Porsche Enthusiasts Club Forum

any thoughts on strength/durability on the steel versus alloy arms?

are the steel arms up to the job on a race car with big tyres and 300/400+bhp, or are the ally arms a safer bet?

in the end i will fabricate some custom t45 arms with bearings and adjustment on track etc, but for the min just deciding wether to put the car together with steel or ally arms.

the plus point of the steels is that the balljoints are bolt on! i could also seam weld the steel arms to give them a bit more strength

downside as far as i can see at a glance is they dont have adjustment at the rear for castor like the ally arms do

steel arms also cheaper and easier to source whereas even used ally arms from s2/turbo are quite expensive these days

thoughts?

regards

Lindsey Racing have steel arms for race cars, might want to check them out for ideas. They are expensive though.

Yes custom arms are expensive but we would fabricate our own as we have done in the past for other vehicles.

for the min just enquiring about the strength of the steel arms, as the ally arms tend to wear out and theb become expensive to repair/replace

regards

Its a good question and Boxsters race on the alloy ones and so I believe they are strong enough but you are clearly an engineer so its your decision

I was horrified at the alloy design to be honest as once the nylon cup breaks down and water gets in (recent floods) the ball eats the arm.

I am a toolmaker and hence have precision equipment available so bored out the original alloy arm and inserted a cassette ball joint made from one of the steel arm jobbies.

In my opinion these are much stronger all round by being a hybrid as it were.

If you have a welder you can box in a steel one apparently which will make it much stronger, I was thinking only this week about changing to steel as it can be rebuilt and are as cheap as chips compared to alloy ones.

As I understand it the ali ones are designed to be frangible. Hence in an accident break instead of transferring energy to the body & breaking that.
The only issues I've ever heard of for both steel & ali is breaking the ball pin when running on slicks & on a very low car, where the ball can lock up.

Now that does look interesting. How did you make the cassette ball joint?


Oli.

I take the joint pictured above the cassette and slice off the flange using a hand grinder and a 1mm blade and holding the parallel shaft in a lathe chuck and the joint body nestled in the alloy cup (pictured) turning the diameters is easy and the cassette is held firmly by being a press fit and cannot go further by the stepped bore and cannot come back out by a circlip and just as Porsche themselves do by Araldite round the clip. (not really needed)
The ball joints original groove is utilised to use the rubber boot so the whole thing looks original.

I have now done both sides on my car and although the offside passed an MOT it was rusty and terribly corroded when I dismantled it.

The joints are made by Delphi and are normally fitted to the steel arms.
I did some research before doing this mod for obvious reasons and found that some manufacturers do fit joints in this way so it is an accepted engineering solution.

Total cost to me was £15 as my time cannot be charged

i recently replaced a ball joint on one of my alloy arms, i bought the kit from 'design911'..to be honest the components in the kit weren't up to the original but on close examination there was nothing wrong with the ball joint or it's plastic cups. The part that had failed was the spring that holds the ball tight in the cups, this had lost strength and shortened by about 5mm, after checking component dimensions for wear I simply re-assembled the original parts with the new spring from the kit resulting in a ball joint with no play, 1500 miles later it's still good so hopefully won't need anymore attention for another 10 years or so.. I hear a lot of horror stories in replacing these ball joints...to be honest it couldn't be simpler as long as the alloy hasn't corroded, these units are very strong and should last a lifetime if maintained correctly. BTW I didn't even take the wishbone off the car, all work was done easily in situ although I did have the advantage of a ramp.

Pete

I've read that lowered cars on road tyres put extra load into the ball pin and can cause failures.