1 2
roninsoldier83
roninsoldier83 Reader
9/4/23 5:48 p.m.

So, I was wanting to pick the brain of the hive-mind in regards to aftermarket/OEM replica rear subframes. 

My dilemma: I'm prepping my E82 BMW 128i for NASA TT5, hoping to get it ready to compete over this winter. Before I bought the car, it was in an accident, where it would appear (based on photos I observed) that a previous owner likely slid the rear-right side into a wall. The damage was repaired before I took ownership and after quite a bit of maintenance, the car now drives very well, but I couldn't help but notice: 

-The car was bone stock when I bought it (6MT w/Sport package car), with 1 glaring exception: a set of rear aftermarket toe-arms. This led me to believe whoever repaired the car had some trouble getting the rear toe into spec, as there are no signs the car was ever lowered, or modified, which might otherwise have necessitated a set of adjustable toe-arms. For reference, I was able to use the adjustable toe-arms to get the alignment into spec. 

I have replaced all the right rear control arms, the right axle (it was visibly damaged, even if I had to look closely to see it) and the right rear knuckle with used OEM parts, for good measure (in the event something else might have been bent ever so slightly).

I've inspected the rear subframe... there might be some slight bending on the right side (one of the protrusions might be off ever so slightly), but honestly it's hard to tell. Overall, it looks like it's in pretty good shape. 

Here's where I'm at: I'm planning on dropping the subframe anyway to install stiffer rear subframe bushings and while I'm at it, remove the diff to swap in a LSD. Since I'm removing the subframe anyway, and I don't know if there's some unknown bending (hard to tell on the right side) or unseen damage, to be on the safe side, I was planning on replacing it. I've got options: 

 

1. Buy a used OEM subframe. Fortunately, the E82 shares the same subframe with the E90/91/92, so they're plentiful. The issue is that most of the ones on eBay are from unknown condition cars- they might look straight in photos, but I wouldn't be able to tell if they have some slight bend from a rear-end accident (they're pretty much all from wrecked cars, right...), leaving me in the exact same position I'm in now. I've also considering heading down to my local pull-n-pay to yank one out, which means a bit more elbow grease, but less likelihood of the rear end being bent (I would only pull from a car that was in a front-end collision). On average, they seem to be around $300-$400 range. 

2. Buy a new aftermarket/OEM replica subframe. I don't know what the quality of them is, with most of them claiming they "meet OEM standards", but they are brand new, so no chances of being in an accident, no rust, etc. They seem to go for around $400-$500, which makes them pretty appealing. 

Before anyone mentions a new OEM subframe, BMW discontinued/stopped making them a while back. I might be able to find some old stock somewhere, but according to the gentlemen at FCP Euro, they appear to cost around $1100, so a substantial upcharge if I could even find one to begin with. 

What are your thoughts and experiences with aftermarket/OEM replica subframes? Would the quality likely be close enough that it wouldn't matter? Keep in mind that I would be installing hardened bushings no matter which route I end up taking. 

For visual reference, here's a snip of one of the suspects in question: 

 

L5wolvesf
L5wolvesf Dork
9/4/23 6:50 p.m.

I don't have an answer but I do have a question. Have you checked to see if the car is straight / square? 

roninsoldier83
roninsoldier83 Reader
9/4/23 6:58 p.m.
L5wolvesf said:

I don't have an answer but I do have a question. Have you checked to see if the car is straight / square? 

No, I haven't. I aligned it, which went just fine... but I'm assuming you mean maybe checking the difference between the distance of the left side hubs vs right side hubs? Or would there be some other way to check that? 

For the record, the frame rails look as straight as an arrow, and the alignment is in spec. Not sure what else I would be looking for. 

roninsoldier83
roninsoldier83 Reader
9/4/23 8:03 p.m.

In reply to L5wolvesf :

I'm not quite sure what the car being straight/square might mean, other than things like the frame rails being straight (which they are). The body work that was repaired turned out pretty well. At first glance, no one would be able to tell it was ever in an accident. Underneath the car, everything looks straight- no signs I can see that the frame/rails were ever pulled straight. My guess is they cut out the dented panels and welded in new (used?) ones. 

Looking at the photos from the accident, it really looks like the previous owner slid into a wall. Most of the body damage looked fairly superficial. The car drives very straight. My biggest concern is that the right rear wheel hit something (wall, curb, both, etc), which bent control arm(s) (already replaced) and the force of the control arms pushing in could have bent the subframe. The OEM toe-arm mount on the subframe looks pretty flimsy to say the least... I could easily see it being bent just a bit from the impact. 

