Charlie944

Hey thanks for checking in...this again is in regards to my 83' Callaway 944. I was told when I bought the car that it had stiffer front springs (does..but not sure how stiff...see my other post), and stiffer torsion bars and Weltmeister sways. Thus far I can confirm 2 out of the 3, but that leaves the torsion bars still. Is there any way to measure their diameter (can I take off end caps, or much much more?) while they are still in the car??
I hate not knowing details about the cars I drive, but this one was such a deal that I could not pass it up despite some of it's "unknowns". I want a balanced system here, and if I needed to upgrade I sure would love to know before race season starts up.

Thank you for any info!!
Take Care!

RedlineMan

You don't wanna go there, Charlie;

You will open a world of hurt if you take that thing apart to find out something you don't need to know. PLEASE trust me on this, if it is working fine... JUST DRIVE IT.

You might try contacting Tommy Thompson (Hudson Valley (I think?) PCA). He has owned one of the cars for many many years and might know about this.

Hans

Not possible without taking the torsion bar out.
The difference is in the diameter of the torsion bar itself, the splines on both ends are identical, so removing the end cap only is not enough.
You need to drop the complete housing to remove the shafts, unless you punch a hole in the rear fender....
You need to re-index once installed again, this involves at least one (but probably more) removal / re-install sessions of the compete set.
As above: you enter a world of hurt.
TakeCare

dgz924s

If done correctly the bar may be sized by the set up on now. If the tech did the job by matching the spring rates to arrive at the proper bar, doing some math may lend an idea? My guess is it is 28 or 29mm as that is the average size I see on cars. But I agree don't concern yourself with it as it is a major job to reindex and balance it. Dal

Adam Richman

Not sure why you couldn't measure the distance from the rear hub to a fixed point on the chassis at full droop and then at static ride height, get your corner weight for the wheel measured and compute the spring rate. I am sure someone here has a progressive rate torsion bar equation that you could plug in the distance and weight to estimate #/in. I think the unsprung bits will uncoil the t-bars at full droop so it would probably throw off your numbers a bit but you could remove wheel, rotor, caliper to reduce this effect. This is all just a SWAG but seems like it should give you a ball park.

Sami951

This is actually a pretty fascinating idea IMHO (the holes). Didn't some very early 924's have those??

Question: if one were to cut the holes in the rear fenders, how difficult would it be to remove/install torsion bars then? If it's simple plug'n'play afterwards, I might actually consider getting something like it done...

*Michael.*

You are still going to have to get the plate off (not sure what it is called) to get the T-Bar out. That means lowering the housing down enough to get the plate to clear the side of the car.



Torsion bars really aren't that hard. I think they have a scary reputation more then anything else. Or the fear of indexing them wrong and having to do the job twice. I did that the fist time that I changed Torsion bars. It took a lot less time the 2nd time around.

keith

Good idea Adam.

- but it does involve math . . .

Kurt R

Do you have access to a scale? Get the weight on a rear wheel. Then add weight to the car, or jack the car with a jack not resting on the scale to raise or lower the wheel one inch in relation to the body of the car. Add or subtract this result from your initial weight, and you will have the wheel rate for the torsion bar. Then you can look at the chart on Paragon and get the size of the torsion bar. Keep in mind if you have 30mm torsion bars you will have to add 670lbs of weight to compress the rear suspension 1 inch, so it's probably easier to jack the car.

Or, without a scale, but with a weight set, measure current ride height at the rear, and add weight over the rear wheels to compress the suspension 1 inch. Has to be right over the rear wheels, or you get a lever effect and the resuts won't be accurate. Divide that weight by two, (two torsion bars) and reference the chart.

Somebody let me know if I'm way off here, this is all theory, but I think it should work.

Hans

Michael: I am affraid you are right, holes are not enoug.
Also modification of the "hub" part is required to allow access to the bar, and even then...

Sami: have a look at the old VW type 3 (the ponton model from the '60's, that is what put the idea of an easy mod in my mind.
They could even supply you with the blanking plate...

Rockfan: adding the weight will give an idea, you would need a "hell of a lot" but in theory it should work. Practically I have some doubds since friction will be disturbing a lot here.
Least of all, removal of the shocks would be required and the car should be on a levelled path (without the hand brake applied!!).
TakeCare

RedlineMan

Hey all;

I STILL think it is a silly idea and a who-the-hell-cares sort of the thing compared to the work involved. And no... experience or brilliant calculations are not always enough. Many times, to get the right height involves LUCK & REPETITION!

But... if you simply must know, I'd do this. Go out and find some nice rubber hole plugs about 1" in diameter. Get a good drill and a 1" hole saw and cut a hole in the torque tube and measure the damn thing!!! Pop in the hole plug and your golden.

Another nice mod for those who have to do this operation to be satisfied in life (or to meet comp rules) is to drill and tap the inner spline for a set screw. With this set screw installed, you can be assured that this spline will stay engauged when you pull out the spring plate. It is much easier to get the height back correctly when one end of the springs original position is known!!!

Charlie944

Thank you everyone for all the responses! I am not a glutton for punishment (RedlineMan sounds pretty good for the ultra curious) so if it drives well, I will leave it alone. Thank you again!

Take Care!

M758

Like this

Link to torsion bar diamter setting tool.

Adam Richman

No, not like that. The guy asked about determining his torsion bar size w/out taking them out. I am suggesting he find out the distance (full droop, static) and weight (of the corner) and use an equation for torsion bar rates and he'll have his answer. That instruction guide is for replacing/reindexing t-bars, I don't see why he'd have to take them off to figure out the rates. As said there, I too would unhook the sway bar on the side you are measuring.

Charlie944

Adam, sounds like a good method, I have access to a set of scales for racing to figure out the weight and acheiving full droop can be done. I guess what I can do is compare my result and match up a torsion bar rating that has been confiugured to how a coil spring rating is measured for ex: X amount of pounds moved it one inch...BUT that is a linear compression....the spring is roughly square to the movement. A torsion bar has a mechanical leverage acting on being the rear spring arm...so can a ONE inch moved at X pounds be accurate when the torsion bar is converted to a poundage rating like a coil spring??

Thank you again for all your responses!