Confused - My Old Shimano ISO Sq Taper is bigger than JIS..

mightymidget":3fujt86q said:

...
Ultimately I'd like to get a sealed cartridge BB to replace this odd cup and cone, something nice like a Royce or Phil wood. But at the moment I can't order anything as I'm unsure what to ask for. If I order ISO I'll get something that resembles Campags ISO tapers, which from the above would be way too small...:?:

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I've just seen this and if you choose Royce, from the what I get from their site and from other people here just send the crank and what length you want and any other details and they'll make it for you
http://www.genisysconsulting.co.uk/royce-uk/

Thanks guys, your replies are really appreciated.

Looks like it must be a BB-7200. That would make sence seeing as the cranks are RC-7200's. Just Shimano's 1981 catalogue states they came with the track BB-7500 in 107/9mm lengths. http://www.velo-pages.com/main.php?g2_itemId=6945 page 23.

Anyways, still baffled about why the ISO axles are so fat, (and fatter than the supposed fattest axel which is the JIS) but hey, I can't sweat this anymore

Thanks for that DL. Lots to look at there. Cheers Andy.

Could of course be a different axle in the 'correct' cups.

FluffyChicken":2bo0em2d said:

Could of course be a different axle in the 'correct' cups.

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Yeah, did consider that. The more I find out the more I think the axle at is a BB-7200.

That Sutherland pdf is great. So much information. Haven't had a chance to digest it but it appears that the 7500, 7300 and 7200 bottom brackets differ from all the other Shimano JIS/ISO BB's at that time.

They aren't interchangable with other models as the Axle is to thick at the cup. They also list JIS as the closest alternative fit rather than ISO as with all the other older shimano ISO BB's. Which would suggest that these had a slightly larger taper than the ISO of the day. JIS being the largest and closest fit.

So initially it looks like during the late 70's early 80's Shimano had 3 different square taper standards. Shimano's original version of ISO, the newly introduced JIS and it appears a slightly oversized Square ISO taper on the 7500, 7300 and 7200 BB's.

I've read of people suggesting Campag ISO tapers with 7500 track cranks because they think Campag ISO tapers offer the closest fit. I'm sure I've even read this on Sheldon Brown's site. But from what I've just learnt it appears that JIS would be the closest alternative.

It's no wonder we all struggle to get perfect chainline with all these unknown factors.

I'll get the '81 and '82 catalogues up, though they lack the detail and well 'bottom bracket' where just an addition as you know and not really listed separately as they are now.

Any pictures of the crankset to finish of this thread ?


I've quite enjoyed looking for the info. You got the DD pedals to go in the crank ?

FluffyChicken":o9km21mi said:

I'll get the '81 and '82 catalogues up, though they lack the detail and well 'bottom bracket' where just an addition as you know and not really listed separately as they are now.

Any pictures of the crankset to finish of this thread ?

I've quite enjoyed looking for the info. You got the DD pedals to go in the crank ?

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Yeah, I've enjoyed all this investigating too. Not got the pedals but I've got the adapters to install my 9/16 Dura-Ace pedals. These cranks are going in my Titanium TT stead. I wanted to try 165mm cranks cause I'm a short ass and these came up on ebay.

I love mixing old with new, what's more the quality and workmanship of the older stuff is far superior to most modern day components.

I expect one day they'll end up on my retro hog but at the moment thats fully decked with 80's Campag Super Record bits.

Here's a few photo's of the cranks and where there heading:

http://i476.photobucket.com/albums/rr128/thehotone25/Shimano BB/attachment-LL9CGV.jpg

http://i476.photobucket.com/albums/rr128/thehotone25/Shimano BB/attachment-MSDYFV.jpg

http://i476.photobucket.com/albums/rr128/thehotone25/Shimano BB/attachment-HO7GGV.jpg

http://i476.photobucket.com/albums/rr128/thehotone25/Shimano BB/attachment-Y736FV.jpg

http://i476.photobucket.com/albums/rr128/thehotone25/Shimano BB/attachment-X90AGV.jpg


And this is where they'll end up:

http://i476.photobucket.com/albums/rr128/thehotone25/Bike Pictures/attachment-9OQYFV.jpg

http://i476.photobucket.com/albums/rr128/thehotone25/Bike Pictures/attachment-5H26FV.jpg

http://i476.photobucket.com/albums/rr128/thehotone25/Bike Pictures/attachment-JLQBGV.jpg