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Torsion Bars


Big Dog

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I need to re-index my torsion bars to allow the rear of the car to be l/2 inch (or so) lower than now on an 88 car.

 

Can I remove the bars far enough to do this without droping the rear end? From reviewing the information Joe P. has posted, I am not sure as I do not need to replace them, only reindex them to allow for lowering the rear as the plates have no more down adjustment left.

 

I have reviewed the information on how to move the bar using the difference in the teeth to readjust the height and think I understand it but if someone can simply tell me how many teeth to move the inside vs the outside to lower the back by 1/2 inch, my life would be easier.

 

Thanks for the help. 944's rock.

 

Jim "Big Dog" Foxx

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Capt Squid

I cut a holes in the side panels opposite the torsion bars with a hole saw. Plastic hole plugs cover the holes. When the torsion bars are out, I drill and tap them to hold a 10 mm bolt for easy future removal.

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944-Spec#94
I need to re-index my torsion bars to allow the rear of the car to be l/2 inch (or so) lower than now on an 88 car.

 

Can I remove the bars far enough to do this without droping the rear end? From reviewing the information Joe P. has posted, I am not sure as I do not need to replace them, only reindex them to allow for lowering the rear as the plates have no more down adjustment left.

 

I have reviewed the information on how to move the bar using the difference in the teeth to readjust the height and think I understand it but if someone can simply tell me how many teeth to move the inside vs the outside to lower the back by 1/2 inch, my life would be easier.

 

Thanks for the help. 944's rock.

 

Jim "Big Dog" Foxx

 

 

Jim,

There are two ways to lower the back end of the 944.

1/2 inch could be achieved by doing the spring plate. These are the two large bolts on trailing arm. These can be done with everything in the car. One bolt is regular bolt and the other is the eccentric use to adjust rear ride height. Typically you can adjust the car +/- 1/2 inch. However sometimes these are not at the middle setting straight away. If they are already to the max on one side other the other you may not be able to get 1/2 inch from them.

 

In that case you need to re-index the t-bars. The procedure I wrote covers that process well. You will not need to replace them, but they will need to be just about removed to adjust the splines.

 

My process is such that you take measurements with the assembly loose and then you keep turning the splines untill you get it right. Make sure you set the spring plate to the middle so that way you have a full range of adjustment once the car is back on the ground.

 

Here is a link to my process.

 

http://944spec.org/944SPEC/content/view/42/25/

 

 

It may be possible to re-index with out dropping the entire assembly, but I have never tried it like that. I have done two t-bar jobs (stock to 28 mm, then 28 mm to 30 mm). I dropped the entire rear suspension both times. It took me about 2 days the first time and about a day on the second time. Both times includeded doing a few other things along the way.

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Joe, I have a question about your steps 10 and 11 please. Every stock setup I have pulled with 23.5 still installed; the trailing arms droop and rest on the large aluminum spacer and bolt at the torsion bar carrier retaining plate. Once that bolt is pulled the arm can extend and completely unload. This would affect the 'H' measurement, no?

 

Thanks

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944-Spec#94
Joe, I have a question about your steps 10 and 11 please. Every stock setup I have pulled with 23.5 still installed; the trailing arms droop and rest on the large aluminum spacer and bolt at the torsion bar carrier retaining plate. Once that bolt is pulled the arm can extend and completely unload. This would affect the 'H' measurement, no?

 

Thanks

 

I guess it may.

However I never had an issue when I did my swap 23.5 to 28 mm.

 

I know many others that have used the process with great sucess. Getting it wrong can happen, mostly from poor measurements from the start.

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Joe, thanks for the info. At the present time, my spring plates are set at the maximum setting for lowering the car so I can not get any lower without re-indexing the bars. I was hoping to avoid having to pull the housing out completely since I only need to pull the bars out far enough to move them on the inside splines and can then readjust the outside plates. To compound the issue, it appears that the left and right sides are not set exactly the same so I will try to determine the correction to one side or the other and then move both the same. I plan to start with the ecentric bolt at about 3/4 down with the car at about 4" so I can lower the car slightly and raise it more in order to be able to raise it to meet SCCA's 4.5" minimum. I selected 4" from what you have written.

 

Unless I hear differently, I am going to start by trying to remove only enough to get the torsion bars to slide out enough to allow re-indexing them with the rear in place as much as possible. As I understand it, the splines on each end of the bars are only about 4" long, inside and out, so it appears that it may be possible. Since I am only re-indexing the existing 30mm bars, I only need to calculate how many splines to move the inside and outside to get the desired car height based on the difference in teeth since the spring rate does not change. It would seem that I, therefore, do not need to do the other calculations that are involved in replacing the bars with different ones. IS THIS CORRECT?

 

If I go this way, I will let you all know what happens. Being able to re-index without pulling the housing completely may be a time saver in the future.

 

Jim

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944-Spec#94

Jim,

Since you are only trying to get ride height change you can in fact skip the initial measurements.

 

Here is what I would do.

 

Center the spring plates or put then 3/4 up. This would put them right where you want them once the car is done.

 

From this point determine the actual ride height change you want. This may mean you want to lower the back by 1" instead of 1/2. In anyevent this number is critical as you will use this later on.

 

Check both sides of the car as it may not be even left to right when you get the spring plates to where you want them.

 

You want to do these with rear sway bar disconneted so that it does not influcence anything.

 

 

Now jack up the car and start. I believe you can get to the parts by leaving the assembly in the car but allowing it droop down to just clear the body. As for getting the t-bars twisted with being able remove them completely I just don't know. I am not sure there is enough space to remove the spring plate end cover (round thing on the end). Maybe there is.

 

What is critical however is to take the measurement from the top of the banana arm. This is shown as H in the proceedure. (see photo as well)

tbar2.jpg

This measure ment is what needs to change by how much you want to lower the car. It is 1 to 1 so 1" lower car means a 1" shorter measurement on that side. I have have always needed to put the t-bar in and losely bolt stuff together 5-6 times until I got the measurement I was shooting for. The good news was that doing this was may be 1 hour total with maby 10 mintues per try.

 

The only issue with rasing and lowering the car for SCCA and NASA is that rear ride height changes impact camber for sure and possibly toe. Lowering the rear on the spring plate adds negative camber.

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Packfill

I have done this many times, and on many cars...

 

Put the car on the lift, pop out the TB caps, put a screw jack under the wheel, and SLOWLY raise it while pulling on the TB. It will pop out.

 

Some people tap the TB, I tigweld a small tab on it.

 

Good Luck.

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  • 12 years later...
Mike Eberlein

Mr. Packfill, where are you located? Thanks, Mike E

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