[vtl]

Have picked up a set of M3 rear arms pretty cheap, so I decided to do a project with them.

Currently this is my rear suspension arm setup:

Toe arm - Hardrace toe arms, ball jointed both ends
Guide rod - TRW M3 arms ball jointed on inboard end, rubber bush on outboard end
Upper camber arm - Stock arm with ball jointed inboard end, with rubber bush on outboard end
Lower camber arm - Stock arm with ball jointed outboard end, with rubber bush on inboard end
Trailing arm - Stock arm with rubber bush on both ends.

I plan on ball jointing the guide rod, upper camber arm and trailing arm bushes, and possibly the inboard camber arm bushing.

You can use the ball join from the stock upper camber arm ball joint from the non M cars. This ball joint can be pressed out of the stock arms or can be bought separately from aftermarket/oem manufacturers. Upgrading to ball joints should in theory reduce compliance steer effects from the rear end (basically preventing rear steer during hard driving) and improve handling.

From my research, these ball joints should be the right size for the trailing arms bushes, upper camber arm bushes and guide rod bushes. They should be an outside diameter of 45.00mm. Since I have m3 arms, the ball joints I need to replace are the outboard ones, which go into the knuckle. The knuckle has a tapered face for the attachment points, which help locate the arms into place. The ball joints will not have this feature so tapered adapters need to be made up.

On the weekend, I cleaned up all the arms and pressed the bushes out of them. Rather than try to find the correct M12 tapered washer for sale (its hard to find specialty fasteners like this in Australia), I decided to use my lathe to salvage the parts from the original bushes. For anyone who wants to simply purchase the parts, they are M12 washers with a 120 degree taper on them. I pressed out the metal slug from the rubber bushes, around 3 tons of force and the rubber shears and the metal slug pops out. I machined off the remaining rubber, then parted off the tapered faces from them. These will now need to be machined to final thickness, which I will wait until I order the ball joints before doing that.