the ramp part is out the back of the car). That way the rear suspension is under load, but you can access the bolts for the trailing arms easily.

Pdwight, when you torque the bolts with the car up in the air, then the bushing is preloaded for the arm in a downward position. When you put the car back on the ground, the arm goes to a level position, so it is twisting the bushing against that preload all the time. The bushing will will fail much more quickly than it otherwise would.

Speedy, you will have to become a bit creative, what I have done in the past is having the rear wheels (most weight) on the ramps and the front axles supported with jack stands under the ball joint right against the brake rotor.

But you have to be careful and put something underneath the frame (on both sides of the frame) to keep the car from squeezing you in case the jack stands slip..

There are only a few bushing on the car that require this. The Bentley only says it about this bushing (in red):

http://986forum.com/forums/uploads02...1539618365.jpg

The instructions for the SPC aftermarket control arms say also to do it for the center bushing in the LCA for the same reasons (in blue, same arm). That makes sense although there is probably a lot less rotational movement there.

Then if we are going to do it there, might as well do it on the rear toe arm as well of that is ever getting replaced, for the same reasons, and that one probably does have a lot of rotational movement, same as the LCA. But the Bentley doesn't say that one either. That one is also in blue, and applies to the rear only.

For that one in red, it really does hold the arm in place pretty well, when you are doing work like removing the axle or changing the strut, you have to release that bolt otherwise the arm doesn't pivot down nearly enough. I wonder how much that contributes to the spring rate/damping? I have monoballs in the front so I don't have to loosen it when doing work, but in the back I still have the rubber bushings and so I do. That is one area where I really like the monoballs, when doing suspension work, even if it is infrequent :)