rear arm

[brembo]

Rear arms on my rep were modified to have turbo calipers fitted at the rear as per rsr.Have discovered the nearside arm appears to be bent,as cannot get the camber set up right.
Does anybody know if it could be "bent" back ,maybe under heat?
Have turbo rear arms ready to fit,but would like to get existing arm sorted first,if possible.
Thanks in advance.

[fetuhoe]

Dougie,

We have a jig and could check to see if it is bent.

Straightening an aluminium casting when it is hot could be a nightmare.

Cast Aluminium Alloys, depending on the detailed composition, tend to exhibit a property known as 'hot short' which means that they can become brittle at high temperature.

This is caused by the alloying elements such as copper, magnesium and silicon forming low melting point compounds during solidification.

When the arm is cold these compounds have little effect on strength but when warm the weaken the structure and cause grain boundary failures and cracks to occur within the structure.

If you warm it too much and bend t too far it could just tear apart but if you heat it less and don't bend it quite so far it may just generate some internal defects.

If it were something that had to be done routinely then you may be able to develop a method but on a one-off basis it's risky and you may not know the level of damage to the structure until the wheel falls off.

[brembo]

Thanks Chris.
Looks like it's beyond sorting then

[fetuhoe]

I would worry about its integrity after it has been heated and bent.

[Dougieboy1]

worth checking on a jig thou, maybe the chassis mounts arent 100% and the arm is ok....?

[Boydyrs]

Chris could temps required to powdercoat these rear arms cause distortion and could that me why Porsche left them bare?

[fetuhoe]

Unlikley - there shouldn't be much in the way of residual stress and typical powder coat temperatures are quite low and times are relatively short.

Adhesion of most polyester based plastics to Aluminium Alloys is quite poor particularly if they have some magnesium in their composition.

Any magnesium oxide present on the surface of the component will reduce adhesion significantly.

The most significant cause of residual stresses in Aluminium Alloys are those which are solution treated and it is the quenching stresses that cause the problem with the 7000 series of alloys being worst affected.

These arms are likely to be LM6/LM7 materials and they are quite corrosion resistant. The floats used on Trawler drift nets have traditionally been cast from LM6 and survive very well in a salty environment.

We don't powder coat any suspension parts now - we use a Lechler Epoxy primer that has good corrosion resistance, good adhesion and is resistant to oil, brake fluid and fuel . It has a good quality satin finish.