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Rear torsion bar sizes mysteries and disinformation.
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Sven F
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PostPosted: Tue Aug 05, 2014 7:15 am    Post subject: Rear torsion bar sizes mysteries and disinformation. Reply with quote

I know this topic was gone over a couple times here, but I am finding it very hard to get proper information about rear torsion bars on Bay windows, and their proper adjustment.
I was doing some welding on my rear torsion tube, and figured i'd change the rubber bushings and readjust the rear for sagging, and I would like to do this only once if possible, I don't enjoy trial & error.

It's been quoted several times on this forum that the torsion bars have 44 inner splines, and 40 outer. THIS IS NOT TRUE, that information refers to beetles. Exclamation

Buses up to '71 have 44 inner, and 48 outer splines and later buses have 48 inner and 52 outer splines. (unlike the bug, buses have more teeth on the outside - torsion plate end, and thus the fine adjustment is done in the opposite direction to beetles.


From what i gathered there are 4 types or gauges of torsion bars available for the bay window. There are tables describing which body types had which, but in reality I found this has little to no correspondence to body type, especially among campers and buses.

The torision bar diameters are:

26.20 mm
26.90 mm
28.10 mm
28.90 mm

I think they are color coded, but don't know which color represents which torsion bar (28.10mm is RED) missing information
The factory angles of spring plate against the body (measured where? frame rails? gutters? missing information) are:

23 +50'
23 +50'
21 10' +50'
20 +50'

accordingly.

Adjusting the plates is simple maths if we add and subtract angles by rotating splines in the corresponding direction.
On 44 spline side, one spline is equal to 8 10' change in angle.
On 48 spline side, one spline is equal to 7 30' change in angle.
On 52 spline side, one spline is equal to 6 50' change in angle



I know the exact body lift / drop cannot be measured universally, but a rough estimate is still very useful when doing this. I heard people say that one outer spline gave them 2,5 inches (63.5mm) lift. We don't know which torsion bar this refers to, but that is a very big change and many have made the mistake of underestimating the splines. Your lift/drop estimates are welcome, so we can get a rough idea of the final result.

Thank you for filling in the blanks, and possibly correcting me, it will help others in the future and we can then make a chart.


Last edited by Sven F on Tue Aug 05, 2014 10:16 am; edited 2 times in total
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richparker
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PostPosted: Tue Aug 05, 2014 7:35 am    Post subject: Reply with quote

I have a early bay. I started with a saggy but at 21* unweighted. I moved the spring plate down one spline and got 28* unweighted. I put it back together and it sucked, it topped out over every bump. Second time I bought an angle finder from HD. I moved the torsion up 5 splines up on the inner and the plate 5 splines down and got 25.5* unweighted. My bus sits great empty of loaded now. Good luck.
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raygreenwood
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PostPosted: Tue Aug 05, 2014 8:31 am    Post subject: Reply with quote

Think about it.....there are only 360 in any circle. You have 52 splines in your circle. Divide 360 by 52.....how many degrees per spline do you get? Wink
Ray
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kreemoweet
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PostPosted: Tue Aug 05, 2014 9:36 am    Post subject: Reply with quote

You must have missed the bit in the Haynes manual that gives 6 deg 55 min per spline for the 52-spline torsion bar.

It has been repeatedly reported here on the forum that the which-torsion-bar-went-in-which-bay-model info in the
Bentley manual (and so also the Haynes and other manuals with the same info) has little correspondence with reality.
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Sven F
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PostPosted: Tue Aug 05, 2014 10:15 am    Post subject: Reply with quote

@Ray: that would be the logical result, but for some reason, the manuals give a slightly different reading. plate slack tolerance?

neither my Bentley nor Haynes mention degrees for 52 splines. My Bentley doesn't even mention such torsion bars exist.
I will correct the information now, thanks. Smile

I have the 28.1 bars, and will aim for no more than 23 and see where i end up.
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raygreenwood
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PostPosted: Tue Aug 05, 2014 11:07 am    Post subject: Reply with quote

Ah.....no....I didn't miss the point.....I didnt quite think it all through. I saw "missing information" and thought you simply needed the math.

But.....they would not have considered outer end sag per -se......That would vary by vehicle. But what i think you were getting at...and you are probably correct....and what is different.....is the total length of the suspension arm from the point of vertex.....I would suspect. Its twist...or load declection which changes due to arm length.

