All you ever wanted to know and more
The diameters are as follows: old front = 22 mm, M-tech = 26 mm
The rear: old = 15
mm, M-tech = 17 mm
The pure theoretical increase in stiffness is by the ratio of the new/old diameters to the 4th power. The actual increase may be less since not the entire bar gets deflected in torsion & the sides act as cantilevers plus there are losses due to the shape of the bars & support locations and compression of the rubber bushings, but the net effect is a night & day difference, you won't be disappointed. It will no longer corner like your Mom's Buick & will be very flat thru the turns with negligible sacrifice in ride quality, in fact I didn't notice any increase in harshness in ride when I put mine on.
A friend just ordered factory BMW M-Tech sways from www.irontoad.com & prices look very reasonable:
Front stabilizer $
Front bushings 7.28 ea
Rear stabilizer $
Rear bushings 5.04 ea
I paid $270 for
both sways from my local dealer with the 10% BMW CCA discount.
Besides the sways & the larger bushings, no additional
hardware is required to install them if the car is already
equipped with factory sways.
Here are the BMW
factory part numbers:
Front sway bar: 31
35 2 226 376
" " larger bushing: 31 35 2 226 365 (2 required, $9.10 ea at the dealer)
Rear sway bar: 33
55 2 226 377
" " larger bushing: 33 55 2 226 315 (2 required $6.30 ea at the dealer)
If you do end up buying them thru a BMW dealer, discuss shipping with the guys at the parts counter. Since they have to be shipped from Germany, there is a way for them to list it as a back-ordered item on their routine air-freight orders for their own in-house parts orders and you'll have them in a few days and they won't charge you shipping. Otherwise, they'll get put the special order list and will come by boat and you'll pay shipping and will have to wait 4 to 6 weeks for them to come over.
Installation is intuitive once you put the car up on jackstands & crawl under it. The front has just 2 bolts each on the bushing brackets, and one stud on each end of the bar at the end of the swaybar link rod. I wire-wheeled the crud out of the metal brackets after taking the old rubber bushings out & used a little liquid dishsoap to get the new one to mash into position. For the link rods on the ends, the back side of the stud has a flat on it for a thin crescent wrench to keep it from spinning. I re-used the "non-re-usable" lock nuts & put a little Loctite on them.
For the rear, I think I removed the left wheel & had to loosen & lower the exhaust to snake the bars out & in. The ends of the rear bar have a dogbone-like link rod which twists off. I put a little liquid dishsoap to twist it onto the new sway bar.
gale, 92 735i
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