I am about to start building my Mk3 front wheel. I have two wheel types here. An assembled original, galvanised spoke wheel with a Dunlop MC275 rim, and the original wheel that was on the bike that had a crusty Dunlop MC288 rim, which was consequently rechromed (and looks much better for it).
there is a lot of chatter on AccessNorton about the two rim part numbers and what that means for differing spoke patterns. However, the original MC275 wheel (definitely a Mk3 hub) and the photos of my MC288 wheel before dismantling both appear to have the same spoke configuration.
Apparently the MC275 rim was used for pre Mk3 and early Mk3 production, later changing to the MC288 rim. My Mk3 (MC288) was registered in 1976, so that would fit.
The question is, why were there two rim part numbers when they both seem to be built up the same? Unless of course there is a subtle difference I have not spotted a far?
Correct, I discovered this…
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Correct, I discovered this and found no answers. The only thing I can think of is that the MK3 hub was going to be changed later in the life of the MK3, the spoke hole drillings are totally different to the hubs in use. I have never seen a later style hub anywhere, so not sure they even made it to manufacture. Also from the drawings there are 3 different lacing patterns, two I have seen and the third never seen. Both the rims with different numbers seem to have the same piercings.
To the wheel building, once laced correctly you can't get the tensioning wrong and not notice. If you check the original wheel spoke tension you might find that the tension on the spokes is quite low, scarily so. Most of the offset is pulled over by spokes on one side, the other spokes will tension as you do this, the majore trick is to get the wheel over as far as possible away from the offset as possible and spokes set correctly ready to pull the rime over to the correct offset.