1990 535i Anti-Sway Bar Upgrade

I went with the M-techs from Pacific BMW all the following info is from Brunos site! ;)

Pricing for M tech Nur Touring Sway bars, 2 weeks delivery from Germany
Price with BMWE34.net discount
2 x 31 35 1 131 622 Frt support bracket $3.42 each
2 x 31 35 1 134 582 Frt Link $21.30 each
2 x 31 35 2 226 334 Rubber mount $4.56 each
1 x 31 35 2 227 276 Frt Stabilizer bar $115.74
2 x 31 35 1 124 995 Rear support bracket $1.14 each
2 x 33 55 1 135 307 Rear link $18.36 each
2 x 33 55 2 227 240 Rubber mount $3.37 each
1 x 33 55 2 227 416 Rear Stabilizer bar $74.46
Total: $ 294.50 +s/h

To order just contact Pacific BMW at 800-909-7278 ask for mail order dept.

...marketed by Electrodyne. Can't recall what the diameters are. The word "beefy" comes to mind - recall them being thicker than the Mtech bars.

I upgraded my car in this order:

- new Dinan springs with Bilsteins with 15" rims
- added 16" wheels
- added RD Sways
- added front camber plates

The car rode quite nicely up until the sways. After the sways it got a little jiggly/nervious. I suspect it's the combo of stiffer suspenders + stiffer sways together that made it this way. Doesn't bang; just a little nervious. For a street car, I'd think you could be quite happy doing the + wheel setup and just the sways or just the suspenders. If I wasn't doing some tracking of the car, I'd likely pull my sways back off and go back to the stock ones.

I think the M5 bars are the way to go, the RD bars are good but the urethane bushings are a PITA

Thanks for the input, Jeff. Your words of caution are well-taken. I have stock 15" rims and recently installed new Bilsteins (HD, not Sport) and left the stock springs, but I'm very interested in the thicker sway bars because I live in the Sierra Nevada mountains (CA) and my day-to-day driving is on twisting, turning mountain and river canyon roads, which are lots of fun to drive with a well-handling car (though the chip & seal roads really eat up the tires).

I've checked into the sway bars and the RD ones seem to be the beefiest (27mm front; 19mm rear) vs. the Mtech bars (25mm front; 19mm or 20mm rear). Since the RD bars are adjustable, I figure I can tone the ride down if necessary.

Sound logical?

You likely have two issues going on here. #1 is body roll due to stock springs and and a high roll center of the car. #2 is sidewall flex in the 15" tires due to a tall side wall.

The body roll creates the impression of slower turn-in as it takes a while for the body to fully heal over on the now compressing springs. Shorter springs will lower the role center of the car and reduce the spring compression required for the car to "set". Sway bars mitigate body role by resisting spring compression on the outside of the car. A stiffer sway bar will increase the load on the outer tire. Not what you want if you have a lot of side wall flex because you'll get more.

A stiffer, shorter tire sidewall will improve your turn-in response by minimizing the tire deflection and rollover. As long as the body role doen't change the camber too much, a stiffer shorter tire will bite faster.

Soooooo....what does this all mean? Haha..that's the good question. It means it's all a system and you tweek on thing and it squirts out somewhere else.

Personally, I think I'd look for a stiffer set of springs first and some +1 or +2 tires before I did the sways. I have Dinan springs on the HD shocks. The stiffer springs will lower the car somewhat and resist role (ala the sways). The stiffer tires will bite faster and, combined with less spring compression, turn-in faster.

I'm not certain you'll get the results you want with big sways on 15" tires. It will certainly be better than what you have but I think you might get more bang for the buck with a spring upgrade first. Then some stiffer tires...16"s seem to be a nice compromise in ride, bite and price. 850 rims and 540 rims can be had pretty reasonable.

Just my 2 cents. Lot's of ways to get from point A to point B.

Anthony....Thanks for the tips. I called BMA and ordered the 25mm M5 front bar and the 20mm rear bar (from Euro M5T), plus all new links (front & back), nuts, bolts and the rubber mounts. The entire list of parts was $386 and change, including tax (plus about $20.00 for shipping). This was slightly less than the $396 RD package and I feel a little better about having the thicker rear bar (20mm vs. 19mm w/ RD package), per your suggestion. Your input was much appreciated!

Great advice, Jeff. I appreciate your 2 cents. I just got new tires and figured they'd take a beating with the new sways (which I just ordered). I'll expect the tires to wear out quickly and will be mindful of the side wall flex on the 15's by not being too agressive on the turns. Those 15's (tires) are hard to find anyway, at least up here in the mountains, so I'll be glad to get rid of them ASAP. In the mean time, I'll be shopping for 16's (rims and tires) and new springs. Thanks much for the input. Yes, it is a system and the tweeking is par for the course. I've printed your reply and will keep it handy.

Thanks for the words Jeff. The tall sidewall of the 15" tyre does create a lot of load with a stiff swaybar.

http://img372.imageshack.us/img372/5...6small23sz.jpg

This was the left front tyre after a hard session. I run my 27mm front bar on soft. I find on the hardest setting and with my stock rear swaybar, the car understeers too much. The car is still predicatable but it gives the impression of less grip. I find the front of the car very quick laterally, it made a vast improvment over the stock front bar.

Chunked it. It's dead.

Yeah, a stiff front bar and soft rear bar should give you more push. If you want more rotation, put that stiff bar in back and then let a little air out of the back tires. Oh..and hang out.

Kriss - you'd love camber plates. You're *really* love camber plates. Front plates.

Quote:

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Originally Posted by BigKriss

Thanks for the words Jeff. The tall sidewall of the 15" tyre does create a lot of load with a stiff swaybar.

http://img372.imageshack.us/img372/5...6small23sz.jpg

This was the left front tyre after a hard session. I run my 27mm front bar on soft. I find on the hardest setting and with my stock rear swaybar, the car understeers too much. The car is still predicatable but it gives the impression of less grip. I find the front of the car very quick laterally, it made a vast improvment over the stock front bar.

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I couldn't help myself but jump in. I won't get into the handling aspects as we all know that upgraded sways help handling.

I have driven all kinds of set-ups with different tires, different swaybar setttings, etc. I will say get what fits you. I bought the RDs because I wanted stiffer plus the adjustability. I do have R-compounds, then 17in summer Pilot Sports staggered, then 16in winter rubber. The adjustability of the sways allowed me to further dial in the sways to balance or alter the balance of the handling to different tires, suspensions, or different driving courses.

The drawbacks of upgraded sways are more energy transer to the other side when hitting bumps or potholes and if poly bushings, you have to regrease. I don't know if Dinan uses poly bushings in their kits.

I still like the RDs after more than 5 years driving of with them. I have used them with 3 different spring/shock combos. With and without camber plates. 15in, 16in, 17in wheels/tires.