View Full Version : DIY: e39 Rear M5 sway bar install

10-12-2007, 08:08 PM
I'll tell ya right up front. My car started life as a non-sport 2003 530i. After 145,000 miles she cornered like a 1950's Buick. The srings and shocks were changed which did help a lot. She just needed a bit less roll in the corners.
So the options were Dinan, Eibach and someone else... Doesn't really matter who. They were all in excess of $450+ for their kits. Definatly that $$$ is not in the budget this close to X-Mas.
The rear M5 sway bar with new brakets bolts and bushing set me back $130 at the dealer. The bar looks to be at least 4mm thicker than the stock 530 bar.
I or anyone else will NOT take ANY responsibility if you screw up your car when following these directions in this easy DIY.
You will need:
1- To be sober, definatly sober.
2- an alignment when finished is recommended
3- good hydraulic jack ( or ramps )
4- 16mm cresent wrech
5- 16mm or 3/8 socket wrench
6- 13mm socket wrench
7- 13mm cresent wrench
8- jack stands ( if using jack )
9- wheel chucks
10- creeper ( not nessary but very useful )
11- M5 sway bar ( part# 33 55 2 229 136 ) and appropriate rubber bushings
12- Bently manual for added security
13- small needle nose plyers
Place wheel chucks around front wheels.
Jack up the car as the Bentley manual says, but doesn't say how. I used the differential which is not the correct place, but no one could say where the appropriate place was. I used an old thick towel to soften the jack. Ramps may be a viable alternative.
Place jack stands under jack pads. Pads are directly in front of rear wheels.
Lower car slowly onto stands. Be sure they are correctly on the pads. BE CAREFUL!!!
Here is the sway bar. It should look very similar to the new one. Visually compare them before unbolting anything.
Use 13mm wrench & 13 socket wrech the loosen / remove this bolt first.
The top of the braket is held in place via a tongue and groove system. Leave the bushings on the bar. Don not move / remove bushings from the bar. You will see why later.
Use 16mm socket and 16mm cresent wrench to rmove the sway bar link bolt.
Ah ha, the Bently manual doesn't tell you this! Place the cresent wrench as shown in the pic. It's hard to even see in person. The backside of the bolt has 2 flat spots to keep it from spinning.
All the nut & bolts undone. Time to wiggle to old sway bar from it's home.
The old & new.
Place new bushings in the same spot on the new bar, as they were located on the old bar.
Reassemble by following the steps in reverse.
Oh, the small needle nose plyers. If by some chance the sway bar link boots came off while using your 16mm cresent wrench, use the plyers to pop the boots back into place. It is hard to see, but the boot is held in place with a nipple and small rubber band system. Do not leave the link exposed.
Good Luck.
Now if someone is daring enough to try. There seems to be 2 different M package FRONT sway bars for the 6 cylinders, which can't use the M5 front sway. They seem to differ in size only. Here's the link for part numbers if you would like to give it a go http://www.realoem.com/bmw/showparts.do?model=DT63&mospid=47587&btnr=31_0257&hg=31&fg=10 It looks to be a jump in size from the standard 22.5mm to 24mm & 25mm.

10-13-2007, 05:06 AM
You did make sure you didnt put any preload on the bar during the install correct????

Dave Apker and the collies

Bruce N
10-13-2007, 09:19 AM
Doesn't that only apply to bars with adjustable end links?

Nice write up BTW!

10-16-2007, 02:15 PM
might wanna look into the TCDesign E39 swaybar bracket.......apparently some E39 M5 owners have had their stock brackets break!


10-16-2007, 04:17 PM
Thanks for the tip. It was mentioned somewhere else that they can break.

11-12-2007, 08:20 PM
I know it's hard to describe, but was the difference great? I read stiffening the rear is what you wanna start of doing to a BMW if you're looking for traction, so the rear sway bar would be a good start. I got the 528i sport and I'm not sure what difference the M5 bar would make. Or if I should check other sway bars. If and when I get that far :)

11-13-2007, 05:10 PM
Did a general search of your car http://www.realoem.com/bmw/showparts.do?model=DM63&mospid=47585&btnr=33_0517&hg=33&fg=45 and found stock rear sway was 14mm. The M5 I think is 17mm. Might want to double check thriugh the above web site. The swat bar upgrade is probably one of the best suspension things you can do to the car. With a little research you could save yourself a couple hundred $$$$ using BMW parts. The Dinan & Eibach are very, very similar in size.

