Replacing the Upper & Lower Control Arms.
The E28 typically needs its upper thrust arms and lower controls arms replaced, somewhere around 35,000 to 45,000 miles of use. That’s been the case with mine, which is now getting its third set of replacements at 127,000 miles. You’ll know when it’s time for replacement, because you’ll start getting what feels like wheel/tire imbalance vibrations in the steering wheel and during times of light braking at about 52 MPH. The vibrations can occur at varaious times and appears to be very sensitive to vehicle load, such as with additional people in the car.
At first, I thought I had a potential wheel bolt torque problem, causing a small lateral run out error with the wheels. Tests below showed this really wasn’t the problem.
Lemforder Thrust (upper) Arms with 750i bushings and stock (lower) Control Arms.
Machined bushing face of the thrust arm with its larger bushing.
Various tools used to remove the ball-joint connection… only two are preferred.
Measuring wheel lateral runout with .001″ dial micrometer
Checking the lateral runout of the wheels, to see if they are in spec and what effect does wheel bolt torque have on wheel lateral run out, using both lightly oiled and dry thread bolts, tightened to 74 lbs-ft. BBS does not publish a spec for run out, so I used the “preferred” wheel run out spec most auto mfg.’s use which is “less than 0.020″. My front wheels measured 0.013″ and 0.015″.
Potential excessive wheel bolt torque was thought to be the cause of steering wheel vibration, when it first surfaced about a month ago. However, the difference between the torque actually applied, using lightly oiled and dry wheel bolts did not show any change in wheel lateral runout! Not with the wheels currently being used (E39 BBS style 29) and also with my earlier 19-spoke 390mm E24 TRX wheels, which I also tried this test on. The earlier steering wheel vibration was due to early signs of control arm bushing/ball joint failure?
The wheels were removed and the brake disc run out was checked on both wheels. Balo spec is not to exceed 0.006″ measuring at 1/4″ from the disc edge and the disc tightened to wheel bolt torque spec, or in our case 74lb-ft + or - 7lb-ft. One disc measured a maximum of 0.0015″ and the other measured 0.0025″, well within Balo spec. I’d also add that I tested again with dry and lightly oiled wheel bolts torqued to 74lb-ft and I saw no difference in the brake disc measurement run out figures.
Measuring disc “run out” of Balo front disc. 0.0015″, spec is 0.006″ maximum
Large flat washers are used under the head of the wheel bolts to approximate the contact area the wheel bolt hole pads make with the face of the brake disc hub. The washers also prevent flaring of the bolt hole edge on the face of the brake disc hub, which can rise above the surface of the hub face, creating a wheel run out problem.
PLEASE NOTE - All fastener torque settings are made with Snap-on TORQOMETER
TE series 2% accuracy torque wrenches, calibrated annually by my neighbor and
SnapOn salesman. $39 I-Beam type make believe torque wrenches are junk!
Installation of new front suspension components has been delayed, as the original attachment hardware (nuts and bolts) have been damaged! Some of it is clearly old and used, such as the locknuts and the bolts appear to have been subjected to a worn 6-point socket or 12-point socket on an air impact wrench. The flats are badly damaged and all hardware must be replaced! And I paid money for this level of work! More delay as only a few pieces are available locally, so back to Mr. Haygood for parts.
New hardware has arrived and work can resume. Cost was $34 including the stainless steel heat shield, not originally on this October 1982 build, nor was it installed by my BMW dealer after BMW advised its dealers to do so in 1984! The right Thrust arm bushing is cooked!
New hardware to replace damaged hardware.
Main front suspension component locations - CLICK TO ENLARGE
Special Note…
The three bolts at the base of the strut, which attaches the steering arm, should be locked with a heavy duty “Red” thread locker, such as Loctite 270 (BMW p/n 81229400086). FYI - Loctite 270 has been replaced by Loctite 271. Because a thread lock chemical has been used, the bolts will be difficult to break loose and remove, unless you apply heat to the bolts area, first. I use a Weller SP175 Marksman Mini Iron (175 watt 900 degrees) with very good results. Simply place the soldering iron tip on the bolt head for several minutes.The Bentley manual specifies that Loctite 270 should be used, but makes no mention of using heat to remove bolts locked with Loctite 270, or equivalent! DO NOT USE IMPACT tools to remove these, as you may break off the bolt head! Do not attempt to use a large breaker bar without first applying heat, or you’ll break the bolts.
Also, the heads of these bolts are not very tall, so make sure you use a 6-point socket that is in good shape and fits the bolt lands snugly and isn’t too loose. If the lands are damaged, as mine were, good luck! These are 10.8 hardness, 130,000 psi minimum yield strength bolts, but torque should not exceed 72.2 Nm or 53.2 lbs-ft. With “Red” thread locker applied, bolts should be tightened to 65 Nm (48 lbs-ft). A data sheet from Loctite about the “270″ and “271″ products is available here.