Either way, the car drives very well. Here's a picture of the previous damage so you can see why I'm thinking the rear end slid into something: 

 

I'm more concerned with the subframe than I am the rest of the car if we're being honest. 

Noddaz
Noddaz PowerDork
9/4/23 8:32 p.m.

If the car will align without problem and tracks straight, MHO is the sub-frame is straight.

You could spend time and money to have the car put on a frame machine to find out if it is straight,  If that makes you feel better you should do it so you will KNOW.

roninsoldier83
roninsoldier83 Reader
9/4/23 9:54 p.m.

In reply to Noddaz :

That's fair.
 

The way I figured, I am going to remove the subframe anyway- the rear subframe bushings on these cars are like Jello and one of the first things recommended to replace/upgrade to help the car feel more cohesive. I figured I could replace them on a questionable subframe, or for just a few hundred bucks I could put new upgraded bushings into a subframe that I know has never been in an accident. It would also break up the job a bit, allowing me to press in the bushings before removal, making the swapping process go quicker/smoother. That was my rationale at least. 

L5wolvesf
L5wolvesf Dork
9/4/23 10:29 p.m.
roninsoldier83 said:

whoever repaired the car had some trouble getting the rear toe into spec

I've inspected the rear subframe... there might be some slight bending on the right side

I have replaced all the right rear control arms, the right axle (it was visibly damaged, even if I had to look closely to see it) and the right rear knuckle with used OEM parts

Those things made me think there could be some bending of the chassis you might not see without taking measurements (straight and square). You can do that with a simple plumb bob and tape measure.

Mr_Asa
Mr_Asa UltimaDork
9/4/23 11:00 p.m.
L5wolvesf said:
roninsoldier83 said:

whoever repaired the car had some trouble getting the rear toe into spec

I've inspected the rear subframe... there might be some slight bending on the right side

I have replaced all the right rear control arms, the right axle (it was visibly damaged, even if I had to look closely to see it) and the right rear knuckle with used OEM parts

Those things made me think there could be some bending of the chassis you might not see without taking measurements (straight and square). You can do that with a simple plumb bob and tape measure.

To piggyback on this.  Frame shops have/had books (probably electronic now) of those data points.  Might take digging, but you should be able to find everything online and start taking measurements. 

roninsoldier83
roninsoldier83 Reader
9/4/23 11:27 p.m.
L5wolvesf said:
roninsoldier83 said:

whoever repaired the car had some trouble getting the rear toe into spec

I've inspected the rear subframe... there might be some slight bending on the right side

I have replaced all the right rear control arms, the right axle (it was visibly damaged, even if I had to look closely to see it) and the right rear knuckle with used OEM parts

Those things made me think there could be some bending of the chassis you might not see without taking measurements (straight and square). You can do that with a simple plumb bob and tape measure.

I should have specified, the only point of the subframe that looks like it might have been slightly tweaked is the mount for the lower camber arm/spring seat (it might be slightly twisted- we're talking a fraction of an inch, maybe). It's tough to tell if it's actually having an effect on the car, especially since the camber is still within spec, but the angle of the right mount looks ever so slightly different vs the left side. I should probably mention that the rear camber is factory adjustable (OEM eccentric bolts), so just because I was able to get it in spec doesn't mean it's perfectly straight. 
 

I don't know if the adjustable toe arms are actually needed, but since they came with the car, I left them on there and used them to get the toe in spec. With that said, the toe arm mounts are very flimsy/thin and easily bent. It would be tough to see with the naked eye if it was slightly bent. 
 

Based on photos from the accident, combined with the design of the suspension, it looks like either the control arms or subframe mounts would bend before the chassis/frame bent. 
 

To be clear, the car drives perfectly straight. The alignment is perfectly in spec. I don't need to swap the subframe. I just figured since subframes are cheap and I need to remove it to upgrade the bushings anyway, it would be a good time to swap in a fresh one. 

Driven5
Driven5 UberDork
9/5/23 10:55 a.m.

It might not be a bad idea to swap out the aftermarket toe arms for some stock ones, and find out if it still aligns correctly.

roninsoldier83
roninsoldier83 Reader
9/5/23 11:47 a.m.

In reply to Driven5 :

Not a bad idea, just to see where it's at. At a minimum I think I might at least measure the distance of the center of the mounting bolt holes and compare the distance to the OEM toe arms. 

mr2peak
mr2peak Dork
9/5/23 12:21 p.m.

