[Elf458]

So, my B8.5 S5 (mine is THE most troubled S5 Audi ever built) has had strange offset discrepancies on both rear wheels. With any decent wheels or wheel spacers, one wheel tucks and the other protrudes. ANNOYING

Here is a guide for anyone with the same problem

Audi stated 6mm is the factory tolerance and this is normal and cant be fixed. Mine is 6mm and that is ALOT! Awful engineering and I can only imagine there will be loads of people with the same problem. B7 A4s seem to be able to fix this by realigning the rear subframe, but everyone I spoke to said the tubular subframe on the b8 platform cannot be moved in the same way.

So here is the proof that it can be done and it's no real difficulty:

You'll need:
18mm Socket,
16mm Socket,
10mm Socket,
T20 Torx Driver,
Blue loctite,
Torque Wrench,
Jack stand,
2x axle stands,
Tape measure,
2 pieces of string with a weight/small bolt tied to the end,
Sticky tape.

As you can see, not good! Even without spacers, trying to hide to issue 🤦‍♂️

First, using a dead level floor surface, get the car up on axle stands, wheels preferably a couple of mm off the ground.

Then we need to undo the 4 rear subframe bolts:

Remove the plastic covers on the rear of the sills, using Torx socket and 10mm socket. This will expose the subframe cover bracket and the two front 18mm bolts on the rear subframe, one each side.

Note: They slide back and then down, do not force them or you will split the brittle plastic.

Then behind the exhaust backboxes, locate the large 18mm rear subframe mounting bolts.

Use a torque wrench to undo all 4 exposed 18mm bolts by about 3-4 full turns.

You should create a little gap of play on each of the 4 subframe bolts like below:

Note: The bolts are very long so dont panic about the subframe falling down... for reference, first picture below shows a safe distance, second picture shows the full length of the thread.
Do not go this far.

Your subframe will now be free enough to wiggle around.

Now stick your string and weight on the rear window with the weight hanging down over the wheel, but not touching the floor. Measure its position against the rear side window, ensuring each side hangs in roughly the same place. This is important as it forms your reference point.

From here you must push, kick and pull the rear wheels into a central position.

Note: Forwards and backwards will impact on your 4 wheel tracking alignment including your camber, so keep it as even as possible.

When it's in a position you're happy with, lower the car to the floor and check it still sits correctly central. I had to do this up and down a few times and actually shift it past centre to create a central position when it was sat on the floor.

This next step is important:
ONE AT A TIME ONLY, remove a single bolt, apply blue loctite and torque it back up to 120NM +90degree turn (115NM +90degree turn for a new bolt, which is probably recommended).

After each one bolt is torqued up, check alignment remains true.

Reinstall sill covers.

Note: You may notice steering wheel is a fraction off centre if you have shifted the subframe more than 3mm. Either way, it might be sensible to get a full wheel alignment and steering wheel correction when you next change tyres/wheels or any suspension components.

Now, marvel at your genius AND your straight rear wheel alignment!

Hope this helps!