Coilovers: what to do with torsion-tube?

beepbeep · 09-14-2003, 12:44 AM

OK, if you want to convert your SC to coilovers (and install G50 gearbox that's quite long for example), what do you do with tube that torsion bar runs trough?

Do you cut it completly or just the part in the middle that obstructs transmission tunnel? Are you weaking the car by removing it?

This is pic borrowed from Rob Justice's thread to better explain what i'm talking about:

Reason i'm asking is beacuse Mattias removed torsion bars and we are going to purchase coilovers pretty soon, and it would be good to get rid of tube if possible, especially if we are to install G50 one day...

Thanx!

Alan.UK · 09-14-2003, 10:23 AM

I have also thought about fitting coil overs on an early car and a G50 and I think I would have cut out the centre section of the torsion bar, I would have then fabricated some brakets for extra support at the cut ends of the torsion bar.

HTH

Alan,UK

Jack Olsen · 09-14-2003, 10:31 AM

As I understand it, the tube does provide some structural strength. Here are shots of the diagonal reinforcements my shop added to my car, when we decided to move the engine further forward (and also eliminate the weight from the center of the tube(:

KTL · 09-14-2003, 11:01 AM

Here's a shot (scanned film picture) from the bay of my 87.

As you can see, the tube is still there between the pickup points for the suspension control arms. Looks like it's smushed a bit to fit the trans. in there? Would make sense because the t-bars on the G50's do not pass all the way thru the torsion bar tube like the earlier cars. That's why the outer ends of the G50 spring plate tubes stick out into the fender well so much more than the earlier 915 & 901 equipped cars.

See what I mean?

By the way, Rob's underbody isn't red enough. Looks like it could use another shot of Guards Red.

Wow!

Glasgow 911SC · Glasgow 911SC's Garage

He he Kevin. You've got a cheak! You could eat your dinner off the mechanics of your car.

MotoSook · 09-14-2003, 03:16 PM

Chris: Around here we call Kevin's car the "Unicorn." It's so clean and rarely out of the Enchanted Forest (his garage).

KTL · 09-15-2003, 05:16 AM

Forgive my ignorance. What's a cheak?

Thanks for the compliments.

Watch it Souk. The Unicorn's got no qualms about sticking you with it's horn if angered.................

It occasionally gets out and gallops. Put about 7000 miles on the 911 since i've owned it. That's more than Mark's. So who's is more the Unicorn?

Glasgow 911SC · Glasgow 911SC's Garage

Sorry. That should be cheek as in cheeky monkey.

Chuck Moreland · 09-15-2003, 08:27 AM

The inner trailing arm link puts a fair amount of load on the tube middle when cornering. Remove it and the remaining stubs would bend under those loads, tearing out of the chassis box sections.

The mods TRE did to Jack's car provide the needed suppoort. Note too they didn't cut away the tube center entirely, they just cut a deep notch.

beepbeep · 08:45 AM

OK, so cutting away most of middle section (going trough transmission-tunnel) w/o touching the rest would be sufficient?

Chuck Moreland · 09-15-2003, 09:23 AM

You need to put bracing in too. Like TRE did.

dad911 · 09-15-2003, 10:52 AM

Mine was triangulated to the roll cage, but I always felt that the tunnel should have been tied in better like TRE did. If you are going to install a G50 'one day' I wouldn't do this mod until then. It's too permanent, and you will have to fab G50 mounts at that time anyway.

Mr9146 · 09-15-2003, 12:53 PM

The tortion tubes are stressed members of the chassis. They provide lateral structural support. Jack's car is a good example of one way to stiffen the car after removing the tortion tubes. Just remember that removing the tortion tubes means that you need to compensate for their load-bearing functions in some other way.

IMHO, don't hack 'em until you need to. You can always remove them when you put the G-50 in ... but I see no reason in hacking 'em out until that time comes.

beepbeep · 09-15-2003, 01:01 PM

That's some good advice there. Nope, i'm not going to hack anything. Just checking with you guys before Mattias get's too Sawzall-happy

My understanding is that 930 box in SC body won't demand removal of torsion-tube. But car was going to be converted to coilovers so we're just checking if tube is still needed there, and the answer is yes.