M030 Upgrade, with torsion bar reindexing

[kdjones2000]

Just thought I would detail for posterity my M030 upgrade. Since I also replaced and reindexed the torsion bars, I have included those details as well.

Hope this helps you in your upgrade path, or at least inspires you to do something similar on yours.

After owning my '88 951 for the past 12 years, I have started to do some autocrossing, and found out that the suspension was woefully inadequate. Here is what we are starting with:





The bump stops are essentially gone, with the dust covers loose at the bottom of the springs. When running AX, the stock tires would rub against the top of the wheel well, especially with a passenger in the car. You can see this at the top center of the pictures.

Time for an upgrade! I found a set of Turbo S struts, shocks, sway bars and torsion bars at a reasonable price (Thanks Brian!):



After separating the front struts, and looking at the rear shocks, it was obvious that they needed a rebuild. With less than 60K on them, I chalked it up to the "barn sour" issue for things that sit too long. Off to Koni USA for refurbishment, and 6 long weeks....

For the WYAIT, new brake pads, rotors and bearings were needed so off to Pelican for those:







Also, time to redo the control arms (Rennbay track kit, not shown), and get some triangulation supports for the stiffer front sway bar. Also, time to replace the caster blocks with the 968 upgrades:



While the car has never been tracked or driven hard before, the old caster blocks still had cracked rubber. This turned out to be the cause of the mild steering wheel vibration at just above 80MPH:




Plus all new rubbers for the front and rear sway bars...

[kdjones2000]

Finally! Pretty newly refurbished struts and shocks, straight from Koni USA:



While pretty much straightforward, a couple of things stood out. Finding the correct clips for the brake wear sensors proved to be a bit of a challenge, as these are not pictured in PET. The same PN's are used both in the front and the rear, but I had to get the correct PN off the pieces directly. The upper strut caps for the Sachs/Boge units are flat and need to be modified to work with the adjustable M030 struts. I took the plastic caps that came with the rebuilt struts and hot glued those into the original caps (After drilling the appropriate sized hole), as opposed to buying OEM parts at something like $26 each.







Okay, time to move on to the rear. First, more WYAIT. The rear transaxle had a very slow seeping leak. Time for a clean up and reseal. Add a bit of Royal Purple 75W-90 synthetic gear oil and:





Also, time to clean and repack the CV's, and put in all new triple-square bolts. One boot was just failing, so it was a good time to catch it and fix it.

Now on to the dreaded rear torsion bar replacement/reindexing.

[kdjones2000]

For the torsion bar reindexing, make sure that you plan ahead accordingly, and take the proper measurements BEFORE you take everything apart! That includes determining how much ride height change you want. For me, I went with the desire to keep the running boards level with the ground, and wanted to have the front control arms level with the ground. The front height was already where I wanted it with the existing stock parts, and I decided to lower the rear by 0.75" to make it level with the front.

After determining ride height adjustments, make sure to get an accurate LOADED and UNLOADED torsion bar measurements. Spring rate is proportional to the torsion bar diameter to the 4th power, so getting accurate measurements is important if you want to obtain the proper ride height on your first try. For the stock setup, the lower/rear bolt that holds the torsion bar end cap on MUST be removed, along with the REAR SHOCKS in order to obtain the correct UNLOADED distance. If you don't do this you risk getting a higher ride height than predicted.

Here is the difference in unloaded measurements without and with removing the bolt and rear shocks:

_________With bolt_________Without bolt (Good)
DS Rear___12 3/4"__________14 7/8"
PS Rear___12 13/16"________14 7/8"

Also, make sure that you have final measurements that are very close on the Passenger's and Driver's side; keep indexing until you get them within a couple of mm difference.

I slightly modified the Excel spreadsheet created by Joe Paluch over at 944 Spec ( http://944spec.org/944SPEC/content/view/42/25/ ). Here are the results for converting from a stock '88 951 (23.5mm) to M030 torsion bars (25.5mm), with a drop of the rear of the car by 0.75":



One thing that really annoyed me about the procedure was that for the measurements you have to bolt up the trailing arms to check on the interim settings. Instead, I scribed an arc at 10.5" from the torsion bar centerline onto the banana bar and the spring plate. I then used the measurements in the bottom area of the spreadsheet for setting up the new torsion bars. All you need to do is to index the torsion bar, then put the end cap on the torque tube, and take your measurement. Repeat until you are satisfied.

Once you have those settings correct, you can double-check them by reattaching the trailing arms and using the measurements in the upper table. Once everything checks out, put it all back together and:



The final result:



The rear looks to be low in this picture, however it is actually that the front of the car could not be lowered to the same height that it was with the previous stock setup. I ended up having to raise the rear up to level the car at the running boards, which was well within the range obtained using Joe's spreadsheet.

A final picture of the fronts:



Parts list:
Front inner drop link bushings (2) P/N: 951 343 794 04
Front stab. bushings (2) P/N: 951 343 793 30
Front outer drop link bushings (4) P/N: 951 343 795 01
Front washers (4) P/N: 477 411 043
Front lock nuts (2) P/N: N 900 876 01
Caster block/Control arm bushing (2) P/N: 951 341 023 30
Rear sway rubber mounts (2) - 18mm: 477 411 313 B
Front brake wear sensor clip (2) P/N: 999 651 202 40
Rear brake wear sensor clip (2) P/N: 999 651 203 40
Strut mounting nuts (2) P/N: N 022 150 1
Koni front strut (L) P/N: 951 343 031 32 (R) 951 343 032 32
Front springs - 2 white/1 yellow (#102) (11.7-12.2mm wire dia.)
Top strut bearing (2) P/N: 951 343 018 30
Front sway bar 26.8mm (1) P/N: 944 343 706 05
Rear Koni shocks (2 white dots at 180 degrees) P/N: 951 333 032 04
Rear sway bar - 18mm: 477 511 413
Rear torsion bars - 25.5mm 951 333 103 30 (L) 951 333 104 30 (R)
Strut boot (2) P/N: 951 343 529 30

Cheers,

Keith

[nize]

wonderful write-up !

[333pg333]

Great writeup and pics! The only thing, could you take a pic of the car on a level road as the rears look way lower than the front?

[kdjones2000]

Remember that I mentioned that I couldn't get the front down as far as I was planning with the standard M030 springs, even with the perches set as low as they go. I therefore had to raise the rear with the eccentric bolt. The picture above is before I did this; here is how it ended up:



That is about as level as we have around here...

My objective was to get the running boards level. I was able to get everything within about 1/8 inch at the running boards. Here are the PS measurements:





The measurements at the belly pan stud and bottom of the torque tube were as follows. (I didn't like the caster block bolt method as some do, as this reference is not permanent).

________BP Stud______TT_______Caster Block Bolt
Before:___7 3/16"____8 29/32"_______N/A
After:____7 5/8"_____8 13/16"_______5 7/32"

You can see that the front is now about 1/2" higher than before the conversion. Short of going to lowering springs, does anyone have ideas on how to get it back down? Right now my spring perches are set as low as possible.

Cheers,

Keith