E30 or E36 rear-end swap into MGB

derricklaukaitis wrote: 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!

Just drill new holes. The diameter of the hub is fine. Viola... matching front and rear.

Redrilling one pattern to another needs to be done well, but is simple enough if you're keeping the same number of bolts. Going from a 5- to 4- bolt (or vice versa) is a little sketchy because of the spacing between the holes.

oldtin wrote: I do like the geometry of the miata subframe alot though. I went simpler and kept a solid axle (triangulated 4-link).

That's exactly how I felt. I ended up with Miata front geometry and a three-link rear based on a 10-bolt Chevy rear with custom axles on my chosen bolt pattern. I was able to keep most of my stock sheetmetal and even the gas tank.

One other thing - check out a circle track or hot rod catalog such as Speedway for a number of good upgrade options for brakes. I don't know what the roundy round guys use for front uprights, but they have ridiculously inexpensive disc brake packages. I think the hot rod guys are all using Mustang II. Not an area of my expertise, but certainly worth investigating - or wait for a few minutes and someone else will pop in with a lot of info for us

I love the idea of going BMW... But I'm pretty sure I'm going to go Ford. Here's the plan for the rear end (as I see it today)... Unbolt and scavenge a Thunderbird IRS from the local junkyard (for an easy $100). Steal the geometry from that rear end setup, but make new upper and lower arms (out of DOM) as well as a new lighter weight cradle that will fit the contours of the MGB more appropriately. (Hey wait... maybe I should make it bolt right up to the original leaf spring hangers! That'd be sweet if it makes sense with everything else in the rear of the car.)

Here is the real challenges for fitting the Thunderbird IRS to an MGB: The rear end of an '89 thru '97 Ford Thunderbird has a track of 60.20" while MGB has a lowly 49.25" rear track. Not a big deal, really, since I'm planning to weld up new upper and lower arms. I'll need to find a shorter replacement for the stock Thunderbird axles. I want a wider stance, but I'm only thinking a few inches each side... Not (let's do the math here...) 5.475" wider on each side! Basically, I want the wheels to tuck up nicely after I add a set of widened Dodge Omni fender flares to the mix.

So then the front... If I'm nixing the BMW rear end, then I am also nixing the BMW front. I'm up in the air a bit on how I'm going to tackle it, but... I think first thing I'm going to do is cut out the stock monstrosity of a k-member. It will be replaced by a tubular setup that will make swapping the motor a lot easier to do. I will need to widen the front stance a bit, make provisions for a set of spindles from a Mustang II setup and switch the car over to a coil-over shock setup. The part I'm on the fence about is whether to fab up my own set of arms based on the lower and upper mounts for the MGB or whether to ditch the MGB setup entirely and go with Mustang II all the way. At the risk of making the car look like a hodge-podge... I would rather utilize the stock mounting locations. I say this because, if I can pull it off, I think (hope) that other MGB enthusiasts might want to make the same Ford spindle conversion. Am I totally nuts or am I on the right track? What are your thoughts??

Just one thing - if you change the upper or lower arms to make the rear end narrower, you're going to change the geometry. Roll center, camber gain etc will all be changed, and probably not for the better. You'd better science that out if you want it to work.

Has it really been over two years since I bought the MGB and started to formulate a plan?? Holy Shnikes!

I have finally brought the MGB into my main garage to be dismantled. All I really have left on the Chassis is the original rear-end and the gas tank. With any luck, I'll have them both out tonight.

I sourced an E36 IRS and front spindles from my local junkyard for dirt cheap (I heart Bridgeway Auto Parts in Moline, IL)! I took my trusty cordless Milwaukee hackzall (and a total of five batteries) to the junkyard and spent an afternoon procuring an e36 rear suspension in its entirety. I removed the whole rear end as a unit that included all mounting points and enough of the chassis to provide rigidity until I got it home. I also procured the front spindles, brake/clutch pedal assembly and the ABS modules.

I sourced a set of Mustang II lower and upper A-arms online that I will need to adapt the E36 front spindles to fit (since the E36 is actually a McPherson strut setup). Geometry is a huge concern on this project since I actually want the setup to perform well. So, I have taken tons of pictures of & measurements from the OEM setup for the BMW. I'll position the Mustang II A-arms to mimic the BMW geometry but will be building a ton of adjustment room into the mounting points.

