Where difficulty is experienced, a suitable extractor should be used. Remember that the claw of the ex-tractor should bear on the cone, not the cage. Removal will be assisted if the shaft is first lubricated with oil.
If the outer race is to be removed, a suitable press or extractor must always be used.
IMPORTANT. On no account should a heavy blow or force of any kind be applied to one race to remove the other. Such a force will be transmitted through the rollers and cau3e indentations in the tracks, resulting in reduced bearing life and noisy running.
Cleaning
The bearing should be cleaned meticulously, using petrol, white spirit, or flushing oil. Chemical degreasers are not recommended. A good quality brush will assist in removing the worst of the foreign matter. The bearings should then be left to soak in clean solvent.
Bearings should under no circumstances be cleaned by blowing out with a high pressure air line after they have been degreased. This practice causes flats to develop where the rollers or balls skid on the casing and materially reduces the useful life of the bearings.
If new bearings are to be fitted, providing that they have been kept in their wrappings, no cleansing will be required.
Before assembly, all bearings should be liberally coated with grease, taking particular care to work the grease into the gap between the cage and the cone. If they are not to be fitted straight away, they should be kept in clean greaseproof paper.
Inspection
The general condition of a bearing may be checked to a certain extent by listening to the sound it produces when running. This may be accomplished by placing an ear against the handle of a screwdriver, the other end of which is firmly pressed against the bearing housing. If, for instance, a whistling sound is heard, lack of lubrica-tion is indicated; a rumbling noise is usually due to pitted bearings or dirt. Sometimes it is not practical to check the noise of a bearing when running, as in the case of the front hub bearings. Removal and careful inspection is then the only course to take. On inspection, certain types of defects such as cracks, etc., may become immediately evident. Other faults, however, may not be so obvious. Listed below are common faults of the latter type.
Flaking—On removing the bearings, the tracks of both races should be examined for flaking. Since the track of the cone is not normally visible, this track can
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Release the inlet hose (between the water valve and the element) at its highest point, dispel the air with the engine idling and re-tighten the hose clip. Top up the cooling system as required.only be checked by "feeling’ for any roughness when the cage and rollers are rotated slowly by hand. The bearing must be absolutely free from dirt since it is virtually impossible to feel the difference between flaking and grit. If flaking is apparent on either track the bearing must be renewed.
Wear—Precise measurement of wear on tapered roller bearings is not normally a practical service opera-tion. Reference should be made to the manufacturers of the bearing if, for special reasons, this should be deemed necessary. An assessment of how much wear has taken place can be made by examination of the rollers and races. A track with a dull grey "lapped"
appearance has suffered abrasive wear probably due to fine particles of dirt within the bearing. Experience will enable one to determine whether the wear is such that the bearing should be scrapped. In cases of doubt, renew. The cage should also be examined for signs of undue wear, cracking, or distortion. If such defects are discovered, the complete bearing must be renewed.
Discoloration—As a rule, discoloration indicates that the bearings have at one time become excessively hot, the cause of which should be investigated. Excessive pre-load and lack of or unsuitable lubrication are common causes. It should be remembered that a light brown stain may merely be an oil stain.
Refitting
Before refitting the bearing, the shaft and housing should be thoroughly cleaned, then smeared lightly with grease.
The cone of the cone assembly fitted on a revolving shaft must be a press fit. If the cones are loose enough to turn (" creep ") on the shaft, overheating and rapid wear of the seating will result. The only exception to this rule is on stationary shafts, such as hub shafts, where a fairly loose fit is permitted to allow for easy removal and proper adjustment. The cup must be a tight fit in its housing in all cases.
If the cup has been removed, a press with a suitable adaptor must be used to refit It. Ensure that the cup enters the housing squarely and that it is pressed right home against the abutment shoulder. The roller assembly can usually be fitted by hand, but if this proves impossible, It should be fitted with the aid of a press or a short length of metal tube whose bore diameter Is slightly greater than the diameter of the shaft, and whose outside diameter Is less than the Internal diameter of the cage. With the tube resting on the cone, the roller assembly may be driven into place by means of gentle hammer blows applied uniformly around the outer edge of the tube.
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