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Track Crankset Gaps

jakewatjakewat Posts: 2
edited September 2015 in Workshop
I received my crankset for my single speed project today. It's a track crankset that came with a BB7418ST Bottom bracket. But when fitting the crankset there were large gaps between the crank arms and the frame, and it seemed as though the holes in the crank arm where a little smaller for the square taper on the bottom bracket. After contacting the seller he told me that his setup looked the same and there was nothing wrong. But I'm not fully satisfied and want some more opinions. Is there anything wrong with having these gaps and if I did want them to be closer could I file the crank arm or BB, or would that be a bad idea?
Pics below:


  • mercia_manmercia_man Posts: 1,368
    Difficult to say from pix but those gaps look normal to me. The crank shouldn't go all the way on a square taper axle because it must not bottom out and risk getting loose. No way should you file out the crank or axle. You will ruin them. A properly fitting crank will go around two thirds of the way along the axle. It will move further along the axle the more you take it off and refit. If you feel the chainline is wrong or the left crank sticks out too far, you can buy an alternative bottom bracket with a shorter or asymetric axle. Some bottom brackets have adjustable cups so you can get axle position just right.

    Square taper axles come in JIS (for Shimano and most far eastern cranks) and ISO (Campag and many European cranks). You are not really supposed to mix types but many people do without problems. ISO cranks will sit out a bit further on a JIS axle and vice versa because of the slightly different tapers.
  • marcusjbmarcusjb Posts: 2,412
    That does look like an ISO crank on a JIS bottom bracket. You can sort of get away with it on geared bikes sometimes, but on SS, it will really not give you a proper chainline, so your life will never be quiet or easy (and could be dangerous if the line is so bad that the chain unships regularly!).

    What is the crankset and we can maybe point you in the right direction for a suitable bottom bracket.
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