The motor I chose is out of a 2005 Dodge Magnum. It's a 3.5L 60 degree V6 that puts out an advertised 255HP and 267Ft/lbs of torque (depending on where you look). I will be scrapping the automatic transmission in favor of a 6-speed Mercedes unit from a 2004 Chrysler Crossfire. From what I've seen, the combination has never been made, but there's always a first:)

It might be late now, but the Mercedes 190E IRS is self-contained.

EWW @ that intake........cool build, I need to keep an eye on this.

Like what I see. I am doing similar with a 302 powered MGB only with a Miata Suspension as the basis.

What I deemed important was to make an MGB feel like a Miata. As such the track and wheelbase will remain Miata and the MGB weight is close enough that it should not tip the Miata suspension off that it is no longer bolted to a Miata.

I think you are on the right track by keeping the geometry the same and not mixing and matching front/rear suspensions from different cars.

Have you given any thought as to how the weight difference and wheelbase difference between the MGB and the BMW will play into the formula?

And a picture to show you how easy the rear end COULD have been! The rig in the picture bolts directly in to an MGB shell

that "rig" gives me terrible ideas for my Fiat. While I do not like how the shocks bolt to it or the angles they are at.. I do like that the front mounts appear to use the spring mounts from the MGB's leafsprings

In reply to NOHOME:

Is the frame something that you made or bought? It looks fairly complicated for someone to build versus taking a self-contained unit and making the mounts for the subframe fit (like I plan to do with my Starlet and a miata suspension).

singleslammer wrote: In reply to NOHOME: Is the frame something that you made or bought? It looks fairly complicated for someone to build versus taking a self-contained unit and making the mounts for the subframe fit (like I plan to do with my Starlet and a miata suspension).

Not my stuff.

Custom Rod Works (Todd Budde) independent rear suspension. 54.25" hub-to-hub width at ride height. QA1 single-adjustable coilover shock absorbers. QA1 250#/inch, 10" free length coil springs. 1996 Chevy S10 4x4 ("front") hubs, Raybestos part# 713061. Pete & Jakes HD Black urethane bushings.

It is a direct bolt-in for a stock MGB, so if it looks complicated, I guess it depends on where you want to do the fabrication; on the tub or on the bolt-in piece?

Not clear on what your concern with the shock mount is? Keep in mind that the tops are not bolted to anything at this point and that will not be the final shock angle. (edit again) Went back and had a look, shock angle does look quite severe in the installed pics!

I am afraid to even ask what it cost!

Here is a picture of the car it is in and a link to more details.http://www.britishv8.org/MG/RobFicalora.htm

As an MGB uses leaf springs for the rear axle.. could you build a subframe that uses all four spring mounting locations to bolt into the car?

mad_machine wrote: As an MGB uses leaf springs for the rear axle.. could you build a subframe that uses all four spring mounting locations to bolt into the car?

I guess you could, but why would you? With an a-arm suspension you need two planes to attach to. The front and rear spring mounts only give you a plane for the lower a-arm.

The flat plates in the pictured suspension bolt to the MGB frame using the mounting bolts for the stock shock absorbers. That combined with the lower mounting points provides decent force distribution into the MGB framework.

NOHOME wrote:

mad_machine wrote: As an MGB uses leaf springs for the rear axle.. could you build a subframe that uses all four spring mounting locations to bolt into the car?

I guess you could, but why would you? With an a-arm suspension you need two planes to attach to. The front and rear spring mounts only give you a plane for the lower a-arm. The flat plates in the pictured suspension bolt to the MGB frame using the mounting bolts for the stock shock absorbers. That combined with the lower mounting points provides decent force distribution into the MGB framework.

that's wjhy I said "subframe". Similar to above, but less monkeybars

I love the idea of the bolt-on Miata subframe that "NOHOME" found! Like you said, it would have made things a lot easier. But I wouldn't have had the "joy" of fabricating everything:)

Miata would be a fantastic donor to bring an MGB up to today's standards since they are about the same physical size and weight. They just don't show up in my local junkyards :( Well... They show up in the "expensive" junkyards... But not the one(s) I pay homage to. Consider this... I picked the BMW IRS and IFS components I was looking for along with the steering rack, PS reservoir and the anti-lock braking system for less than a Benjamin. Basically, they allowed me to walk into their yard with my Milwaulkee Hackzall and have my way with a '96 328i that someone had already updated with M3 brakes and a full Eibach suspension package.

