[james008]

I was installing new rear rotors and pads cleaning the brake dust off and came across this!! Glad I saw it now and not while stranded on the side of the road.

But... I do not know what this part is, please help.
Sorry for the blurry gopro pic I realized the pic didn't come out well so I took some pictures of the other side which is still intact.

Plan to make an appointment for next Monday just hope it hangs on till then.

[SGe92is]

looks like part of the hub assembly

[james008]

found it. Looks like it's item #1 wheel carrier housing. Probably not a DIY for me. What a pain. I suppose if they are in there I may as well have them do the rear bearings?

Anybody seen this happen before?

[Tiago@VRSF]

Looks like someone may have slid into a curb at one point.

[raceyBMW]

That does look to be the outside edge of the wheel carrier, very strange for that to crack like that. I would definitely have the wheel bearing replaced at the same time because I can't imagine damage like that with the wheel bearing also not being damaged. Also I would have that entire side of suspension arms inspected by someone qualified, it is very likely that something else could be damaged as well.

Here's what the hub flange looks like, so pretty sure the broken part is the wheel carrier that the wheel bearing slides into once I looked at it again.

[Tiago@VRSF]

Yeah looks like it's just the hub assembly. The knuckle looks fine but if this is broken due to blunt force the knuckle could be bent which will throw off your alignment.

[james008]

Had two alignments done in the past 6 months neither time could they get that wheel to camber to spec. But, neither could figure out why. Just refreshed the front suspension, we then went over the rear and everything visually looked fine. Once the rotor came off last night and I cleaned up the area this crack was pretty apparent. I have owned the car for 2 years and haven't had any rear end issues but who knows what the previous owner did.

Do I need to do both wheel bearings or can I just do the one side.
Just this month I have done:
Wife's 528i:
4 new tires
oil change
transmission pan and fluid
My 335i:
oil change
front end suspension refresh (m3 control arms & adjustable endlinks)
front and rear rotors and pads

It's adding up faster then I can afford...

Originally Posted by Tiago@VRSF

Yeah looks like it's just the hub assembly. The knuckle looks fine but if this is broken due to blunt force the knuckle could be bent which will throw off your alignment.

[Tiago@VRSF]

If the car is approaching 100k miles I'd do both since he other one may require replacement soon.

[raceyBMW]

In my opinion, wheel bearings really aren't needed as preventive maintenance...they either work or they are going out (very very rarely seize). You will know if they are going out long before they actually do. I wouldn't bother doing the other one right now unless you just don't feel comfortable doing one...its really just overkill.

Think of it this way, if you were going on that philosophy, then why wouldn't you need to replace all 4?

[cwarren]

Just out of curiosity was the car lowered ? Seems pretty odd this would happen for no apparent reason .

[Tiago@VRSF]

I've destroyed a few knuckles and hub assemblies in the past, the only thing that's going to cause that is either a major pot hole or a slide into a curb

[james008]

Originally Posted by cwarren

Just out of curiosity was the car lowered ? Seems pretty odd this would happen for no apparent reason .

Car was lowered on race springs when I bought it. I put bc coilovers on it to bring the height up some and meatier 235/40/19 & 265/35/19 rear still has a lowered look but without the scrapping. I have no wear symptoms on the bearings but bought 2 anyway. The broken side obviously needs it.

No rear end damage on my watch, two track days, no auto cross. Car has had a rough life ( lots of scars) but i've committed to drive it to its grave.

I too am surprised at the crack it seems in a weird spot.

[qbuilt]

Car must of hit a curb at some point. You need a new knuckle, which cannot
be replaced without replacing the wheel bearing. Also, you may have bent
the rear subframe slightly, casusing the camber issue. The rear toe arm mount is very easily damaged on minor impacts. Take it to a dealer or Good BMW shop and ask them to inspect the rear end for any signs of accident damage.

[Eat.Sleep.Race]

It won't be too hard of a job if you have an impact gun! 3 hours is a good guess for that, as long as you don't have to press in any bearings. It should be about 4-5 bolts/nuts

[james008]

Originally Posted by qbuilt

Car must of hit a curb at some point. You need a new knuckle, which cannot
be replaced without replacing the wheel bearing. Also, you may have bent
the rear subframe slightly, casusing the camber issue. The rear toe arm mount is very easily damaged on minor impacts. Take it to a dealer or Good BMW shop and ask them to inspect the rear end for any signs of accident damage.

Car has been to about 3 or 4 very reputable alignment shops/ Indy shops and no one has found anything. I agree though I think the rear subframe might be bent a little. I was quoted $240 labor and I sourced the parts myself from bow cheaper then the shop quoted. Car goes in Thursday.

[raceyBMW]

If it were curbed at some point on that side, I would bet the lower trailing arm or toe arm is probably bent...they are pretty flimsy when put in compression like that.

I would doubt the actual subframe is probably bent because those arms will give long before the subframe does.

[AWDBooSTIn90]

Originally Posted by raceyBMW

If it were curbed at some point on that side, I would bet the lower trailing arm or toe arm is probably bent...they are pretty flimsy when put in compression like that.

I would doubt the actual subframe is probably bent because those arms will give long before the subframe does.

+1

The rear lower arm is pretty flimsy looking.

[Tzu]

I worked on a car that was curbed pretty bad in the rear. #11 in the diagram above was collapsed completely, and it appears that particular arm was designed to fail that way. The subframe was noticeably bent where the #14 trailing arm attaches to the frame, it's stampted and welded sheet metal there, and should have been gusseted from the factory IMO.