Rear trailing arm swop!
 

I'm in the process of upgrading my 83s brake system to the brembo s4's. Does the rear trailing arm from an 88 s4 directly replace the one from my 83! I've seen units at the right price, and thought I would just swop the corners over, as long as the fittment was the same!

The brakes will bolt right on to what you have, no need to swap anything... unless you want to, the arms will bolt in too.

The reason I ask is I, was told you need 3mm spacers to put on the later brakes?! Also the discs are 10mm larger, so the splash guards won't fit on my original set up. I have a rumbling rear wheel bearing, which would be cured also!

The wheel bearing is in the wheel carrier, the control arm is a separate piece. A new wheel carrier would probably not be a bad idea in your case as long as you can confirm the bearing is still good. If it was off I'd be inclined to press new ones in though.

the early cars had a different front mounting point VS the S4 version
The S4 version has aluminum brackets bolted to chassis the control arms are bolted to these .
A look through PET will compare the LCA part numbers

Sorry for hi-jacking, but would an 86 arm fit a 78 chassis?

Yes I put one in my car. The early cars have steel mount that's part of the body and the later cars have a aluminum bolt on mount. Both are in the same location and use the same arm

The s4 ones I've seen include the aluminium brackets too, also, it's a complete unit with the hub/ carrier/ discs!

You need to be sure you have upgraded the ball joints to the latest forged steel ones. I had an original aluminum one fall apart, dropping the car fender onto the tire. Luckily I was backing it out of the garage and had turned the wheel. They wear out the housing because of the direction of the spring pressure, and won't show wear if you do the "jack it and pull/push the wheel in and out. Some have failed on the road with the expected tragic results.

I thinks he's only doing the rear.

Nope, doing the brakes all round, so will be replacing the ball joints on the front as well!!
Didn't expect it to be such a job, when I first had the idea[emoji23]

The upgrade to S4 brakes on the front is more involved. You'll either need an adapter bracket to use your early control arm/spindle or the entire S4 set up. (upper/ lower arms, spindle ect)

Yep, I've got the calipers,hubs,carriers,discs,pads, flexi's and lower wishbones so far! Just the upper control arms, sway bar and ball joints to go-I think!


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The sway bar is different, maybe links are too. The cooling air guides are different.