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The left side of my '79 IM is 3/4" lower than the right when I measure from the hub center to the top of the wheel opening. It is 3/4" lower at both the left front and left rear when compared to the right. Is there any way to adjust this so it is sitting level?

Thanks, Chuck

Chuck:

You need to adjust the left rear torsion bar DOWN about that amount to bring the left side up to level. Both rear torsion bars have an adjusting bolt and can be adjusted independently. That's the good news.

The bad news is that I've only heard about this terrific feature and never seen one for myself. I'll have to let one of the IM guys on here tell you exactly how to adjust it, but can assure you that it is easy to do and shouldn't take you more than a few minutes.


gn

I have the same problem on my JPS. It sits about 1 1/2" lower on the left side also. I just changed front shocks and that didn't change a thing. I had heard something about the rear adjustment some time ago but other than a mention, no details. Really be interested in trying the remedy. Will get the shop manual out and do some reading tonight.

Bruce

Is there room with the speedster body in place to pull the torsion bar to reset it ? Have wondered this but no one up 'till now has mentioned it that I know of.
Alan M

Alan , I was 1 1/2 high on the divers side , I drove the speedster to "Bugformance" in Sacramerto, I think they charged about $150.00 to level it by readjusting the torsion bars.


GClarke

Its probably written up better in some of the Petterson VW manuals but here is a link -

www.geocities.com/aussiebug1970/rearaxle.html

You can get aftermarket adjustable spring plates too.

Guys,
I've both lowered and raised my CMC rear-end, and it is easy, but there's a lot of steps to it. The torsion bar doesn't have to come out to adjust, I don't think; mine has a short-length torsion tube and housing, so I have about 16" or so between the bushing plates and the body. Otherwise you can't get the bar out without cutting. Raise the car, Remove the rear wheel, pull off the T. tube cover plates, mark one tooth and the spline socket for ref., separate the spring plates (3 bolts) raise the rear plate up high for clearance, jack the front spring plate off of its rest, pry it out a little from the rest, let the jack down gently, and it should release the torsion. Now, the spring plate can be re-positioned on the spline shaft.
Mine has 45 teeth on the outside end; 8 degrees per tooth, or about 2.5" of lift per tooth. The inner spline had 40 teeth, which is 9 deg., or ~2.8" per tooth.
Adjustable rear ends aare much better for simplicity and fine adjustment. Mine didn't actually move 2.5", but something less. My car also sags a bit, but not so much unless you're looking for it.
-Time

Alan et al:

At least on a CMC (with no hole plug on the body to completely remove the torsion bar) you can pull the bar out far enough to adjust it properly.

Rear torsion bar inner and outer splines are different. Inner splines move 9 degrees per notch, while outer splines move 8 degrees, 10 minutes per notch.

Measuring my car (1969 Beetle pan with IRS) shows 17 inches between the centerlines of the torsion bar and the axle, so using C = pi(D) you get 106.814 inches of axle line circumference (imagine drawing a big circle with the torsion bar center at the middle and the axle centerline defining the circumference). Break that up into degrees and it's .297 inch per degree and .005 inch per minute. Follow so far?

OK, then

Gawd.....it seems to much easier and cheaper to just have a reputable shop do that process

Gary - yup, you're right. It's a lot of work and trial and error.

I'm on my third iteration.......just went out and measured everything and mine is about 1/2 inch low on the Drivers side. I know I tried to correct it before I did all these calcs, and always ended up either way too high or way too low. Finally did the calcs to find out what was going on and get it right. Now I know that one spline moves the rear up or down over 2 inches, and that's about what I saw before. I Now have to move one side more than the other to equal them off AND lower both to where I want them. With these calcs it should be easy.

BTW: The Haynes manual tells you to level the car frame, then use a special, degreed protractor (VW special tool) to get the spring plate to the right angle, then put everything together. The angle they give is for the correct height of a Beetle sedan - not a Speedster!

You should be able to do this knowing what the splines do for you, but I'm doing mine tonight and should know better tomorrow. I'll even take pictures!

Gordon

Gary, It's not that difficult. You built a beautiful car, I know you could adjust torsion bars. Take rear suspension apart, relax the torsion bar, Put a refrence mark on the inside of the wheelwell, directly above the lower rear corner of the spring plate, measure down to the very bottom corner, make a note of distance, then pull spring plate off of torsion bar, pull out torsion bar so you can turn it. I think there are 40 teeth on the outer end of torsion bar and 44 teeth on the inner end of the torsion bar, that way you can adjust it. Turn the torsion bar and slip the spring plate on to it and measure down from your mark. If you want to raise the car 1", the end of the spring plate should be 1" lower than before. It may take 10 or 15 tries, but it won't take that long. Then put it all back together. Good Luck, have fun.

