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happily, the 1970's era Gran Sport came with a 24TPI steerer and HS.
HS is a product called the Aletet (also spelt Alatet) from Brampton of Birmingham, England.
ball size is 5/32"; a full complement is 26 balls per race.
the outside diameter of the pressed-in head cups is 30.0mm.
the inside diameter for the fork crown race is 26.9mm, intended for a seat of 27.0mm diameter
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steps -
the first thing i would do would be to mill, or have milled, the ends of the head tube and the fork crown to make sure everything is square.
if the head cups are slightly loose in the head tube that is the fault of Raleigh and can be remedied by shimming. aluminum beverage can material is adequate, brass is better. when shimming one must take care that the shim material does not get between the race and its seat. shim material must all be in vertical plane.
when reassembling use all new grade 25 balls.
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Last edited by juvela; 07-07-20 at 12:37 PM.