K-Bike Wheel Bearing Replacement
By Jack Gilbert
While riding my '85 K100 I'd start to notice a slight droning noise similar to the noise you'd have from aggressive AT tires on a light truck. Since the bike was relatively new to me and I had not logged that many miles, I chose to log the noise in my things to check memory as I got more accustomed to the bike's general characteristics.
After logging a brisk 300 mile run south on Florida's I -95, again the noise started to infiltrate my senses, I started to try a highway diagnosis by shifting my weight right to left and paying strict attention to listen for any audible change. When the lean was hard to the driver's side the roar became more pronounced, which led me to a bearing diagnosis. At 39k showing on the odometer, surely the bearings were due for a replacement. I retired to my "Clymer" manual where I found the recommendation to purchase BMW tool #008 570 "bearing extractor". A quick call to "Bob's BMW," whom I use for all my parts, informed me of a purchase price of approximately $190.00! Time to fall back and punt!
Since I did not believe I'd change enough bearings to ever recover the price of the tool, I would need a reliable alternative method, better call Fred (of CYCLE RECYCLED). A quick comical dissertation on the ridiculous price of tools brought us both to the following method of replacement.
Before you even begin to start have these things ready:
Some sort of 2 x 4 wooden cradle to allow you to work on the wheel while it is laying on its side without putting pressure on the discs. Tire changing levers, rim protectors, tire valve tool, brass or aluminum dowel, two brand new wheel bearings to be placed in your freezer at least 2-3 hours before installation, and a socket in which to drive new bearings in with (should put pressure only on the outer rim while driving them in).
Of course you will also need your usual acumen of tools for the various jobs entwined here.
Now comes the good part! You will need an oven pre-heated to 400 degrees Fahrenheit
- Jack and secure bike, allowing enough clearance to remove front wheel.
- Remove one brake caliper, and hang from wire supporting weight do not let hang on brake hose!
- Remove wheel fastening hardware from forks as needed to remove wheel.
- Place wheel on some type of wooden cradle so that it is supported by the outer rim and not lying on the brake discs. I used an old truck pallet with the slats taken out of the middle to let the wheel cradle inside.
- Label both brake discs right & left. I used masking tape and magic marker on discs and wheel and marked valve position & rotation on wheel & tire.
- Remove both discs from wheel by loosening the four allen headed though bolts. Try and note position of heads (which side of wheel) on well run in units, as I believe these parts sort of settle in and may effect general balancing on wheel. Remove discs by gently nudging with mallet and wooden drift from other side - be careful not to drop and damage them when they dislodge suddenly.
- Remove tire from wheel, remove valve stem and any balancing weights.
Hope this helps you all out, I depend on you out there for your help too,
- Place wheel in pre-heated oven and carefully time ten minutes. That should be sufficient if your oven is operating within a 25 degree range, which most residential ovens I'm told fall. If hesitant use a separate oven temp gage.
- Remove wheel and gently drop the wheel evenly on wood cradle. That should be enough shock to have the bearing fall out of bottom side. You may turn wheel over and drive the remaining one out with an aluminum drift or brass dowel from the inside careful to notice spacer location and placement when removed.
- Now some accurate haste is needed before wheel cools, or you will have to re-heat to temp. Grab the bearings from your freezer and quickly tap into place using socket, making sure to drive new bearing evenly into recess against the machined shoulder in cast wheel. Flip wheel over and replace spacer as it was, and drive in final bearing! Quickly go to refrigerator and remove your favorite beverage! You deserve it!
- Every thing after this is academic, remember to properly re-torque all fasteners and add loctite wherever it calls for. You've saved $190.00 on the tool and whatever on labor and you've done the job well!
God bless you all,