The
front wheel bearings of rear - drive cars and the rear wheel bearings
of front -drive cars should be checked whenever brake rotors are removed
for brake inspection. Brakes should be inspected every 20,000 Km or
whenever trouble is suspected. Clean the bearings in kerosene or solvent,
and examine them and the bearing races, which can be found within
the hub, for signs of pitting or other surface damage. Some minor
discoloration is normal. If the bearings are okay, repack them with
wheel bearing grease.To repack, place a substantial amount of grease
in the palm of one hand, cup your hand and push the side of the bearing
cage into your palm with your other hand . Make sure you force the
grease past the rollers. Continue until it begins to ooze out of the
top of the cage. Rotate the cage, pushing each uncoated area into
the grease. Make sure all rollers are covered completely.
Reinstall the bearings along with a new grease seal. Tighten
the hub nut to about 20 ft- lb. While rotating the wheel. Back the
nut off to release the load on the bearing and then bring it back
up to finger tight. Position the hub nut lock or the castle nut off
to release the load on the bearing and then bring it back up to finger
tight. Positon the hub nut lock or the castle nut slot so that it
aligns with the hole in the spindle and install the cotter pin. When
you're finished, there should be less than a noticeable amount of
end play (about 0.001 to 0.003 in.) and the wheel should spin freely.
In the new generation vehicles the wheel bearings are of a sealed
type and are not repairable the same would need to be replaced if
diagnosed faulty. If while the vehicle is travelling at about 40 to
50 kmph and a rumbling noise is heard, accelerate up and down the
intensity of the noise should increase or decrease respectively, in
such an instance mostly the wheel bearings are in need of replacement.
Check
tyre pressures every time you check oil, which means at every other
gas fill up. It's a good idea to keep your own tyre pressure gauge
in the
glove box, as you may find a wide discrepancy from one service
station gauge to the next. Keep an eye on your tyres for excessive
tread wear or unusual wear patterns. Excessive tread wear has occured
when less than 1/16-in. of tread-groove depth remains. Unusual wear
indicates incorrect inflation or wheel alignment problems. On bias-ply
tyres, wear that occurs only on both outer edges of the tread is a
sign of under inflation. Wear that occurs only in the centre of the
tread is a sign of over inflation. Radials though, due to their stiff
tread construction tend to retain shape over a wide range of inflation
pressures. Excessive camber, a wheel alignment adjustment, causes
one side of the tread to wear more than the other side.
Incorrect
wheel toe-in or toe- out causes the edges of the tread to feather.
Cupping, scalloping or bald spots are generally due to unbalanced
tyre and wheel assemblies and/or failure to rotate tyres.
Tyres
should be rotated every 10,000 Km, following a conventional cross
rotation plan .When a spare is included in the rotation, the left
front goes in the trunk, the spare goes on the right rear. The right
rear goes to the right front, the right front goes to the left rear,
and the left rear goes to the left front.
When
reinstalling wheels, tighten the lug nuts with a torque
wrench as illustrate here. You'll find specifications for
wheel bolt torque in your service manual. Torque each one
to half of the recommended figure the first time around,
then bring each to full torque. If you can't find a spec
in your service manual, torque 1/2- in. wheel lug nuts to
85 ft.-lb., torque I/i6- in. lug nuts to 70 ft.-lb
Check
your brakes at intervals of approximately 15,000 Km, unless prior
experience indicates that less frequent inspection will suffice. Begin
by looking for hydraulic fluid leaks at the master cylinder, calipers
wheel cylinders and at every junction or valve in the hydraulic system.
If you find hydraulic system problems, you may want to seek professional
help. At the very least, you should be equipped with a complete service
manual and any required tools before attempting to rebuild or replace
calipers, wheel cylinders or a master cylinder.The safe operation
of a car's brakes depends on the hydraulic system. If the hydraulic
system checks out okay, inspect disc brake pads and drum brake shoes
to make sure that the lining has not worn to the point where replacement
is necessary.
If
you know for sure that your disc pads are of the bonded type, rather
than of the riveted type, you might be able to inspect the lining
thickness through an inspection hole provided for this purpose in
the top of many calipers. If the pads are bonded, the thinnest section
of the friction material should be at least as thick as the pad backing
plate. If you don't know whether the pads are bonded or riveted, you'll
have to remove the caliper to check pad thickness. In most cases,
the job is not very difficult. Exceptions would include some rear
wheel disc brakes that incorporate parking brake mechanisms. Once
the calliper has been lifted off the rotor, check the friction material.
If it's of a non-metallic type, the pads must have more than I/i6
in. of material above the rivets. Semimetallic friction material should
be at least 1132 in. above the rivets. While you're at it, check the
rotors for excessive discoloration or any beat cracking. If the rotors
are damaged, they'll have to be machined or replaced and the pads
will have to be replaced. If everything looks okay and there's plenty
of friction material on the pads, you can go ahead and bolt it all
together.
To
check the linings of drum brake vehicles, the drums must be removed.
In most cases, the shoes will have to be retracted before the drums
will come off. To retract the shoes on most vehicles with self-adjusting
brakes, locate the adjusting slots, which are either in the backing
plate (most likely) or in the drum. The slots should be filled with
rubber insert plugs. On cars with slots with a very small screwdriver
and lift the self- adjusting lever away from the star wheel. Insert
a brake-adjusting tool in the slot alongside the screwdriver. Engage
the brake-adjusting tool in the star wheel and turn it to back off
the adjustment. Often you'll have to move the brake- tool handle upward
to retract the shoes. If the slots are in the drums, use a hook to
the hold the adjusting lever away from the star wheel for most applications.
Insert the brake tool next to the hook to turn the star wheel. Once
the shoes have been retracted, cover your mouth and nose.Inspect the
friction material and drums for visible damage. If the drums are scored,
they have to be replaced. Check the lining for the excessive wear.
Bond linings should be replaced when they have 1/16 in. or less of
friction material. Replace riveted linings when they wear to within
1/32 in. of the rivets.
We would suggest
that you leave the brake repair job to professionals as if not done
as required the same may prove fatal. Only inspection of the system
need be carried out by the home mechanic.
