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1 Poor Bedding-In
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Main Reasons:
Drum diameter is larger than lining radius. Drum wear.
Possible consequences:
If the wear pattern differs across the axle, vehicle pull can result; also excessive brake noise. Low efficiency.
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Main Reasons:
Lining radius is larger than actual drum diameter. Bedding-in period for the lining was too short.
Possible consequences:
Vehicle pull and exessive brake noise may occur. Low efficiency.
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Main Reasons:
Bedding-in period for the lining was too short. Drum wear.
Possible consequences:
Rapid lining wear. Vehicle pull and exessive brake noise may occur. Low efficiency.
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2 Steps in the lining surface
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Main Reasons:
There may be a step in the brake drum surface. General drum wear.
Possible consequences:
Rapid lining wear. Vehicle pull and exessive brake noise may occur. Low efficiency.
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3 Scarred lining surface
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Main Reasons:
Poor drum condition. Eg, heat crazing.
Possible consequences:
Rapid lining wear. If linings not 100% bedded-in. Low efficiency can result.
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4 Circumferential grooves
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Main Reasons:
Poor drum condition.
Possible consequences:
Vehicle pull and excessive brake noise may occur. Low efficiency.
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5 Grooved lining surface
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Main Reasons:
Small loose particles in the brake.
Possible consequences:
Very high lining and drum wear. Squeal..
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6 Deep irregular circumferential grooves
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Main Reasons:
Large particles loose in the brake. Very poor drum condition.
Possible consequences:
Very high lining and drum wear. Squeal.
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7 Uneven lining surface
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Main Reasons:
Wrongly adjusted or worn axle bearings.
Possible consequences:
Very high lining and drum wear. Squeal.
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8 Lining surface tapered
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Main Reasons:
Brake shoes misaligned with the brake drum.
Possible consequences:
The linings may lock onto the drum when braking from high speeds. Vehicle pull and excessive brake noise may occur. Low efficiency.
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9 Glazed lining surface
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 recommendsMain Reasons:
Low brake actuation. The linings are not working hard enough, probably dur to the incorrect adjustment of the braking mechanism, wrong size brake chambers or sticking brake shoes.
Possible consequences:
Rapid lining wear on another axle. Low efficiency. Squeal.
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10 Greasy lining surface
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Main Reasons:
Broken or improperly mounted hub oil seals. Excessive lubrication of the bearings or the braking mechanism.
Possible consequences:
Vehicle pull and excessive brake noise may occur. Low efficiency.
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11 Spray painted brake linings
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Main Reasons:
Careless spray painting.
Possible consequences:
Vehicle pull and excessive brake noise may occur. Low efficiency
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12 Dirt on the lining surface
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Main Reasons:
Dirt particles in the brake.
Possible consequences:
High lining and drum wear. Low efficiency. Vehicle pull and excessive brake noise may occur.
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13 Build up of dirt between lining & brake shoe
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Main Reasons:
Shoe radius out of line. Shoe platform not parallel. Lining rivited incorrectly (wrong rivets, riveted with too low force).
Possible consequences:
Cracks in the lining material. Loose linings. Squeal.
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14 Cracks around rivet holes
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Main Reasons:
Too heavy riviting force. Wrong shape of rivet heads. Brake shoes radius does not conform to lining radius. Brake shoe platform is not clean or even.
Possible consequences:
Lining and drum breakage. Brake over heating. Noise.
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15 Large fractures in lining surface
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Main Reasons:
Faults in brake mechanism. Sticking brake shoes (weak return springs). Excessive use of brakes at high speed. Overloaded vehicle. Too large air chambers.
Possible consequences:
High lining wear. Vehicle pull and excessive brake noise. Low efficiency.
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16 Burnt lining surface
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Main Reasons:
Faults in brake mechanism. Sticking brake shoes (weak return springs).
Possible consequences:
High lining wear. Vehicle pull and excessive brake noise. Low efficiency.
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