There is nothing wrong with the stock FC3S side seals; the side
seals see very little wear and stress when clearanced properly. 
You can usually resuse your old side seals; make sure to inspect
them for obvious signs of damage.  Try to keep the side seals
in their original positions when you put them back during the
rebuild.
Stock OEM side seals from Mazda are not cut down to
the proper length, so most of you have to cut them yourself. 
We like to clearance them on the tight side, 0.002" - 0.003" for
street engines. 
The best way we found to clearance side seals is it have a
used, bad rotor as a jig.  Find the biggest grind stone (on
a Dremel tool) that fits into the corner seal hole.  Lay
the bad rotor on it's side, and slip the brand new side seal into
a groove.  While keeping the grind stone turning in the corner
seal hole, slowly slide the side seal into the rotating grind stone
to shave the seal.  Be sure to do cutting in very small
increments and check clearances periodically in your good rotor,
preferaably in between the pair of installed corner seals in
the proper groove - the side seal grooves do not have
the same dimensions so you have to clearance every side seal
one-by-one.  Make sure to "deburr" the cut end of the side
seals, as to eliminate binding when inserting into the side seal
grooves.
Questions?  Comments?  Send email to: 
reted@fc3spro.com
03/13/2004