M758

Hey gang, I don't know if you guys can answer this, but here is goes anyway.

My 84 944 Race car currently has 28mm Tbars. I Have 30mm bars at home waiting to be installed. I am doing this to improve my handling balance with my front 350# springs. - I can't use coilovers in the rear per my race rules.

I want to install these bars ASAP. I have done it before (when I did the 28s) and do not have problem other than it will take some time.

The early cars came with steel rear control arms. The later cars including 924S, & Turbos came with cast aluminium arms. I have 87 924S parts car with all of these parts & the correct offest rear arms. (86 951 part numbers, proper 1/2 shafts & shocks). To change the arms I need to also swap out the spring plates & that is whay the torsion bar swap is involved.

I assume that since the later cars and turbo cars came with Aluminium that these are better? The problem is that they are going to take much longer than I have time allowable to swap due to alot of little things.

Question????????????
Are the Aluminium REAR control arms better than the steel REAR control arms???
If so how much better?
Just a little bit or alot?
Would I ever notice the difference?

Thanks.... As I said I want those 30s in there ASAP and I can do that quick with out he arm swap,but I would hate to find out that I should have done the swap in year and then do it all over again.

PorschePlayer

In my opinion if you are planning on racing, stick with the steel arms. Although the weight advantage is nice with the aluminum arms, the steel arms are MUCH stronger.

I just replaced almost the entire rear suspension on my 87 951, after a rear end accident bent my right control arm (which translated into a bad torsion tube, spring plate, and axle.)

Skip

I agree - keep the steel. The bottom shock mount is theoretically stronger - though, I have no actual data to support that.

Also, the shock requirements change - the early shocks use a smaller bolt. This can be overcome, but is not ideal.

Levish

I would agree with the previous posts

for 02 Audi went with Aluminum control arms (in front though) and there have already been posts about bent arms, where previously these were very uncommon. In racing they would take a serious amount of beating.

perhaps some tubular steel arms if you were interested in saving weight. I am not sure who would make them for P cars though.

M758

[quote]Originally posted by Skip:
<strong>I agree - keep the steel. The bottom shock mount is theoretically stronger - though, I have no actual data to support that.

Also, the shock requirements change - the early shocks use a smaller bolt. This can be overcome, but is not ideal.</strong><hr></blockquote>

Skip, I agree about the shock mount. The steel arms puts the bolt in 3point bending and the aluminum arms are cantilevered.

Also I have KONIs for both type.... Long story, but between me any my father we have plenty of places to use the shocks so neither will be wasted.

My concern is really this.
Stiffness of stamped steel & welded construction vs single piece casting of Aluminum.
1) Would the steel deflect more than Alu arms?
2) Why would Porsche put "lesser" arms on later cars and the Turbos?

Honestly I would rather keep the steel arms since it is easier for me. I just don't want be in the position a year from now knowing that I could get 1/2 sec faster with the Aluminum arms.

The torsion bar job is too big to do twice, let alone 3 times!

Paul Bloomberg

M758,
Go with the aluminum.
Paul

Tabor

M758,

The factory went with the aluminum ones because they flex less than the steel ones. Is it worth changing them... I don't know.

PS They are semi trailing arms, not control arms. (Just so you know).

Skip

I'm not sure there is any real advantage to the cast - I lean to the side of ease-of-use. With steel arms you get easy wheel bearing replacements. I guess another option would be to somehow seam-weld the arms for increased strength - never seen it done, and never heard of a reliability or flexing issue with the steel arms. Maybe I'm just lazy... <img src="graemlins/sleep.gif" border="0" alt="[sleep]" />

S

M758

BUMP

924RACR

Not sure if the class you're building for allows reinforcement of the arms (my basis is IT, which doesn't), but if so, you could do as the factory did...


<img src="graemlins/jumper.gif" border="0" alt="[jumper]" />

M758

Guys,
Thanks for the good info, BUT I am still not convinced either way..... So

BUMP