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Continuing saga putting my '85 Euro S2 rear suspension back together (think I am making a meal of it compared with others). I have replaced the upper control arm bushes, inserted with soap solution as I couldn't locate Capella Oil B. I am wondering if Capella is just to assemble rather than offer lubrication during use (maybe Capella is non petroleum based?) My question is having put the bushes in, should I remove and find a non petroleum base grease (Molybdenum?) to reinsert the bushes as I am not understanding which bits rotate when the assembly is bolted back on the car
Where is the relative movement?;
- does the conical end of the bush aluminium insert rotate against the crossmember, in which case the movement is between the conical core and the bolt?
- or is the aluminium core clamped to the crossmember in which case the bush rotates against the core i.e. this interface needs to be greased?
The intent is for assembly and to use something that will not degrade the bush material long term. Once the end bolts are tightened flexure occurs through the body of the bush moving.
When I did mine I tightened the bushes with the car on its wheels taking load. I did not have the facilities to pull it down and tighten so I drove it some, undid the nuts and then retightened them for whatever that may be worth.
A good thing to adhere to, on a 928:
Leave every rubber bushing in the suspension (including sway bars), front and rear, loose until the car is settled at ride height.
I am replacing the rear upper control arm bushings in association with TT rebuild, centering spring replacement in G28 11 etc.
1. Do I press the bush in with the metal liner / barrel removed, that is press in the bush only or as one unit (barrel and bush together?) . Shop manual looks to show keeping metal liner in place in diagram on 42-13 in WSM
2. Bolt of the arm to aluminum subframe, PET looks to show bolt being inserted from the rear of the car, (nut on body side) else need to drop the subframe to install? Which way is correct?
I am replacing the rear upper control arm bushings in association with TT rebuild, centering spring replacement in G28 11 etc.
1. Do I press the bush in with the metal liner / barrel removed, that is press in the bush only or as one unit (barrel and bush together?) . Shop manual looks to show keeping metal liner in place in diagram on 42-13 in WSM
2. Bolt of the arm to aluminum subframe, PET looks to show bolt being inserted from the rear of the car, (nut on body side) else need to drop the subframe to install? Which way is correct?
1: Correct, press in new bushing with metal barrel installed. Meaning press the whole thing in as one unit. Pay attention to the orientation of the bushings, as they are opposite at each end of the control arm.
2: The rear cross member must be dropped some to gain enough clearance to reinstall the control arm bolt. Ask me how I learned this. The hard way...
A good thing to adhere to, on a 928:
Leave every rubber bushing in the suspension (including sway bars), front and rear, loose until the car is settled at ride height.
This is recommended for all cars. This is auto mechanics 101 and a good example why the WSM should not be considered a step-by-step how to guide for working on a 928. Some things Porsche assumed the tech would know. At least Porsche did go as far as developing a factory tool for pulling down the nose of the 928 since we all know, unlike most cars, the 928 nose doesn't want to settle on its own.
For most rubber-into-metal bushing installs, glycerin is a fabulous lubricant, maybe better than the petroleum-and-soap Capella that is sometimes recommended. There are "rubber lube" products that do a great job of this too, both the automotive and "personal-lubricant" flavors.
When the bushings are manufactured, the inner sleeve is in place when the rubber part is injected into the mold. The rubber them vulcanizes and bonds to the sleeve. When the sleeve no is no longer bonded to the rubber, the bushing has failed and is considered junk. Consider that you need to put all the pressure on the outside of the rubber when installing the bushing into a control arm or link. Do everything you can to minimize the pressure and distortion of the rubber during installation. Any shaer loading of the busing is across the same section where you want the rubber to be strong once installed. No reason to intentionally damage that part of the rubber in the press. A good press fixture will have a shallow recess to hold one end of the rubber, and a guide pin in the center to help keep everything lined up on the way in. I've seen some pretty creative production pieces for use when you might be doing a lot of bushings, particularly guides that are tapered inside to help compress the leading edges of the bushings into their new homes. Regardless of the exact method used to press the new bushing into place, --flood-- the bushing and receiving section with lubricant prior to insertion.
10-30-2020, 07:35 AM
Upper control arm - which bit moves, lubricants?
