I was at the FL state TTs yesterday, and saw a couple of tandems using race wheels that (presumably) had 130mm spaced hubs. Since in at least one case they used the same wheelset for their solo TT rig, it had to be something easily changed. I'm working on restoring a mid 90s Burley Duet, which is supposed to have 140mm rear spacing. Hubs for this spacing seem to be uncommon..so seeing this got me thinking. Dangerous, I know.
I thought I might do this with a spare set of HED Deep wheels I have, by buying a longer axle and using spacer washers on each side. Standard road axles are ~141mm, to allow 5.5mm of axle engagement in each dropout. Nobody seems to sell a common 151mm axle for the 140mm spacing, but I can cut down a 158mm one, I suppose. The catch will be to get enough axle engagement on the tandem, but not have it protruding through the dropouts on the single bike. Sheldon Brown seemed to think that 1-2mm per side engagement is enough, so I'm hoping I can find a happy medium that'll fit both bikes.
Anybody done this and have advice to offer?