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derricklaukaitis
derricklaukaitis None
10/14/10 1:58 p.m.

Basic question... Which of these two rear-ends should I swap into my 1977 MGB project car: The BMW 3-Series E30 or E36?

Actually, both front and rear suspension systems will be transplanted into the MGB so they will work in harmony. I realize the width difference will mean the addition of fender flares, but I like that idea anyway, so that's not an issue. The new motor will be an all aluminum Duratec 3.0L from a 1996+ Ford Taurus, so BHP will remain within spec for either rear-end (around 200 to 250 with a few tweaks to the engine).

The E30 is a very simple and straightforward design and would be simple to transplant. I've heard the E36 performs remarkably better, but the rear suspension is much more complicated and is more finicky to set up. Is the performance difference worth the added aggravation on a car that will mainly be used on the street?

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
10/14/10 2:01 p.m.

The answer might be miata.

It is definitely NOT e30.

derricklaukaitis
derricklaukaitis New Reader
10/14/10 2:05 p.m.

Any reasons to stay away from the E30?

Although it may not be the best reason for their consideration, E30's are easy to come by and Miata's are a rarity in the junkyard.

oldtin
oldtin HalfDork
10/14/10 2:55 p.m.

BMW subframe mounts and perhaps the trailing arm mounts are going to land in difficult places on an MG. I don't know what your fabrication skills are, but you can make lots of stuff work once you break out the sawsall and welders, but I'd look pretty close at the effort vs. return/improvement.

WilberM3
WilberM3 Reader
10/14/10 2:57 p.m.

e30 isnt bad but its very wide and has no adjustability stock, and still isnt easily adjustable modified for it. easy to pick gear ratios though, as theyre everywhere and lsd were common back then.

e36 works well but isnt a self contained unit. the trailing arms going forward are going to need a structural component to mount to. i havent seen them cheap either unless you part one out perhaps.

what about a tbird supercoupe rear end? 8.8, lsd, self contained IRS though i'm not sure how adjustable it is. certainly strong enough though.

derricklaukaitis
derricklaukaitis New Reader
10/14/10 3:15 p.m.

That's the type of answer I was hoping for WilberM3. I completely agree about the E30 and E36 rear ends... The E30 is easy to get and easy to change ratios in but difficult to adjust while the E36 is a much better rear assembly, it isn't a self-contained unit. I can actually pick up a full E30 or E36 front and rear setup for $200, so the cost is absolutely minimal (this is about my fourth odd project coming from the same junkyard, so they really work on prices for me).

T-Bird... I had not thought of this. How are they to adjust? Are they track-worthy? They're about the same width as the E30/E36, so that's not outside the realm of possibilities.

derricklaukaitis
derricklaukaitis New Reader
10/14/10 3:25 p.m.
oldtin wrote: BMW subframe mounts and perhaps the trailing arm mounts are going to land in difficult places on an MG. I don't know what your fabrication skills are, but you can make lots of stuff work once you break out the sawsall and welders, but I'd look pretty close at the effort vs. return/improvement.

My aim is improved handling, better brakes and a wider stance. All three are satisfied by the BMW front and rear subframes. With that said, I completely agree about watching the R.O.T.I. (Return on Time Invested). The E30 IRS would be an easy fit once you consider the idea of re-designing the factory BMW chassis mounts. Fabrication is no real question... I've been building cars/trucks as a hobby for ten years or better now. The real question becomes "how much it would improve handling over a different IRS that's out there?"

Keith
Keith SuperDork
10/14/10 3:26 p.m.

Whatever your answer, keep us up to date. Sounds like a cool project.

For comparison (not necessarily for this MG, but for anyone else who is comparing), here's the Miata. Because it's a double wishbone, you don't need to deal with side loads on the shock tops. It might be a lower setup than the struts too.

PDF with mounting points

derricklaukaitis
derricklaukaitis New Reader
10/14/10 3:33 p.m.
Keith wrote: Whatever your answer, keep us up to date. Sounds like a cool project. For comparison (not necessarily for this MG, but for anyone else who is comparing), here's the Miata. Because it's a double wishbone, you don't need to deal with side loads on the shock tops. It might be a lower setup than the struts too. PDF with mounting points

I definitely like the Miata IRS for the point that it's a tried and true, track-proven, self-contained unit. It just isn't easy for me to come by one around here. As with the E30, the shocks could easily be swapped for a set of normal coil-overs for easier mounting.

Anyone have an extra one just laying around? :)

tincetti
tincetti New Reader
10/14/10 7:28 p.m.

In reply to derricklaukaitis:

Consider first gen Z car

Jensenman
Jensenman SuperDork
10/14/10 7:34 p.m.

Having butchered a few Britmobiles to accept the Mazda stuff, I vote Miata as well. The camber/toe changes are controlled in a much simpler way.

Crunched Miatae should be thick on the ground pretty much everywhere. What part of the country are you in that they are in such short supply? Try Copart http://www.copart.com/c2/copart_home_page.html to see what might be available reasonably close to you.

mad_machine
mad_machine SuperDork
10/14/10 7:45 p.m.

something you may not have considered.. the front suspension on the e30 and e36 is a strut based design. How would you fit such a system under the nose of a BMW?

