Working on T-Bar Merit Badge. Have 1 Question.

[onZedge]

So I read all the info I could find on replacing/re-indexing the T-Bars, and settled on using the calculations and spreadsheet from 944spec org. The Paragon Tech-Session has a good assembly/disassembly write up.

Before any major disassembly, I measured everything:
Measured camber.
Measured toe.
Measured "loaded" ride height (with shocks, sway bar, and stop bolt INSTALLED).
Measured "loaded" ride height (with shocks, sway bar, and stop bolt REMOVED).
Measured "UN-loaded" ride height (with shocks, sway bar, and stop bolt REMOVED).

What I have not been able to determine is which "loaded" ride height measurement do I use: With shocks, sway bar, and spring plate stop bolt all installed, or all removed?

[thomasryan]

Typically, measurements are from the torsion bar center to the center of the axle stub/wheel center after things have settled.

With a 40/44 spline combo, one tooth up and one tooth down is .812*

[kdjones2000]

It shouldn't matter which loaded height you use, and those 2 measurements should be essentially the same.

The key thing to keep in mind while doing this is to make sure that your left and right final measurements are the same or close.

That spreadsheet works very well, and I have used it 2-3 times on my turbo and race cars. I did do some modifications to it so that you don't have to keep attaching your trailing arms to take measurements.

PM me if you are interested.

Good luck!

[onZedge]

Originally Posted by kdjones2000

It shouldn't matter which loaded height you use, and those 2 measurements should be essentially the same.

I agree this is true for strictly hydraulic rear shocks, but with Koni Sport gas charged shocks connected, the "loaded" height will be (in my case) 3/16" higher.

Originally Posted by kdjones2000

That spreadsheet works very well, and I have used it 2-3 times on my turbo and race cars. I did do some modifications to it so that you don't have to keep attaching your trailing arms to take measurements.

Oh hell yeah - I came across your earlier post where you scribed a 10.5" arc on the banana arm and spring plate (and I will do that), however I noticed that if you change the "length of control arm" from 16.5" to any other value, it seems to have no effect on the calculated delta H values, just the calculated angular values.

Your thoughts?

[onZedge]

Before - 23.5mm T-Bars. Rear bumper height was 44mm higher than front. Supposed to be approximately equal.



After - 26mm T-Bars, poly-graphite spring plate bushings, 95A durometer polyurethane swing arm and tube mount bushings. Rear bumper height is now 3mm higher than rear. Note that as rear bumper height drops, the front goes up a little as well. Set rear camber to -1.45deg and thrust to 1mm total toe-in.



This was actually not at all hard to do, however it is extremely time consuming to research, make many detailed "before" measurements, disassemble, sweep floor, inspect and clean parts, reassemble, sweep floor, align, take many more detailed measurements, and finally bleed brakes. I figure I spent at least 40H start to finish, after having all the parts, tools, and new hardware ready and on hand. Remember that this was my first time and I was doing this part time because I was on vacation, so YMMV. Oh - and I got the indexing spot on THE FIRST TIME thanks to the "spread sheet" from the 944-spec (dot) org web site.



Test drive was at night on my favorite twisty road (Indian Crest Drive) and kept being interrupted by pesky deer crossing the road... Wow. Why the hell did I wait so long to do this?



Surprisingly, both upper mounts are in almost new condition considering they are 30 years old.

It is now clearly evident that I have to address front control arm/tie rod geometry correction - rear is MUCH flatter but front still rolls around tight corners. Overall it is now flat on high speed big wide sweeping turns (i.e.: interstate interchange ramps). My entire suspension is now on poly (even the front strut mounts, but that is a whole new thread for later).

[kdjones2000]

Glad it worked out. That spreadsheet should be posted somewhere for others to use beyond just the 944 Spec site.