Compatible cranks-bottom bracket?
06-07-19, 02:47 AM
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Compatible cranks-bottom bracket?
Ok guys, I'm new here so be gentle.
I recently just renovated my old Saba track frame. It's a fixed gear set up. While trying to perfect the drive chain I noticed some issues. First off there is a slight nicking sound coming from the rear cog. As far as I can tell (and calculated). The chainline is spot on,new Izumi chain & lubed up (1/8 X 1/2).
Second issue, there seems to be tight spots in the chain as I turn the pedals, too tight to ignore. The first thing I did was check if the chain ring was central, which it is. Also checked at what points the chain gets tight in relation to either rear cog or cranks. The tight spots don't seem to correlate to a revolution of the rear cog or the chain ring individually on each complete turn but after a few revs it does fit into a pattern together. Also, without a chain on, the cranks look slightly on the piss. As if they don't sit perfectly on the spindle and doesn't go round 100% smoothly.
The bottom bracket is about a year old (Shimano UN55) Italian thread and being Shimano I think it's JIS, but not completely sure.
Crankset is a Sugino Pista , also new which is also JIS.
I think the tight spots must stem from the cranks not seating properly on the spindle. But if both parts are JIS why wouldn't they play nicely together?
Maybe I might just try another bottom bracket!
Any sort of feedback would be much appreciated.
I recently just renovated my old Saba track frame. It's a fixed gear set up. While trying to perfect the drive chain I noticed some issues. First off there is a slight nicking sound coming from the rear cog. As far as I can tell (and calculated). The chainline is spot on,new Izumi chain & lubed up (1/8 X 1/2).
Second issue, there seems to be tight spots in the chain as I turn the pedals, too tight to ignore. The first thing I did was check if the chain ring was central, which it is. Also checked at what points the chain gets tight in relation to either rear cog or cranks. The tight spots don't seem to correlate to a revolution of the rear cog or the chain ring individually on each complete turn but after a few revs it does fit into a pattern together. Also, without a chain on, the cranks look slightly on the piss. As if they don't sit perfectly on the spindle and doesn't go round 100% smoothly.
The bottom bracket is about a year old (Shimano UN55) Italian thread and being Shimano I think it's JIS, but not completely sure.
Crankset is a Sugino Pista , also new which is also JIS.
I think the tight spots must stem from the cranks not seating properly on the spindle. But if both parts are JIS why wouldn't they play nicely together?
Maybe I might just try another bottom bracket!
Any sort of feedback would be much appreciated.
06-07-19, 07:42 AM
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Chainrings are seldom perfectly round, nor are the mounting holes on the crankarms necessarily perfectly coaxial with the bottom bracket. This is seldom a practical issue unless the eccentricity is enough to allow the chain to derail. You can play around with re-mounting the ring until you find a position that minimizes the eccentricity. The more you spend on your crank and chainrings, the closer they are likely to be to round and coaxial.
Otherwise, it's fine to mount the wheel in the dropout slot such that the chain still has a little slack in the tightest position and ride it like that. If the chain gets too tight, you will ruin your bottom bracket and/or hub bearings in short order.
Otherwise, it's fine to mount the wheel in the dropout slot such that the chain still has a little slack in the tightest position and ride it like that. If the chain gets too tight, you will ruin your bottom bracket and/or hub bearings in short order.
06-07-19, 08:03 AM
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Compatible cranks-bottom bracket
Thanks for the reply,
You are absolutely correct, that is precisely what I tried a few hours ago out of desperation. The chainring bolts had more play in them than I originally expected but rotating the ring over a couple of bolts has done it.
I just hope it doesn't move out of position once some force is applied to it!
You are absolutely correct, that is precisely what I tried a few hours ago out of desperation. The chainring bolts had more play in them than I originally expected but rotating the ring over a couple of bolts has done it.
I just hope it doesn't move out of position once some force is applied to it!
