E32 trailing arms onto an E28

[iamsam]

(entire original post deleted)

So I finished my E32 trailing arm swap on my E28.

Key lessons and observations:

No modification required to make it work, the tires don't rub the fenders if the fenders are rolled. (I had rolled mine previously).

Stock US E28 axles work fine

You will need bigger wheels to fit over the breaks

Major benefits:

Bigger brakes

sliding ball bearings instead of RTABS, more precise, durable, silent, etc.

Only few pics I have, a really crappy cell phone pic. You can still see the tiny stock 520i axle flanges in the background (which I replaced w/ US E28 ones)



After E32 trailing arms installed. Not a noticeable increase in track width.

[senorcarey]

When I put the E28 sub in the Bavaria, I used the arms off an E32 740. I used the diff flanges and CV joints from an E28. They fit together swimmingly.

I honestly don't remember what the length difference was between the two.

[iamsam]

When I put the E28 sub in the Bavaria, I used the arms off an E32 740. I used the diff flanges and CV joints from an E28. They fit together swimmingly.

I honestly don't remember what the length difference was between the two.

So what part fit to what exactly? E28 CV axles bolted to E32 trailing arms? E32 TAs had original inner flanges (for the axles to bolt to)?


Also, I measured my stock E28 CV axles just now, and came up with this:

Axle length from mounting face to mounting face (i.e. NOT including the dome-like protrusions on each end) = 17.75", or about 450mm.

Bolt circle diameter = 86mm

Note: This is an '84 520i euro spec, so these measurements may not be consistent w/ US E28s.

Can anyone verify these measurements, or give me measurements from your US E28 or E32 740i?

Thanks again.

[senorcarey]

Let's see...
I had considered changing the hubs, as E28ers have an issue with spacing with the E32 hub and rotor. On the Bav this was not an issue. I could run 285s easy with my set-up.

I used:
Late E28 subframe
E28/30 diff (med case)
E28 diff drive flanges
E28 CV
E32 740 (early) trailing arms and brakes. These are the same arms and brakes as E34 M5 and E32 750.

The E32 CVs were too long, IIRC, but the hub bolt diameter and spacing are compatible.

I had no issues, but I did measure a lot. It bolted together fine (at least that part of it). Let me know if you need pics or measurements.

[iamsam]

Let's see...
I had considered changing the hubs, as E28ers have an issue with spacing with the E32 hub and rotor. On the Bav this was not an issue. I could run 285s easy with my set-up.

I used:
Late E28 subframe
E28/30 diff (med case)
E28 diff drive flanges
E28 CV
E32 740 (early) trailing arms and brakes. These are the same arms and brakes as E34 M5 and E32 750.

The E32 CVs were too long, IIRC, but the hub bolt diameter and spacing are compatible.

I had no issues, but I did measure a lot. It bolted together fine (at least that part of it). Let me know if you need pics or measurements.

Interesting.

My E28 CV axles are clearly too small (bolt circle) to bolt to the E32 arms, but that's probably because it is a grey market car and has different axles. I don't know if my E32 trailing arms are "early" or "late", but they were from a '93 740i if that helps.

Also, I am using a subframe from an early US E28 if that matters. (what is the difference between early and late US E28 subframes?)

So if it's not any trouble, could you actually measure the bolt circle diameter of your E28 axles/flanges?

Or if anyone has some US E28 axles, diffs, or trailing arms lying around, it would be super easy to measure the bolt circle diameter with a pair o' calipers, my measurement above was from center to center of two bolt holes across the bolt circle.

The diagram on the right describes what I'm getting at quite well.

[iamsam]

also, does anyone know if E34 and E28 axles are swappable?

[iamsam]

Went to the junkyard.

E32 740i axle is too long for an E28, and has a 95mm bolt circle diameter.

E34 530i axle is shorter, but still too long, and has a 85mm bolt circle diameter.

I NEED TO FIND SOME E28 AXLES!!! DOES ANYONE KNOW THE BOLT CIRCLE DIA OF A US E28 AXLE???

[senorcarey]

Don't quote me on this, but E34s changed subframe or diff design somewhere along the run. You also have an early M10 car which may not have as stout axles in back. I had no problems with E28 axles bolting up to an e28 LSD and the hubs on the E32. Remember, all of the arms are the same dimensions, but the subframe spacing moves them farther apart due to the wider cars.

See if you can get an axle if each at a local parts store to measure.

[iamsam]

Don't quote me on this, but E34s changed subframe or diff design somewhere along the run. You also have an early M10 car which may not have as stout axles in back. I had no problems with E28 axles bolting up to an e28 LSD and the hubs on the E32. Remember, all of the arms are the same dimensions, but the subframe spacing moves them farther apart due to the wider cars.

See if you can get an axle if each at a local parts store to measure.

My E28 has an M20B20 actually, but still tiny with small axles.

From what I have been hearing (from you and others) my answer is US E28 axles and the matching diff flanges, so I am on the hunt.

[iamsam]

Also, what is the difference bewteen early and late E28 axles? They seem to be different on all parts websites based on whether they are pre or post 1984 or something...

[Robotin]

i kind of just scanned through through this thread, so sorry if my question has already been asnwered...

but u could probably could just use a whole e32 diferential subframe and axels and rear driveshaft. and it would have a largert load capacity. and probably a stronger rear end

[iamsam]

An E32 subframe is too wide.

[iamsam]

deleted and re-did first post. I have completed my E32 trailing arm swap (except for the ebrake cables) so if anyone has any questions, post here!

[mar1t1me]

May I ask what tire size and wheel offsets you are running?

[iamsam]

May I ask what tire size and wheel offsets you are running?

E38 style 5s (16x8, ET23 iirc) and 225/50/16. The tires are old Dorals that I swear are much wider than 225, but the size is 225 apparently.

Put it this way: The rear tires rubbed with all stock suspension and trailing arms on moderately cut springs until I rolled the fenders, but on a previous E28 I had with identical setup but Kumho tires, there was no rubbing at all, with un-rolled fenders.

here is a pic before I installed the E32 trailing arms, the rear tires rubbed in this configuration until I rolled the fenders:


Front wheel pic: