Identifying BB taper JIS versus ISO

[KEELIEDW]

I wish to replace the original Stronglight triple chainset on my c.1990 Peugeot trekking bike with a modern Shimano triple.
Am I right to assume that the original BB for this vintage would be ISO and therefore unsuitable for a Shimano chainset. Is there a method of identifying the two types of chamfer?

[bertbeerpot]

Sheldon Brown has a useful page on this:

http://sheldonbrown.com/bbtaper.html

He seems to be suggesting that the combination may work, but with some caveats (like ... errrm .. it may not).

There's also this:

http://www.sheldonbrown.com/bbsize.html

[Mick F]

Beat me to it!

Same angle of taper, different length of taper. Best not to mix JIS and ISO, but you can maybe get away with it.

[Brucey]

if in doubt, remove a crank, and try a JIS spindle in it.

(Your LBS scrap bin will be full of them)

cheers

[KEELIEDW]

Just dismantled everything and found that the new Shimano triple chainset needs a far shorter BB, furthermore the old BB bearings were dry and rusty, so an easy decision - I've fitted a much shorter Shimano cartridge BB and everything works fine. Thanks for advice anyway!

[SA_SA_SA]

Why do two such almost the same standards exist?

Surely either one would have done and avoided confusion:

otherwise surely it would be better for them to be more different?

[LWaB]

All of the bicycle standards are derived from proprietary standards i.e. a company's choice from the 19th century when it was irrelevant what some other manufacturer was doing over the border. English bicycle threads are derived from BSA, who sold their fittings to other bike makers. Raleigh didn't, so their unique threads remained orphaned.

[Brucey]

quite so. Someone pointed out to me that if anything, Raleigh adhered more closely to the agreed BS cycle standard, which called for 26 tpi on everything, more or less. Maybe they helped push the standard through or something.... but cycle standards are like language; usage is everything, and 'specifications' don't count for much by comparison.

cheers

[[XAP]Bob]

[SA_SA_SA]

But aren't both square tapers relatively modern: so if JIS already existed surely the ISO should have simply adopted it and vice versa.....

[recordacefromnew]

But aren't both square tapers relatively modern: so if JIS already existed surely the ISO should have simply adopted it and vice versa.....

They kind of did, and is still trying - JIS adopted ISO geometry in 2008 despite nobody noticing, then in 2011/2 ISO proposed a reversal and adoption of JIS geometry, which I believe is still "under development" within ISO. For the history see:

http://www.thun.de/fileadmin/user_upload/documents/Glossar/Handout_DIN2.pdf