Torque setting for bottom bracket and crank bolts
- Thread starter trxrincon
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mountainloz
Gold Trader
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http://www.parktool.com/blog/repair-help/torque-specifications-and-concepts
this is from parktool, should be all you need
this is from parktool, should be all you need
feetabix
Retrobike Rider
i had problems with a crank falling off a square taper bb until i spoke to a most helpfull chap at a demo day at cannock.......he laughed as i produced a multi tool to retighten it, went off for 30 seconds to return with a huge torque wrench more in keeping with a kwikfit fitter and proceeded to put the correct amount into the bolt, it has remained problem free since.........the point of my ramblings being the correct torque for a bb bolt is more than i ever thought.....get it right and it should be sorted.....
mountainloz
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+1feetabix":3qr1pgpm said:
especially if it has come loose or come off once, it will damage the tapers and could result in having to bin your cranks
MCsanandreas
Mountain Cycle Fan
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i never put much force into BB's and always remember to grease the threads too. one day you will want to get it back out.
crankarms do get a good "swing" on the bolt.
crankarms do get a good "swing" on the bolt.
Uncle Monty
Retrobike Rider
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Sorry to drag this back up. The park tools link above gives a spec of 305-391 In/Lb for square taper crank bolts and lists lots of manufacturers apart from Shimano (unless I can't see it). That converts to 34-44 Nm. I have had a practice with reinstalling some old cranks and to be quite honest anything over 38 starts to feel a bit brutal. I am about to fit a NOS M900 chainset to a UN91 BB so I would rather not get this wrong. Any advice would be gladly received.
Uncle Monty
Retrobike Rider
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Thanks.
I have a good calibrated wrench, Cleaned the tapers, greased the bolt and the outer washer face. I had heard 42 Nm quoted so set the wrench to this and started to tighten up to the point where I felt it was too tight and still had not clicked. I then backed off the wrench a couple of Nm at a time until I found where I was. I had hit 38 Nm so I think my 'feel' was about right if a little over. I think you are correct at 35Nm -I found that figure quoted on a web page by Highpath engineering this evening.
Suprised not to find this in the tech section. Can this thread be tidied up and moved there once these figures are confirmed as correct? The old dry taper versus greased will always be a bone of contention. Local bike shop mechanic said dry, Highpath say greased etc. Re- checking after the first ride seems to be common and good advice.
Cheers.
I have a good calibrated wrench, Cleaned the tapers, greased the bolt and the outer washer face. I had heard 42 Nm quoted so set the wrench to this and started to tighten up to the point where I felt it was too tight and still had not clicked. I then backed off the wrench a couple of Nm at a time until I found where I was. I had hit 38 Nm so I think my 'feel' was about right if a little over. I think you are correct at 35Nm -I found that figure quoted on a web page by Highpath engineering this evening.
Suprised not to find this in the tech section. Can this thread be tidied up and moved there once these figures are confirmed as correct? The old dry taper versus greased will always be a bone of contention. Local bike shop mechanic said dry, Highpath say greased etc. Re- checking after the first ride seems to be common and good advice.
Cheers.
The problem is those who read the instructions for fitting cranks you will find "do not grease the tapers". If you do any form of bike mechanic training you will also be told do not grease the tapers. I however until now have not greased tapers but I can see the point of doing so, particulaly with anti sieze. I think manufacturers ask you not to grease the tapers because they do not want you torquing up the crank bolts and amming the cranks on distorting the crank arm. If you are careful with the torque wrench I do not see a problem in applying anti sieze to axle tapers.