You can swap out to M3 parts, like the 1M runs.. sorry if I just cost you a ton of money with that info

z31maniac
z31maniac MegaDork
9/5/23 4:28 p.m.

An LSD for that car is $3k+, right? 

So $500 for a used subframe of unknown provenance, or $1100 for a known quantity. Is the extra $500-600 that big in the scheme of things given what you're spending?

Have you reached out to Steve at Blunttech or Levent at GutenParts? They may be able to get you a known good used unit, or possibly a better price on a new OEM. 

roninsoldier83
roninsoldier83 Reader
9/5/23 7:28 p.m.

In reply to z31maniac :

The used subframes are even cheaper than that- in the $300-$400 range. 

For $500, you can get a brand new, OEM replica subframe. Which is why I was asking if anyone had any experience with them. 

I agree with your premise: in the grand scheme of things, a few hundred extra bucks is nothing for a new OEM subframe. Unfortunately, they've been discontinued. I'm sure I can find some leftover stock from Europe, but I've had a couple of less than stellar experiences shipping overseas, so I'm wary to spend not-so-small sums of money on parts that ship from Europe. 

I have not reached out to those folks! I didn't even know who they were! Thanks for the recommendation- I'll reach out to them for sure! Thank you, sir! 

z31maniac
z31maniac MegaDork
9/5/23 8:36 p.m.

In reply to roninsoldier83 :

No problem, they are good people! Done many thousands of business with them when I was still in the BMW world. Levent even got my 318is for me and did a bunch of custom work to it before I flew out and drove it home. 

P3PPY
P3PPY SuperDork
9/6/23 12:45 p.m.

When looking at used, car-part.com listings will often have pictures of the donor car. From there you are certainly not guaranteed anything, but you can get an idea of what caused the car to be totaled. 

Slippery
Slippery PowerDork
9/6/23 1:21 p.m.

I did not read the whole thread but based on what I read here are my thoughs:

1. I very much doubt you can determine whether the sub-frame is bent or not based on looking at it. 
2. I am not sure you can determine whether the car has been lowered previously or not. ie, my M3 is lowered and I kept all the stock parts, there is zero rubbing. You would have a hard time knowing if I did not tell you. 
3. If you want the convenience for when you get new rubber, then go for it. Pick one from a junkyard from a car that has no rear damage. They are everywhere.
4. If you want the real answer, put the car on a frame machine.

5. Subframes are available from BMW, not sure why FCP said otherwise.

- What brand are the rear toe arms?
- Measure the threads and see how many are exposed on each side, or better yet remove and measure mount pt to mt pt, to see if there is a big difference from side to side. This should take 20 mins max. Even then, it could be compensating for a bad bushing elsewhere. 

I would remove the subframe to redo bushings and assess at that point, most likely its fine. The stock camber arms are made of butter.


 

roninsoldier83
roninsoldier83 HalfDork
6/10/24 7:18 p.m.

It's been a while since I've given this much thought, for a variety of reasons. I haven't bothered jacking up the rear of the car to measure the length of the adjustable toe arms. The car drives great and for a while I was using it as a daily (not a track car), so I wasn't too worried about it. At this point, I'm back to my original plan of tracking the car and am giving some more thought to the rear subframe. 

I called around my local area, trying to see if someone could do some measurements for my own peace of mind... all of the major body shops told me they're currently only working with insurance companies/insurance claims... called 1 local non-chain body shop that told me they don't even measure subframes (you should have seen the confused look on my face), saying I should try to find a frame shop (I wasn't aware that was even a thing!)... I finally found a shop about ~45 minutes away that can do the measurements, but there are a few catches: 

1. They're all booked up until January 2025... they said they can probably squeeze me in between jobs if I just leave the car with them for an undisclosed amount of time. 
2. They said measuring the car will likely cost me about ~$400. 

At this point, I think I'm just going to skip measuring the car, find a wrecked car from local salvage yard with front-end only damage and pull the rear subframe myself. My rationale: it will cost me $400 just to measure my current subframe- I can literally buy a subframe from a front-end damaged car for less than that. Might as well just get a used one from a front end damaged car and put the bushings in it myself while it's sitting in my garage. I might try to find one with a 3.73 rear diff attached to it while I'm at it... 

I could buy a new subframe from BMW apparently, but my inner cheap bastard is really kicking in pretty hard right about now. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
6/10/24 7:48 p.m.

