SWB ARB Options

[Schläfer]

Hi Guys,

Sorry I know ARB questions have been done to death and I've read through all the search's and now I've got a few questions.

A bit of background, the car is a '65 SWB and at present has standard torsion bars, Bilstein dampers, turbo tierods, Elephant Racing polybrone and rear mono balls, it's on 5.5 inch steels with Avon 185 tarmac tires. The torsion bars are also open to opinion. It's primary use is a road car, but will get some track time each year.

Firstly I'm going to need to fit a rear ARB bracket, I read quite a few warnings about the bracket pulling out of the body. The WEVO rear ARB mount seems recommended and because I've got to fit one anyway should I just go straight ahead and fit the WEVO rather than learn the hard way and have to do it twice, or am I over worrying an will the standard Porsche part be up to the job? WEVO also warns about modification required to fit pre-69 can someone expand on this?

My next question is: Is there a size limitation for a front ARB which will fit through the body? I've looked at the ones from Elephant Racing and Smart Racing Products. Any recommendations based on the fitting and quality of the parts? I don't want to have to modify the body.

Size is the next question and I know this is a personal preference, but some of my racing friends are looking at factory (non adjustable) 15mm front and rear. From my search 18mm front and rear seems popular on this board, but if I bought adjustable I could get a range, so maybe that would be the best bet. What size adjustable would be recommended to cover the best range?

Thanks in advance
David

[Bobs 67S]

David,
it might help to look at what the factory did at the extremes in the 1960's and the early 1970's.

Your original 1965 front/rear Torsion bars were 19/23 with a 13mm ARB on the front only.

On the other end of the spectrum is the 1972 RS Conversion #491 (race only RSR) had T bars of 22/26 and ARB of 20mm adjustable front and 18mm adjustable rear. They were also on 9"/11" rims.

Wow, it seems the factory was "way conservative" for suspension. But the stiffness relationship % from front to rear is very consistent with all the factory combinations and after much analysis those relationship percentages seem to be still valid to racing 911 cars today. (There was a great thread on Pelican on this topic).

My 1965 - while track, racing and street driving I ended up running 22/27 T bars on the 1965 911, and ended with 19mm / 16mm adjustable ARB's. The Koni adjustable shocks gave a very rough ride on the street but adjusted to 1/2 turn off full soft front and 1/2 turn off full hard rear - was the starting point for most high speed tracks here in the US. On some tracks with tight and off camber turns like Mid-Ohio, Mosport, and Heartland Park, disabling the drop link to the rear bar had good effect.

For street duty the Koni were set to full soft front and back. I now run stock Boge's front and back - even with the stiffer T and ARB bars for a very tolerable street ride. (Judy no longer bounces to the roof at railroad crossings).

Look to the 1967-68 911L and S for the rear ARB setup. (Parts book illustration 5/1 b)

The body mount in section is a "L" bracket . The long leg is welded to the body and the short leg is the console for attachment of the ARB. After market brackets are beefier cast material and have center bridging support. Look to Bruce Andersons Performance book to see the "butterfly" support that can be welded to the stock mount and give support to - really big - AR bars. It is more than adequate for our needs.

The position of the mount bracket is the same for both the short wheel based cars and the LWB, but the 2 1/4" longer distance on the LWB allows for adequate space for the after market ARB's. The 1967 L and S bar have "U" bent bar ends with drop links to pins welded to the banana arms. This allows a quite short distance from mount to drop link - the after market bars will be 2 1/4" (57mm) too long and hamper a good mount geometry to the banana or spring arm.

The S rear ARB's came stock in 15mm and 16mm with matching bushings. These would be a good fit to your car without hanging down. Completely stock looking, too. I kludged my set up (Weltmiester) and have never liked the droop on that rear bar. The geometry of the drop links has always been poor and restricts adjustment to the middle of the potential bar adjustments.

If you were to use a larger rear ARB I'd look at custom shorter adjustment arms and a pin or angle bracket welded to the banana arm for the drop link attachment. (Factor in: Less leverage = stiffer relative bar rate).

The front thru the body openings accommodate a 19mm ARB without any opening modifications. If your going much larger you should reinforce the panel in conjunction to the beefier mounting bracket and bolts. Verify if the bar gets too big it has adequate room behind the gas tank.

Hope this helps.

[mike curnow]

What is an ARB?

[EARLY911ZOO]

anti roll bars = sway bars

[John Fusco]

I'm pretty sure the original cars had a 13mm ARB front.
The 15 was stock front on the '67 S.

[Bobs 67S]

John you're right the 1965 stock bar is 13mm, thanks for catching that. 67S is the 15mm.

There was also part numbers for the 11mm 911L , with a 14mm and a 16mm as optional in the 1967 parts book.

Easy way to measure the bars - use an open end metric wrench.

[John Fusco]

Just proofing all your excellent information

The factory (from Frere ) suggested :

Circuit racing: 16f and 16r

Hill climbs: 14f / 16r

Rallies: 15f / 16r

Of course that was with old tech 165 tires on 4 1/2 or at most 7 rims.
I remember Tom Tweed (and others) in some thread way back impressing that modern tires make those #'s merely starting points.

I've come to the conclusion (as have many others) it is all black magic.

[Neunelfer]

Lots-o-good information herein.

My advice would concur. Don't go too crazy with t-bars and anti-roll bars, especially if it's a street and occasional track car.

Personally; I left my t-bars stock in front and went with 26 in the rear to accomodate a slightly heavier engine (930/07) and to compensate for hp "squat" with around 240 proposed. For Anit-roll bars I opted for the 18mm thru-body turbo bars up front on all my cars (911 and 914-6/GT clone) and I c-o-u-l-d n-o-t b-e h-a-p-p-e-i-e-r. I have it's mate on the rear of my 911 as well.

One thing I've yet to suss out is the cost of an 18mm bar from your local Porsche dealer. A few years back Pano had an article with a chart and part numbers. If I recall, the parts are all available and not too expensive. I think it's the turbo arms that may be a bit harder to find (they have some extra gussetting (sic) ).

[John Fusco]

Eric;

You guys with later cars have it easy (r).
The SWB is another animal.

[40cylinders]

I feel like a real 1st timer here but I have just finished installing an Elephant Steet/track 2 system in my 68SWB...at first I did not change the rear brackets...then after review and reading the same comments regarding the failure issue, I decided to install the WEVO brackets... Yes, you must modify the bracket and grind some body material away to make a proper fit...the ARB must fit up very close up in the transmission support bracket...1/2" clearance top and side...find that measurement before tack welding the brackets to the body... mount the bar, check the clearance and weld away...Didn't have any issues up front...truth is, I still don't have brakes and rotors yet so I haven't dropped it on the floor ...if I've made any mistakes, I'll find out another day....it sure looks a lot stronger than the parts that I cut off...