Seized front brake

[Sunny Jim]

What's happened here then:

Took my bike for an MOT this afternoon to find another customer there who'd had a 1200 '08 plate RT in the garage for some work done on it, which included new front pads and brake fluid flush front/rear. (It's fair to say right here that this bike was in pretty poor order).

The mechanic had literally pushed it from the garage 10yds into the yard awaiting customer to collect and, when the customer attempted to push it off the centre stand, he found the front wheel completely seized.

Reservoir level was as it should be and when the mechanic released fluid from the bleed nipples the wheel was able to move but was by no means free. After a few 'pumps' on the brake lever the wheel locked up again.

I saw them working on the reservoir nipple and again the wheel freed up a tad then seized again.

I couldn't hang around too long and missed the result.

So, what was it boys ?

Knackered piston in the reservoir
Knackered internals of the brake pipes
Knackered piston(s) in the calliper

Answers on a postcard please...

I've seen something like this on an 1100 once and it had to be recovered - something described as 'hydraulic lock' as I seem to recall.

Whatever it was it certainly left them baffled while I was there.

 

[bisbee]

Answer B

 

[Delboy777]

Id guess at B. Seen it before on cars.


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[Tractors are go]

B

What's the prize ?

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[patzx12]

brakes on any vehicle have to be stripped, inspected, cleaned and lubed one a year.
lots of stuff on youtube.
If the chrome surface on the pistons is worn i would junk the caliper.

 

[Bendy toy]

Master cylinder seals allow air past so make bleeding the brake very difficult.

Brake hoses with broken rubber linings can have a non return valve effect but its unlikely to happen on braided hoses.

If the cylinders are good, you can get new pistons and seals for a front calliper at about £60 from BMW. You cannot get just the seals for a front caliper.

Low miles callipers on eBay might be cheaper but corrosion is caused by time and storage not mileage.