Which bushings need to be preloaded before being torqued?

[WoGGo]

Arith2 mentioned in the Handling dynamics off after subframe reinforcement?thread that bushings need to be preloaded before being torqued.

Which bushings specifically?

[DESMDR3]

Arith2 mentioned in the Handling dynamics off after subframe reinforcement?thread that bushings need to be preloaded before being torqued.

Which bushings specifically?

Only for rubber bushings . If spherical, no preload needed


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[FBloggs]

Any moving suspension parts that have rubber/flexible matrix.
The car sits at normal ride height and the fasteners are then torqued.
There is an illustration in the E30/36 Bentley manual that covers torquing the rear trailing arms bolts with the console. The console is positioned relative to the trailing arm at an angle simulating static ride height.
Then the console is fastened to the chassis.

[Tbonem3]

Shock bottom bolt in the rear (if rubber, not like my MCS's bearing).

Rtab (if stock).

Think that's it. Fcab, strut mount, engine/tranny mounts, subframe and rsms are the only rubber left I think.

[zzyzx85]

my rear lower control arms (aka ARCAs or rear camber arms) still use a bushing so I tighten them when the car is on ramps.

[Tbonem3]

Ah I forgot the inner bushes on the rear arms. Outers are bearings.

[K-Dawg]

Rear trailing arm bushing (RTAB), rear upper control arm inboard bushing, rear lower control arm inboard bushing, rear shock lower bushing.

[lvm3sm46]

thetypicalm3guy I have a feeling this might lead you to finding your issue.

[Tbonem3]

Not pre-loading them just hastens wear. I don't believe it leads to any handling change or feel change. Maybe, if anything, it might make the rubber stiffer as it's already stretched?

[lvm3sm46]

Not pre-loading them just hastens wear. I don't believe it leads to any handling change or feel change. Maybe, if anything, it might make the rubber stiffer as it's already stretched?

I had a issue where one of the bolts on the rear controlling arms were tightened when the arm was way out of range so when swinging the other side to line up to the other bolt it had tension on it. It caused tramlining im guessing because of the tension on the rubber pulling. Hard for me to explain without showing.

[thetypicalm3guy]

thetypicalm3guy I have a feeling this might lead you to finding your issue.

I am on polyurethane revshift green bushings from FCP, i think preload is for OEM lemforders only right?

[BigDave]

Arith2 mentioned in the Handling dynamics off after subframe reinforcement?thread that bushings need to be preloaded before being torqued.

Which bushings specifically?

The center support BEARING for the drive shaft needs to be preloaded forward about an 1/8 of an inch. You need to keep it forward while a helper tightens the two nuts on the bracket.

[Arith2]

If it's rubber and flexs under the movement of the suspension, it needs to be torqued.
I recently replaced an axle on an X1 and I thought of the forum because this had come up. There's a straight tension arm that goes straight to the front subframe from the kingpin. It has a rubber bushing. I preloaded the suspension the best I could when tightening the nut but did not torque. It was on at about 10 to 15 ft lbs. From the I pulled out of my bay, onto the alignment rack. This one I paid close attention to. Even with attempting to preload, loosening it after the full weight of the vehicle was on it, the bushing still twisted another 20 degrees or so. I had barely hand tightened the bolt and it still held the bushing in place. It's a small detail but loosen fully whatever bushing your torquing once it's preloaded otherwise, it may not be in the right position. I was surprised so little torque prevent it from twisting.

[Tbonem3]

That's right, I fogot the tranny bushes you are supposed to push the bracket similar to the CSB, though that type of preloading is different to the suspension bushings that rotate like shock bottom and rtab.