How to Rebuild Star Hubs
Posted by Panhead Jim on 12th Jul 2022
Prior to 1936, Harley-Davidson used a complicated wheel hub/brake design which used internal splines to mate the hub to the brake drum. Since a good portion of the hub was taken up by the splines, there was only room for one set of bearings inside the hub, which meant the second set of bearings had to be installed in the brake drum. Starting in 1936, Harley-Davidson improved upon this design with the introduction of the star hub which was produced until 1966. This new design eliminated the splines between the hub and brake drum, switching to design which allowed the brake drum to be bolted directly to the hub. The removal of the splines also allowed for all the bearings to be housed inside the hub, greatly simplifying the overall design. With a thirty-year production span (not to mention an even longer aftermarket production span) these style hubs are very common. Unlike modern hubs, they rely on twenty-six individual roller bearings which must be sized correctly for proper function. While complete rebuild kits are readily available, they contain only standard sized roller bearings which will not provide the correct tolerances if the hub has any wear. You can purchase replacement bearings separately in 0.0002” increments which allows you to get back to the original factory clearances as your hub wears over time. I’ll take you through the ins and outs of disassembly, proper measurement and reassembly so you can see how to correctly rebuild a set of star hubs.
- Flathead Screwdriver
- Split Ring Pliers
- 0” – 1” Micrometer
- 1” – 2” Micrometer
- 1 1/4” – 2 1/8” Telescoping Gauge
- Dial Caliper with an Adjustable Magnetic Base
- Blue Loctite
- Grease Gun loaded with Bearing Grease
Step 1: Remove the five screws which attach the thrust bearing outer cover to the hub using a flathead screwdriver.
Step 2: Lift off the thrust bearing outer cover and the thrust bearing housing being careful to keep the thrust washers intact inside the cover.
Step 3: Remove the bearing retainer and roller bearings.
Step 4: Flip the wheel over and use a pair of snap ring pliers to remove the outer roller bearing spring lock ring.
Step 5: Remove the retaining washer and cork grease retainer.
Step 6: Use a pair of snap ring pliers to remove the inner roller bearing spring lock ring.
Step 7: Remove the hub inner sleeve.
Step 8: Remove the bearing retainer, roller bearings and roller bearing washer. Note that the roller bearing washer often sticks to the bottom of the bearing retainer.
Inspection and Measurement
Step 9: Clean and layout parts in order to be reassembled. This is also a good time to bead blast and Parkerize the external parts to prevent rust.
Step 10: Using a telescoping gauge and a micrometer, carefully measure the inner diameter of the hub on both sides where the bearings come in contact with the hub. This measurement is critical, I recommend taking at least six measurements to make sure you are getting it exact. The measurement needs to be made to four decimal points (0.0001).
Step 11: Using a micrometer, carefully measure the outer diameter of the hub inner sleeve on both ends where the bearings come in contact with the hub inner sleeve. This measurement is critical, I recommend taking at least six measurements to make sure you are getting it exact. The measurement needs to be made to four decimal points (0.0001).
Step 12: Now for some basic math… First take the average of the six measurements you made for the hub inner diameter and the hub inner sleeve outer diameter. Subtract the average of the hub inner sleeve outer diameter from the average of the hub inner diameter. Take the result of that equation and subtract 0.0015 from it. This is your bearing clearance and is necessary so that there is room for grease to fit around your roller bearings. The result is the total diameter taken up by your bearings. Since there is one roller bearing on each side of the hub inner sleeve, you need to divide this number by two to get the size of each individual bearing. Repeat these steps using the measurements you made for the other end of the hub and hub inner sleeve. Note: You may need different sized bearings on each side.
Step 13: Thoroughly grease the brake side bearing retainer and roller bearings before inserting them back into the hub with the open side of the bearing retainer facing out. Once installed, rotate the bearings multiple times to ensure that the grease is well distributed.
Step 14: Apply a light coat of grease on the hub inner sleeve and insert it (narrow end first) through the brake side bearings.
Step 15: Install the inner roller bearing spring lock with a pair of split ring pliers.
Step 16: Install a new cork grease retainer, making sure it seats against the inner roller bearing spring lock. Note: The cork grease retainer will fit very tightly and you will no longer be able to turn the bearings easily once it is installed.
Step 17: Place the retaining washer on top of the cork grease retainer. When installed correctly, the retaining washer should be just below the outer roller bearing spring lock groove.
Step 18: Install the outer roller bearing spring lock using a pair of split ring pliers.
Step 19: Flip the wheel over and add some grease through the central grease fitting to verify it is functioning properly. Note: Do not overfill with grease as it will make it impossible to finish assembly.
Step 20: Apply a light layer of grease onto the bearing retainer thrust washer and insert into the hub.
Step 21: Thoroughly grease the bearing retainer and roller bearings before inserting them back into the hub with the open side of the bearing retainer facing out. Once installed, rotate the bearings multiple times to ensure that the grease is well distributed.
Step 22: Place a new thrust bearing housing gasket onto the hub.
Step 23: Lightly grease and place the thrust washer on the end of the hub inner sleeve.
Step 24: Lightly grease and sit the thrust bearing sleeve on top of the thrust washer.
Step 25: Lightly grease and install the second thrust washer onto the thrust bearing sleeve, aligning the “hump” with the thrust washer installed in step 23.
Step 26: Place the thrust bearing housing onto the hub, making sure that the “humps” on the thrust washers are lined up and fit underneath the grease fitting.
Step 27: Place the thrust bearing outer cover over the thrust bearing housing and secure with the five screws using a flathead screwdriver.
Step 28: Flip over the wheel and check the side play on the hub inner sleeve with a dial indicator. Mount the dial indicator so that it is reading on the brake side end of the hub inner sleeve. Press down on the hub inner sleeve until it reaches the end of its travel and set the dial indicator to zero. Press up on the hub inner sleeve until it reaches the end of its travel and write down the measurement. This is your total side play, if the side play does not fall between 0.005” and 0.007”, add necessary shims to remove excess play. Note: If you are just doing a rebuild, you should have the correct shims already, but unless you were the last one to rebuild the hub, it is always best to double check.
Step 29: Remove the thrust bearing cover and thrust bearing housing and install the appropriate number of shims needed to achieve the correct end play onto the thrust bearing sleeve.
Step 30: Reinstall the thrust bearing housing and place the cork grease retainer onto the end of the thrust bearing sleeve. If previously removed, reinstall the grease fitting on the thrust bearing housing.
Step 31: Reinstall the thrust bearing outer cover using a flat head screwdriver. Make sure to use blue Loctite on all the screws.
Step 32: Add grease to both grease fittings. When the hub is filled with grease, the excess grease should squirt out of the three holes on the thrust bearing sleeve to lubricate the axle. Grease should not come out of the ends of the hub if your cork grease retainers are installed correctly.
If you followed all the steps correctly, your star hub should now be rebuilt and ready to go back on the bike. When servicing wheel bearings, it is always good to take a test ride and to stop periodically to feel the hub to make sure it is not getting hot. A hot hub is a sign that your bearings are not properly lubricated and could seize up if you continue riding.