The 25.5mm hollow bar is lighter than the comparably stiff 22mm solid bar - the h-sport website says the hollow bar is 5.5 lbs.
Texas Speedwerks (TSW) has a 19mm rear sway bar custom made for us by KW to our specifications. It has large urethane bushings with impregnated teflon mesh, which means they don't squeak and never need lubricated.
I think the confusion comes in by how the different vendors state their percentage increases and what size stock bar they compare to (16mm or 17mm). For example, I believe you need to reduce the MiniMadness numbers by 100% to compare to the H-Sport numbers. I believe they both compare to a 16mm bar. All things being equal (such as hole locations): The 22 solid bar is 2.57 times stiffer than a 16mm bar. The 25.5 hollow bar is 3.41 times stiffer than a 16mm bar. Thus the 25.5 hollow bar is much stiffer than a 22 solid bar (even stiffer than a 23mm bar).
Why do you think you need to subtract 100% from the MiniMadness numbers? From my experience, a 25.5mm hollow bar is about the same stiffness as a 22 or 23mm bar. This is from going through all the calculations...not just seat of the pants feel. But this was a different car and bar length makes a difference. Still I'd expect it to be pretty close. If they're the same stiffness, I'd still get the H-sport hollow bar to save a little weight. - Andrew
My calculations come up with a stiffness increase over a 16mm as: 2.57 times stiffer for a solid 22mm bar. 3.41 times stiffer for a hollow 25.5 mm bar. However, the hollow bar stiffness depends on the wall thinkness. I assumed a wall thickness of 3.1875 mm (1/8 dia) which would be a common wall thickness. Thus the calculated different between the 22 solid and 25.5 hollow is about 84%. MM states the rates at 228, 297, and 384. Hotchkis states the rates at 226, 294, and 383. Which looks to be about the same but I do not think they can be the same because they should be about 84% different. I could be wrong and when I asked various vendors specific questions about their staetd bar rates, I could not get direct answers.
Ahh, I see. To be honest when i did the calculations for the other car it might have made it = 23mm bar, which could be the difference. I like my bar rates in lbs/in. - Andrew
I've found that most go too far on the rear bar. the result is a car that can be too unstable for most drivers needs. I know I'll get flamed for this position, but I just call it as I see it. Camber plates and a 19mm bar is good for pretty much any car but a dedicated track car. Have at it! Matt
No flames here....I agree 100% and even most track cars do not need more than a 19mm bar. Size does matter, one can go too big.
+1 on the rear bar can be too stiff. From personnel experience, I can say that a 25.5 hollow bar is too stiff with camber plates for the street. However, I found the 25.5 hollow bar OK without camber plates. This time, I am going with camber plates and 19mm bar.