Ultimate Fix for Chasis Flex

What’s the Ultimate Fix for Chasis Flex?

Having the chasis welded by rabid English structural engineers

The rear cross member is made of folded metal. Chasis flex is what happens when this member is under heavy loads. The fix is to have Peter at Crayford Coachworks, in Marina Del Rey (310-577-9830) with years of experience reinforcing the Porsche GT2 race cars, go wild. They choose to seam and stich weld a new member into place that had been reinforced with steel tubes. They also seam and stich welded other areas of the frame. The frame of most cars such as BMW, Porsche and Mercedes have little spot welds when they come from the factory. These little welds do not last if you drive your vehicle hard and have a large object hit the underside of your vehicle.

Why I choose to fix my frame

If you find that you have to have the rear lower suspension replaced, you might as well take advantage of the opportunity and have them seam/stich weld the frame. They can also reinforce the rear cross members. I had a large object hit the underside of my vehicle. The Frame had cracks that started from hairline cracks into what you see to the right.

The strongest M Roadster Frame in the World!

Not happy with the way BMW attached the differential, they decided to reinforce that as well. Now I am ready to add the MechTech Turbo Charger!

Racing Dynamics Swaybars

Pros: Better handling, adjustable, solid design, more durable
Cons: Installation kit incomplete
Cost: $339

If you like to take exit ramps at speed or participate in Driver’s Schools and Autocrosses, larger Sway Bars will significantly improve the ‘turn-in’ of your Z3 and reduce understeer. The Racing Dynamics Swaybars sets include a 27mm front bar and a 17mm rear bar along with all of the mounting and reinforcement hardware necessary for the proper installation.

It took a lot of thinking to talk myself into trying this upgrade. After all, the Z3 handles better than any car I have ever been it (let alone driven). It was on the last day of the first Z3 reunion that I got a chance to talk to Mark Hughes who owns and drives the BMW sponsored Z3 race car. There were four or five of us talking to him when the conversation turned to what improvements he would suggest for the stock Z3. To make a long story short he stressed how well the Z3 was designed to be a performance car, but how the design was compensated to meet mass market approval. He said that a good first step would be thicker sway bars. He cautioned against stiffer springs and shocks if the Z3 was your everyday car, but said thicker sway bars would improve handling without compromising ride comfort.

Okay so that’s how I got talked into it, now that I have them I’m going to track down Mr. Hughes at the next reunion and buy him a beer, or two, or three. Just like he promised I haven’t been able to tell any loss of ride comfort, but put the Z3 into a hard turn and you’ll immediately notice how little the car leans. It will take you most of a Saturday to install the things, but it’s time well spent. If someday I upgrade from my 1.9 to a 2.8 these things will moving with me.

Sold By:

HMS Motorsport

www.hms-motorsport.com

(888) HMS-3BMW

Install Front Swaybar




This is an OCR/Scan of the original instructions.

FRONT & REAR SWAY BAR KIT

BMW Z3 6 CYL 97> / Z3 4 CYL 6/96> E36

PART # 196.81.36.013

READ INSTRUCTIONS THOROUGHLY BEFORE BEGINNING INSTALLATION.

2 POSITION ADJUSTABLE 27mm FRONT SWAY BAR

1. Jack the vehicle up and place on jack stands. DO NOT WORK UNDER THE VEHICLE WITHOUT USING JACK STANDS. I used a pair of jack stands on the left and right front jack points, so during installation of the front sway bars the Z3 was kind of doing a wheelie.

2. It is suggested, but not required, to remove both front wheels to ease installation. I did not find it necessary to remove the front wheels.

3. Disconnect the stock sway bar end links from the stock sway bar ends by slipping the open end of a 16mm combination wrench between the tire rod boot and sway bar. Then loosen the tie rod nut using a 17mm combination wrench. The picture on the right shows how I accomplished this task. Be somewhat gentle so you don’t damage or tear the rubber boot on the wheel side of the sway bar.

4. Remove the bushing clamps holding the sway bar to the chassis using a 10mm deep socket, and remove the stock sway bar and rubber bushings. After unbolting these clamps the sway bar will be free of the Z3.

