View Single Post
      04-04-2013, 08:03 AM   #20
CSBM5's Avatar

Drives: 2011 M3, 2001 M5, etc
Join Date: Nov 2005
Location: Raleigh, NC

iTrader: (1)

Originally Posted by kaotik182 View Post
Check out Turner's sway bar comparison. Not sure it's worth it to swap out for a 6% stiffer bar. The Dinan is solid and bigger than H&R, so it will be stiffer than H&R.
I agree on it not being worth it to install the E93 bar. The H&R bar though is 42.52% stiffer and...

Here are some thoughts I posted in Richbot's autox thread about bar stiffness comparisons:

I tried to run some numbers on the stock versus various aftermarket options, but the stock bar is hollow, and without cutting one in half, I don't know the inside diameter. So I ran across a FAQ on Turner's web site on the H&R front bar where someone supposedly did the calculation for a 27mm solid H&R versus stock, and they claim that one is 1.425 times the stiffness of the stock one. I assume the moment arm is equivalent to the stock bar.

I'm looking at all of this since I ended up buying a Dinan 28mm solid front bar on sale for 40% off, and I'm wondering if this will prove to be too much front bar on street tires. Interestingly, Dinan adds this bar to their spring kit (i.e. moving from their stage 1 to stage 2) without changing the rear bar, so clearly a car with just their springs versus springs + front bar is going to be a good bit different, but they must feel it isn't too much bar. All that is an aside...

So if I assume Turner's H&R vs stock calcs are correct, then the Dinan 28mm bar (same moment arm as stock) should be: 1.4252 x (28^4 / 27^4) = 1.65. Hence it (Dinan bar) is 65% stiffer than the stock bar.

Direct link to post in Rich's autocross thread.

Current Stable:
2011.5 M3 sedan 6MT, Silverstone, slicktop
2001 M5 LeMans Blue/Silverstone
2006 330i 6MT Red/black, ZSP, Nav, etc
2007 328i wagon Silver/gray