Aluminium Front Cross Member

Lukesportsman · 11-01-2004, 04:44 PM

Has anyone swapped this out on an early car?

How much weight loss was there?

Did it stiffen up the front end and if so at what spring rate do you think it becomes noticeable?

How much should someone spend on an aluminum cross member?

Randy Webb · 11-01-2004, 04:49 PM

Yes. See the wt. compilation web page for this (search on my name and weight).

Remember it is in front and low on the car - so less worthwhile. It does save wt. overall tho. If you still have steel rear contrl arms, do that swap to Al. first.

Lukesportsman · 11-01-2004, 04:55 PM

Thanks, Randy

I'm trying to negotiate for them as we speak. Your logic makes good sense about CG and bias. Just a great one on Ebay for sale as we speak. Guess I should wait till I'm redoing the front suspension for another reason first. Bored and it looked tempting

$175 if someones in need for about an hour.

Do you mean the weight compilation page on early 911R's ( http://www.early911sregistry.org/jCalzia.html )or something on Pelican?

Zeke · 11-01-2004, 04:58 PM

Luke, why would a AL cross member change anything except the loss of a couple of lbs.?

And, Randy, I didn't look at your list (there's another one on the Early S Reg site), but it seemed like the rear changeover resulted in about 3 or less lbs.

When you look at the pieces in question, it occurs to me (and someone else too, because I've seen this posted before) that the real reason for AL supercessions was due to the lower cost of a casting vs. a welded up assembley as they both are in the early car.

Price? I paid $50 for one and then the guy I bought it from told me He could use it after all. No problem there, I sold it back for same. I'm using the stock steel one.

Lukesportsman · 11-01-2004, 05:14 PM

Milt,

Strange that the search engine could not find anything about this under "Aluminum front cross member" or other related searches. Anywho I was just thinking that a thicker Al casting may not be "stronger" but maybe stiffer.

Wow, I almost spent all that $$ for something that I guess I don't need coming from two sources that both know Porsches better than myself. BUT, then again that is why I posted it here....to gain more knowledge.

As always, thanks for the time shared by those who are helpful.

Randy Webb · 11-01-2004, 08:33 PM

I forget the wt. savings in the rear but it is about 12 lbs. The Al rear bananas _are_ cheaper, but they are also lighter, stronger, and stiffer. It's a no brainer. The front piece is les desireable but was worth it to me. And... it won't rust.

I forget the thread, but if you search you'll find one on my ocmpilation which is complimentary to Jim Calzia's -- also a lost of readings on light wt. 911s - factory and recent ones. The thread will point you to a Pelican's web page - he is hosting my xls sheet and the .doc file with the comparison.

Vintage911Racer · 11-01-2004, 08:42 PM

I made the cahnge on my car. Works great...

Rufblackbird · 11-02-2004, 12:24 AM

Here's the page, hosted by Thom

http://vintagebus.com/911/

arrivederci · 11-02-2004, 04:12 AM

I've heard that it is also necessary if you're going to put bigger brakes on the car and upgrade your 19mm MC to a 23mm MC. There's more clearance for the larger MC.

wevoid · wevoid's Garage

The 23mm M'cyl fits with the steel cross beam, we did this recently as a part of our brake tests into my '72. It looks tight, but there is adequate clearence in all directions, and required no changes to slot right in.

Regards

Hayden

Chuck Moreland · 11-02-2004, 07:05 AM

The AL member saves maybe 5lbs. They typically sell in the $100 range salvaged.

They do nothing for stiffness, it is a just a weight savings. But what car could be considered complete without one?

Randy Webb · 11-02-2004, 10:45 AM

re stiffness - some more explanation for my & Chuck's stmts above -- remember the A arms pivot off of the Xmember, so none there. Also, it is held to the body with 2 bolts -- so no matter how stiff it was that would be a flex pt. -- if there is any flex there, and I doubt there is.

BTW - with the Al member you have dissimilr metals abutting in a critical area -- I bought all new fasteners using the p/n's for the _new_ Al bar. Not spendy and worth some peace of mind - we know that is OK and don't have to investigate galling or corrosion issues, etc. Jim Sims could tell you if this is really needed.

Tyson Schmidt · 11-02-2004, 12:10 PM

The aluminum X-member is actuallt weaker in the one area that it does flex. The aluminum x-member allows the steering rack to move forward and backward much more than the steel one.

The tie-rods are not parallel to the x-member, but rather angle forward quite a bit as they meet the rack. The road forces that are transmitted into the steering tend to flex the x-member forward and backward. I've seen many of them bend or break from a curb shot. But I think that it's probably good from an accident standpoint, but bad from a steering response standpoint.

Just something to think about.