Have you considered going the "locost" route? You can get suspensions for the Lotus 7 clones online.. then you just need to fab up mounts

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
10/14/10 8:01 p.m.

The real problem with the E30 rear is toe control in compression & droop. It has a very narrow effective range so for things with sporting intent you have to make it so stiff that it becomes a liability or drive around the wonky rear steering behavior. Its just not very good to start with so grafting it under something on purpose seems silly.

The E36 or E46 are good candidates for leveraging some of but not self contained so you have to fab support for the links. They are also kinda flimsy and non-adjustable. If I were planning to use anything - I'd copy the geometry, borrow the hubs and fab up the rest with tubing, rod ends and swaged rods to suit my needs. I do dislike the spring location - I'd go with a real coilover. That also means changing the lower shock mount a little or using a push rod - which I may be tempted to do... bringing the springs and dampers inboard.

Mikey52_1
Mikey52_1 Reader
10/14/10 8:18 p.m.

Of all the choices above, the prime candidates for butchery and hoonage would be 1) Miata, and 2) T-bird. Both cheap, both easy.

derricklaukaitis
derricklaukaitis New Reader
10/15/10 1:57 p.m.

The more research I do, the more I'm leaning toward the T-Bird rear end. Basically, because that is one of the rear ends of choice when Miata guys go for more HP. If I do choose to add a turbo to the Duratec 3.0l (I've read the stock internals can handle a twin turbo setup boosting HP up to a whopping 450bhp) then I wouldn't have to re-engineer the rear end once again.

I'm not closing the book on the rear end... But I'm getting close. Any thoughts?

derricklaukaitis
derricklaukaitis New Reader
10/15/10 2:09 p.m.

Perhaps a meld of the Miata suspension and the t-bird center-chunk (as "Boss Frog" uses in their V8 conversion for the Miata)... http://www.bossfrog.biz/Miata_V8_Swap.html

Keith
Keith SuperDork
10/15/10 2:12 p.m.

The Miata rear can actually handle quite a bit of power - it's the transmission that lets go. But if you're looking to go that far, then the range of gearing and LSD options for the T-bird rear could certainly come in handy.

A middle ground would be to use the Miata setup for now, then stuff a Ford differential inside later if that becomes necessary. Then you get the Miata geometry and packaging. As an added bonus, the bolt patterns should match your BMW front end.

(edit - looks like you figured the latter out on your own :) Flyin' Miata can also provide 8.8 conversion parts as well as parts to install a Getrag rear that's smaller and lighter)

derricklaukaitis
derricklaukaitis New Reader
10/15/10 2:14 p.m.

BTW... This is the thread I read about getting the Duratec 3.0L up to 450bhp. In case it's of interest... http://forums.nicoclub.com/duratec-3-0-w-t5-manual-turbo-swap-t334079.html

oldtin
oldtin HalfDork
10/15/10 2:15 p.m.

if you're hitting a junkyard - lincoln LSCs (edit - it's Mark VIIIs) sometimes get overlooked. Another source for an aluminum 8.8 IRS. On the front - mustang II spindles are easy to source - you can do double wishbones with a little fabbing and circle track parts and same wheel bolt pattern or for a street car the whole mII crossmember and arms. The MG crossmember is way heavy - you can drop 70-80 lbs out of the front end by going to a tubular crossmember. I know some guys who put in a jag rear - inboard brakes seem more pain than they're worth - I'd opt ford for cost and parts availability. I do like the geometry of the miata subframe alot though. I went simpler and kept a solid axle (triangulated 4-link).

derricklaukaitis
derricklaukaitis New Reader
10/15/10 2:17 p.m.

That is a good plan Keith... It wouldn't take much to swap the diff later.

derricklaukaitis
derricklaukaitis New Reader
10/15/10 2:27 p.m.

BMW would give better brakes (nearly for free), but the complication doesn't seem to be worthwhile. Matching front and rear hubs are a "must," in my book. So, since BMW uses a 5x120mm bolt pattern and the closest any other mfg comes is 5x120.7mm... Ford front (in the form of Mustang II) / Ford rear (in the form of Mazda Miata) sounds like the best combo.

So much for going exotic! Love the idea of keeping the cost down though!

derricklaukaitis
derricklaukaitis New Reader
10/15/10 2:32 p.m.

BTW... Nice build up oldtin! Very nice!!

MCODave
MCODave New Reader
10/15/10 2:34 p.m.

Not that it contributes to the thread, but I never knew until today that the 89-98 T-Birds had IRS. Doesn't the Mustang still have a live axle? Weird.

oldtin
oldtin HalfDork
10/15/10 2:37 p.m.

There's good wilwood (and others) brake options for the MII spindles. The cheap version is more like GM metric calipers, granada rotors and good pads.

JThw8
JThw8 SuperDork
10/15/10 3:12 p.m.
MCODave wrote: Not that it contributes to the thread, but I never knew until today that the 89-98 T-Birds had IRS. Doesn't the Mustang still have a live axle? Weird.

The IRS was tried breifly on mustang and noone liked it, most of the guys ended up swapping it to a live axle. Go figger.

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