# How tight should my crank bolt be?



## alaskadude (Nov 9, 2013)

Im in Nepal, down in the flats. There are no bike shops.
OK, my bolt on the non-chainring side was coming loose. It is a square taper. It has a bolt that I tighten with an 8mm hex.
I was afraid the square hole on the crank arm would enlarge if it wobbled around on the square taper. I tightened it a couple times a day.
Then I found a washer and put that in there. I cleaned off the grease off the bolt, and tightened it pretty tight.
Im afraid if I tighten it too much I will break the bolt(?) maybe this is not possible? I put a lot of strength into tightening it, with the washer and grease wiped off the bolt with a rag.
It has not come loose now for two days. Im afraid if I keep tightening it, it will make the situation worse. But now it seems to be holding tight for a couple of days.
Anyway, is it possibe to tighten it too much?
There is no torque wrench here, or a replacement bolt.


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## *OneSpeed* (Oct 18, 2013)

yes it is possible to brake it by tightening it too tight. however those bolts are pretty strong and you can crank them down good and hard. really the only way you should be able to break it is if you are trying to. I've tightened them to 95% of my strength with no problems. 

i've also had crank bolts that got worn and kept coming loose every ride. i tried grease and washers etc., nothing worked. eventually i cleaned off all the grease and used Locktite (thread locker). that solved my problem. crank stays put now.


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## Harold (Dec 23, 2003)

Those need to be pretty tight. Quick search turns up a torque value of 45Nm. Without access to a torque wrench, that's "pretty damn tight" in my book.


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## alaskadude (Nov 9, 2013)

OK, I did 'pretty damn tight." like most of my arm power without thinking I might snap it off. It has held for 2 days.
Im in East Nepal. I dont know if they have loctight, but there are motorcycle repair shops. If I have any more problems, Ill stop in and see if I can find someone that speaks English and see if there is some type of locktight type of stuff.
Today I saw freshwater dolphins in a river. Ill be Bike touring in Asia all winter, until MArch.


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## J.B. Weld (Aug 13, 2012)

'Pretty damn tight' is an apt description of the proper torque. If the crankarm or bolt continues to loosen it is likely that the square taper on the crankarm is deformed, and if this is the case the only cure is a new one.


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## eb1888 (Jan 27, 2012)

^^^^What he said is now most likely the case...but you might as well try the Loctite blue and/or take the 8mm allen and extend its arm by hooking a large closed end wrench over it. Then torque it down with the extra advantage the longer lever gives you.


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## zebrahum (Jun 29, 2005)

alaskadude said:


> OK, I did 'pretty damn tight." like most of my arm power without thinking I might snap it off. It has held for 2 days.
> Im in East Nepal. I dont know if they have loctight, but there are motorcycle repair shops. If I have any more problems, Ill stop in and see if I can find someone that speaks English and see if there is some type of locktight type of stuff.
> Today I saw freshwater dolphins in a river. Ill be Bike touring in Asia all winter, until MArch.


The bolt probably isn't the issue if you keep having the arm come loose, it's more likely the taper getting worn. What you really need is a new crank arm and possibly a new BB but if those are hard to come by then you need to find a type of locktite called sleeve retainer. Put the sleeve retainer on the spindle and tighten things down, you'll need a torch to get it back apart but you'll be able to keep riding.


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## alaskadude (Nov 9, 2013)

OK, thanks for the answers.
I think I got lucky and no damage was done. I tightened it up, and it seems to be holding.
I think what happened is since the pedals both tighten as you ride, and the chainring side bolt keeps tightening as you ride, I assumed that the non-chainring side would get tighter as I ride. This is not the case--if it is not tight enough, it will unscrew as I ride.
It needed to be really tightened up.
Ill ride it a few days more, see if it stays, and if not go into a 'shadetree' motorcycle shop and see if they have anything like loctight here in rural backwoods Nepal.
But actually I think I got lucky and no damage just needed more torque on the bolt.


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## root (Jan 24, 2006)

Sounds good! With a normal Allen key you'd be hard pressed to tighten it too hard by hand, unless your the Hulk. You need to use a cheater pipe or a 18" breaker bar with 8mm head to easily get into realm of breaking the bolt.
If it keeps loosening & your in desperate shape, I've heard if people mcgyvering soda can shim onto the tapers.
Greasing threads actually allows you to tighten more. Do not grease the tapers though.


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## mack_turtle (Jan 6, 2009)

Most square taper crank arms should be 29 ft-lbs. That is pretty darn tight. As has been mentioned, if it came loose, the crank arm is likely damaged beyond repair already and needs to be replaced.


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## Fleas (Jan 19, 2006)

mack_turtle said:


> Most square taper crank arms should be 29 ft-lbs. That is pretty darn tight. As has been mentioned, if it came loose, the crank arm is likely damaged beyond repair already and needs to be replaced.


Beat me to it.

I would go 30 ft-lbs. 

-F


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