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Rear suspension mounts (part 1)

Because the springs in our rear suspension are positioned over the shock absorbers, we needed to strengthen the original shock absorbers supports. We also used this opportunity to raise them about 7cm in height.
By doing this we have a longer suspension travel.



Luckily we bought a rear quarter of an M3 in the UK, which was very handy to create a mold for the suspension supports. It prevented us to get in and out the trunk the whole time.

Compressed wood, some paper tape and a file are the ideal ingredients to make an appropriate example. To make our lives miserable, BMW decided 25 years ago to make the left and right support slightly different. After some measuring we were able to cut the steel plates to our needs.

We left off with a 3mm steel plate, maybe a bit too thick but it’s not a big penalty in weight. We also thought about our mechanics. The shock absorbers can be removed by unscrewing only 2 bolts. The top mount is made with 42CrMo4 bushings, to avoid wear. No nuts are used, in the bushings we tapped M14 threads at the inner side.
A little remark for those who are interested: be aware when welding 42CrMo4 on steel. Both materials needs to be preheated to 200°C before welding.
You also need special welding rods suited to this purpose.
If you don’t do this, it will start to crack when it is cooling down.

In the meantime Carl has finished off the 2 suspension supports, now they are waiting to be welded into the car.

When everything is in place, we can continue to work on the roll-cage, because most of the rear tubes will connect to this supports.
to be continued…

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