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loose crank / bottom bracket question

gvlieghegvlieghe Posts: 42
edited November 2008 in Road general
I've bought some nice Stronglight Track cranks, and am running these on a plain old Shimano cartridge bottom bracket that I already had (UN-53 I think).

I am having to tighten the crank bolts every few days, which is something I've never had to do before.

Is there some square taper compatibility issue here that I'm forgetting about? Any other solutions that people have found to this problem?

Posts

  • Are you using a torque wrench ad winding them up to the correct tension? Is there room for a split washer?
  • DickieDickie Posts: 1,489
    Usually Stronglight are ISO taper and Shimano are JIS.

    The JIS taper is larger and if you put a ISO crankset on a JIS spindle it will no longer fit the ISO spindle as it will enlarge the taper.

    I always assemble my cranks dry ie no grease and they don't come loose. Some people use grease which I personally don't agree with from an engineering point of view.

    Whatever works for you really, hope this helps.
    The disclaimer: It is not my intention to start a grease or not grease thread.
  • ISO and JIS taper angles are the same but an ISO crank tapers to a smaller cross section. That means that an ISO crank on a JIS BB will sit further out and a JIS crank on an ISO BB further in to the extent that it may bottom out before it is properly tight.

    As always, consult Sheldon http://www.sheldonbrown.com/bbtaper.html

    I'm fairly certain that Stronglight track cranks are actually JIS.
  • DickieDickie Posts: 1,489
    As I said larger, I didn't say the angles were different. Tighten an ISO crank on a JIS spindle then try and put it back on an ISO spindle and you will find there is no draw left as it enlarges the taper.

    All my Stronglight stuff is ISO but that of course doesnt mean the track crank is.
  • thanks all. I checked the Stronglight website, and they recommend a JIS BB for their track crank, so I'm guessing the cranks are JIS too, so compatible with my Shimano BB. I'll try removing the cranks and cleaning off any grease or oil, and hopefully a dry fit will remain tight.
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