rear trailing arm

[brembo]

Does anybody know if it's possible to straighten a bent/twisted aluminum rear trailing arm?
Thanks in advance.

[fetuhoe]

I would really worry about trying to hot bend a cast aluminium part.

It is tricky to provide completely accurate information without a detailed specification of the alloy but there are a few general considerations that would suggest that it isn't a great idea.

Most Cast Aluminium Alloys behave in a manner which is know as 'Hot Short' which basically means that the material is prone to cracking when heated and stressed.

The cause of this problem is due to the nature of the grain boundaries that are developed during solidification.

Many alloy systems exhibit this type of behaviour and this is commonly due to impurities that a present at grain boundaries.

Unhappily, in the case of Aluminium, it is the basic alloying elements that are responsible and even with Silicon levels as low as 1% Aluminium will display this type of behaviour. The presence of magnesium and copper will make this problem worse.

As the Alloys used for the manufacture of castings typically contain between 6% and 12% Silicon you are almost certain to encounter this problem.

If you don't warm the arm to a high enough temperature to activate the Hot Short behaviour you will be cold-working the alloy and will simply run out of ductility.

If the arms are made of a heat treatable casting alloy such as LM25 it is also possible that heating can cause a catastrophic loss of strength which wouldn't be apparent until you applied some shock loading.

Temperatures as low as 250degC can cause this type of problem in 'Age Hardened' alloys.

If it was a non-structural, decorative part I may be tempted to try but otherwise I would give it a miss.

Just out of interest 6082-T6 which is the material used for Fuchs wheels tend to be modestly hot short and needs to be forged in a very careful and controlled manner.

[Nige]

Surely they're not that expensive/uneconomical to replace with new or a used item.

Plus how to you know to bend it back to?

[fetuhoe]

If they are Turbo Arms - following an earlier thread - then they are quite tricky to find.

We also have jig which will check the alignment of a Turbo Arm as we have converted quite a few steel arms to an RSR format.

[brembo]

It's not a turbo rear arm, it's a modified ally arm to suit 930 calipers fitted to the rear of the disc.

[fetuhoe]

We have a large collection of Aluminium Arms, early type with ball pins late type for the SC and Turbo and a jig to fit the Turbo Style Caliper Brackets. We have to steel brackets to mount the Turbo Arms onto the standard torsion bar tubes as well.

[NurLinks]

I have a pair of 1974 arms if interested. Sent you a PM.