Rear Ride Height Question

[jjeffries]

Hi Everyone,

I'm fitting 27mm torsion bars in my 87 924S; I've already installed 250lb lowering springs in the front (Weltmeister). I've done t-bar setting in my 911SC (easier!), so I have some feel for the degree-ing process with the splines.

I've read everyting I can find, choosing thus far to follow something of a combination of the Clark's method and this one:

https://members.rennlist.com/m758/TbarReindex.htm

*I cannot find an active version of the calculator Excel sheet ... links are all too old. I did try the 944 Spec site also. Anyone have a copy they would point me to?

I did make the tool to measure droop, loaded and unloaded. I also measured the same in terms of degrees, using an old-skool magnetic angle finder. And I scribed the outline of the back half of the spring plate's relationship to the trailing arm and to the front/shorter element of the spring plate, on both sides. The torsion tube is now out and I'm ready to have at it.

With the front springs in (as part of overhauling the front struts), the rear of the car sits high (expected), at ca. 26.5" from wheel wellto the ground. Ca. 25" is my goal ... I will corner balance the car once I have it roughed in.

So ... looking at the screen shot of the Excel calculator, I'm extrapolating (i.e., kinda guessing) that going from the stock t-bar (presumably 23.5mm) to 27mm, and wanting 1.5" inch less ride height, I should reduce the unloaded angle of the spring plate by 9-10 degrees. For those with prior knowledge/expertise, do you agree?

And can anyone send me (please) an active copy of the Excel calculator?

Thanks in advance,
John

[944 Ecology]

This site might help...

https://vw.zenseeker.net/Wheels-TorsionBars.htm

[jjeffries]

Thanks much George. If anyone’s looking for me, I’ll be reading …

John

[jjeffries]

Another good one for me:

https://www.thesamba.com/vw/forum/viewtopic.php?t=709310

The conversion re t-bar size is the tricky bit.

Easy to forget that it’s Super Beetle tech (as in, parts) in these cars.

John

[kdjones2000]

I have the XLS file if you need it.

[jjeffries]

Yes please. Email address in a PM.

Big thanks.
John

[Fast Freddy 944]

Ed China did a 951 on wheeler dealers, I think he changed the torsion-swing arm bar and measured the drop both sides of the rear end.

[9FF]

Originally Posted by jjeffries

…With the front springs in (as part of overhauling the front struts), the rear of the car sits high (expected), at ca. 26.5" from wheel wellto the ground. Ca. 25" is my goal ... I will corner balance the car once I have it roughed in.…

Couple of things to keep in mind. When you do corner balance, your 25” height measurement will go out the window and don’t be surprised if all four corners end up at a different height from the ground.

Also, new Welt lowering springs may actually raise the height at the front compared to your 30+ year old factory springs.

Just something to be aware of, gl

[jjeffries]

Thanks gents.

The front 250lb springs did lower the front about an inch. And point taken about the side effects of corner balancing; I did it on my 911 after installing Rebel RSR bushings along with my (first) string alignment, mainly because a friend (albeit, 200 miles away) offered me the use of his scales. It was an interesting experience and reassuing, in that the results were all repeatable after I developed the feel as to how X adjustments caused Y results.

It's funny ... more like, stupid of me: I'd thought I'd taken all possible measurements before doing disassembly, BUT I'd missed a key one: the length of the side of the triangle opposite the spring plate pivot at the torsion tube ... i.e., the height. I did make the measuring device to note the loaded/unloaded distances at the torsion tube end carrier, but anyone else would be well advised to measure it further back.

Instead, with the torson tube out I think I've been able to measure that angle and thus calculated the height. With this I can (I think) make proper use of the spreadsheet calculator Keith so kindly sent.

I found a very cool only tool, www.triangle-calculator.com. Understanding that I'm awful at trig, algebra etc, this was really helpful to me. I'll make more thorough notes in my main thread.

Thanks Al Gore for the internet!


Cleanliness is always a goal,

Thanks everyone for responding when I called for guidance and for the most helpful feedback. Tune in to my regular thread later this week to discover if I can put it all to use ...

Kind Regards,
Jon

[Rasta Monsta]

https://www.924board.org/viewtopic.php?t=31669&highlight=database

[Rasta Monsta]

VERY IMPORTANT:

The ride height eccentric should be in the center position on reassembly, which will allow fine tuning in either direction if needed!

[jjeffries]

Roger that.

Much appreciated.

John

[TheSecondChris]

A previous owner adjusted my rear spring plate to lower the car a bit. The thing that confuses me is that the car seems lower, however visually the car does seems to be level. I haven't taken measurements at the front and rear sills, so could be wrong about that.

How does lowering the rear of the car not result in a car that is lower in the rear? Why wouldn't this result in a car that looks like it's sagging in the back end?

I've read that US DOT required the bumpers to be higher than ROW heights. Does this spring plate adjustment to lower the car just make it level as was intended?

Confused as usual. Thanks for the help.

[jjeffries]

Chris, the adjustments in that cam device on each spring plate are very fine … one needs to do the reindexing to change the geometry enough to make big visual (and functional) changes.

John

[Rasta Monsta]

Originally Posted by TheSecondChris

I've read that US DOT required the bumpers to be higher than ROW heights. Does this spring plate adjustment to lower the car just make it level as was intended?.

This is correct. US cars had high asses and rake due to DOT bumper height requirements. Adjustment was done at the eccentric...full range of that eccentric is larger then you think.

[9FF]

Originally Posted by Rasta Monsta

This is correct. US cars had high asses and rake due to DOT bumper height requirements. Adjustment was done at the eccentric...full range of that eccentric is larger then you think.

Mmm, I’m not convinced that the factory used the eccentric to adjust the height requirements for US/ROW cars. It would make more sense to use shorter springs at the front and set the rear height using the torsion bars.

[Rasta Monsta]

This theory is not backed up by PET. ROW & US front springs are the same.

[9FF]

Originally Posted by Rasta Monsta

This theory is not backed up by PET. ROW & US front springs are the same.

mmm idk, eg: in PET the ROW early cars had 477 411 105 Q and the US had 477 411 105 S, I assume the difference is the length. If it wasn’t a different spring height I’m curious how else do you think they raised the front ride height for the US cars?

[jjeffries]

Maybe with a spacer under the strut top?

John

[9FF]

Originally Posted by jjeffries

Maybe with a spacer under the strut top?

John

There is a spacer in PET (9) but it appears in both the US and ROW versions with the same part number so it’s not that. The ROW PET (pic below) shows spring ending in “Q” whereas the US PET ends in “S” though they also show a “Q” version. Iirc the last digit in VW part numbers was a “modification”, so it could refer to a higher version of the same rate, but I’m just guessing.