I would be glad to assist if you plan to DIY.

11-13-2007, 08:52 PM
Yup!! A Stiffer and Thicker Anti-Sway bar will improve the Steering bias and over handling(Increased oversteer) of the car. It will increase stability in high speed cornering in the form of managing wheel lift. You may want to check the health of the end links often though as this will increase the load on the endlinks. I recommend getting beefier endlinks to support the change in anti-sway load.

The only other improvement I'd suggest is to find same camber plates to increase the negetive camber. A -1.6 degrees of camber will be civilized for street but you will not believe the handling change in and out of corners and Beltway exit ramps.

11-14-2007, 08:30 AM
Sway bars should be used to fine tune the handling of a car not to increase stability. That should be left to the springs and the shocks.
Using the sway bars to increase stability usually results in increased loads on the links and mounting tabs causing the tabs to rip out.

I cant remember right now if going to larger rear sway bar will increase or decrease understeer in a stock E39. However you do need know and you also need to drive the car after your proposed mod in wet parking lot and use it as skidpad so you know what will happen when traction decreases.
But I can read sheep!

Any suspension mods should be done after much research and thought.

If I was doing the mods on this car I would consider 540i OEM sport springs, or M5 OEM springs, compatible Bilstein shocks, all new bushings and adjustable antisway bars front and rear. Stock size or slightly larger but adjustability is the key here. You are using springs and shocks for better stability and handling.

Dave Apker and the collies.

11-14-2007, 09:27 AM
Any suspension mods should be done after much research and thought.
Dave Apker and the collies.


Understeer is when the front end of your vehicle travels less acutely than the intended angle, therefore the front wheels slip slightly around the turn and you must add more steering angle to compensate.

Oversteer is when the rear end of the vehicle takes a wider turning angle than the front end of the vehicle, and you must reduce steering angle to compensate.

Understeer and oversteer can be caused by a variety of factors: tire pressures, staggered tire sizes, suspension firmness (As Dave said...Springs, Shocks, etc), front vs. rear sway bar bias, front vs. rear. vs. all wheel drive, weight distribution, etc.

The E39s in stock form are set up for an understeer bias, presumably because they were designed with the high speeds of the autobahn in mind. The front sway bar is thicker than the rear. An increase in Rear sway bar stiffness will increase the oversteer. The simplified formula is to divide the thickness of the front bars with the thickness of the rear bars. That is the bias. IIRC, Lower Bias = Increased Oversteer.

A slight understeer is considered the safest and most stable setup for high speed, civilian highway driving.

11-14-2007, 09:32 AM
BTW JC5...the bottom of your car is cleaner than the interior of my daily driver. :icon_yike :biggrin:

11-14-2007, 10:55 AM
I prefer a car that can be driven using all pedals and the steering wheel.
That is what I miss most now that I dont have my E30325i. Miss being able touch the gas or brake to put the car in the correct attitude. Or just
give it a little gas to straighten out when the car was drifting through a corner in the snow. Or just a little more or less steering.

A prefer a car that is neutral and using the various inputs to make it either loose or push.

As 3 series have grown, become more portly and the increasing use of electronic nannies they have lost this ability.

Maybe is BMW builds the 1 series with the turbo 4 etc it might return.

Dave Apker and the collies

11-14-2007, 05:16 PM
BTW JC5...the bottom of your car is cleaner than the interior of my daily driver. :icon_yike :biggrin:

Thanks. We just got done some work over the past few months (including springs and shocks). It's a hell of a lot easier to work with when everthing is nice and clean.

Oh and she has close to 150,000 miles on her :icon_joy: not bad for an '03

11-14-2007, 06:59 PM
Any suspension mods should be done after much research and thought.

If I was doing the mods on this car I would consider 540i OEM sport springs, or M5 OEM springs

Be careful with this. The 540's an M5's are heavier than the six's. Those springs may have a different tolerances to them.

11-15-2007, 07:50 PM
Interesting read. most of what I know about suspension and handling is from that yellow BMW enthusiast book from BMWCCA and Roundel that I read through during a roadtrip in an RV to California and back. It's obviously not easy to get the car "better", as there will be compromises and several factors to weigh. Research is definitely a key!