T H E O L D G R E E N B E E M E R
RIDING A 1974 BMW R90/6 FLAT TWIN
BRAKE PERFORMANCE PART FOUR, CALIPER WEAR
If rattling goes on..., check the upper fork fingers for wear. Right on the spot where
the outher brake pad touches the upper finger. Over the years a cavity will form
and create extra free play for the brake pad in vertical direction, causing
again a lot of rattling when you ride the bike on uneven bumby roads.
Looking into the outer brake pad headquarter, minus dust seal.
Under braking the upper finger is the only support for the brake pad. The
center pin is only for horizontal centrering and is loosely fit in the brake
piston. An small O ring is used here to prevent rattling. The loose fit
is important to ensure the brake piston doesn't suffer, as the pad
likes to ride upward forcefully when it's pressed against the ro-
tating brake disk. The upper fork finger and the hinging pin
must to take that load, not the brake caliper's piston.
Over time the outher brake pad wears out the upper fork '' finger '', this is
not something that happens overnight but takes many years.
I am not a great fan of mechanical noises that shouldn't be there in the first
place, so I got to work and found a solution. Best would be: Fill the cavity,
by welding, not the easiests of tasks, so I went for this experiment, I just
covered the area with a thin 0,3 mm piece of yellow copper. I simply
used epoxy resin to glue it in place and it does the job just fine,
I have to see how it will last. I've rode several K's untill now.
No more rattle.
Continue to Brakes / Part five: Adjustment
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