Once the front sway bar was removed I compared it too the replacement front sway bar. As you can see the racing dynamics (green) bar is larger and ticker than the stock (black) bar. In this picture you can also compare the stock rubber bushings (black) to the urethane replacement bushings (blue).

5. Lubricate the insides of the urethane bushings with a lithium or moly based grease before installing on the bar in the stock location. NOTE: Failing to grease the bushings will cause them to squeak and wear prematurely. The grease didn’t come with the kit, so make sure you have some before you take your Z3 apart. I found some lithium grease at the local hardware store. Would have been nice if they could have included a small tube of in in the kit.

6. Secure the new bar to the chassis using the factory bushing clamps. but do not tighten the nuts. Because the urethane bushings do not compress as easily as the factory bushings, it may be helpful to spray the outside of the bushing with lubricant, then secure the clamp with a vise grip while aligning the holes. Make sure the bushing seats correctly in the clamp. I used a little of this lithium grease on the outside of the urethane bushings to make them slide in easier. The warning about not tightening the nuts is because they want the rod to move freely until you lower the car. Then once the bar is in it’s natural position under the weight of the Z3 you will tighten it.

7. Attach the sway bar ends to the stock sway bar end links. For more under steer, choose the sway bar: hole furthest from the end of the bar. For less under steer, choose the hole nearest to the end of the bar. Don’t get too tied up with the two different settings right now. You will enjoy feeling the effect of the two different settings on your own so I recommend you start on the loose/outside/hole nearest the end of the bar setting. I started on the loose setting, then went to the tight setting. I prefer the tight setting on the front sway bar.

8. Reinstall the front wheels and lower the vehicle so the full weight of the car is on the suspension. While checking for adequate clearances and proper bar centering, torque the bushing clamp to floorpan hardware to 20 ft/lbs. Okay here’s where is gets difficult. The instructions tell you to lower your Z3 then crawl under it and torque these nuts. Well folks most of us don’t fit under our Z3 without a little help. I ended up parking the Z3 at the end of the driveway where there is a slight drop off to the street. That way I could lay in the street and get under the Z3 to tighten the nuts.

9. Retorque all hardware after 500 miles. At 500 and again at 1000 miles I rechecked the torque and found that additional tightening was not needed. (but to be safe I’ll would still recommend checking.

Install Rear Swaybar


This is an OCR/Scan of the original instructions. Original instructions are in black my additional comments and suggestions are in red.

FRONT & REAR SWAY BAR KIT

BMW Z3 6 CYL 97> / Z3 4 CYL 6/96> E36

PART # 196.81.36.013

READ INSTRUCTIONS THOROUGHLY BEFORE BEGINNING INSTALLATION.

2 POSITION ADJUSTABLE 17mm REAR SWAY BAR

1. Jack the vehicle up and place on jack stands. DO NOT WORK UNDER THE VEHICLE WITHOUT USING JACK STANDS. I used a pair of jack stands on the left and right rear jack points, so during installation of the rear sway bars the Z3 was kind of standing on its head.

2. It is suggested, but not required, to remove both rear wheels and the spare tire to ease installation. Okay this time you definitely have to remove the tires and the spare tire.

3. Disconnect the stock sway bar end links from the lower control arms using two 13mm combination wrenches. It is not necessary to remove the links from the sway bar.The picture on the right shows how I accomplished this task. The vise grips were very handy since I really couldn’t get both hands into this area very easily.

4. Remove the bushing clamps holding the sway bar to the chassis using a 10mm deep socket. After unbolting these clamps the sway bar will be free of the Z3. However this sucker is going to be a pain in the ass to remove. It will be like trying to trying to solve a rubix cube. With the bends in the sway bar you’ll keep getting hung/stuck on the cage that holds the spare tire and other things. I ended up lowering the exhaust a little by removing one of the exhaust rubber hangers and that helped.

5. Remove the sway bar towards the passenger side of the vehicle noting its original position. If necessary the rear control arm can be supported with a jack while the lower shock bolt is removed to allow the shock to pivot clear as the bar is removed. Like I said in the previous step, this sway bar thing is really tough to get free of the Z3. The suggestion about “lower shock bolt is removed to allow the shock to pivot clear” kind of scared me because it sounded like they wanted me to mess with the shock and I didn’t want to do that. Don’t get too frustrated, like I said it’s like solving a rubix cube. Take your time and you will figure out how to get it out of there.

