1976 - ish Japanese bike
recent shimano sealed BB cartridge installed was 68x124
same oem crankset reinstalled: supermaxy 52/42T, 171.5mm

Works fine. A little bit on the long side.

I want to go to a 170mm crank. I hope it will make a bit of a difference, shortening the downstroke. The bike is a touch large for me (about 5' 8", 58cm or 23"). Thompson seatpost comes in tomorrow - cant wait.

I determined that the Superbe (or maybe Superbe Pro) are actually ISO (or Campy style square taper), so they are off the list.

The situation appears to leave me with the following JIS crankset options which should slip right on:

Ultegra or 600 model 6400; the only square taper in this line

Dura Ace 7200 or 7400 series

That is a pretty short & not cheap list when those auctions end, and yet there are Campy NOS 170/52/42 or 52/39 cranksets on the cheep...so tempting to try...what other cranksets should I be looking for in a 170 mm length with JIS square taper? Thanks

Tange (IRD) makes very nice BBs, JIS too. For sizes, try https://store.somafab.com/components.html

Circa 1994, Campagnolo changed over to JIS.

I don't think you should be concerned about JIS or ISO taper because you're most likely not going to find another crank that can use a 124mm spindle! Are you sure that's right? Choose your crank a get a new cartridge bottom bracket in the size that crank calls for.

If you wanted to gear it down a bit, the Sugino XD is a very nice crank for a good price. You can look at them at rivbike.com and probably find them cheaper elsewhere.

Thanks much for the replies & info.

I too question the 68x124 BB but that is what the old school wrench wrote down. We discussed sizing the BB at the time, so I could record it. I sure dont see anything else in that size.

However, does spindle length make a difference, if I run the BB as is, I am really only concerned with the taper, right? The width of the BB would only be of much greater concern if I needed another new BB, and I'm not there yet.

1994 Campy went to JIS? First I've heard of it, and I've studied all the online info I could find. Did they stay with JIS till the present? I thought there was a huge brouhaha about JIS vs Campy (some mix, some dont, many get angry).

Regarding Sugino cranks, they do look nice, but they cost more than NOS Veloce, Xenon, Mirage & Centaur cranksets.

I'd be a bit excited to install a campy crank, but I could also get excited about some of the old school dura ace cranksets out there. Those should hook right up, if what I read on the internet is true.
Thanks riders.

Your spindle needs to be the correct length for the crank you are using. Chainline is important for proper shifting. Cartridge bottom brackets are cheap. It's silly to try to use the oddball extra long bottom bracket you have. You need to pick a crank and buy the BB appropriate for that crank.

I paid $65 for my Sugino XD.

I've never heard of a 171.5 crank; 172.5 is pretty common, though. And I agree, that's a little on the long side. But I can't imagine you'll feel much difference with a 170, the difference is really negligible. Unfortunately hardly anyone makes cranks shorter than 165, and even those are hard to find.

I use 140 mm BMX cranks. For other options, take a look at this.

171 and 171.5 both exist...

I think you should go buy a Campy since your mind is already made up and stick it on that 124mm spindle. Some people need to learn the hard way.

Imperial measurements nosed their way in. Its design is as a 6 3/4" crank (=171.5mm)

I have a wierd SR crank from a '80 Schwinn WS that uses a long spindle like that. Also has a 118mm small ring BCD and the large ring is something ginormous (above 151)

ouch. But thanks for the earlier comments about spindle length & chainline. The BB - spindle length - taper -crank business is a new world of wonder to me and it seems there sure are a lot of ways to go wrong.

so if I just get, for example an ultegra (600) or dura ce or sugino XG crankset w/BB included I should be all set? It will fit right up to my frame no problem? That solves all the interoperability problems?

I thought I had done all the research & cognescenti was in plurality agreement that one sticks with JIS or Campy, so I am surprised to learn about this issue. Thanks for your patience & educating me.

If you buy the crankset and BB as a package you should be fine. Just make sure the BB threading is English/BSC (1.37"x24tpi).

FWIW: The square taper 600 uses a 113-115mm spindle, and I think the 74xx DA does, too.

Thanks Mr Barker.

I did some further checking and found a 68x124 BB indeed. The intended use of such wider spindles seems to be triples, though I must have lost a ring as I'm on a double. I certainly have plenty of room on both sides to move inwards so maybe I'll make a play on a vintage Dura Ace w/BB auction or something like that. Campy's cool and all but it's a Jap bike with Jap parts so I dont feel bad at all about sticking with Jap parts. Vintage Dura Ace is actually pretty cool stuff.

Those very long spindles are found on mountain bikes. They need to be longer to clear the stays, which are wider spread to to clear big tires.

That may be true, in which case, there may be market for my almost new BB cartridge if it ends up as surplus.

Anyway I just scored a nice dura ace FC7400 w/BB 170mm 53/42T. Since the bike was configured for a triple, this should mean that I could expect to install the dura ace spindle around 115mm, and still have the right chainline and front derailleur throw...on paper...we'll see what happens in real life. Thanks for the help you guys are a wealth of useful info. It's really fun to have a bike from way back when, and be able to find affordable state of the art components from it's time in conjunction w/better modern gear where applicable (like clipless & seatposts & debatably saddles).