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Posted by: i love porsche Mar 5 2007, 08:32 AM

what size torsion bars are available for our cars?

ive been thinking abou it..and how do the sized equate to the springrates...just looking for some info and reccomendations here

Posted by: Dr. Roger Mar 5 2007, 08:45 AM

i think there's almost no resources for 914 tortion bars. please someone chime in if i'm mistaken.

almost everything i found was for 911's, hence another reason to switch over to 5 lug.

Posted by: Joe Ricard Mar 5 2007, 09:01 AM

You can get torsion bars for 914/4 al day long. 21mm and 23mm also hollow bars. from smart racing.

I suggest you do some soul searching before up grading to stiffer bars. 19 to 21 is like doubling the spring rate. 23 is pretty much race only.

Posted by: Travis Neff Mar 5 2007, 09:18 AM

You can go 19mm if you swap for 911 A-arms and torsion bars. You can do 20mm from troutman, powerbars in 21, 22, 23

Posted by: Lou W Mar 5 2007, 09:34 AM

I just installed 21's on my car, I ordered them through Glenn Sager at Pelican Parts, they carry "Sway A Ways". Im running the stock 914-4 setup with 914-6 struts.


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Posted by: woobn8r Mar 5 2007, 09:54 AM

My '72 911 (street car) had 23mm up front and 26mm in the rear...firm but liveable

For the teener, it's tougher to guess the right size as you need to match to the rear spring rate...
Somewhere (on one of these boards) I saw a chart with spring rates corresponding to torsion bar size...if you can find that (I wish I'd printed it) your bar selection would be much easier....
please post what you find out!

Good luck,
Sean

Posted by: shelby/914 Mar 5 2007, 09:59 AM

Pelican has 17, 21 & 22mm solids and 21, 22 & 23mm hollow torsion bars. PO had left in the origional 17mm bars but changed the sway bar to a 22mm which gave it a horrible bouncy ride. Switched over to 21mm torsions and a 19mm sway bay. Rides and handles a lot better.

Posted by: Dave_Darling Mar 5 2007, 10:06 AM

The stiffness of a torsion bar (or a sway bar) goes up with the FOURTH POWER of the diameter. Which means when you go from the stock 17.9mm bar to the 21mm bar, you are getting (21^4 / 17.9^4) ~= 1.9 times as much spring rate.

The exact rate depends on the "lever arm" that the bar affects the suspension through.

--DD

Posted by: i love porsche Mar 5 2007, 10:10 AM

that is pretty much what im looking for...i should do a search

Dave, that is very helpful too..thank you!

Posted by: Aaron Cox Mar 5 2007, 10:17 AM

i run 22's with 225 lb springs in back....

very livable.

Posted by: John Mar 5 2007, 10:42 AM

I made a spreadsheet for determining equivalent front spring rate based on torsion bar sizes, but it is at home somewhere. It's not difficult to calculate if you know the distance from the center of the torsion bar to the center of the ball joint.

Let me know what that distance is and I'll make a new spreadsheet.

Posted by: Travis Neff Mar 5 2007, 10:47 AM

The smart racing products catalog has the charts for torsion bar size to lb sprin rate.

Posted by: John Mar 5 2007, 10:55 AM

That works as well.

Posted by: John Mar 5 2007, 03:34 PM

Here is a small table:

http://www.instant-g.com/Data/911CoilConv.html

There is also a PDF on Rennlist. I would post it here but I didn't get permission. Here is a link

http://tech.rennlist.com/911/pdf/torsionbars.PDF

I know it's 911 stuff, but our cars use 911 front suspensions (except the splines are different in number).