Looks like the rear end of my car...sank 10mm so?

[W12x]

About 63K miles on the car and all original suspension.

Was working on installing the front BBK, and replacing the 4 brake lines in the rear along with rear pads this past weekend.
Jacked up the rear using the rear diff.

After we put everything back, it felt like the rear end of the car sank maybe 10-20mm..? I am actually not sure if it looked that way for a while since I haven't been driving it a lot lately

Car felt normal driving around, but it looks like the rear end sank 10-20mm on both side. I'm on 275/35-19 and 10.5 wide wheels and not rubbing, but the tire does look a little more tucked into the fender.

Don't have a pic right now but it looks closer to the pic attached than stock height

Going to try to figure out more later this week, but what could cause this? This has been bothering me since Sunday but the Texas heat and work is preventing me from working on the car right now

[DrFerry]

Originally Posted by W12x

About 63K miles on the car and all original suspension.

Was working on installing the front BBK, and replacing the 4 brake lines in the rear along with rear pads this past weekend. Jacked up the rear using the rear diff.

After we put everything back, it felt like the rear end of the car sank maybe 10-20mm..? I am actually not sure if it looked that way for a while since I haven't been driving it a lot lately.

You mentioned you jacked your car up by using the Diff as a jacking point.... Perhaps the Diff mount bushing bolt(s), - or the Diff bushings themselves - are now broken? It's just a guess..

[tbuck]

^This. Never a good idea to use the diff as a jacking point. The diff floats in 3 rubber bushings that are not designed to handle 1800 pounds of car suspended above. Don't think this would make it sit lower and it definitely does seem to be sitting rather low if stock suspension.

[roastbeef]

Jacking from the diff won't make the suspension sag.

Some settling over the years is normal.

[Helmsman]

Believe the diff actually is market out as one jack point. I've certainly used it without issues.

[nrubenstein]

1) Using the diff as a jack point isn't a big deal.

2) Even if you completely broke the diff mounts, that has ZERO impact on ride height. I'm not sure where you guys even get that idea from. Take the diff out entirely, and the only impact on ride height is from the weight reduction.

[baba louey]

I just went out to check my 2012 M3 with stock competition suspension and I can easily see over the top of my rear tire in the wheel well. I agree that yours seems to be sitting a bit lower. There should be a factory specification that you can compare to.

With regards to suspension spring aging, I recently replaced the rear springs on my Audi A4 because one broke. After I finished the replacement and lowered the car, I noticed that the rear sat higher. Upon comparing with some older pictures of the car and factory specs, the new height was indeed back to normal. I think suspension changes happen so slowly that we don't even notice them. Only when we make repairs do the changes become noticeable.


baba louey

[Adriano917]

Its in your head, mine sits about the same.

[W12x]

Originally Posted by DrFerry

You mentioned you jacked your car up by using the Diff as a jacking point.... Perhaps the Diff mount bushing bolt(s), - or the Diff bushings themselves - are now broken? It's just a guess..

Originally Posted by tbuck

^This. Never a good idea to use the diff as a jacking point. The diff floats in 3 rubber bushings that are not designed to handle 1800 pounds of car suspended above. Don't think this would make it sit lower and it definitely does seem to be sitting rather low if stock suspension.

The diff was marked at a jacking point by BMW hence why we used it....but I went back to the car this morning and it's actually not as low as the pic I posted here, probably a normal sag over the years and didn't notice it until now

[W12x]

Originally Posted by roastbeef

Jacking from the diff won't make the suspension sag.

Some settling over the years is normal.

Originally Posted by Helmsman

Believe the diff actually is market out as one jack point. I've certainly used it without issues.

Originally Posted by nrubenstein

1) Using the diff as a jack point isn't a big deal.

2) Even if you completely broke the diff mounts, that has ZERO impact on ride height. I'm not sure where you guys even get that idea from. Take the diff out entirely, and the only impact on ride height is from the weight reduction.

I wasn't sure about the diff as jack point so i looked it up before and it is marked as one by BMW...
but looking at the car again, it's not as bad as I first thought and probably just settling since the car is 10YO and on all original suspension

[W12x]

Originally Posted by baba louey

I just went out to check my 2012 M3 with stock competition suspension and I can easily see over the top of my rear tire in the wheel well. I agree that yours seems to be sitting a bit lower. There should be a factory specification that you can compare to.

With regards to suspension spring aging, I recently replaced the rear springs on my Audi A4 because one broke. After I finished the replacement and lowered the car, I noticed that the rear sat higher. Upon comparing with some older pictures of the car and factory specs, the new height was indeed back to normal. I think suspension changes happen so slowly that we don't even notice them. Only when we make repairs do the changes become noticeable.


baba louey

I think you are definitely right about the last part, it becomes more noticeable after you work on a car lol

I changed the wheels and tires on mine so it might be a little different compared to stock ZCP setup, but with the settling I can barely see the top of my rear tire, lower compared to new, but not as bad as I thought, probably had a heatstroke that day and my head wasn't clear lol

Originally Posted by Adriano917

Its in your head, mine sits about the same.

You running any suspension mods with all that supercharger and stuff?

[Scharbag]

Originally Posted by tbuck

^This. Never a good idea to use the diff as a jacking point. The diff floats in 3 rubber bushings that are not designed to handle 1800 pounds of car suspended above. Don't think this would make it sit lower and it definitely does seem to be sitting rather low if stock suspension.

As others have said, the diff is noted on TIS as a jacking point. Just no not use the aluminum fins!!!

Think about this: the S65 produces 295ftlb of torque at the flywheel. In first gear, with a 4.055:1 gear ratio (6MT here), the driveshaft is trying to twist the diff with ~1200ftlb of force. Then you run that through a 3.85:1 final drive and you are dealing with ~4600ftlb of force (well, assuming zero losses but still…).

And this is for a stock S65. Think of the diffs in boosted S65s putting out over 450ftlb at the crank.

Bottom line, diffs have to be VERY stout.

[tbuck]

Originally Posted by Scharbag

As others have said, the diff is noted on TIS as a jacking point. Just no not use the aluminum fins!!!

Think about this: the S65 produces 295ftlb of torque at the flywheel. In first gear, with a 4.055:1 gear ratio (6MT here), the driveshaft is trying to twist the diff with ~1200ftlb of force. Then you run that through a 3.85:1 final drive and you are dealing with ~4600ftlb of force (well, assuming zero losses but still…).

And this is for a stock S65. Think of the diffs in boosted S65s putting out over 450ftlb at the crank.

Bottom line, diffs have to be VERY stout.

Ok, I was not aware it was an approved jack point on these cars. Back in my E36 M3 days we were always warned never to do that, to use the subframe instead. I would have assumed that would be the case here, but you know what they say about assumption....

[Cyberdemon]

Originally Posted by tbuck

Ok, I was not aware it was an approved jack point on these cars. Back in my E36 M3 days we were always warned never to do that, to use the subframe instead. I would have assumed that would be the case here, but you know what they say about assumption....

The rear subframe is tubular on these cars so if you want to drop it off the jack, use the subframe.

Flat spot in front of the diff fins is the approved jack point. Just need a good block to get past the fins.

[Scharbag]

Originally Posted by Cyberdemon

The rear subframe is tubular on these cars so if you want to drop it off the jack, use the subframe.

Flat spot in front of the diff fins is the approved jack point. Just need a good block to get past the fins.

I have a custom piece of 2x4 just for this purpose!!!

[looking_lost]

i think i have the same issue with my rear suspension too. lots of chat about rear diff .. (but is the rear suspension a problem and do i need to replace ? )

my driver side (RHD) seems really low when compared to the passenger side.