brakefluid_brakefluid是什么意思_brakefluid颜色(13)

Some drum brake designs use two single piston wheel cylinders, one for each brake shoe。 Wheel cylinder pistons are normally made of aluminum and fit close to the smooth bore of the wheel cylinder。 Brake fluid is contained in the wheel cylinder by the wheel cylinder cup。 The cup has a flared shape that will allow fluid pressure to force it tighter against the cylinder wall to ensure sealing action。 The end of the cylinder has a flexible boot that either fits into the end of the bore or is stretched over the end of the cylinder。

This boot prevents moisture and dirt from entering the cylinder bore。 Between the pistons of the wheel cylinder is a light spring。 This spring holds the wheel cylinder cups in alignment with the bore when the brakes are released and keeps slight pressure on the cup lip to maintain the seal。 Some wheel cylinders include cup expanders, a thin metal dish that fits into the inside of the cup to maintain sealing pressure on the cup lip。 Wheel cylinder problems are leaks, and frozen pistons。 Leaks can show up as, fluid dripping from the drum in severe cases, to damp spots near the bottom of the backing plate in more moderate cases to wet stains on the cylinder around the boots on cylinders that have just recently begun to leak。

Seized or frozen pistons can be discovered by careful brake pedal application by an assistant while the cylinder is watched for movement。 Care must be taken not to push the pedal so far down that the pistons are pushed out of the cylinder。 Another problem with some wheel cylinders is looseness at the backing plate。 If the cylinder clips into the backing plate it may move around and enlarge the backing plate hole。 While not a direct cylinder problem, it is the result of cylinder movement and once it begins will make itself worse in a short time。

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