986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post - Sway-bar size...?

John V · 11-01-2007, 06:39 AM

The effective diameter of a tubular bar is calculated by raising the inner diameter and the outer diameter to the fourth power, then taking the fourth root of the difference between those two numbers.

The GT3 bar (26.7mm and 3.5mm wall thickness) on full soft is 67% stiffer than the standard 23.1mm bar. The 24mm solid bar should be 55% stiffer than the same bar.

Granted this assumes the 24mm solid Eibach bar has the same lever arms as the stock bars and this calculation neglects the bending effect of the lever arms, which could be significant with a tubular bar. The GT3 bar is bent differently than the stock bar (which is what allows it to be adjustable) but it does have the same length lever arms.

11-01-2007, 06:39 AM	#12
John V Registered User Join Date: Oct 2006 Location: MD Posts: 447	The effective diameter of a tubular bar is calculated by raising the inner diameter and the outer diameter to the fourth power, then taking the fourth root of the difference between those two numbers. The GT3 bar (26.7mm and 3.5mm wall thickness) on full soft is 67% stiffer than the standard 23.1mm bar. The 24mm solid bar should be 55% stiffer than the same bar. Granted this assumes the 24mm solid Eibach bar has the same lever arms as the stock bars and this calculation neglects the bending effect of the lever arms, which could be significant with a tubular bar. The GT3 bar is bent differently than the stock bar (which is what allows it to be adjustable) but it does have the same length lever arms. Last edited by John V; 11-01-2007 at 06:42 AM.