Nelson Riedel's write up at Buckeye clearly states that either style (early or
late) caliper piston
and dust boot can be used on any TR250 or TR6 caliper -- either 16P or 16BP. He
says there was no
change to the caliper casting other than the number (16P or 16BP)
A parts supplier is telling me that the later style piston and dust boot
requires a spring ring clip
(which is true) to attach the dust boot to the caliper and there's nothing to
attach it to on the
early 16P caliper.
I believe Nelson says the later style piston and dust boot were in an early 16P
caliper in the
example he rebuilds.
I don't have a 16BP caliper to compare with my TR250's 16P.
Is Nelson Correct?
Thanks,
Don Malling
Nelson's comments...
Caliper Variations: There were two changes in calipers during the TR250-TR6
manufacture. The first
change at commission number CC29930 (early 69?) was to the front of the piston
to accommodate
different style boot (the later boot had a spring clip to retain it to the
caliper) The photo at
the lower right shows the difference in the pistons. These are new stainless
steel pistons; the
later style is on the far right. The type number on the casting was changed
from TYPE 16P to TYPE
16BP when the piston style was changed. There was no change to the caliper
castings at this time
other than the number. The two style pistons are exactly the same size 2.125"
(2 1/8") diameter and
1.140" depth. The 16P caliper is from my '70 TR6 commission number CC53270.
The factory
equipment for that commission number was the Type 16PB. My guess is that
rebuilt calipers were
installed at some time and with the early castings and late pistons
Caliper variations Summary: Based on these data and checking the various
catalogues I conclude the
following:
Either piston type will fit in all TR250 & TR6 caliper castings.
Any style replacement caliper might be found on any year TR250-TR6.
When rebuilding the calipers, the important information is the style of pistons
because different
rebuild kits are required for the different style pistons.
Moss says all replacement calipers they sell are the TYPE 18 BP (later piston)
with standard (non
metric) threads. This matches the factory equipment for '70 through '72.
Some catalogs indicate one rebuild kit and replacement piston for TR250 through
'72 TR6 and another
kit and piston for after '72. This is an error; the change for the pistons
(and rebuild kits) was
at commission number CC29930 (early 69?).
It is necessary to know whether the calipers are metric or not if the input
pipe, bleed nipple,
attachment bolts, pad retaining pins or pads are being replaced. This change
was made at commission
number CC81079 (end of '72).
With that all said, I plan to use only the later style pistons whenever I have
to replace the
pistons because I think the later style boot is a more effective shield. Since
the pistons are the
same size I see no reason why the different version of calipers can't be mixed
on a car. However,
it could get very confusing with different rebuild kits for each side due to
different style pistons
or different type bolts and fittings due to metric or non-metric. I don't
think I'll mix calipers
on any of my TRs.
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