BMW E28 Alpina V12, the usual corrosion UPDATED suspension turret upgrade

On the E30 V8 build, some people criticize the use of such a mint car to build a custom car out of. Engine upgrade swaps and big projects have been on my agenda since I was 17 and bought my first car, so clearly there is a reason for this. Once you’ve spent all that money on the V8 conversion, you don’t want to end up with a car that’s not in mint condition. With costs going all the way up to the price of a not-so-used Porsche 911, it’s understandable that the best basic car possible is desired.

On the E28 however, things were completely different some 4 years ago. I had to build the car in a very limited timespan (less than 4 weeks, in contrast to the 2 years we’re working on the E30 now), and I spent most of the time not turning the car into a driftcar as I wanted, but solving the many problems the base car had. At the end of the 3rd week, we had gone through a complete roll of welding material that usually lasts over a year.

After we drifted the car for some years with considerable success (the top drifters laughing miserably at first from their new M3’s and 130i’s have come to senses and bought an E28 as well). The 288.000 km, tired M30 engined bodes well for drifting still and apart from a spectacular rear axle blowout, the car did great untill the M30 finally blew its headgasket. We had a Hartge M30 standing ready, but then the super-rare Alpina V12 fell into our lap really. As you all know and as can be seen in other posts, the V12 is in and we’re in the middle of constructing the car, making it lighter, stronger and easy to work on with the V12 inside. Of course, I didn’t have time in 2007 to look into making it a mint shell, so some things were left unattended for then. Now, I feel like doing it all to the max on our unlimited winter time budget. So, the rust-prone area next to the strut tower had seen some repairs by the previous owner’s mechanic that were as bad as I expected.

E28’s usually rust in this area between the wing and the turret. In this case, someone simply welded a big slab of metal on top of the corrosion and smeared copious amounts of bondo on it. Bad idea. The rust will of course prevail in this high-stress, triple plated area.

Of course this is not acceptable once we start to put 350+ HP and 460Nm in the car. The turret top needs to be upgraded, being a weak area, since we plan on using 18″ slick tires for trackdays. The area that takes the load from the turret needs to be perfect therefore. I had only one choice, and that is to cut everything away. However, there is a structural frame underneath that goes all the way ‘around’ the turret which I prayed I could still use.

Thankfully, there appears to be an E28 God and the frame could still be used. It can be seen in the above picture as the square strips located between the turred and where the wing should be. We will strengthen them up from underneath once the car is on the hoist and I have better lighting from the bottom. Right now, we fix the large gap where this came from:

And the welded-in piece by an amateur-night welder:

Clearly this is not the way. Tons of rust can be seen that have formed between the sheets of metal. As said, this is a high-stress area of the body so no shortcuts must be taken.

On the left of this picture, the wing-carrying part of the inner frame can be seen, corroded beyond repair. New pieces will be made here. Obviously, we start out with the sheet-metal on top first. Cutting out a nice square area, where one takes in consideration that it needs to be easy to weld, with such old , thin material. Fitment is super important, you’re better off throwing two wrongly cut pieces away then to try and weld an ill-fitting piece into place. You’ll burn right through it.

Clamping down the cut-out piece is important to make sure you take the right measurements. Without the wing and such a large area cut out, the front part of the steel tub easily gets misaligned, being flimsy from the 70’s BMW body. Then, make a template on metric paper, make it fit perfectly and then recreate that template into sheetmetal. Take the best metal you can get, since it will need serious welding.

Then, fit the sheet-metal into place and tack it. Don’t weld it all the way in one place as the thin material will warp easily. Just do strips of one inch welding on one side, than move to the other side and leave time to cool off untill you’ve seen it all.

As this is a racecar, I won’t grind the welds down to smooth surface. Also, the shock turrets will be further reinforced and the rollcage attached to them. So, we’ll just leave them with a quick coat of primer for now. As said, the bottom area will be reinforced from underneath.

Another weak point in the E28 body is the actual suspension turret. Once fitted with larger wheels and serious brakes, the added unsprung weight combined with higher speeds and curbstone-clipping can easily warp the hat. On modern BMW’s like the Z8, this is even the case on street cars. BMW uses stamped 3mm metal for most of the structural parts like this turret. Our improvement kit consists of a single cold blue steel plate (5,03mm) of the highest specification and lowest age. The design is more square than the original section so camberplates can move even more. Also, welding the rollcage to the turret becomes a lot more easy with this 27 year newer, higher grade material.

Ofcourse, its eminent that the original geometry must me sustained. We decided to raise the height of the tower by some 6mm, lowering the center of gravity of the entire car without compromising the best workload reach of a coilover suspension.

First, one needs to fixate the new top plate externally, I used a profile and a U shaped spring metal tube. The tube is shaped like this to allow one to get to work on the tower without being blocked. Grinders and saws tend to be big so the more room you leave the better. This is a job that requires a lot of measuring, measure twice, cut once!

The more precise you work when cutting, the easier the extensive welding will be.

Tape off the exact line and cut accordingly. A large hacksaw is needed to achieve the angle on the last 15cm width.

Now, carefully create a strip (approx 25mm, 19mm from the cut and 6mm from the raise of the top plate) and form it around the plate. I decided to do the ‘serious’ welding on the inside, where the fitment is best and there is more space to weld. Also, this makes for a much cleaner look on the top:

Once the strip is welded (don’t weld it all in one line, work your way around to dissipate heat!) the holding profile and spring tube can be cut off and ground down.

I leave a small gap on the easy side so that I can see my welding on the inner tube better as this is the structural weld. The small gap can of course be closed off easy with a small strip. Strip thickness is 3mm.

With the correct tools, this is a 3 hour job provided the top plate and lateral strip are measured up and doublechecked already.

Old vs New:

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This entry was posted in Alpina, BMW, E28, Racing, Wheelmen and tagged , , , , , . Bookmark the permalink.

4 Responses to BMW E28 Alpina V12, the usual corrosion UPDATED suspension turret upgrade

  1. Pingback: E28 V12 conversion, rust repair on front suspension turrets - The Unofficial BMW M5 Messageboard (m5board.com)

  2. Wout,, were are you getting 560NM out of the M70B50 from ALPINA

    • wheelmen says:

      typo, should be 460 I guess

      Would be interesting to see how much she gains from cat delete and airboxes. However I think there isn’t much gain in the std. head with std. displacement.

  3. Great entry, thanks for the update Wheelman!

    -Evergreen Junk Cars

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