Markeologist

Do any of you who have Shimano catalogs from the mid to late 70s see Dura Ace tandem cranksets offered? If so, could you paste in an image in a reply? Also, its my understanding that there were no triple cranksets available for First Gen Dura Ace, can you confirm? Thanks....this is in regards to my recently purchased 1977/78 Ritchey road tandem which has early Dura Ace on all but the stokers drive side which currently has a later Specialized triple installed (pic not mine, taken by member Icepick Trotsky at the Marin Bicycle Museum).

embankmentlb

I believe in those days tandem groups were just combinations of the regular road cranks. I have seen 7700 cranks done that way for tandem use.

T-Mar

No, it's not that simple. Using standard crankarms, the threading for the pedals would be incorrect for all but the drive side, stoker crankarm. The pedals would tend to loosen and you'd have to Loctite them. In this case particular case, they are quill pedals with a definite left and right pedal, so to fit in standard crankarms, you'd also have to swap the axles for all but the drive side stoker pedal.


I have all the Shimano catalogues for 1st generation Dura-Ace, except two, and I don't recall tandem sets being mentioned. The only catalogues in which I can recall seeing specific mention of tandem cranksets are TA and Stronglight.


More likely, given the small production runs for a tandem, a special order was placed by the tandem manufacturer through their local Shimano division. The back of the crankarms should have dual letter date codes which will allow us to determine the year, at which point we can double check the appropriate catalogue.

Darth Lefty 

There seem to be a lot of midgrade tandems with crank arms that are/were not available aftermarket. I think they must buy them by the batch from the crank manufacturers. But that wouldn't explain DA.

Many MTB tandems right now are coming with 1x systems that allow the use of a single regular crank in front and a double crank in the rear with one serving as the timing ring, and Boost rear spacing is about the same as tandem spacing, so there's no upcharge for tandem compatibility. It's still not ideal for a road tandem, you always want a wider gear range and narrower q-factor than a MTB

Markeologist

Nope...if you have the synchro chainrings on the left side (cross over) your pedals would work themselves loose if standard cranks flipped around were used. TA, Campy and Stronglight had tandem-specific cranks in 60s and 70s with the sychro chain placed on left.

Markeologist

I too prefer drive side photos...but in this case, the timing/left side is the issue...are these original Gen 1 Dura Ace tandem cranks...guess I’ll have to pull some pedals to see. As noted, the stoker drive side is a more recent Specialized triple crank set. If the Dura Ace on timing side as well as the captains drive side are original, I think some previous owner wanted a triple w/o going through the bother of tapping the Dura Ace double crankset to accept a granny.

merziac

Wow!

Regardless of and including the crank puzzle, this is cool as heck, Tx for posting.

Can we have lots more pics of both sides plz?

They are all but guaranteed to bring more discussion to the table.

bulgie 

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

Markeologist

Great info, much appreciated Mark B. I’ve been riding tandems since the 1980s and I just don’t recall seeing Gen 1 Dura Ace tandem cranksets...mostly TAs on bikes from the pre-Specialized era, then lots of Specialized and Sugino appeared. There were always those who had beautiful Campy NR set-ups. I have the Specialized tandem cranksets on my 86 Rodriguez, they have held up incredibly well.

As I noted initially, my new Ritchey has a Specialized triple on the stokers position. I assume a previous owner wanted a triple without going through the bother of drilling the original Dura Ace. I’ll ride it this way for a bit while I search for a Gen 1 Dura Ace drive side side crank...maybe find a triple-mod version off a Santana...anybody have one of those out there? Thanks again, Mark(eologist).

bulgie 

Ah, too bad your Rodriguez isn't a couple years older -- I made them up until summer '84. They were not as good after I left. Yes that's a pretty blatant brag, but it's true, the guys who were making the frames were less experienced after Glenn Erickson and I moved on. (You know Rodriguez didn't make them himself, right?) Much later, Dennis Bushnell was the frame boss there, and he is awesome, but your '86 is in the "valley" between me and him.
If you want, I can drill a D-A crank to triplize it for you. I can do 86 mm BCD just like those Santana cranks -- but I'd recommend 6 mm threaded holes in the spider, not the 5 mm through-bolts that Santana used. I don't trust 5 mm to be strong enough for a tandem.

But drilling and tapping holes isn't really necessary anymore -- you can just use a triplizer chainring such as those made by TA, Willow, FSA and others. I like this one, made by Stronglight, which looks great, partly because it's "hidden" behind the spider arms -- you hardly see it from the right. Downside is it requires you to saw off the 5 little "shelves" on the backside of the spider arms -- basically turning it into a track crank, know what I mean? I'm good at sawing those shelves off, if you want to send it to me, but a clever home-handyman can manage it, if you have a vise and some skillz. All the other triplizer chainrings, that go on without removing the shelves, have to bypass (go around) the shelves somehow, which makes them more visible from the right -- more "busy" looking. (There's no downside functionally though, I'm only talking about looks)

Here's my wife's '85 D-A 7400 crank with the Stronglight triplizer:


Mark B