Joined: Nov 2006
Posts: 19,810
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From: NJ, NYC, LI
Bikes: 1940s Fothergill, 1959 Allegro Special, 1963? Claud Butler Olympic Sprint, Lambert 'Clubman', 1974 Fuji "the Ace", 1976 Holdsworth 650b conversion rando bike, 1983 Trek 720 tourer, 1984 Counterpoint Opus II, 1993 Basso Gap, 2010 Downtube 8h, and...
When you have the old crankset off and the new one not yet on, weigh them both. I'm curious exactly how much weight you'll save. When I compared the steel Williams crank on my Norman to a late 90's Shimano 105, I found the weight difference to be pretty negligible.
Replacing the cups is not an option; Raleigh used a proprietary 26 tpi thread while 24 tpi is standard. You can run a 24 tpi tap through there, but it will remove a lot more material than you want. Fortunately, as OFG said, there is no need to replace the cups.