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Front Wheel Bearing Replacement
 
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Pelican Technical Article:

Front Wheel Bearing Replacement

Steve Vernon

Time:

4 hours4 hrs

Tab:

$20 to $120

Talent:

****

Tools:

Socket set, flathead screwdriver, hammer or press

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Bearing kit

Hot Tip:

Be careful when driving the old race out

Performance Gain:

Restore a tight feeling to the front end of your car.

Complementary Modification:

Replace brake pads and discs

If you are starting to hear a low rumbling sound from your front end or your W123 has over a 100,000 miles on it, you should inspect your front wheel bearings for replacement. As the mileage increases on the car, heat and lack of lubrication can cause the bearings to wear and possibly fail. Replacing the bearings isn't a difficult procedure, but it does involve a commitment to the job as you will be destroying some old parts in removal and will not be able to use the car until the new ones are installed. Make sure you have everything you need before you start.

Before you begin the job place the new races in the freezer, preferably over night if you can. Freezing the races will decrease the outer diameter and make installation into the hub easier. Note: Your hub appearance might differ slightly but the procedures are the same.

If you purchase a bearing kit it will come complete with everything you need including grease and new caliper bolts, otherwise you will have to source all the parts separately.
Figure 1

If you purchase a bearing kit it will come complete with everything you need including grease and new caliper bolts, otherwise you will have to source all the parts separately.

Begin by safely jacking up and supporting the vehicle and removing the front wheel.
Figure 2

Begin by safely jacking up and supporting the vehicle and removing the front wheel. Next, remove the caliper. Please see our article on jacking up and supporting your W123 along with removing your brake caliper.

Use a large set of pliers or a punch and remove the grease cap from the end of the spindle.
Figure 3

Use a large set of pliers or a punch and remove the grease cap from the end of the spindle.

Next use a 5mm Allen and loosen the pinch nut on the end of the spindle (red arrow).
Figure 4

Next use a 5mm Allen and loosen the pinch nut on the end of the spindle (red arrow).

Unscrew and remove the pinch nut from the end of the spindle.
Figure 5

Unscrew and remove the pinch nut from the end of the spindle.

Lightly pull the rotor a little forward and remove the outer bearing; if you end up pulling the rotor completely off make sure you catch the bearing so it doesn't hit the ground.
Figure 6

Lightly pull the rotor a little forward and remove the outer bearing; if you end up pulling the rotor completely off make sure you catch the bearing so it doesn't hit the ground.

Remove the hub and rotor from the spindle (red arrow).
Figure 7

Remove the hub and rotor from the spindle (red arrow). Inspect the spindle for any damage, this would include burs, gouges, scratches or heat damage. A note about grease. People tend to grease up the spindle; you do not need to grease the spindle as the bearing is designed with an inner race that sits on the spindle. The bearing should turn around the races and not the spindle.

You are going to need to remove the five 10mm Allen bolts that attach the rotor to the hub (red arrow).
Figure 8

You are going to need to remove the five 10mm Allen bolts that attach the rotor to the hub (red arrow).

The rotor is attached to the hub with a fair amount of torque and usually some blue Loctite.
Figure 9

The rotor is attached to the hub with a fair amount of torque and usually some blue Loctite. One trick to getting the bolts off is to hit them with some penetrating oil and then attach the hub to the wheel with three bolts. You can either lay the wheel on the floor and have a friend stand on it or position the wheel upright against a wall and break the bolts free that way.

With the bolts removed, the rotor will easily separate from the hub.
Figure 10

With the bolts removed, the rotor will easily separate from the hub.

With the wheel hub removed from the car, turn it over to the back side.
Figure 11

With the wheel hub removed from the car, turn it over to the back side. You'll see an oil seal pressed inside (red arrow). You'll first need to remove this seal to remove the inner bearing and race. Use a seal puller to remove the old oil seal from the wheel hub. If you don't have a seal puller you can use a large flat head screwdriver and something to give you leverage. It will take a fair amount of force to pry the old seal from the hub, so don't be afraid if the old seal deforms or bends as you pull it out. These are designed as one time use items and you will more than likely destroy it as comes out.

Remove the inner tapered bearing (red arrow).
Figure 12

Remove the inner tapered bearing (red arrow). Again there is enough grease in this hub to do several cars worth of bearing replacements (yellow arrow).

Clean the inside of the hub and check the condition of the races.
Figure 13

Clean the inside of the hub and check the condition of the races. They should both be clean and smooth with no signs of scoring, heat damage or grooves. If you are replacing the bearings you should change the races out as well. Use a hammer and punch and gently but firmly remove the old races (red arrow). Make sure you use care not to scratch or mar the inside of the hub. When installing the new race take it out of the freezer and press it back into place making sure the tapered side is facing correctly.

Take the new inner bearing race and place it in the bore on the rear of the hub.
Figure 14

Take the new inner bearing race and place it in the bore on the rear of the hub. Mercedes makes an expensive tool to seat the race but you should be able to use the old race to help seat it.

Another word about grease.
Figure 15

Another word about grease. The packet of grease that comes with the kit is all the grease you need to install the two bearings. Grease is only needed on the races and bearings. If you are going to use a bearing packer you will need more grease than this to load up the packer but you do not need to apply a greater volume of grease than is in this package.

Before installing the bearings into the wheel hub, it's necessary to pack them with grease.
Figure 16

Before installing the bearings into the wheel hub, it's necessary to pack them with grease. The idea here is to fill all the open spaces of the needle bearings. There are a couple different ways of doing this. You can buy a wheel bearing packer, which uses pressure to push the grease in from the open ends or if you are doing it by hand push grease in through the openings on the ends (red arrow) until grease comes out the other end, then rotate the bearing back and forth.

I highly recommend getting a bearing packer (yellow arrow).
Figure 17

I highly recommend getting a bearing packer (yellow arrow). Pelican Parts sells a few different ones; they are cheap, very effective at packing the bearings with grease and make what might be one of the messiest jobs in all of motorsports clean and easy.

Be sure to also put a coat of grease on the face of the bearing race (red arrow).
Figure 18

Be sure to also put a coat of grease on the face of the bearing race (red arrow). Once the bearing is packed, drop it in place on the hub. It's not a bad idea to hold the inner part of the needle bearing and then turn the hub to distribute more grease thru the bearing. Clean any grease that may be on the inner races of the bearings (red arrow) as you want the bearings to spin in the races not the races to spin on the spindles.

Clean up any grease that may have gotten on the outer surface of the hub where the oil seal fits and center the seal in the bore.
Figure 19

Clean up any grease that may have gotten on the outer surface of the hub where the oil seal fits and center the seal in the bore. Carefully tap the oil seal into place taking care that the seal does not get cocked in the bore on the wheel hub (red arrow). Keep tapping the seal until it bottoms out in the bore.

Attach the rotor and fit the wheel hub back over the spindle and push it back until the seal pops over the flange on the back of the spindle.
Figure 20

Attach the rotor and fit the wheel hub back over the spindle and push it back until the seal pops over the flange on the back of the spindle. Install the freshly packed outer bearing keeping in mind that the tapered section of the bearing fits into the race facing inward. You'll now need to adjust the wheel bearing. While rotating the disc and bearing hub tighten the locking nut in small increments until the rotor stops moving then back the nut off a 1/4 turn. Tighten the 5mm bolt on the end of the nut to spec. The last step is to put a little of the high temp grease on the inside of the dust cap and place it back onto the hub. Use a hammer to lightly tap the hub back into place.

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