Oval beetle, adjustable spring plates and torsion bars?

[petew]

I'd really like to put adjustable spring plates on my 56' beetle. Problem being, I can't sort out which ones I need. I looked up the sway away site and that was as clear as mud without pulling the whole car apart.

Can I get adjustable spring plates for a pre-60 car?
If not, will later torsion bars fit in early torsion splines?
Are late type 3 fastback torsion bars going to fit?
What other things should I consider

P.s. the car is swingaxle still.

[ChadH]

Interesting question, I always assumed the spline count was the same, and just the length and diameter of bar was different between the years, but I don't know for sure.

I know that the adjustable spring plates are quite thick. It seems like the added thickness would alter the effective spring rate, since the spring plate twists as the swing axle moves. Again, not sure how much affect it has though.

[FJCamper]

Gentlemen,

The thicker spring plates do add a lot of resistance. They are literally twice as thick. We mounted a generic set to our 1965 road race Ghia and that really stiffened up the rear end.

The factory intended for the stock plates to be flexible, to decrease oversteer. Remember, especially in swing axles, we need less roll resistance in the rear and more in the front.

That means you don't just go installing stiffer rear torsion bars unless you're offroad or mount a 911, Corvair, etc., engine. We use stock rear torsion bars on our LeMons Superbug and Historic Sportscar Racing Ghia.

Now, by the book, a 1950's rear torsion bar can be swapped for a later bar -- the splines are supposed to be the same -- but I have not personally made such a swap.

FJC

[petew]

Interesting, because oval torsion bars are very stiff to begin with.

[ChadH]

Interesting, because oval torsion bars are very stiff to begin with.

My guess - it wasn't originally fast, or intended to be a "handling" platform. ..And Ralph Nader hadn't been invented yet.

[Bruce2]

The torsion housings are all the same. This means you can put any torsion bar in any chassis. All you have to do is match the spring plate with the torsion bars. So if you want to use 60s short bars, you need 60s spring plates.
If you want to stick with your 50s spring plates, stay with the length of bars you have now.

[FJCamper]

Hi Chad,

Both Porsche and VW, working together, concluded by 1954 that the VW/Porsche 356 chassis needed a stiffer front end than rear end. The 356A Speedster got a front sway bar in late-1954, early 1955. VW followed suit with a front swaybar on the then brand new Ghia, and I think it was in 1956 the VW sedan got a front bar.

Porsche greatly softened the rear torsion bars on the 356B, and introduced what we still call the camber compensator, but which was actually a traverse leaf spring that helped support the rear suspension since the torsion bars were now less stiff.

VW didn't make such a dramatic rear torsion bar change until the 1968-69 IRS rear suspension.

If you can find a chart of VW Type 1 rear torsion bars for the Sedan, you'll see a step-by-step reduction in diameter over the years.

FJC

[petew]

Interesting. So putting later bars in it might actually be a good thing. I've already got a camber compensator.

[Ol'fogasaurus]

Pete, for what it is worth, and if my memory is still good, there might be a difference in length between the swing axle spring plate and the later IRS spring plates. Also remember that in '68 the swing arm setup was different than the earlier version but I don't know just exactually how much.

(US: not sure if this is applicable to you) '69 to some time in mid-'72 the IRS rear suspension now had dual arm spring plates and was the first to use the longer torsion bars so the internal mount spring plate perch is longer to match the longer torsion bars plus the bolt pattern to the trailing arm had 4 bolts rather than the later 3 bolts (more to it than the hole count).

In mid-'72 and later there was another longer torsion bar w/a now single (thicker material) arm spring plate.

To use the later longer torsion bar/single arm IRS spring plates I think they would have to be shortened some and redrilled to match the connection to the swing axle tubes.

If wrong I am sure to be corrected quickly.

[petew]

I think all swingaxle spring plates are identical length, because you can transplant any trans/axle tubes from 1945-74 into any car. Torsion splines I'm not sure about and torsion bar lengths do vary as well.

[Marc]

http://vintagebus.com/parts/wog69/121.png

Note also that the 22mm, 552mm-long bars introduced in Aug 1959 (Chassis #2528668) were the first to be pre-set for loading and specific for Right or Left side.
When the Z-bar (which effectively does the same thing as the transverse-leaf camber compensator but does it with a torsion bar) was introduced in `67 the 552mm bars were reduced to 21mm, to reduce oversteer even further.

1mm difference doesn't sound like a lot, but torsion bar rate varies with the fourth power of the bar diameter so it makes a 20% change in this case. The wider rear track of the `67/`68 also increases the leverage on the torsion bar making it effectively weaker but I'm not considering that (or changes in wheel offset, which can have the same effect).

The reduction in diameter from 24mm to 22mm was accompanied by a length reduction (which increases the rate) too, resulting in about a 20% change in spring rate then also.

Going from the long 24mm pre-Aug`59 bars to the short 21mm `67/`68 bars would result in about a 45% reduction in spring rate.

[Piledriver]

How much heavier were the 68s vs the 58 models (chassis)?
I know they are a bit heavier than the early 60s models.

[Marc]

Comparing the unladen weights specified in the `56 and `68 owners manuals, there's a 110kg difference (242½ lbs) in overall vehicle weight. The `67-up Z-bar functions as an overload spring but it only takes effect once there's enough weight onboard to take up the slack in its connecting links, so most of the time the puny 21mm t'bars are carrying all of the weight - that's why most `67/`68s on the road are draggin' ass, because the t'bars have taken a set.

[Bruce2]

In mid-'72 and later there was another longer torsion bar w/a now single (thicker material) arm spring plate.

For a long time Sway-A-Way used to have in their catalog a mythical 73 and later torsion bar. Perhaps that's what you were thinking of. In reality, VW kept things simple. In 1960 the short 552mm bars came out for all swing axle cars up to 2003 model year.
When IRS appeared in 68, the 676mm bars were used in all IRS cars up to 1980. Nothing changed as far as torsion bars go anywhere between 68 and 1980. Even Porsche liked this bar, using them in all 924s and 944s. 968s too.

The first spring plates for IRS cars in 68 were double plates. They were used up to very early in the 71 model year when the single spring plate came out. Except for Type 3s; they continued using the double spring plates. All IRS cars use the same bars.

To use the later longer torsion bar/single arm IRS spring plates I think they would have to be shortened some and redrilled to match the connection to the swing axle tubes.

You can't use an IRS spring plate in a swing axle car, the spring plates are too short. Going the other way can be done. I know someone who cut down 60s swing axle spring plates when he converted his 67 to IRS for that stealth look, in case someone looked inside the wheel arch at the torsion cover.

[petew]

Ok, but what I want to know is if 60' on bars will fit into 56' housings. Thoughts?