Old 08-01-20, 06:42 AM
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bulgie
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Location: Seattle
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I know Shimano would make you proper tandem-crossover cranksets on demand, because we got them at Santana when I worked there, about 1978. By proper I mean the pedal holes were LH threaded for the two left side cranks and RH threaded on the right.

Note also the Shimano E-type disk brake, the worst disk brake ever. But that's a topic for another day.

We converted the right-rear cranks to triple there at Santana by drilling the spider arms at 86 mm BCD, and using Stronglight 99 rings.

(Sorry about the blurry pic, I was a terrible photographer in the '70s. Oh yeah I still am.) Maybe you can see how the spider arms were drilled through at 5 mm, then a 5 mm bolt was run through the unthreaded hole with the head of the bolt on the outside. The M5 bolts threaded into the chainring bolts in the granny ring, which were tapped M5 on the inside. Using 5 mm bolts there seemed risky to me -- Campy, Avocet/Ofmega and just about every other triple of this type used 6 mm bolts. Did the 5 mm bolts last? I don't know.

I moved to Seattle not long after that, so I don't know for sure, but I think Santana stopped doing the custom drilling -- those were probably put on only a very small number of tandems. Maybe because they broke in use? Just guessing. But here's one, that was owned by Mark Ritz.


Mark R will remember more of this story than I do, like how long the triplized D-A cranks lasted.

I still drill racing cranks (mostly Campy) at 86 mm for 99 rings now and then, did one last year. But I use Campy #818 bolts, which thread into the spider arms with an M6 thread, proven reliable.

Mark B in Seattle

Last edited by bulgie; 08-01-20 at 07:10 AM.
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