I own a 1990 944 S2 Cabriolet. I am currently considering putting coilovers on the rear. I will be putting Bilstein(hope I spelled that right) shocks with 250 lb progressive rate springs on the front and the same shocks with the same springs on the back. I have a very knowledgeable mechanic by the name of Garrity Repta who is helping me. He says that when he has done this on 944 coupes in the past he has usually just taken the torsion bars out. One time he lathed the torsion bars down so they were very thin and were basically just used to "hold the place of the torsion bars" there was really no noticeable difference with the smaller torsion bars in or out. But because I have a cabriolet I was wondering if anyone out there had any ideas on if keeping a thinned down torsion bar or removing them all together is the best option. I know that if we kept them indexing ride height would be a bugger, where as if they were removed it would be a simple matter of adjusting the coilovers. I am inclined to just remove the torsion bars but I am worried that I am over looking something. I am very new to the Porsche world and am very aware that I don't know much and what I do know is possibly wrong so any help you can give me would be appreciated

 

I don't know anything about pulling the torsion bars except people have done it. It's more interesting where Garrity ended up since leaving Saint Louis. There are probably still some folks out there looking for him.

You should put his name in the subject line and see if the replies build up.

 

hi brownry,
welcome to the board
(Makis) a mate of mione (and 944 techsupport for Thames Valley Region TiPEC) has done this stuff,

he's often on this, always on not-just-porsche, details in sig
hope this helps

Ade

 

Thanks for the reply's. Hey Craig001 I have only known Garrity for a couple of weeks but he really seems to know his stuff. When you say there might be some people looking for him what do you mean? I plan on working with him quite a bit to get my Porshe to the level I want it at but I always want to know who I am working with.

Also adrian__jaye thanks for the info, I appreciate any advice I can get on this subject

Thanks

 

I don't see the difference between keeping the torsion bars (in the stripped version) and just removing them entirely. The only reason to keep them if going with coilovers is so you aren't putting as much stress on the shock mounting points (which it has been argued aren't strong enough to take abusive street driving.....but that's not my argument). What you do really depends on the springs you have though...are they 'helper' springs (designed to be used with torsion bars) or regular springs (designed to be used without torsion bars). Since you said you have 250lb springs, then I'm assuming they're designed to be used without....so go without.

 

250 in the rear without torsion bars is not going to be enough spring to compliment 250lb springs in the front. IIRC rear coilovers are something like 56% effective while the front springs are 85-90% effective. Your going to be wildly undersprung in the rear and suffer significant understeer.

The argument about the suspension points in the rear not being strong enough is based on the fact that the shock mounts (lower only IIRC) are in single sheer, which is a huge no-no in suspension engineering.

 

Once again thanks for the info. The springs I and shocks I was thinking about putting on the rear are definitely strong enough. They are not helper springs but I wondered if there was an advantage to using helpers. I don't know if the torsion bars contribute to the stiffness of the car or if they strictly control spring rate.

I really do appreciate the help, I am just learing about the awesome and exciting world of Porsche.

brownryce

 

The springs I was looking at are not helper springs. I just wondered if there were any advantages to going with helper springs. I think I understand most of the disadvantages of leaving the torsion bars in I just wondered if there were any advantages.

Anyone else got any ideas?

I appreciate any help I can get.

 

Well, whether the strength issue is an actual issue or not is up for debate. The problem isn't so much with the shocks though, it has to do with the lower mounting point for the shocks on the swing are. That mounting point is in single sheer, meaning the fastener is only supported on one end. That end is also the weakest end, where the threaded length transition to the grip (smooth) section. So the potential problem isn't that you will burger the shock or rip the bolt out of the trailing arm, but rather that the bolt itself will sheer. I can't say I have actually heard of this happening to anybody on these forums, but in theory it should under hard driving.

 

I didn't realize there was a 2nd page of reply's so I thought my first explanation about what type of springs I was thinking about didn't make it onto the thread. So I posted another. That is why there are two post's from me that say essentially the same thing,

When I found the 2nd page I also found Manning's explanation about being undersprung. I am actually really worried about what he said about the mounting points not being strong enough. Does that mean I should leave the torsion bars in and add helper springs to the car? I could do that myself without help from a mechanic it would save me some money and time but I am worried I couldn't get the car level without reindexing the torsion bars. So at that point why not take them out all together, unless I need them because my mounting points are weak.

Any other feedback would be greatly appreciated I am more confused that before.

 

Manning are you out there right now? If so is there a way I can chat with you?

 

I think the springs would actually be tender springs if you left the bars in. Tender springs add or suppliment rate of an existing spring (your t-bars) while helper springs has very little spring rate and is meant to keep a coil sping from coming unseated at full droop.

Anyway, do a search on these forums for the KLA rear coilovers. Tifosiman for example has them on his car with 250lb/in springs front and 100lb/in or 140lb/in rear supplimenting stock t-bars (IIRC). That should be closer to proper balance than what you describe doing above.

 

Thanks for the help Manning I am going to do the search right now

 

I am about to finish lunch, so no chat right now, maybe later after work and some yard work.

There are also a ton of other folks here who should weigh in on this subject.

 

I would love to hear from them. At this point I think I have learned the following.
There are many different opinions of if the mounting points in the rear are strong enough to support the full suspension load without t-bars
The springs in the rear should be heavier than the front springs to get optimal handling if t-bars are removed
There are a lot of knowledgeable people out there,
Anybody who has done this type of thing?
If so how would you do it if you could start over?

Thanks again for any help