shimano crank bolts
Hi,
Hopefully a nice easy question and thread. I have had some problems with slight slipping with either crank/BB (brand new chain/cassette and chain rings only 6 months old), so decided to remove and re-grease everything.
Unfortunately the left crank arm bolts have threaded so I had to find 2 very quickly from somewhere. Don't throw too much abuse my way, but Halfords was the only place close-by selling bolts. Bolts needed for Sora triple 3503 set are M6x19mm, but Halfords and many places online only have M6x20mm. Before installing them I had a quick look and you can see the difference, but should it cause any problems? They have tightened well up to 10nm so appear to be OK. Thoughts?
Also, if you can think of what could be slipping having new parts fitted then any suggestions would be great. The slipping very rarely happens. Once on a 10 mile commute for example.
Hopefully a nice easy question and thread. I have had some problems with slight slipping with either crank/BB (brand new chain/cassette and chain rings only 6 months old), so decided to remove and re-grease everything.
Unfortunately the left crank arm bolts have threaded so I had to find 2 very quickly from somewhere. Don't throw too much abuse my way, but Halfords was the only place close-by selling bolts. Bolts needed for Sora triple 3503 set are M6x19mm, but Halfords and many places online only have M6x20mm. Before installing them I had a quick look and you can see the difference, but should it cause any problems? They have tightened well up to 10nm so appear to be OK. Thoughts?
Also, if you can think of what could be slipping having new parts fitted then any suggestions would be great. The slipping very rarely happens. Once on a 10 mile commute for example.
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Comments
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Provided the bolt head is small enough to fit into the recess in the crank I can't see an extra mm making a difference. Did you tighten the plastic preload cap before doing up the crank bolts? Have you got the little plastic spacer / safety tab in the slit in the crank? Did you retrieve and reuse the washers from the original crank bolts?0
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yeah it all looks snug. Yes, I tightening the preload cap (Just over finger tight). Can't remember being given washers to use with the bolts, but if I did then they are still in the sockets as didn't remove them. Oh and yes, the safety tab is still in place.0
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Then I'd say you've sorted it out. Good job!
May I enquire what you were doing with the original bolts to bugger up the threads? (I'm assuming that's what you meant by 'threaded'. IME new bolts are threaded, and when knackered they are described as stripped, but I digress...)
I'd have thought that over tightening a steel bolt into a threaded hole in an alloy crank arm would be more likely to strip the alloy thread than the steel. However I confess that I am no metallurgist. Biologist by training, mechanical tinkerer by inclination...0 -
Ha, yup, really long day and actually meant stripped. And to this, I must have over tightened them. None the less, the new ones are in and going strong..
Cycle home didn't slip/crunch at all.
Whether it was a chain misalignment (have just added the spacer that I forgot to use on the left crank arm, I don't know, but we will see.0
