Navarrette, Vance wrote:
> Don:
>
> This is just a swag, so don't panic. Any chance the pistons or
> seals are the
> wrong ones? There were Metric and English calipers, and I *presume* that
> the pistons
> likewise would be English and Metric. In any event, Moss lists two
> different pistons
> depending on when your car was commissioned. Likewise, the earlier
> English calipers
> had two different, non-interchangeable sets of seals. Another
> possibility is that
> the brakes were swapped at some point during the car's lifetime, and you
> now have
> metric instead of English, or vice versa. Looking at the letters at the
> end of the
> casting number on the calipers gives you the tip-off. English = B,
> Metric = BP.
> My car is later, and had the metric fittings. When I replaced my
> pistons, the were
> a firm, non-binding press fit by hand after I lubed the seals with DOT
> 5. Interestingly,
> my new pistons were black instead of steel colored. I presume this was
> some sort of
> passivation to prevent rust, but that is just a guess. My original
> pistons were
> rust colored =:-o
> You are correct, the pads will drag lightly on the rotors even
> when everything
> is new. Current disk brakes are specifically designed to "lift" the pads
> from the
> rotors when not in use, to save fuel.
>
> Cheers,
>
> Vance
>
So far as I know the only metric/english difference had to do with the brake
pipe threads. There are
two different caliper designs: the early 16P and later 16PB design. I think the
early 16PB were
English threads and the later were metric. So far as I know the only difference
between the 16P and
16PB was the design of the dust boot -- also affected the groove in the pistons.
It's a TR250 and I'm the original owner. The calipers are marked 16P. I have
the correct pistons and
dust boots. They match the old ones. I also have a set of 16PB pistons and dust
boots for my 71 TR6.
I am familiar with the differences. They look different.
Interestingly I cleaned up the original pistons. The base of the piston (first
end to enter the
caliper cylinder) was clean and not corroded. It is a very tight fit in both
the old caliper and the
rebuilt one. (I rebuilt one side at a time).
I can push the new pistons in the rebuilt calipers by hand, but I can't pull
them out or rotate them
by hand.
I know nothing about disk brakes, but I understand when you replace the pads
you use a big C clamp
to push the piston back into the caliper cylinder. Seems they must naturally be
a tight fit if you
have to use a C clamp. Why not just squeeze them back with your hands -- the
fit must be too tight
for that? When you replace pads can you push the piston back into the cylinder
by hand?
I believe the black pistons are anodized -- prevents rust.
Confused....
Don Malling
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