There are those who argue that the camber compensator was just a leaf spring to help in overload from Porsche softening of its rear torsion bars in the 356B, and there are those who argue that the compensator is supposed to resist severe positive camber changes as the swing axles swing downward.
They're both right.
In the illustration above (1) shows swing axles swinging downward and what kind of extreme positive camber it causes. The situation is called "jacking" as in the photo (2).
Jacking occurs in sharp changes of directions and causes spins and crashes.
(3) depicts a current bolt-on camber compensator design that resists downward axle movement.
Porsche softened its rear torsion bars in the B-series to aid handling by making the front suspension more responsible for roll resistance. The 356B's had gotten the 2-litre 4-cam Carrera engines and they needed all the help they could get staying right side up in the hands of average drivers.
Rear roll resistance in a swing axle actually works against you by making jacking occur quicker. The 356 series ended before the Porsche engineers could implement the Z-bar that VW got.
The Z-bar (which merits it's own post) is the most efficient swing axle tamer ever invented.
CAMBER REGULATOR
There has been a myth built up over the S-90 camber compensator since 1960. By itself, it does nothing to improve the handling! The factory put it on when they installed softer rear torsion bars, so the back of the car could still have the same load-carrying capabilities. The softer bar made the rear of the car roll more, so the front end would take more of the cornering loads. This increased understeer, only making it seem like the car had decreased oversteer. The factory compensator is incapable of preventing the rear wheels from "jacking up" during hard cornering, which is the biggest detriment to a swing axles cornering abilities. The S-90 compensator, when pre-loaded, actually pulls the rear wheels toward positive camber. The 356 Enterprises "Camber Regulator" will improve the handling because it works like a Z-bar and will decrease rear wheel jacking. It is an easy bolt-on installation, with adjustable links to ensure proper pre-loading. It also functions perfectly well as a load-carrying spring. Heavy-duty version recommended for Vintage racing, Autocrossing, and speed events. Complete assembly, including hardware, fits 1956-65, tunnel case transmissions only.
RACING VERSION...$425.00 SOFTER-STREET VERSION...$400.00
The photo you show isn't an original Porsche compensator, but a very nicely modified 356 Enterprises leaf spring product with adjustable end links. It allows for more axle control than the generic design I showed.
EMPI developed and sold the first compensator for VW's just months after the Porsche Super 90 came out. The original EMPI used straps on the end of the leaf spring to hold the compensator to the axles. Tightening the straps "preloaded" the axles by pulling the axles and leaf spring together, and made the axle/spring combo work together as a single unit.
The design I show lets the axles swing up but not down, so the outside "unloaded" tire cannot run on its outer edge.
The 356 Enterprises compensator you show gives you the advantages of the old EMPI strap design but with more precise adjustment because of the threaded end links.
Yes, I should been clearer about what the picture illustrated.
Here`s the original Porsche compensator. I assume it preloads the wrong way pulling the axles down and giving positive camber, while the VW unit
pushes the axles upward going to negative camber.
So the strap version gives control of both upward and downward movement, thereby also acting as a overload spring. But wouln`t this like the original Porsche unit preload wrongly, as giving positive camber?
Great photo. Big finned aluminum brake drums are still sexy after all these years.
The Porsche spring -- or the original EMPI -- will pull the axle downward if you take out the end slack. To prevent this, the original Porsche design has a little travel in the ends of the leaf spring where the mounting bolt goes through. You have to have the car on the floor, weight on the suspension, to see this.
The EMPI leaf was actually stiffer than the Porsche and pushed up a little higher. VW hotrodders that tightened the straps "felt" the rear axles staying straighter, whereas the Porsche allowed more deflection before it acted.
I personally do not advise preloading either the Porsche or original EMPI design. Some people like the feel, but they are usually street racers who are not wringing the suspension out to the limit.
("Feel" vs lap times is a touchy subject. A car can feel scary to the driver, but only lap times tell the story! As a rule, secure-feeling cars are not the fastest. This is crew chief advice.)
The Porsche people who fabricated Z-bars mounted them below the axles rather than above. It costs ground clearance, but a well setup Z-bar keeps the axles straight.
Porsche racers have tried so many things to control the rear axles that it would take a book to cover them. On the winning cars, you can see that there is NO axle droop when they're on jackstands in the pits!
It's the Sway-A-Way I have in my drawing, and the one I picked for use on our Carrera Panamericana Ghia.