You are not just looking for the exact angle created by a specific number of splines from say a 12 o'clock 0 point on the suspension arm.
You are looking for the exact distance the center of the axle produces from a horizontal line running from 9 oclock through 3 oclock on that same clock face.

Its a triangle. The diagonal angle on the trailing arm produced by the spline position....is the hypoteneus. From the centerline of the axle straight up (which is leg "a") to an imaginary horizontal line made between the center point of the torsion bar and across to right over the axle centerline. .....which is leg "b".

But.....if the length of the trailing arm gets longer or shorter (the hypoteneus).....and the spline angle stays the same.....then the triangle grows. Legs a and b get longer even though the torsikn bar angle stays the same. The effective height of lift is now different.....and more importantly. ....the leverage produced on the torsion bar is increased....more twist.....a change in effective angle on the trailing arm that each spline makes is effected.

So it may be that some book writers are listing calculated (and rounded up or down) angles....and some are listing angles "as measured" at the arm when under load.
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PostPosted: Tue Aug 05, 2014 2:38 pm    Post subject: Reply with quote

@Sven F: Haynes VW Transporter 1700/1800/2000 Owner's Workshop Manual, p. 113, art. 8.6. Since evidently the 52-spline bars
were not used on the 1600 models, it is reasonable they would not be mentioned in the Haynes 1600 bus manual.
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Sven F
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PostPosted: Wed Aug 06, 2014 12:00 am    Post subject: Reply with quote

Ray, you lost me on the hypoteneus, but i'll just take it as some type of "slack" was calculated in. It's not a big difference, so shouldn't have much effect on up to a couple splines adjustment.

kreemoweet: My Haynes is 1600 '68 through '79 I know this forum and information is mostly US based, but we had 1600 engines all the way through here in Europe. So i have a '78 bay with an original 1600 engine and 52 spline torsion bars. The Haynes mentions 52 splines, just doesn't give the angles for it, Its the Bentley that doesn't mention it at all.
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Joey
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PostPosted: Wed Aug 06, 2014 6:05 am    Post subject: Reply with quote

Sven F wrote:
...and I would like to do this only once if possible


I've adjusted several buses and Beetles rear torsion bars and most times after setting both sides to "X" degrees I had to go back and tweak one side for whatever reason... weak torsion bar, loose splines, etc.
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raygreenwood
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PostPosted: Wed Aug 06, 2014 6:30 am    Post subject: Reply with quote

Sven F wrote:
Ray, you lost me on the hypoteneus, but i'll just take it as some type of "slack" was calculated in. It's not a big difference, so shouldn't have much effect on up to a couple splines adjustment.

kreemoweet: My Haynes is 1600 '68 through '79 I know this forum and information is mostly US based, but we had 1600 engines all the way through here in Europe. So i have a '78 bay with an original 1600 engine and 52 spline torsion bars. The Haynes mentions 52 splines, just doesn't give the angles for it, Its the Bentley that doesn't mention it at all.


Jeeez....its "grade school" geometry.....and you guys are calculating your own suspension angles?.... Rolling Eyes Laughing .....just being pointy though its true...but anyway.......
quickly put I was pointing out that difference in what the different books list for angles is probably one of two things.

1. From dividing some of the angle numbers listed in the books....I found that some are spot on straight mathematical calculation......meaning they simply divided 360 by the number of splines and then converted decimal to degrees, minutes, seconds.

2. Others dont match anything exactly.....which is what the original point of the post was right?.....that is most probably from either weak torsion bars (age and fatigue most probable).....or too much extra weight in the project vehicle when they were measuring.........and that last point is one that is worth taking note of.

Why?

Because outside of Bentley Publications that "generally".....but not always. ...lists most critical measurements straight from factory specs.......you have texts like Haynes, Clymer, Chiltons, Drake, intereurope and others.....that supplement factory specs with #'s they have measured from actual vehicles they disassembled and photographed.....and none of those vehicles were new or perfect.