Lastly, several people have suggested that “Red” thread locker need not be used. That is sheer folly and a real danger to you or anyone who operates the vehicle!
steering_arm.jpg
Steering arm bolt locations.
Attempting to confirm control arm bushing problems
While the Bentley manual and others have suggested grabbing the control arms with large water pump plyers and checking for excessive movement of the control arm, this process doesn’t easily identify boarderline bushings, that seem fine when you’re all alone driving the vehicle, but exhibit shimmy under braking or at various speeds when additional people are in the car, sometimes just one additional person, such as was my case. Further, looking at the bushings may show nothing, unless they are in really bad shape, which I didn’t consider mine to be… and I couldn’t see anything wrong with them while on the car.
Still, with all the symptoms, especially the steering shimmy above 50 mph, I figured the vehicle probably really did need its third set of upper and lower control arms, after only 35,000 miles, even though water pump plyer tests and close visual inspection showed nothing apparent with the current arm’s bushings. It was only after I had removed the arms, that I could easily tell that they were trouble.
The primary culperts are the upper thrust arms, with the right one showing heavy wear (and heat stress), the left bushing looking better, but still with very deep major cracks or breaks and bushing separation on both sides, when placed in a large vise and moved as it would move in the vehicle. The bushing wear was there, very easy to see. A further test was to place both the old thrust arm and the new thrust arm with a 750i bushing, side-by-side in the bench vise and move them together to feel the difference. The removed thrust arm was clearly at the end of its service life, with its rather shocking amount of movement and significantly less resistance to movement, which couldn’t be felt while on the car and using the water pump plyers test! Based on my own observations of this, I would say the shimmy at braking, especially with several people in the car, is a very good indicator about probably needing upper thrust arms… and perhaps ball joints, too, as noted below.
In view of the bad condition these thrust arm bushings were found to be, once off the car, I’d suggest that the water pump plyers test is not a good test of bushing condition. It did not show my bushings to be in such a bad state!
New thrust arm with 750i bushing (left) and stock worn out 528e thrust arm (right).
Inspecting and comparing the used lower control arm with a new replacement control arm, placed side-by-side in the bench vice (shown below), showed no detectable differences, other than the old arm bushing feeling a tiny bit less rigid compared to the new arm bushing, while moving them both at the same time. Not very scientific, but the lower arms certainly had less of a difference then the upper thrust arm bushings clearly showed. The cracking visible in the rubber bushing surface is surface cracking with no depth. Not the same as the upper thrust arm cracks or breaks in the rubber bushings which are very deep, perhaps penetrating the full depth of the rubber.
control_arm.jpg
New lower control arm (left) and old lower arm (right)
There was, however, a bad cut in the ball joint boot on this control arm (below) that was not visible while on the car, as it was next to the brake backing plate. It had allowed some of the grease to escape and dirt and water to get in over time and the operation of this ball joint is sloppy and notchy, suggesting bad wear on the joints surfaces.
The right front tie rod also had a sloppy ball joint and mistreated tube and clamps, both were over tightened and one clamp bolt head broke off during my removal. Use of Vise Grips to rotate the tie rod tube, without ever fixing the problem (replacing the rusted and jammed tie rod) shows unacceptable judgement and workmanship on the part of the technician who last worked on this! The left tie rod was only slightly less damaged, but was totally frozen and could not be adjusted (it was not serviced) but both ball joints were sound.
So, while the lower control arm bushing appeared to still be performing, the loss of lubricant and wear to the ball joint and another sloppy ball joint on the right tie rod, certainly required that these be replaced. It probably contributed to the shimmy problem, too, if only in a small way, but was there none the less.
With respect to the issues of damaged attachment hardware, requiring replacement and unacceptable workmanship by people employed by BMW dealers or so called qualified independent servicing shops, I’ll certainly be conducting my own inspection of completed work, in the future, before my vehicle leaves such facilities. I’d suggest others do the same, given the results I’ve seen on other BMW’s I’ve looked at or worked on.
Removed tie rod with sloppy ball joint and badly treated shaft. Frozen, can’t be adjusted!
Assembly
Aside from taking this opportunity to clean up the area, with the suspension components out of the way, don’t forget to chase the threads in the base of the struts, where the steering arms will be reattached using red thread locker.
You may have replacement parts with different attachment configurations, such as below, where one ball joint uses a castle nut and cotter pin to lock the nut, while the other uses a nut with a nylon insert to lock it. You can see the difference in the shafts. Never use a nylon self locking nut on a shaft designed for a castle nut!
Threaded shaft for castle nut (left) shaft for nylon insert locking nut (right)
When replacing parts that use a castle nut and cotter pin attachment, give thought to the position of the cotter pin to permit future work and easy removal and replacement. Below, the left tie rod arm ball joint is attached to the center link with the ball joint cotter pin hole positioned so that the cotter pin can easily be accessed from below, since its head is at the bottom of the assembly. Tapping on the rear edge of the ball joint housing (not on the large cap) with a plastic mallet, will help seat the tapered shaft, so that it won’t rotate while torquing down the shaft nut. Position the other castle nut/cotter pin ball joint ends in the same way, allowing good future access.
You’ll appreciate this little attention to assembly detail, when it comes time for parts renewal… as will the next person who works on it, if you don’t. The white stuff on the ball joint threads is not Lithium… the new ball joints were removed from the tubes, cleaned and lubed with DuPont Krytox grease! Water proof and vastly superior protection.
I’ve had a number of E-mails indicating that trying to find DuPont Krytox grease in a small quantity has been very difficult, if not impossible to find. Indeed, it is difficult to find, but the Loctite product is identical (so I am told by DuPont) and is readily available from major sources, such as R.S. Hughes Co., Inc. in a 3 Oz. tube for less than $10. Let me know if you have a good DuPont source.
Left tie rod attachment to center link next to steering pitman arm ball joint
Parts ready for installation on the car.
I use small box tops to contain the hardware that is going to be installed. You can see that I’ve already attached the lower Control arms to the steering arms (BMW calls them “tie rod levers”, Bentley calls them “steering knuckles”) and have properly torqued the ball joint nut. I’ve found it easier to just install the lower Control arm and not the Thrust arm at this point, as it makes it easier to position the steering arm back on the bottom of the strut. With both arms attached to the steering arm, it gets a bit unwieldy. Besides, the Thrust arm is easy to attach to the steering arm once the steering arm is installed.
As I indicated earlier, the lack of a heat shield on the right side Thrust arm resulted in the bushing being cooked, to the extent that comparing the two Thrust arms mounted side-by-side in a vice, showed the cooked bushing to have much less resistance to movement. Upon close inspection, it appears a heat shield was never mounted at the factory, as there are no marks on the mounting area or the attached flat nuts. It simply was never installed.
Heat shield installed on right side Thrust arm bushing mount.
Heat shield attachment.
If you have an early model E28, I’d certainly check to see if the heat shield is in place, as it may never have been installed, or not replaced during Thrust arm replacement or exhaust down pipe work. It clearly is needed, given what the heat did to my stock Thrust arm bushing. Without a heat shield, would the plastic in the larger 750 bushing start to deform? Become soft or brittle and fail? I only discovered this heat shield, after seeing it in the front axel parts breakdown, while identifying replacement attachment hardware to order from Steve Haygood.
While you’re under the car, you might want to clean off the steering box center index, perhaps adding a bit of white paint to make the index marks much easier to see. The Bentley manual picture of this is confusing, as it looks like the universal joint seam is the reference point, not the collar with the raised mark on it. A few other tips follow…
Convert an old 5/8-inch wrench for swaybar link use, by grinding it down.
Update August 25, 2006 -
Finally finished and all back together, with the bushing bolts torqued down with the specified vehicle weight pre-loading in place. Certainly worth all the effort, to get the steering and front suspension back to very tight and responsive condition, probably even more so than stock was, with the use of 750 bushings in the Thrust arms. Yes, the steering shimmy, braking shimmy and the other associated problems are gone! Let’s hope these 750 bushings last a bit longer.
Finished! View of the right front underside, completed.
150lbs of sand bags in each seat and rear center to preload for alignment. This is CRITICAL!
alignment.jpg
Friend and Master Mech., Roger Davis of VIP Auto setting up for computer alignment.
Final thoughts…
I like the feel of the 750i bushings, a bit stiffer and what sounds perhaps a bit more noisy, but not as noisy as the urethane bushings I once tried, nor as harsh. In fact, several E28 owners, most recently Philo, talking about his E28 M5 said “I have Grunts bushings in there now (third set) and I think I’m going to go with the 750s this time. The Grunts, or urethane bushings in general, develop a memory and become constantly sloppy. The reason I went to urethane was because I had a bad experience with the 750s.., I had the green plastic inserts crack and fall out which then made the front end plain dangerous!”
Several others have commented to me on their urethane bushings becoming sloppy, too, as well as being more noisy than stock BMW bushings. I hope that these current generation 750i bushings in the E28 arms remain stable and provide good service life.
The bottom line, now with over 500 miles of testing at speed and on west Virginia twisties, is that the overal improvement in my steering and front suspension is quite evident, making the car feel much more precise and controlled. Road irregularities now have little effect and moderate stuff does not require small steering corrections, as was necessary before the work. The car continues to feel stiffer in fast corners, especially with additional people in the car. Several people have suggested that the larger bushings are probably not responsible for the increased roll resistance, but I think they are in error… nothing else changed to explain this performance observation.
Surprising how much precision and performance can drain away over time and we really don’t notice it, until it is renewed back with fresh components, bringing back what BMW intended. It brings a smile to my old face!
And always, special thanks to my wife, Shelley, who supports my desire to do these projects, lends a hand when she can, loves the car and is a great co-pilot during road testing after the work is completed. Over the years she has developed a keen sense about what the car is doing, or not doing. All male wrenchers should be so fortunate.