Thanks guys for all the info. I will save Gordon's calculations for future reference. I am assuming from the replies that adjusting the rear torsion plates will affect the height of the front on that side as well. Is this correct?
Thanks again,
Chuck

Gordon,

Thanks to your calculations, I too have something to work from !
Off it goes to the shop wall for posting.....Thanks !

Chuck:

Yes, raising one side of the rear will affect that same side on the front, but to a lesser degree. To make matters worse, since all four wheels are truly independent, doing something to one corner will affect all three other corners to a subtle amount. It can be aggravating, but if you take your time (and walk away from it like I did last night when it was getting too late) it'll all work out fine.

Alan: If I were still working, I would probably have all this on a spreadsheet programmed up such that you enter the amount (in inches) and direction (either up or down) and it would give you the notches this way and that on each spline set.
That's if I were still working........is that sick, or what? Glad I still know what to do with a calculator, pencil and paper.........

Gordon,

Remember the days before calculators when the engineers all had slide rules hanging from their belts? What ever happened to all those slide rules? I used to have one but it has disapeared over the years. I bet they come back along with Nehru jackets, LOL.

Bruce

Check the pockets of the old leisure suits!

Actually, I looked back at Joel's post and it makes a lot of sense, ESPECIALLY when you have to pull off the outer spline can and just about the time you can see the torsion bar the can lets go and is loose - so much for scribing a reference line!! You can still scribe a line, but it's objective, at best. I think, though, that for each inch of spring plate corner travel (as Joel describes it) you'll get 1 1/4" or so of travel at the axle - we'll see.

I had one side that was a particular PITA so I'll try out Joel's approach tonight and report back. I think I'm in the ballpark with my calcs, but I really won't know a thing until I get it back together and let it back down on the floor, then look at it and think: "SOAB!! and start over again. Never thought about that outer spline can obscuring the splines.

gn

P.S.: even though it's a simple operation, it keeps looking like something someone ELSE would enjoy doing.

This thread speaks volumes about the advantages of adjustable rear swing plates!!!

Just remember, that ALL of the Apolo flights, the X-15 and SR-61, the Hoover dam, and every single automobile designed before 1968 were accomplished with slide rules. And that's just the beginning!

I had a lowly Post, but my wife (the REAL engineer of us two) had an ivory K&E - beautiful instrument, and she still has it.

All that is nice, but I remember a guy named Hans Kleber at Hamilton Space Systems, back in the early 70's. If someone were to say: "I wonder what it would look like if we calculated it like this?" Hans would give an answer to a complicated calculation in a second or two, right off the top of his head. He was usually right, and to at least a couple of decimal places. I've often thought that the Apolo lunar back packs would have been the size of pickup trucks if it were not for Hans figuring out ways to miniaturize things.

True, but I've also heard that those spring plates, unless modified, only hold the plate in one direction and rattle a lot. Besides, if you do the height set-up right the first time or two, then that's it for the rest of the time you'll have it.

Gordon,

You mentioned in your original post to this thread "adjusting bolt". What bolt are you talking about. Short of the adjustable spring plates that I agree can rattle, or pulling and turning the torsion bars I don't know of another way.

Patrick:

Ah Ha! Those clever guys at IM, and possibly Beck and others using a frame chassis, rather than a pan chassis, have incorporated a really trick adjusting bolt on the INNER end of the torsion bars, near the middle of the car. Want to raise'er up? Give a few twists this way.....want to drop'er down? Just a few twists the other way. Want to level'er off? Just twist one side. Very clever, and way cool compared to a pan chassis with no easy adjustment.

OK, just finished working on my car. Originally, it was 1/2" lower on the left side, and was about 1 3/4" higher at the rear than the front, measured along the bottom of the sill below the door (I extended that line with a straight edge to the front and rear to the centerline of the wheels). All that meant that I needed to drop the right more than the left by about 1/2", and get the rear down about 1 3/4" overall once leveled for where I wanted it.

The closest my calculations gave me was to drop the right 2.179", and drop the left side 1.685. This would get me where I wanted (at least on paper) AND level it all off left-to-right as close as I would want (let's not split hairs, here).

It was tricky, since, as I mentioned above, when taking the plate/bar apart and you can just about see the torsion bar itself, the outer spline can falls off the bar making it difficult (but not impossible) to mark it for reference.

The calcs gave me the following:
Right side (down 2.179")
inner 1 down
Outer 2 up

Left side (down 1.685")
Inner 3 down
Outer 4 up

I'll be damned, but it came out exactly as I wanted it. I almost couldn't believe it! Should have sat down and made these calcs before the last two times I tried doing this!

I've attached a before and after of the rear wheel (right side) so you can see the difference. I wanted the top of the well to just kiss the top of the tire height, and it does ( more matching the fronts).

Nice to have something work out as planned for a change! I'm so pleased, I'm taking the rest of the day off to go for a ride!

Gordon