Options for out of round subframe bushing opening

[tortexal]

Hi All its been a while!

I started replacing subframe bushings and had a heck of a time removing the driver side. Torch/sawsall/chisel later... now I see why.

The new poly bushing is a circle and the subframe is an oval:
drivers01.JPG
Interestingly enough, the driver side rear alignment was within spec as of 7/28 w/ new polly RTAB, dog bone, shock mounts, and the old subframe bushing.

What options exist short of replacing the subframe to get this thing closer to round to get the new bushings in?

I'm certainly not opposed to replacing the subframe. Apparently part # 33311090566 is still available from bmw which is amazing. I just wont have time to tackle it until next summer :/

[moroza]

Bend it 'n' send it.

[Tre0Tre34]

Is there a mark on the underside from some kind of impact?

I dont believe Ive seen or even heard of this condition before, and my e34 has done a decent bit of offroading.

[tortexal]

The drivers rear quarter was hit by another vehicle back in 2008 if I recall. The car aligned perfectly after the trailing arm was replaced. I suspect the smooshing of the subframe mount went undetected due to the proper alignment during the accident repairs.

I'm not 100% sure how to bang this thing out enough to get the new bushing started to press on further. It's already a slip n slide in there with all the lube.

[tortexal]

I'm wondering if something like this:
shaper.jpg
from https://www.amazon.com/Lisle-32000-P.../dp/B0002STSO4

or
expander.jpg
from https://www.amazon.com/Powerbuilt-94.../dp/B004KEIHAC

would work well enough to re-round each side of the bushing opening to be able to get the bushing in there enough to press in the rest of the way.

I have zero experience trying to re round a circle, especially on a subframe that is in an odd spot and short of removing the entire thing from the car.

[m60power]

I'm honestly shocked the subframe barrel had enough force going into it to oval the hole. The steel is pretty beefy there and the OE bushings have a lot of radial compliance. Must have been quite an impact. Is the elongated part of the ovaled hole in line with the subframe beam, or is it perpendicular to the main support beam? If perpendicular you could try lowering the subframe enough to get a vise or something on the barrel and compress against the elongated portion until it is more or less circular.

I doubt that pipe expander tool will do much at all to re-circularize the hole. I've watched a few videos of people reviewing them for flaring out exhaust pipes and 90% of the time they are basically useless on all but the thinnest wall tubing...

[tortexal]

I got the top bushing pressed in!

The machine shop guys at work recommended several ideas. The one that I went with was to grind an angle on the lip where the metal was interfering w/ the bushing, basically just making a feed ramp on either side.

I did this with a beveled hand file until the bushing was flush with the outer barrel on each side. I set the bushing on top, and put 1 washer on the top of the bushing on the side neared to the front of the car so that when I jacked up the subframe the bushing would hit the body flush and hopefully press in square.

It worked!

Now for the next challenge, getting the metal cylinder pressed into an oval polly bushing
PFR5-507BLK.jpg

Food for thought: The machinist indicated that trying to expand the barrel back to a circle would be a bad idea because it'll expand out to the widest existing radius and the opening will then be too big for the bushing. As long as the center axis didn't change after getting hit, the center of the beam will still be aligned with the body. idk if that'll pan out exactly like that. I suspect I'll need a new subframe anyway with all the chicanery, and I'm doubtful that the thrust angle will actually align properly when I'm done. I just hope it's not worse than what it was before, but we'll see.

[ross1]

I got the top bushing pressed in!

The machine shop guys at work recommended several ideas. The one that I went with was to grind an angle on the lip where the metal was interfering w/ the bushing, basically just making a feed ramp on either side.

I did this with a beveled hand file until the bushing was flush with the outer barrel on each side. I set the bushing on top, and put 1 washer on the top of the bushing on the side neared to the front of the car so that when I jacked up the subframe the bushing would hit the body flush and hopefully press in square.

It worked!

Now for the next challenge, getting the metal cylinder pressed into an oval polly bushing


Food for thought: The machinist indicated that trying to expand the barrel back to a circle would be a bad idea because it'll expand out to the widest existing radius and the opening will then be too big for the bushing. As long as the center axis didn't change after getting hit, the center of the beam will still be aligned with the body. idk if that'll pan out exactly like that. I suspect I'll need a new subframe anyway with all the chicanery, and I'm doubtful that the thrust angle will actually align properly when I'm done. I just hope it's not worse than what it was before, but we'll see.

Don't overthink or complicate the job.
While not designed for this one of those pipe expanders might do the job or at least ease the situation. A GOOD one(not that overpriced POS from Senor Bezos, same at Harbor Frt for $20 BTW) with Acme screw threads has a much better chance.
Machinists deal in thousandths or less. You don't need precision. It will expand as far as you make it. Maybe heat it first.
Brute force (and heat) is always your friend when doing suspension work.

[tortexal]

Thanks for all the pointers. I got everything installed. It's a night and day difference with the powerflex blacks for the subframe and rtabs. The car finally feels planted to the ground again. I'd skip the powerflex yellow and purples and go straight to black (race) they feel excellent. No clue if road noise is greater or not, I can't hear anything over the Direzza Z3s anyway. Additionally, I can't feel any difference in alignment/thrust angle which was off by 0.29 degrees prior to the subframe bushing replacement. I'll get it aligned again after the centerlink and idler arm bushing replacement and report back.