911vet

I have an (irrational or justifiable?) fear of my torsion bars failing. I'm considering replacements.

OE bars for 87 were 19mm front (really 18.8) and 25mm rear.

I can't find those sizes in aftermarket bars. And they are getting hard to find from genuine Porsche outlets as well.

I can go to 21mm front, 27mm rear using aftermarket bars. But I have been "warned" that doing so will require me to re-valve my shocks. Anyone have an opinion on that? I've got new Bilstein HDs. Is going up to 21/27 really such a dramatic change that I'd have to adjust the shocks?

I was also told 21/27 would be "too harsh" for the street. And that my stock (tired) Cabriolet suspension couldn't handle it and I should upgrade everything else if I do it. And it could be too stressful on a Cab body.

Opinions?

Note: I have brand new shocks, turbo tie rods, ball joints, sway bar bushings. The rest of the suspension is OE and 20yrs old as far as I know.

Ed Hughes

Only an inspection by removing all of the t-bars will tell whether your fear is irrational. If they've been scratched or have other signs of corrosion, the fear may be justifiable.

Next, your Bilsteins would work OK with heavier bars. They won't be optimal, but I've run Bs Sports for 2+ years with 22/29mm t-bars, and there was no huge performance issues. I'm just now currently re-valving as part of some tweaks to take it to the next level.

If you are DE'ing the car, the 21/27mm bars will improve your handling on the track a bit. But, you will compromise some ride quality. Elephant racing has hollow 21/27's which will be similar in stiffness to smaller, probably 20/26mm solid bars. They may be worth looking at, plus you'll shed a few lbs. Of course, it goes without say that you need to replace your bushings.

Rick K

Hey Shannon, I will let more knowledgeable folks than I discuss the cab part of your question. But I went with 22/28 Tbars on my car and found the ride to be certainly more firm, but much improved/predictable from my tired stock tbars. Much better on the track for sure, but also improvement on the street. I think Ed's suggestion of 21/27 might be a good compromise for you.

It sounds like you have already paid a great deal of attention to the front end of that car, and IMO, if you're going to get new Tbars, certainly spring for the elephant rubber bushings in the rear (springplate bushings) and definitely consider doing the front control arm bushings as well as the upper strut bushings (I suggest rubber b/c you're concerned about ride quality, although my choice is the PBronze).

If you have some local folks around you that you track with, see what Tbars they're running and ask if you can drive it on the street for a few miles. Good luck!

Edward

Since yours is a cab, and is thus inherently less stiff a chassis, I personally wouldn't go heavier than a 21/28 setup for a street-track car. In my SC, I had 22/28, which was nice on the track, but a bit stiff for the daily rigors of street ...albeit great if it is an occasional "fun car." But if I were streeting it regularly, I would opt for a 21/28 setup. Some like 22/28, but I found she understeered more than I like, so if you do want a bit more stiff than 21/27, go with a 22/29 for better f-r balance ...IMHO of course. If you have new shocks as you state (Bilsteins?), you'll be perfectly fine with up to the 22/29s.

BTW, do you have stock sways? You get much better body control with OE 22mm/21mm sways ...find em used and they are a killer bargain upgrade that, along with a T-bar upgrade, really transforms the handling. And unlike T-bars, thicker sways won't appreciably degrade your ride compliance.

Edward

KeithC2Turto

All 911's at this point have a high probability of the front torsion bar rubbing do to bushing sag or flow and the springs being comprimized. If you are going to act on your fear, you are looking at a major expence to replace all the bushings, set ride height, align ($200), and corner ballance ($700).

Do note that failure seems quite rare. Further, if one did fail I suspect it would not be a major failure and the remaining three bars and the sway bars should let you get off the road safely unless your car is really slammed.

I agree w the above of inspecting them for dammage. If they are good, I would reuse them. There is also a lot of stock bars left over from others upgrading.

Going to 21/27's will stiffent up the car about 57% on the spring side when going accross RR tracks. It is not really that much over pot holes as the Sway bars are part of the spring rate so it is more like 30%. For referance. 22/28 is concidered a street/track setup and much more popular of an upgrade for the heaver 3.2's. They have a spring rate that is about 85% stiffer. 911's are not really sprung that stiff compaired to other sports cars so what you are doing is a good upgrade.

Tire choice can have a significant effect on ride quality to.

I suspect the ER hollow bars are like other hollow bars and a 27mm hollow is actually larger but has the same spring rate as a 27mm bar.

The HD shocks are a very good match to said bars.

Thus, have the front and rear inspected externally for sag and enjoy the car as is knowing a failure is a small probablity and not a big deal. Or, do a full suspention rebuild w all new bushings adn 21/27's that I suspect will be over $2k.

Enjoy.

84_Carrera

It IS a big difference on my '84 Cab, having done a bunch of suspension changes.

I went with 22/29 hollow bars, elephant poly-bronzes, new shocks, new mounts, sway bushings, turbo tie rods, ball joints, etc. Wasn't cheap, I did the labor, and align / corner balance is north of $400 / south of $800 typically.

I have a roll bar bolted in, which helps reduce the tweaks a bit to the chassis, but yes, there is a noticeable change in "road friendliness", especially if you're up north on frost heaved roads w/ potholes.

sig_a

[QUOTE=911vet;6523145]

I can go to 21mm front, 27mm rear using aftermarket bars. But I have been "warned" that doing so will require me to re-valve my shocks. Anyone have an opinion on that? I've got new Bilstein HDs. Is going up to 21/27 really such a dramatic change that I'd have to adjust the shocks?

I was also told 21/27 would be "too harsh" for the street. And that my stock (tired) Cabriolet suspension couldn't handle it and I should upgrade everything else if I do it. And it could be too stressful on a Cab body.

Opinions?

To revalve your shocks is up to you. It is not a necessity, and could be done later if you want more performance.

For many, "too harsh" might start at something like 23/31. Tires will also effect ride quality as well.

If your front and rear bushings are serviceable, you might consider Sander Engineering 22/29 hollow T bars on page 13 of their cagalog. These t-bars should firm up your suspension making it better at DE's without being harsh on the highway.

http://www.sanderengineering.com/cat13.htm

KeithC2Turto

Steve and Rennsport Systems is very much an expert on these cars. See his web side on suspention where he recomends torsion bar sizes and shock combonationa.

http://www.rennsportsystems.com/1-e.html

911vet

I debate endlessly whether to continue to modify my Cabriolet for the track or put it back to stock, sell it, and find a dedicated track Coupe. But then I drive the Cab on a beautiful 80 degree day, and I wonder why I'd ever consider selling it.

So... I think 21/27 (or similar) t-bars are in my future. I'll upgrade the bushings and possibly a sway bar too. Looks like I've got next winter's project set.

Edward

Good call, Shannon. I was on that road of "track prepping" my 993 many years ago. Then realized that a more purpose-built car (if one has the luxury of being able to swing it, of which I am blessed to have) is the better way to go. So off came the bits and pieces to return my 993 to its former glory for dedicated commuter bliss, and I got an SC to be my dedicated Trackmeister.

As you already have found, the key is enjoying the car, not chasing upgrades. IMHO, 21/27s with your HDs are an excellent dual-purpose setup. As I had said, even better would be 21/28 (more neutral than a 27 rear which has more understeer). And the carrera sways are easy add on: cheap and plentiful on the used market, though the 21mm rear is a bit harder to find. Remember to do T-bars and bushes at once to minimize your cost for alignment/corner balance. At least the sways you could do at any time. Enjoy the cab ...yeah, those particular top-down days make me long for my Alfa Spider.