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Benjamin Gradler
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15 July 2009 07:13 The rear hub for my 1959 Manx has been skimmed out to the point where actuating the brake lever does not move the shoes with good linings against the drum. Does this make the hub trash, or is it common to bore these out and shrink-fit a new lining? Thanks!
 
Ken McIntosh
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16 July 2009 10:11 The rear hub is originally 7.000" diameter and will stand a limited amount of machining oversize. The main problem is the already thin spigot the sprocket sits on becomes too thin to support the sprocket. The original brake shoes have a minimum of 1/4" thick linings and should always be machined to size after being assembled to the brake plate. A suitable mandrel and a large lathe are needed. The linings should be machined to the exact drum size after 0.040" (1mm) shims have been inserted between the cam and the shoe. If the linings do not clean up over 90% of their surface, put in more packers until they do. This process will ensure the radius of the shoes matches the drum exactly. The lining will not need any "bedding-in" If required, it is then possible to make a pair of packers of (up to) 2mm thick sheet steel, to permanently clip on to the shoe end plate. It is also possible to use this method to get a more favourable lever angle (less than 90 degrees with the rod) as the brake linings wear, as long as the brake rivet heads are still well clear of the drum. It is possible to fit a new cast iron brake liner into the hub, but this is complicated by the original liner being cast into the magnesium hub when manufactured.
 
Benjamin
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17 July 2009 10:12 Thanks Ken. I guess the shoe linings are worn much below 1/4". I put an inside micrometer in the rear drum and it is at 7.050 inches.

I guess I will have to send my shoes to you for re-lining and turning to that size?

Ken, you could write the definitive book on Manx Nortons. Is that in the works?
 


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