 Torsion Bar orientation |
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| Kansas 914 |
 May 15 2011, 06:43 PM
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#1
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Advanced Member  Group: Members Posts: 2,999 Joined: 1-March 03 From: Durango, Colorado Member No.: 373 Region Association: Rocky Mountains 
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I understand that the bars should not be switched from one side to the other (pre-tensioned or something). When I pulled mine the other day they were stamped R and L but the one marked R was on the right side when standing in the front of the car looking back at it and not as oriented from the driver seat like everything else is.
Is this accurate? |
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Replies(1 - 6)
| CliffBraun |
May 15 2011, 07:59 PM
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#2
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Member Group: Members Posts: 252 Joined: 26-April 06 From: San Luis Obispo,ca Member No.: 5,933 Region Association: None |
So the theory behind this (as far as I can tell) goes: "so the metal gets used to twisting a certain direction and if you reverse this twisting it's more likely to fail." (Reading again i see a "pre tensioned" so my rant below may not have anything to do with this... I suspect it doesn't really matter that much though, I don't really know of any treatment to add hysteresis to the elastic portion of the load curve)
I've heard this a bunch before, and I always try to follow it because hey, why not? When I changed my axles I never knew which way the replacements had been installed and havn't had a problem in several autocrosses and a lot of spirited driving. Also none of my engineering textbooks mention anything even resembling this effect. I'd put it back the way you found it and not worry too much. |
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| Eric_Shea |
May 15 2011, 08:33 PM
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#3
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PMB Performance Group: Admin Posts: 19,275 Joined: 3-September 03 From: Salt Lake City, UT Member No.: 1,110 Region Association: Rocky Mountains  |
Fairly well documented in the factory manual stating that they are "pretensioned". They should be left and right from the drivers seat.
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| Dave_Darling |
May 16 2011, 01:27 AM
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#4
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914 Idiot Group: Members Posts: 14,990 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California
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Bruce Anderson was asked this question a number of years ago, about 911 t-bars specifically. His reply was that the new bars are not directional. When you use the bar on one side of the car, the bar is stressed in one direction. Reversing that stress can lead to early failure.
So the bars should be put back in where they came out of. --DD |
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| Kansas 914 |
May 16 2011, 06:43 AM
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#5
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Advanced Member Group: Members Posts: 2,999 Joined: 1-March 03 From: Durango, Colorado Member No.: 373 Region Association: Rocky Mountains
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Thanks for the replies - I swear mine came out reversed (R & L). I was being very conscious of this as I had read before I pulled them not to switch sides. My '72 is very unmolested (I have owned it since '78) but anything is possible. It is even possible I had a brain fade.
I will re-installed the "R" bar on the right side as seen from the driver's seat (and the L on the left). Cheers! |
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| Eric_Shea |
May 16 2011, 07:24 AM
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#6
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PMB Performance Group: Admin Posts: 19,275 Joined: 3-September 03 From: Salt Lake City, UT Member No.: 1,110 Region Association: Rocky Mountains |
Page from the FM...
Torsion_Bar_Installation.pdf ( 200.99k )
Number of downloads: 154CAUTION! Torsion bars are pretensioned during production... |
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| Kansas 914 |
May 16 2011, 07:39 AM
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#7
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Advanced Member Group: Members Posts: 2,999 Joined: 1-March 03 From: Durango, Colorado Member No.: 373 Region Association: Rocky Mountains
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QUOTE(Eric_Shea @ May 16 2011, 08:24 AM)  Page from the FM...
Torsion_Bar_Installation.pdf ( 200.99k )
Number of downloads: 154CAUTION! Torsion bars are pretensioned during production... Yep - agreed - I think I even read it in Haynes manual so I was being careful. But I will get them installed properly when the suspension comes back from powder coater. |
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