skpyle

Hello Gentlemen,

I just bought the complete rear suspension from a 60,*** mile 1988 S4. It is in better condition than the rear suspension from my 168,*** mile 1986.5 S3. I have pored over the PET for both cars. I have only found a few different part numbers between the rear suspensions, and need some clarification:

Wheel hub:
1988: 928 331 065 07
1986.5: 928 331 065 07, OR 928 331 065 07 widening of rear track

Wheel bolt:
1988: 928 341 671 02, OR 904 341 671 00 M 393 (Club Sport?)
1986.5: 928 341 671 02, OR 901 331 671 01 widening of rear track

Spacer ring:
1988: 951 331 611 02 17MM M 393 (Club Sport?)
Spacer tube:
1986.5: 477 501 701


I am going to assume the M 393 (Club Sport?) items will not be present on the rear suspension I just bought.
For 1986.5, what is 'widening of rear track'?
The 1986.5 shows rear wheel spacers, but the 1988 does not.

My 928 came with the 21mm 477 501 701 spacers and 7J x 16 manhole cover rims.
Will these fit fine on the 1988 rear suspension?
Do I leave the spacers off?
Do I leave them on and push the rear wheels out a bit towards the fenders?

I believe my first step should be to measure and compare the length of the wheel studs on both rear suspensions.


For what it is worth, here are photos of the rear suspension that I bought:















***

skpyle

Hmmm...I think I figured something out. Comparing photos of the 1988 and 1986.5 rear wheel studs, I think my Red Witch DOES have the 'widened rear track'. Meaning, it has the longer 901 331 671 01 wheel bolts. I should have realized this because I have the 21mm wheel spacers.



1988 rear wheel studs, look relatively short protruding from the brake disc.






1986.5 rear wheel studs, harder to tell, but they seem like they protrude further out of the brake disc.






1986.5 rear wheel studs, harder to tell, but they seem like they protrude further out of the brake disc.



So, it seems like I have a few choices:
-find 8" rear wheels and tires. I will need to find 8J x 16 chromed manhole covers
-find 21mm bolt on rear wheel spacers.
-swap rear wheel hubs between the two rear suspensions. This will entail replacing the rear wheel bearings.

If I go with bolt on rear wheel spacers, do I go wider than 21mm? I have seen reference to running 35mm spacers on the back of some pre-87 928s.


Hmm...

Michael Benno

skpyle

FredR

Seems as though you have got yourself caught up in a dilemma!

The S4 rear end uses an 8 inch wheel with 52.5mm offset and no spacer carrying 245x45 rubber. Your model year seemingly must have 225 rubber at the rear if it has a 7 inch rim so, they mounted it further out by fitting a spacer that needs longer studs.

Clearly you understand that changing studs is not that simple. Thus if you want to fit the S4 rear end and retain your stock rear wheels, you can fit a bolt on spacer but what the minimum thickness would have to be I do not know- that will be controlled by the protrusion of the S4 wheel stud from the flange.

Given all that you have done to date a set of GTS wheels plus 235/265 rubber would finish your project off nicely but $$$'s?

At this rate it seems as though nearly everything has been replaced or refurbed except the body shell!

skpyle

Hi Fred!

As of right now, I am leaning towards getting bolt on hubcentric spacers. Still need to figure out what size. Yes, the Red Witch is fitted with 7" wheels and 225 tires all the way around. At this time, I am not ready or willing to replace the rolling stock. I like the chromed manhole covers.
Changing the studs is a 'no-kidding' event. Yes, it would take care of replacing the rear wheel bearings. However, I am hoping to avoid that.

Thinking it through, bolt on spacers would be a better option. It would leave the door open for future modifications, IE different wheels. If I swapped hubs and kept the 86.5 studs and 21mm spacers, I would be limited to 7J x 16 wheels.

Thanks!

FredR

Hi Seth,

Whereas I agree that the S4 rear gives you more immediate options your stock hubs/spacers can accommodate wider wheels just that you need more offset. Remember, the GT's have a 17mm spacer and carry a wheel with a ET60 offset compared to the S4 with ET52.5. The rear end has more flexibility space wise than the front end. The GTS is different Gain because of the wider arches and carries a 38mm spacer with ET55 rear offset.

Also remember that another option is to dump your spacer and run with a narrower one or non at all- the only caveat being that you need to fit open nuts. This what I do on my rears on the GTS. I run with wider rubber than the GTS, typically either 295's or the current 285's. With 295 I found that the rubber was too close to the fender so fitted a pair of 24mm slip on hub centric spacers and bolt it up with open nuts. That does not appeal to everyone but does not bother me. Now that I am running 285's I could fit the stock spacer if I could be bothered, however the centre of my wheel is currently sat within 1mm of where the stock GTS wheel runs and the car handles excellently so I see no reason to change back. You do not really notice the open wheels nuts unless you go looking for them.

Bottom line- you understand the issue and the options. What is the height of the S4 stud relative to the hub face?

hacker-pschorr

IMO leave the studs alone, fit the stock wheels as is & get the car running & down the road. At that point you can measure the gap and decide how "wide" you want to make the rear-end.
Changing the studs is a major PIA with the potential to damage something.

My S4 is sitting on 9" et65 wheels with a 1.5" bolt on spacer. Hindsight I could have gone with 2" spacers and I might still change them. My 78 & 79 currently have stock S4 wheels on the rear without any spacer, no clearance issues.

DeWolf

Seth, I can tell you from experience with the S3's (5 of them) I've owned that with the standard 'S' manholes you can use a 30mm spacer and have no rubbing issues whatsoever. Cornering, hard bumps etc. I just put 35mm bolt ons on the 79 with manholes and I reckon it will require a lip roll which I'm reluctant to do.

skpyle

vanster

I had to ditch the manholes and go to a larger wheel because of switching to GTS "big blacks" We cut the rear studs after removing the spacers. The wheels are 17" from a Cayman

skpyle

Hello Vanster! Good to know, thank you sir.