torsion bars

Jeff Alton · 10-01-2003, 08:07 PM

I am going to upgrade the torsion bars on my 84. Car has koni sports and upgraded sway bars. I use it for everything- track days, autocross, daily driver. Is there an advantage to using hollow bars over solid ones in the real world? I do not mind spending the extra coin if the hollow bars will be noticably better.

Thanks for any suggestions, Jeff

89turbocabmike · 10-01-2003, 08:26 PM

I think most will agree there is little difference other than WOW factor. That being said, for the extra coin I went with 22/31 hollows. I like having that WOW factor and if they are better...., I'll take that too

island911 · 10-01-2003, 08:33 PM

What he said. . . .you're paying for a small weight savings.
(read: hollow bars will not be noticably better.)

Chuck Moreland · 10-01-2003, 09:07 PM

The hollow bars save a few pounds each, with the biggest savings in the thicker rear bars. Your looking at a 10-12 lbs savings all in. Definitely significant for a lightweight race car.

You will probably pay about $100 extra / axle to get hollow bars. So is it worth $200 to save 10-12 lbs? That's probably about mid-scale on the lbs saved/dollar basis.

Consider aluminum trailing arms save about the same weight, and go about $300 / pair used.

Fiberglass fenders save maybe 10 lbs each, cost about $350.

Fiberglass hood saves about 30 lbs, cost $350.

Racing bucket saves 25 lbs, cost $350 - $1000.

There are very few big-hitters when it comes to weight savings. It's the accumulation of 10 lbs here, 12 lbs there that make a lightweight. I put hollow bars on my car and consider it money well spent.

ChrisBennet · ChrisBennet's Garage

Not to mention, hollow bars are good for smuggling!

-Chris

Jeff Alton · 10-02-2003, 07:31 AM

Thanks for the input guys!!

Jeff

Dantilla · 10-02-2003, 09:56 AM

An engineer once explained to me why hollow bars are far superior to solids, for reasons beyond weight. I sure can't explain it like he could, but the bottom line is hollow is better.

island911 · 10-02-2003, 11:34 AM

I would like to hear that engineers "far superior to solids, for reasons beyond weight" explaination.

How about a hint?

In fact I would like to hear even "minutly superior to solids, for reasons beyond weight" explaination. . . .engineering explainations; not "better for smuggling" types, as was covered.

IROC · IROC's Garage

Quote:

Originally posted by Dantilla
An engineer once explained to me why hollow bars are far superior to solids, for reasons beyond weight. I sure can't explain it like he could, but the bottom line is hollow is better.

As an engineer, I'll make the statement that hollow bars aren't necessarily superior to solid bars - they're maybe just more efficient. I'm not buying into the "faster response times" and all that stuff.

When you look at a bar in torsion, the stresses in any given portion of the bar is a function of the load applied and the radial distance your arbitrary portion of the bar is from the center of the bar. As you can see, the center of the bar essentially sees no stress and even the portions of the bar *near* the center are seeing very little stress. The outer portions of the bar are doing all the work. Hollow bars simply take advantage of this by removing the portions of the bar that don't add much strength.

Driveshafts are hollow for the same reason.

Mike

Wil Ferch · 10-04-2003, 10:50 AM

I am a Mechanical Engineer and IROC is correct. Mainly weight issue.
---Wil Ferch

Randy Webb · 10-04-2003, 11:24 AM

I'm not a mech. engineer, but the above is a correct first order approx. as I understand it. The 2o effect would be that the stress curves will not be going thru empty air on the hollow bar but some would be going thru the intrior metal in the soldis.

I'm gonna get hollow as they are only $10 or so more and save wt. -- I see no other reason to do so.

BTW, avoid "gun-drilled" bars -- you want them made hollow not alter after the metal has cooled with a particular structure.