Mountain Bike Reviews Forum banner
1 - 6 of 6 Posts

·
Registered
Joined
·
162 Posts
Discussion Starter · #1 ·
I have been running square tapered BB's & cranks from many different brands for 15 years without issue. Now suddenly I seem to have one.

I have a set of HSCycle custom 195mm cranks. I bought them used off of ebay and put them on my cyclocross bike with a 120mm Ritchey sq taper bottom bracket. Rode them like this for over a year without issue.

I decided to try them on my Mountain bike which would require a wider bottom bracket so I mated them to a 127mm UN72. I torqued them to spec with a torque wrench. Problems started immediately. They began to creak and the bolts started coming loose. I havn't ridden them much and just took them off for fear of doing damage to the tapers of the cranks.

I cleaned them up along with a couple of bottom brackets and notice something interesting. When you look at a square taper BB, it really isn't square. It has 8 sides. The four main sides, then small sides where what would be the corners of the square are. The small sides of the Shimano get much larger as you move away from the end of the spindle. When I slide the arms onto a Shimano BB (I tried 3 of them), the bb spindle goes almost all the way through the tapers of the crank arms. I think when I tighten the crank bolts, they are bottoming out before the arms get properly seated on the spindle. The Ritchey BB slides into the tapers in a much shallower position. I think the cranks will work fine if I mate them to the Ritchey again.

The odd part is when I dig out a set of Race Face turbines. Both the Ritchey and Shimano BB's sit at about the same depth inside the taper of the RF cranks - which is about the same depth as the Ritchey/HScycle combination.

What exactly is the difference between ISO and JIS tapers? I assume that my Ritchey and all the Shimano's are JIS, but how can you visually identify JIS vs. ISO? Any other ideas on what is going on here?
 

·
Doesntplaywellwithmorons!
Joined
·
10,939 Posts
Ritchey has offered both ISO and JIS taper BBs... depending on whether they were being sold for use for Campy (which is ISO) cranks or not.
 

·
wyrd bið ful ãræd
Joined
·
1,725 Posts
very interesting bit of information :thumbsup: cheers! ... which cleared some issues i had sometime ago but just never bothered to find out as i just changed over to the external bearing cup system ...
 

·
Registered
Joined
·
162 Posts
Discussion Starter · #6 ·
My issues sounds backward from ISO vs. JIS

If I read the Sheldon Brown page correctly, then an ISO should go much further into the crank than a JIS. I've got 3 Shimanos (UN53, UN72, UN73) that all look the same and am just sure they must be JIS. The tapers are exactly the same length on the Ritchey and the Shimanos, so I'm guessing they both are JIS.

When I look closer, the difference appears to be that the spindle on the Ritchey is larger in diameter. This changes how they transition from being round to being square. The end square of both are identical in size.

I'm going to guess that maybe putting the HSCycle cranks on the RItchey BB somehow deformed them enough so they won't work with the Shimano's. It's frustrating due to the cost of the HSCycle cranks and the fact that my Turbines were used with both the Ritchey and a Shimano with no issue. I've got a set of Mr. Whirly's coming so I'll probably just throw the HS Cycle cranks and Ritchey BB in the attic until I get an itch to play with them again.
 
1 - 6 of 6 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top