SWAYBAR Stiffness Conversion Chart - Focus Fanatics
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Old 01-28-2010, 09:11 PM   #1
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SWAYBAR Stiffness Conversion Chart

Want to change your swaybar? This is an approximate percentage (%) increase in torsion stifness for bars of the same shape, design and material specifications.



Choose original bar diameter from left column, then follow across to the right to determine % increase in stiffness required. Or, check % stiffness of a new bar size against the original.

For example, the Original bar has a diameter of 20mm You would like the new bar to be approximately 50% stiffer. Sighting across you would be about 46% stiffer with a 22mm bar.

This really illustrates the fact that swaybars gain stiffness to the 4th power as diameter increases. Take an SVT with an OE 21mm SVT RSB and throw on a 28mm Steeda "race" bar--and its 216% stiffer! Keep this in mind with respect to Focus LCAs and their propensity to fracture when stiff sways are combined with not-so-stiff springs.

The formula is : (larger bar/smaller bar)^4


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Old 01-28-2010, 10:27 PM   #2
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Thanks for posting that! I was thinking about the eibach sways but I actually feel it may be overkill for me at this point in time.
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Old 01-28-2010, 10:41 PM   #3
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Quote:
Originally Posted by Auto-X-ZTS View Post
Want to change your swaybar? This is an approximate percentage (%) increase in torsion stifness for bars of the same shape, design and material specifications.

<<pic deleted from quote to keep down clutter>>

Choose original bar diameter from left column, then follow across to the right to determine % increase in stiffness required. Or, check % stiffness of a new bar size against the original.

For example, the Original bar has a diameter of 20mm You would like the new bar to be approximately 50% stiffer. Sighting across you would be about 46% stiffer with a 22mm bar.

This really illustrates the fact that swaybars gain stiffness to the 4th power as diameter increases. Take an SVT with an OE 21mm SVT RSB and throw on a 28mm Steeda "race" bar--and its 216% stiffer! Keep this in mind with respect to Focus LCAs and their propensity to fracture when stiff sways are combined with not-so-stiff springs.

The formula is : (larger bar/smaller bar)^4
So when I subbed the stock 20MM bar with my 28.5MM Steeda bar, this was a 300% increase!!! .....

No wonder my car is so edgy, but I love it.

Good info.
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Last edited by tb1999; 01-28-2010 at 10:42 PM. Reason: deleted pic from quote
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Old 01-28-2010, 11:03 PM   #4
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Moderators......Please sticky this (at least the chart!!!!!) Thanks
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Old 01-28-2010, 11:03 PM   #5
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Great info thanks for posting! I will add this to the sticky up top.
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Old 01-28-2010, 11:09 PM   #6
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Great info but doesn't the stiffness of the bar also depend if it is hollow or not? I thought not all sway bars are created equal. Hollow ones have different stiffness than a solid right?
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Old 01-28-2010, 11:47 PM   #7
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Great info but doesn't the stiffness of the bar also depend if it is hollow or not? I thought not all sway bars are created equal. Hollow ones have different stiffness than a solid right?
Yes, you are correct. A hollow bar would be bigger in diameter than a soild bar of equivalent stiffness. What is saved is weight. I would assume the chart is for solid bars since the majority of bars sold are solid. But I'm willing to guess that the chart could be used for comparing hollow bar to hollow bar.
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Old 01-29-2010, 01:02 AM   #8
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^^ok cool just making sure the knowledge in my head is correct lol.
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Old 01-29-2010, 06:17 AM   #9
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Doesn't it also depend on the alloys of the metals in how stiff they are. I mean a 23mm titanium bar will be a lot stiffer than a 19 mm steel bar. LOL good chart just being a smart ass
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Old 01-29-2010, 07:12 AM   #10
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Quote:
Originally Posted by Geezer View Post
Yes, you are correct. A hollow bar would be bigger in diameter than a soild bar of equivalent stiffness. What is saved is weight. I would assume the chart is for solid bars since the majority of bars sold are solid. But I'm willing to guess that the chart could be used for comparing hollow bar to hollow bar.
It for comparing solid to solid or hollow to hollow--read the top line above the chart again...
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