7400 cranks - b/b axle length?
- Thread starter ededwards
- Start date
Elev12k":3v79e7nj said:
Very speedy response, many thanks.
Looks like this http://www.sjscycles.co.uk/shimano-shim ... ?src=lfgss will do the job.
£5 cheaper at CRC http://www.chainreactioncycles.com/Mode ... elID=17473
one-eyed_jim
Old School Grand Master
I've got a strong feeling that the 7400 bottom bracket used ISO tapers, and the UN54 will have JIS. There's contradictory information about this on the web, but generally the sources I trust lean towards ISO for the 7400 models, with 7410 being the shift to JIS.
I think the 7400 axle was also asymmetric.
EDIT - here's Andrew Muzi, writing five years ago:
"The asymmetric 1046a Nuovo Record BB assembly has an
identical spindle with the Shimano BB7400 for the first New
Dura Ace. That pattern is correct to another dozen cranks
of top quality in that era. Or an original Phil Wood #2 BB.
That was a de facto standard among professional quality
bikes for over twenty years, across nearly every major
brand. (OK, not the two big French houses but they were
always intractable on purpose)"
https://groups.google.com/group/rec.bic ... 160f0c7230
I think the 7400 axle was also asymmetric.
EDIT - here's Andrew Muzi, writing five years ago:
"The asymmetric 1046a Nuovo Record BB assembly has an
identical spindle with the Shimano BB7400 for the first New
Dura Ace. That pattern is correct to another dozen cranks
of top quality in that era. Or an original Phil Wood #2 BB.
That was a de facto standard among professional quality
bikes for over twenty years, across nearly every major
brand. (OK, not the two big French houses but they were
always intractable on purpose)"
https://groups.google.com/group/rec.bic ... 160f0c7230
one-eyed_jim":1byw81l7 said:
Interesting, I just assumed that Shimano would obviously be JIS
No real issue though as I've used JIS cranks with ISO b/bs and vice versa in the past with no issues and should be even less of an issue with a sealed b/b when there isn't the need to remove the cranks to service the b/b - I think it's the regular crank removal that messes up the taper rather than the interface itself. Not ideal admittedly, but should be fine in the real world.
The asymmetry sounds more of a concern but the judicious use of a narrow spacer or two should address that - I'm assuming that the axle needs to be longer on the drive side and if that's not the case it could be a little trickier.
Compatability - you've got to love it
one-eyed_jim
Old School Grand Master
That's true, but you might want to pick a slightly shorter axle. ISO cranks sit a good couple of millimetres further out on JIS tapers.ededwards":1rsffeqi said:
The asymmetry is only a couple of mm rightward bias. You can see the difference in length of the unmachined section at the base of the taper in Simplex's picture.
Just incidentally, SunTour Superbe Pro cranks also used ISO tapers, right up until the mid nineties.
one-eyed_jim":2i0197oc said:
Thanks for that, and for pointing out where the asymmetry on that axle is - I was staring at it for ages!
It sounds like the 113mm I've ordered might well be ok, especially without the drive side bias. I can't change the order now so I'll see how I get on and if clearly no good then I'll have to order another!
