Bearing Cup & Race Replacement

[BrianInAriz]

Proper procedure for the removal of neck bearings and bearing cups, without a press:

If the bearing cup is damaged or worn, skip to the bottom

Drive out the bearing cup(s) with a long drift slightly smaller than the outside diameter of the bearing cup boss (the part that’s in the neck). A 3/4” diameter threaded rod works well, and will be used later in these instructions.

Using long pliers, hold the bearing cup with the boss in the upwards position (race facing down), and using a propane torch (Plumber’s torch), heat the large diameter of the bearing cup evenly. The residual grease will smoke and possibly flame, and that’s ok. Try not to inhale it – it won’t get you high…

Gently tap the bearing cup on a firm to hard surface while holding it with the pliers – when you see that the race is moving out of the cup, it is hot enough. Use two screwdrivers to pop out the race (or use one screwdriver alternating sides – just make sure that it comes out fairly straight). If the cup is caked with gunk, you can quickly quench it under water – this will cause most of the junk to come off quite easily.

Place the new bearing races in the freezer for at least 4 hours, overnight is better though.

Use a Dremel tool (or similar) with small wire wheels to clean the inside and outside of the bearing cup. This is important – it needs to be CLEAN. If you want to paint them, you can, but do not get paint on the inside of the cup or the boss.

Now the fun part: You need a large, heavy washer with a 3/4” ID, about 1/8” thick, that slips inside the cup – you can get it at any hardware store (don’t use machine bushings). It needs to be close to the inside diameter of the cup. Place the new race in the bearing cup (taper facing you) until set by hand. Place the cup with the race facing down on the washer. Use a hammer and GENTLY tap the cup boss until the race is fully seated.

Now, using the 3/4” threaded rod (with large washers and nuts) as a press: Place the top bearing cup in the neck and insert the threaded rod with one washer and nut through the cup, and out the bottom. Be careful not to scratch the race in the process. Insert the bottom cup over the rod, into the neck. Place the other washer and nut on the rod. By tightening the two nuts, it will act as a press, and both bearing cups will go into the neck firmly. Remove the rod, and you’re all done – just remember to pack the bearings…

Okay, but how do you get the bottom bearing off of the steering stem, you ask. Well, that’s easy too. You will need your Dremel again, though. And your torch.

Use the Dremel with a heavy duty cut-off wheel and cut the outer bearing cage at the top. Use a screwdriver and pry up on it so the bottom of the cage is accessible. Cut it open, and remove the bearings. Now the hard part: Use the same cut-off wheel and make a cut through the inner race at a 10-15 degree angle from the stem (almost parallel to the stem). Don’t cut into the stem or the bottom plate. Now heat the inner race almost to the point it glows – focus the flame as much as possible on the race. Drive a large screwdriver vertically into the slot that you cut with a hammer. If the race is hot enough, it will fracture along that slot, and you will be able to remove it with 2 screwdrivers. Allow the stem to cool, and place it in the freezer like you did with the outer races (it will make driving on the new bearing a lot easier. Speaking of that, you can use a piece of black pipe that is longer than the stem, just slightly larger diameter to slip over it, to drive on the new (and packed) bearing. Work quickly so the stem stays frozen.



How to repair the bearing cup after it fell out, because it is worn and loose:

Well, if you have a friend that is a machinist, you are good to go. If not, break out the phone book and find one who will do small odd jobs, cheap.

Basically, you need that Dremel again. Use a fine grit sanding drum and GENTLY clean up the inside of the neck (where the boss is pressed into). Use calipers (digital or dial), and get a measurement all the way around, in different spots. You should have a fairly accurate and nominal measurement. There may be a few spots that are slightly larger, but use the dimension that is most prominent (the one you get the most, probably around 1.190). Write that on the bearing cup so you don’t forget it by the time you get to the machinist’s.

Have your machinist knurl the boss to 0.003 larger than the nominal dimension you wrote on the cup. Diamond knurling is best, but straight will work. WARNING: DO NOT REMOVE THE BEARING RACE PRIOR TO THIS BEING DONE – THE LATHE WILL CRUSH THE CUP AND YOU WILL NOT BE ABLE GET IN A NEW RACE. Unfortunately, this process of knurling will compress the cup, so it will be more difficult to remove the race.

To remove the race, use the Dremel with a heavy duty cut-off wheel. Make two 45 degree cuts towards each other (making a 90 degree “V”), from the top to the bottom of the race. Try not to go so deep that you cut into the cup, but as far through the race as possible. Use a screwdriver in one of the sides of the “V” and break out the triangle shaped piece. Heat the bearing cup as described above. It will most likely be more difficult to remove the race in any case. You may have to break the race when heated at the small part of the “V” to get it out, but it will work.

Finish everything as above, and you are good to go.

Hope this will help someone with that question, “What do I do now?”…