VW didn't soften up the rear torsion bars until 1967 (intro of Z-bar), so on all pre-67's, the Sway-A-Way is a good choice because all it does is resist downward axle swing and thereby keeps camber within reason.
We ran stock ride height, Avon 175x15 racing radials on 5.5 steel wheels, a 19mm front sway bar, and HD EMPI oil shocks all the way around and had good handling.
All I can tell you is that my Bug handles a whole LOT better with the Z-bar removed and a CB camber compensator installed. It's a night and day difference. I couldn't believe it.
The factory Z-bar is very light and has considerable slack in it so that it does not work until extremes begin. Shimming the slack out helps.
I would imagine your camber compensator is working full time, and that would feel a lot different and keep the rear end stable.
Something a lot of guys don't think about is how rear end lift under hard braking causes swing axles to begin to swing down and jack up the rear.
This is why, when the rear tires go up on tippy toes and lock up due to lack of adequate contact with Mother Earth, that the car spins out. Most teams don't understand the real reason, and blame brake bias.
A stock but shimmed Z-bar is good. It is too light to be excellent. Geometrically speaking, a Z-bar does everything right (keyword "everything"). It adds resistance during rebound of both wheels, and controls camber, but adds no roll resistance.
The important point, however, is racing Z-bars are usually in the 12mm to 19mm diameter range, whereas the factory Z-bar is more like the stock VW front sway bar!
A camber compensator does almost everything right (key word "almost") in that it resists jacking and positive camber but without the precision of a Z-bar, adds no roll resistance, and helps somewhat in rear spring overload, but not rebound.
Both are critical aids and no swing axle car used in spirited driving or all-out competition should be without one or the other.
Personally, I praise Z-bars, but settle for the easy availability of the camber compensator.
Z - bar: helps on both positive and negative camber (both stiffens and soften), constant in engagement
Strap-camber compensator: helps on both positive and negative camber (both stiffens and soften), almost constantly in engagement.
Cradle-camber compensator: helps only on positive camber(only soften), no support for reducing negative camber, part time engagement
What would be interesting to find out is what camber the neutral position of the different types tries to achieve. The stock z-bar can be shimmed on both sides, depending on what one tries to achieve. I guess both the others are preloaded to reduce the rear suspension stiffness, giving more negative camber, but I`m curious too what angle it is in neutral.
The 356 enterprise version for a VW would be the best. It would be in constant engagement, and also enabling to set the preload one wants. Perhaps using the lower shockmounts are axle tube/bearing housing as anchoring points. It is a really nice item!
PS: the camber compensator and Z-bar posts should perhaps be merged?
Yes, the Z-bar and camber compensator threads could be cojoined now, that we've moved past intros into application.
To set up a racing Z-bar, you decide what is your desired "at rest" camber and call that normal. Shim or adjust so that your normal setting is what the bar tries to maintain. You test this by slowly jacking up the rear end of the car and watching how quickly the Z-bar ends are stressed.
Some people "preload" by shimming or adjusting so that the upward travel or pull of the end link is in tension, on the theory that the axles are then forced into negative camber.
I always set the adjustment in normal, ran a few laps, then decided if more negative was a good thing. My usual compromise was either to leave it in neutral, or go just a tiny bit negative. Sometimes that just meant taking out all the slack.
Remember, whatever you get as lift on one axle is push on the other!
One thing I see in all the aftermarket compensators except the 356 unit - the mounts to the trans are "U" shaped, slip on openings. No matter how hard you try, it's almost impossible to get those tight enough to take serious loads. Like most of the nuts & bolts, those were ones I checked before every session, so I know they were properly torqued when I went on course. I had a compensator remove itself heading into the apex of Turn 5 at Willow Springs in my 1960 Vintage Racing Bug. The end result of my 40MPH off road excursion was very expensive(more because the 'run off' wasn't very smooth). Not surprisingly, the compensator was sitting off the edge of the track with a few minor scuffs. When I remounted it to my next car(the bug was totalled), I had washers welded to the "U" brackets. I never had any problems with it after that.
Yes, the "U" shaped slots are inherently weak, and your experience proves it.
However, we ran a slip-on style compensator in the Carrera Panamericana on our 1965 Ghia, and it left here and came back (about 4000 miles, 2000 of which were racing) as tight as the day I mounted it.
That you had bad trouble and we didn't might be attributed to us using a Kafer bar, which really keeps the rear end solid. I'm of course not positive about this, but the Kafer bar might have kept wiggling and flexing down enough to allow our compensator to stay tight.
Of course, I'd still advise anyone to do your washer-mod.