Is that simpler?
Sorry for thinking out loud and injecting math info an otherwise purely metaphysical conversation. I think a short massage and some hot rock therapy will fix the ailing torsion bar in no time at all. Wink
Ray
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richparker
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PostPosted: Wed Aug 06, 2014 6:54 am    Post subject: Reply with quote

It's not that hard to do, no need to over think it. I've adjusted mine twice now, once incorrect (topped out on stop) and once correctly. Both times I did it with out the book. Just get in there and get your hands dirty.
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Mellow Yellow 74
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PostPosted: Wed Feb 18, 2015 12:19 am    Post subject: Reply with quote

Maybe if you thought about it more and used the book you wouldn't have had to do it twice...
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PostPosted: Wed Feb 18, 2015 5:35 am    Post subject: Reply with quote

Looking replace my spring plate bushings and asked in the stupid question thread about doing this without remove the shock or any brake components. Would the following work safely?

1. Jack up rear end nice and high on stands
2. Jack up entire real wheel assembly until spring plate is off lower stop.
3. Remove wheel and support assembly w/ blocks
4. Support fwd portion of spring plate with jack
5. Remove spring plate cover
6. Break/remove 4 bolts holding plate to rear wheel assembly
7. Pry spring plate past lower stop and lower w/ jack to remove torsion bar tension.
8. Replace bushings and reverse/re-assemble
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PostPosted: Wed Feb 18, 2015 7:56 am    Post subject: Reply with quote

Mellow Yellow 74 wrote:
Maybe if you thought about it more and used the book you wouldn't have had to do it twice...


True. I did watch a video on YouTube and did exactly what he did and it worked. I didn't understand about moving the inner splines at the time. I also had a rear wheel cylinder blow out on me. You have to tear the brakes down to do the adjustment on an early bay so I was 1/2 way there and decided to do it all. The angle finder was the biggest help, no guessing if the formula you are using is correct.

What's up kkjellquist? You are missing a few steps. You have to tear down the rear drums (on an early bay anyway), remove the shock, and remove the bearing housing from the spring plate before you losen the 4 bolts and pry the plate out. Buy an angle finder, I got mine from HD to like $20. Got luck.
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PostPosted: Wed Feb 18, 2015 8:18 am    Post subject: Reply with quote

richparker wrote:

What's up kkjellquist? You are missing a few steps. You have to tear down the rear drums (on an early bay anyway), remove the shock, and remove the bearing housing from the spring plate before you losen the 4 bolts and pry the plate out. Buy an angle finder, I got mine from HD to like $20. Got luck.


Hey Rich...heater is great. Assuming the check finally arrived.

If I am not adjusting the angle and simply replacing the bushings I'm still not sure why all that stuff has to come apart. I have a magnetic angle finder, but I should be able to mark the torsion bar positions w/ paint or notches and just re-assemble?
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PostPosted: Wed Feb 18, 2015 8:29 am    Post subject: Reply with quote

Once you release the swing plate from the retainer plate and pry it past the stop it will rotate to far down. The brake lines and shock won't go a far as the plate. It is also under a lot of pressure and a dangerous job. I would recommend taking the extra time and take it apart. It's safer then Trying to release the tension with the weight of the hub on the end of the plate.

Got the check, Thx. Did you get the second package with the directions? Sorry I forgot to include them the 1st time.

Rich P.
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PostPosted: Wed Feb 18, 2015 8:39 am    Post subject: Reply with quote

atomweks sells a tool, that you can make, that holds the plate from breaking your knee caps.
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PostPosted: Wed Feb 18, 2015 8:39 am    Post subject: Reply with quote

richparker wrote:
Once you release the swing plate from the retainer plate and pry it past the stop it will rotate to far down. The brake lines and shock won't go a far as the plate.


(I did get the instructions..tx)

at that point I have the wheel off and the hub/drum assembly supported....they wouldn't move. Like this pic where you can see the blocks supporting everything and jack to slowly lower & release the plate tension;

Image may have been reduced in size. Click image to view fullscreen.

I do realize the shock is off in this pic Smile
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PostPosted: Wed Feb 18, 2015 8:56 am    Post subject: Reply with quote

i don't see what you couldn't do it that way. That pic looks like a late bay like you have. The bolts behind the backing plate might be a bitch to get loose.
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PostPosted: Wed Feb 18, 2015 9:13 am    Post subject: Reply with quote

Edit:

I answered a question that didn't exist. Carry on Cool
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