Henry Szeto has borrowed a CCM mountain bike from a
friend for the summer, and he is getting a lot of squeaking from the
rear wheel at the axle. I asked Alan Medcalf what Szeto should do. He replied:
"On a CCM or other inexpensive bike, the hubs will most likely have
serviceable ball bearings. These bearings require bicycle grease rather
than oil, which can migrate out of the bearings, leaving behind a gritty paste which
quickly clogs up the bearings. When this is dried out as well, the
bearings will rust and start squeaking...
"As a general rule of thumb, hub bearings ought to be overhauled
at least every other season for lightly-used bikes, and more often for bikes
used regularly or in dirty, muddy or rainy conditions. A commuter bike
may require hub overhauls two or three times a year.
"It’s easy to tell whether your hub bearings need overhauling. First, spin the wheel and ensure that it doesn’t have any wobble that
causes the rim to rub against the brake pads, or the tire against the frame. If this is happening, have your local bike shop repair the wheel first. It may just need truing, or there may be loose or broken spokes, or the rim may
be bent.
"If that’s not the problem, next grab the wheel at the top
and with the other hand on the fork (front) or seat tube or seat stays (rear),
try and wiggle the wheel back and forth sideways. If the hub seems loose
or 'knocks' against the axle, then the bearings need adjusting and may
as well be overhauled at the same time.
"If you try to spin the wheel and it spins with difficulty, or
slows down quickly instead of spinning on and on, then there’s lots of
friction in the hub, and it needs an overhaul. Another good test, with
the wheel off the bike, is to hold the wheel steady and rotate the axle with
your fingers. If it doesn’t feel silky smooth, if there’s
resistance or it feels gritty or hard to turn, the bearings need overhauling.
"Unless you know what you’re doing, a hub overhaul is a job
for the mechanic at your local bike shop. It involves disassembling the
hub, cleaning all the parts, packing with fresh bicycle grease, putting in new
balls, reassembling, and adjusting the bearing preload correctly. It’s important that the grease is formulated for bicycle
use. It’s lighter than automotive grease, and designed to work best
for the conditions found in cycling."