sway bar lengths? - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

koyv90 · 05-29-2013, 04:12 AM

Anyone know the difference that sway bar lengths will have on the frs/brz.
For example Cusco has 2 front sway bars; 16 and 22. What is the difference?

rx3 · 05-29-2013, 04:24 AM

That's the thickness in mm (not length).
22 mm has a much higher torsion stiffness than 16mm.
If they were solid rods the 22 mm rod would be 260% stiffer than the 16 mm rod.

ft_sjo · 05-29-2013, 04:25 AM

Quote:

Originally Posted by rx3

If they were solid rods the 22 mm rod would be 260% stiffer than the 16 mm rod.

I think your sums are a bit wrong there.

koyv90 · 05-29-2013, 04:36 AM

well dang i was ignorant. But what does the thickness have to do with handling?

rx3 · 05-29-2013, 04:39 AM

Quote:

Originally Posted by ft_sjo

I think your sums are a bit wrong there.

Torsional resistance is proportional to the diameter^3.

Example: Doubling the diameter of a rod doesn't just double its torsional stiffness but increases it by a factor of 8.

rx3 · 05-29-2013, 04:42 AM

Increasing the stiffness of the swaybar reduces body roll.

Also, increasing swaybar stiffness in the front increases under-steer.
And increasing swaybar stiffness in the rear increases over-steer.

koyv90 · 05-29-2013, 04:43 AM

Quote:

Originally Posted by rx3

Increasing the stiffness of the swaybar reduces body roll.

Also, increasing swaybar stiffness in the front increases under-steer.
And increasing swaybar stiffness in the rear increases over-steer.

what if you want to have the same settings as stock but stiffer sway bars?

rx3 · 05-29-2013, 04:45 AM

Then you would need to increase swaybar stiffness in the front and rear equally (replace front and rear sway bar).

Body roll will be reduced but the suspension will be stiffer and for instance have more difficulties to deal with potholes.

koyv90 · 05-29-2013, 04:45 AM

Quote:

Originally Posted by rx3

Then you would need to increase swaybar stiffness in the front and rear equally (replace front and rear sway bar).

cool thanks for the much needed info

!

ft_sjo · 05-29-2013, 05:40 AM

Quote:

Originally Posted by rx3

Torsional resistance is proportional to the diameter^3.

Example: Doubling the diameter of a rod doesn't just double its torsional stiffness but increases it by a factor of 8.

Incorrect, it's ^4 (for a solid bar).

A 22mm bar is approx 360% stiffer than 16mm one. Of course once you factor in your lever arms etc. that figure goes out the window, but for a straight bar it's correct.

rx3 · 05-29-2013, 06:44 AM

You're right. I mixed it up with torsional tension which is proportional to d^-3.

Xauterus · 05-30-2013, 02:25 AM

Isn't one of the Cusco sway bars tubular?

05-29-2013, 04:12 AM	#1
koyv90 Rocket Bunny FRS Join Date: Dec 2011 Drives: 2013 Rocket Bunny FRS Location: United States Posts: 447 Thanks: 15 Thanked 29 Times in 24 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	sway bar lengths? Anyone know the difference that sway bar lengths will have on the frs/brz. For example Cusco has 2 front sway bars; 16 and 22. What is the difference?

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05-29-2013, 04:24 AM	#2
rx3 Senior Member Join Date: Mar 2013 Drives: BRZ Location: Europe Posts: 350 Thanks: 53 Thanked 114 Times in 71 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	That's the thickness in mm (not length). 22 mm has a much higher torsion stiffness than 16mm. If they were solid rods the 22 mm rod would be 260% stiffer than the 16 mm rod.

05-29-2013, 04:36 AM	#4
koyv90 Rocket Bunny FRS Join Date: Dec 2011 Drives: 2013 Rocket Bunny FRS Location: United States Posts: 447 Thanks: 15 Thanked 29 Times in 24 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	well dang i was ignorant. But what does the thickness have to do with handling?

05-29-2013, 04:42 AM	#6
rx3 Senior Member Join Date: Mar 2013 Drives: BRZ Location: Europe Posts: 350 Thanks: 53 Thanked 114 Times in 71 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	Increasing the stiffness of the swaybar reduces body roll. Also, increasing swaybar stiffness in the front increases under-steer. And increasing swaybar stiffness in the rear increases over-steer.

05-29-2013, 04:45 AM	#8
rx3 Senior Member Join Date: Mar 2013 Drives: BRZ Location: Europe Posts: 350 Thanks: 53 Thanked 114 Times in 71 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	Then you would need to increase swaybar stiffness in the front and rear equally (replace front and rear sway bar). Body roll will be reduced but the suspension will be stiffer and for instance have more difficulties to deal with potholes.

05-29-2013, 06:44 AM	#11
rx3 Senior Member Join Date: Mar 2013 Drives: BRZ Location: Europe Posts: 350 Thanks: 53 Thanked 114 Times in 71 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	You're right. I mixed it up with torsional tension which is proportional to d^-3.

05-30-2013, 02:25 AM	#12
Xauterus Senior Member Join Date: Jun 2012 Drives: GTS 86 Galaxy Blue Location: Brisbane Australia Posts: 212 Thanks: 8 Thanked 35 Times in 26 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	Isn't one of the Cusco sway bars tubular?

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