If it has toe adjusters installed on BOTH sides, it isn't a subframe problem.  Maybe a ride height issue, maybe the stock adjusters were seized (common) and the do it once and get it out the door ASAP option was just putting adjustable links in.

 

Lemme tell you about the time someone destroyed a 540i Sport rear subframe with a little too much heat trying to get the adjusters to move... the subframe melted before the adjusters moved.  And the subframe was specific to that one trim level, apparently, as it took over a week to get a used one from the other side of the country.

WonkoTheSane
WonkoTheSane UltraDork
6/10/24 7:55 p.m.

Soo, forgive me if I missed it, but what problem are you trying to solve (maybe even just define)?  

 

The car drives correctly, the car aligned to specs you're happy with.... 

roninsoldier83
roninsoldier83 HalfDork
6/10/24 8:52 p.m.

In reply to WonkoTheSane :

That's a fair question that I probably should have written out. 

So, the subframe bushings on the non-M cars are essentially made of jello. BMW did this to cover up some of the associated harshness that comes with OEM run-flat tires. For track car purposes, I will be removing the squishy OEM subframe bushings and installing some flavor of much stiffer subframe bushings (hardened rubber, poly, aluminum, etc). 

As of right now, the car aligns within spec and tracks straight. I'm not sure if during the accident the subframe twisted at all and if I'm only able to align it properly due to the adjustability of the aftermarket toe arms. 

The last time I had the car on the alignment rack, it aligned within spec just fine: 



^^^Pay no attention to the extra front camber- that was completely expected when I installed the M3/1M front control arms (they add close to an extra 1* of front negative camber). 

My thoughts: in order to upgrade the subframe bushings, I have to actually drop the subframe. If I'm dropping the subframe anyway, it's not a whole lot more work to just replace it. If my stock subframe is perfectly fine, it would save me a bit of money (between $150-$500 on average) and time/effort (not having to remove the diff/axles/hubs/etc) to just re-use my stock subframe. However, if it's twisted just a bit, this would be more of a "while I'm in there" kind of job. The idea of pulling an extra subframe also has a bit of additional appeal: I hate replacing suspension-type bushings. Doing it all in one weekend doesn't sound like a good time if I don't have to, whereas replacing them slowly on the garage floor allows me to take my time and just swap out a subframe as a whole unit without having my BMW on jack stands for potentially days at a time. 

I started this thread because of the available aftermarket subframes available on places like eBay for like $400-$500. For reference, most used subframes (they're plentiful) on eBay go for ~$300. In a local junkyard, I'm sure I can pull one for around ~$150 or so, but it does require a bit of brain power or a 2nd set of hands, as they don't allow you to bring in a floor jack- I'm not sure if they would care about my tranny jack?? Eating ~$1100 + shipping on a new subframe from BMW is a hard pill to swallow when my stock subframe still manages to align okay... $150? Yeah, I think that could be worth it. I could even justify $400-$500 on an aftermarket subframe if I knew the quality to be within OEM specs- hence me asking if anyone had any experience with them. 

So, it's less about "fixing" something and more about optimization "while I'm in there", if that makes sense. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
6/10/24 8:55 p.m.

I didn't even know aftermarket subframes existed until today.

My experience with aftermarket control arms is that they are almost never the same dimensions as factory.  Fun is when one side is short and the other side is long, or one gives more or less caster than the other.  I would expect nothing less from a subframe.  This is end of life care type of stuff: it doesn't have to be perfect, just good enough to limp along another couple of years.

 

Oh! Also, large items usually get bent in shipment even if they were made perfectly, unless they were extremely well packed, like bolted to a crate.

OHSCrifle
OHSCrifle UberDork
6/10/24 9:56 p.m.

I thnk before spending a couple hours in the JY I would try very hard to find out the exact measurements for the subframe and check that sucker in place. 

roninsoldier83
roninsoldier83 HalfDork
6/10/24 10:02 p.m.

In reply to OHSCrifle :

If anyone happens to know where I might be able to acquire such knowledge, I'm all ears! 
 

I have a manual (either Chilton's or Haynes) in the garage, but I'm not sure it it would be listed in there or not. I suppose I could check. 

Slippery
Slippery UltimaDork
6/10/24 10:06 p.m.

I wouldn't even bother with a junkyard if you want an wxtra one:

1 2

You'll need to log in to post.

Our Preferred Partners
SUzZMSXOMbzDFuvbzx3ig9LpvXWciFLbEcdlt0DDtNGClg7KvJKqyQUGuIfE40UU