Turning down Al subframe bushings

[Solo_S14]

I took a few quick measurements from the subframe this weekend, and I want to run something by the forum before going ahead with it. Basically I want to raise my rear subframe to correct some geometry, while it's out and getting bushings anyway.

The Al bushings that I have are 29mm high each (total height of 58mm).
Each bushing has a 9.2mm lip on the end with a larger diameter (75mm) than the subframe "cup" that it sits in (66mm). Essentially the amount of bushing that will be inside the subframe is 39.6mm if installed as is.

I measured the height required to fill the subframe, which is 58mm with the stock metal bushing cup that is pressed into the subframe, and 55mm with this cup removed. So I'm working with 55mm.

Basically if I install these as is, they won't completely fill the subframe space, but that's fine since they'll be pressed in and held with the bolt from the frame of the car. I don't want to install as is though, I want to cut the 75mm lip down to 66mm (the od of the rest of the bushing) so that I can raise the subframe by 9.2mm on top.

Basically I'd be putting the upper bushing on the lathe and turning down the lip so that it sits inside the subframe and raises it that amount.

The problem that I run into is that if I only turn down one bushing, they won't completely fill the subframe, and I think the upper bushing will just move into the subframe, not making contact with the chassis.

I can:

1) Turn the upper bushing down and also turn the lower bushing down until it has a 3mm lip, filling the subframe with aluminum bushing completely, and keeping it against the chassis.

2) Turn down the upper bushing, leave the lower bushing as is, and use a spacer to fill the subframe.

3) Only install the lower bushing, and let the subframe rest against the chassis.

So given that I want to raise the subframe, I obviously don't want any bushing material above the subframe, I'll either have to turn down the upper bushing, or not install it at all.

Will I have any issues not installing the upper bushing?
Any issues with the subframe against the chassis?
Do I want a bushing pressed into the subframe regardless?

Is a 3mm lip too small on bottom? Maybe use a washer in addition?
Other comments?

Note:
The metal insert that the bolt runs through in the stock bushing is 68mm (I think), so would my total height change really be (58mm - 9.2mm) or (68mm - 9.2mm) with this modification?
I guess that the overall height change depends on the distance from subframe to chassis with the stock bushing?

Thanks.

[Matt93SE]

At first glance, I don't see a huge issue with removing the top bushing altogether assuming the subframe doesn't move relative to the chassis. With an aluminum bushing in the bottom of it, I don't think it would move.
you might stick a large fender washer in there and tack weld it to the subframe just to get the subframe more meat to sit against than the vertical walls of the tubing.

Or turn down the bushing so that it's a lot thinner on the top, and you don't need it to protrude into the subframe more than about 1/4". based on what you're saying, the alu bushings protrude into the subframe quite a bit. As long as you have enough meat to hold everything in place, you can cut down all the bushings to maybe 1/4" or 3/16" thickness inside the subframe to save a pound or so of weight.

[Solo_S14]

Yeah they fill a lot of the subframe, they're just a generic bushing like these:

[logr]

I would want the bushing against the subframe to keep the load against the attached part of the bolt. I wouldn't put only the bottom one in for this reason. Whichever way is easier after that. Turning down both bushings seems cleanest.

[Def]

Why not turn the bushing down then toss in a washer or something to take up the extra space?

[Black R]

What brand did you buy? eBay generics?

The spl ones I got press in from below and sit flush with the subframe where it mounts to the chassis:



I'd turn down the upper ones you have till they're flush like that.

[Solo_S14]

Why not turn the bushing down then toss in a washer or something to take up the extra space?

What extra space are you talking about?

If I turn down both bushings, there won't be any extra space inside, just a 3mm lip on the bottom. If I just turn down one, yeah there will be some extra space inside that I could use a washer to fill, but I'd be weary about the washer getting pressed in not centered and gettign in the way of the chasis stud passign through. Or do you mean use a washer above the busings (between the top bushing and chassis)?

I think the best option will be to turn them both down, then possibly use a washer below to reinforce the small 3mm lip from the bottom bushing. You guys think so?

What brand did you buy? eBay generics?

They're Bings (bings.ca), but yeah they're the same as ebay generics I guess.

[Def]

Yea, I guess you could turn down both so there's just a slight bit above the subframe cup. I was thinking if you just turned down one and had some extra space to take up. Don't think it matters much if it's centered or not.

[Sleepy_Steve]

Bumping this old thread: Same question, but with polly energy suspension subframe bushings.

In order to do a bit of roll center correction, I have to turn down the top 1/2'' or so of the bushing and the metal sleeve on the inside of the bushing to raise the subframe up an equal amount. Other than spacing the subframe down from the chassis by a half inch, is there any reason to keep the top 1/2'' of the bushing that I think I need to be cutting off here?

[BeerBringer]

Consider ebrake cable clearance. I have read it can be a problem.

[Sleepy_Steve]

Its already a problem, those suckers are getting relocated during this procedure.

[Black R]

If I could, I'd turn down the subframe mounting points a little to suck it up tighter to the car...