6. Install the new sway bar with the arms facing toward the front of the car. The middle of the bar should be bent downward and positioned above the differential housing. Getting the new bar is easier than getting the old bar out (thank god). By now you should be VERY familiar with how everything is positioned so this won’t be very difficult.

7. Lubricate the insides of the urethane bushings with a lithium or moly based grease before installing on the bar in the stock location. NOTE: failing to grease the bushings will cause them to squeak and wear prematurely. Same grease as on the front sway bar. Put a little dab on the outside too.

8. Secure the new bar to the chassis using the two factory bushing clamps, but do not tighten the nuts. Because the urethane bushings do not compress as easily as the factory bushings, it may be helpful to spray the outside of the bushing with lubricant, then secure the clamp with a vise grip while aligning the holes. Make sure the bushing seats correctly in the clamp.

Here’s where the shit hit the fan in my installation. If you look at the picture on the left you will notice two different brackets. The bracket on the left is the stock rear bracket off my October ’96 produced Z3. Trouble was the new urethane bushings were designed for a bracket like the one on the right (apparently BMW changed bracket designs sometime between October 1st 1996 and January 1st 1997). Problem was I didn’t have a bracket like the one on the right (BMW Part number 31-35-1-124-995), and this is not something that the local BMW dealer stocks. I called HMS and they in turn called Racing Dynamics, who located the correct brackets and shipped them too me. The Z3 remained in this stage for three days until the new brackets came. So be sure and take a look at your rear brackets before you start. If they look like the one on the left hold off installing the rear sway bar until you can locate a pair of brackets like the one on the right.

Once the new brackets arrived I still couldn’t get them to go over the protruding bolt until I bent them a little. The picture on the right shows how (using a hammer) I slightly bent them so the hole would be perpendicular with the protruding bolt. Even then I could just barely get the bolt to come through the hole, I ended up having to use vise grips to get the bracket down over the bolt (slightly messing up the threading on the bolt but not enough to hurt anything). Look back at the first picture on this step to see what I’m talking about.

9. The metal break lines mounted to the inside of the rear control arms must be moved downward to avoid interference with the end links. Rotate the clips that anchor the line to the arm so that the line runs under the screw that holds the clip to the arm. Or remove the the white plastic clip and metal stud from the control arm altogether. Brake line is secured at both ends of control arm by other clips. I tried to figure out a way of moving that white clip but was unsuccessful. I ended up removing the white plastic clip and metal stud. It made me nervous to do it but after seeing the finished result I’m okay with it.

10. Attach the sway bar ends to the control arms with the end link hardware provided (see diagram). For more oversteer, choose the sway bar hole furthest from the end of the bar. For less oversteer, choose the hole nearest to the end of the bar. Mine is on the loose setting. One of these days I’ll try the tight setting but after finally getting the rear sway bar installed I’m really not looking forward to getting back under there, removing the spare tire, and messing with it again. The adjustment would have to be made while the car is under its own weight (ie not on jack stands).

11. Reinstall the rear wheels and lower the vehicle so the full weight of the car is on the suspension. While checking for adequate clearances and proper bar centering, torque the busing clamp to chassis hardware to 16 ft/lbs and the rod end hardware to 20ft/lbs. 8mm end link bushing hardware should be torqued until the bushing just begins to bulge. OVERTIGHTENING WILL DAMAGE THE BUSHINGS. Once again this is a lot harder than it sounds. The instructions tell you to lower your Z3 then crawl under it and torque these nuts. Well folks most of us don’t fit under our Z3 without a little help. I ended up parking the Z3 at the end of the driveway where there is a slight drop off to the street. That way I could lay in the street and get under the Z3 to tighten the nuts.

12. Retorque all hardware after 500 miles. I must have originally torqued a little too much because after 500 miles I actually loosed the hardware a little.

Note: the drop link does not have to be perpendicular to the sway bar, nor does the sway bar need to be parallel to the ground for proper operation.