There is no doubt, I'll have a tough time dialing this suspension in given the weight difference between the BMW and the MGB. But I enjoy a good challenge:) ...And I love the fact that it will be different.

Any updates on this project? I have similar notions of doing this to a volvo. Need more grist for fantasy.

Calculon wrote: Any updates on this project? I have similar notions of doing this to a volvo. Need more grist for fantasy.

Updates coming... I just need to get my 1950 Dodge Panel Van out of the way first. :) Check back in about six months.

In reply to Giant Purple Snorklewacker:

I agree with all of this. I looked long and hard (because I had a spare one in my garage) at putting the rear suspension of an e30 into a fiat spider 2000 which is a bigger car than the MG. . the assembly is way too wide for the fiat (mounting points are. A good 2" outside the body on both sides) and more than that it is very heavy by comparison. I also came to the conclusion the miata suspension front and rear is better all around for that car. My guess is the MG is similar.

Another vote for the Miata suspension. The picture will give you an idea of what it looks like.

While I also thought that Miatae were scarce in my hood, once I started looking I found that there were plenty to be had. And the stuff is cheap to buy and service.

IF you did decide to go with a Miata suspension, rather than just use the subframe, consider using the entire rear clip. Once you get over the ludicrousness of it, it makes sense since it puts a lot of pieces in place. If you leave the trunk pan alone rather than bob-it like I did, (On my first trial) it should extend all the way to the back of the MGB where you can easily blend it into the rear structure of the MGB. I know because I also have an MGB GT and I measured!

http://i1063.photobucket.com/albums/t520/NOHOME1/PEST/DSC06549_zpsa6a21729.jpg

Using the Miata clip actually cuts down on fabrication since it brings along all suspension and shock mounts, all brake line mounts, and even a fuel tank pre-plumbed for efi. (The thought of never having to deal with an SU fuel pump alone makes this a worthwhile swap) Leave the inner half of the Miata wheeltubs on the clip. Attach the Miata clip to the MGB at the Bpost/sill area, blend in the wheeltubs and fabricate a mount at the rear valence and you are done. Best of all, when viewed from below, it will look like factory.

I will warn you that with the MG and Miata wheelbases being very close, this rear clip game can quickly escalate into just dropping the MGB over the Miata chassis.

If the above all seems too crazy, then consider a triangulated 4 link and coil springs for the rear. I have a kit made by Classic Car Conversions and have to say that if makes a noticeable difference in how the car crashes down the road. Still MGB, but much nicer.

EDIT:

Damn all that writing for a Zombie thread! Was kind of fun to read where I was going 3 years ago versus where ended up!

itsarebuild wrote: In reply to Giant Purple Snorklewacker: I agree with all of this. I looked long and hard (because I had a spare one in my garage) at putting the rear suspension of an e30 into a fiat spider 2000 which is a bigger car than the MG. . the assembly is way too wide for the fiat (mounting points are. A good 2" outside the body on both sides) and more than that it is very heavy by comparison. I also came to the conclusion the miata suspension front and rear is better all around for that car. My guess is the MG is similar.

Yes, you are absolutely correct. The E30 (and E36) are way wider than the MGB.

Just looking at track widths:

E36: Front: 56"; Rear: 56.9"

MGB: Front: 49"; Rear: 49.5"

So... I will do a custom frame and the MGBimmer will get a nice body kit :) My plan is to stop by Preform Resources while on a trip to Ohio so I can pick up a "Fiberglass MGB Speedster Body Kit" (http://www.preformresources.com/store.htm#MGB)

Check out this finished car with the body kit installed (the guy did an AWESOME job on it!):

Here are a couple more pics: