Wheel Bearing Care

In caring for wheel bearings, here are a few things to consider:

First, get the MB Chassis manual for your car so you can do the job right.

In my experience, the grease should be changed at the 90,000-mile service - I found my OEM grease was getting a little stiff by this mileage.

Use MB wheel bearing grease part no 001 989 23 51 10 or a good grade of lithium high temperature bearing grease - Kendall Blue comes to mind. Of course, buy new inner hub seals.

Pull a bearing cap and look at the grease - if it is stiff and wax-like, it is long past time for bearing re-pack.  Anyway, I do bearing grease at 90,000 miles interval (third 30,000-mile service) since MB now uses that new green high temp grease in all cars since 1986.

If your bearings are OK, but if the hubs are coming off anyway for rotor change, change bearing grease and install new seals.  Thoroughly clean the hub and bearings of ALL old grease.  DO NOT SPIN BEARINGS at high speed with air gun to dry them - be gentle with the air. Some mechanics like to have fun by making that high pitched whine using compressed air to spin and dry out cleaned bearings - it is really hard on the bearings to do that.

Next, pack bearings by hand with MB grease - save all excess - weigh out correct grams and pack it into hub in accordance with the MB chassis manual. There's a reason for the specified grams of grease for the bearings and inside the hub. Too much leads to overheating and too little starves the bearings of grease. The grams specified for inside the hub and the bearings just fills the hub cavity such that centrifugal force during rotation forces the grease outward in both directions to continually pressurize the bearings and keep them lubricated. It has been shown that the grease actually "circulates" inside the hub and through the bearings to keep them lubricated - which is why properly lubricated MB front wheel bearings can last so long, and that is the reason for that 45 grams of grease.

Use the rest of the grease to fill the hub cap. In this manner the inside seal stops the grease from leaving the bearing due to centrifugal force, and the cap, being full of grease, keeps the grease inside the hub/bearing area.

The 150-gram tube of MB grease will do both front wheels - about 60 grams per hub plus 30 grams for bearings - simply follow the MB factory chassis manual procedure.

Here's data from Technical Data Manual:

For a 150-gram tube of MB wheel bearing grease, here's how it breaks down:

(From TDM Section 33)

(All weights are approximate)

107, 124, 201.03 models: total 65 to 70 grams - 50 in the hub with bearing; 15 to 20 in the hub cap

116, 123, 126: total 60 grams - 45 grams in the hub; 15 grams in the hub cap

201.02/1: total 50 grams- 35 grams in hub; 15 grams in the hub cap

Be sure to maintain the specified charge. Suitably weigh entire charge prior to starting assembly of front wheel hub. Weigh quantity filled into hub. Fill roller cage of tapered roller bearing well with grease. Also provide roller faces with grease. Fill hub cap approximately to beaded rim.

Starting 12/88 all models use 150 gram tube - green grease part no. 001 989 23 51/10

DO NOT MIX GREASE TYPES - unexpected results may occur.

As to setting the free play, certainly the dial gauge method is preferred.

Here's how I did it ON A 107 before I bought a dial gauge: (N/A for 126 and those w/o washer)

Re-assemble the washer and adjust nut and tighten it about 25 to 30 Nm while spinning the wheel.  Back off the adjust nut just enough so that you can barely rotate the washer behind it by hand - that should be as close as you can do it by feel. Tighten the lock bolt and check that the washer can still be rotated by hand - it should be a little stiff, by movable.

If you replace the bearings and races, you should repeat the above after a few hundred miles to assure that adjustment is correct. I've always had to re-adjust after bearing race change, so plan on doing it anytime you replace bearings and races.