how tight to do up a square taper chainset

moorjohn
moorjohn Posts: 89
edited August 2008 in Workshop
I get a ticking on the 2 big chainrings, and I think I can sometimes feel a movement when I'm on the little 30t one.

Tried sheldon's tip of greasing the bolt. It helped a bit, but not cured.

Do people use normal allen keys, or big long ones? Do they tighten by hand, or stand on the crank + use body weight, or what?

any other hints gratefully received

thanks

Comments

  • andrew_s
    andrew_s Posts: 2,511
    I use a big long allen key, tightened up as hard as I can with a bare hand.

    I'm lead to believe that you should to remove and refit a crank, rather than repeatedly tightening it on the taper. Apparently this can end up splitting the crank.

    Don't forget to check for other sources of clicking noises, such as dying BB, BB not fitted tightly, pedal bearings, loose chainring bolts ...
  • whyamihere
    whyamihere Posts: 7,708
    If you can already feel movement, the crank arm's probably knackered unfortunately. If you ride them loose, then the BB axle will cause the hole in the crank arm to go round, and if that's happened then it will move and creak however tight you do it. By all means try tightening it (you won't really be able to overtighten it, do it as hard as you can), but I'm not convinced it will help.
  • maddog 2
    maddog 2 Posts: 8,114
    I use 45 Nm (and no grease on the tapers!)

    If you don't have a torque wrench then this is perhaps more than you think - about as hard as you can turn with a 8 inch lever.

    as the other poster says, if the crank is deformed even slightly then it's does tend to work itself loose over time.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • sps137
    sps137 Posts: 247
    You'll never put enough torque on it with a standard allen key, even if you're built like arnie. The torque levels required are about 2/3rds of a car wheel nut and you'd generally use a 1/2 meter breaker bar to tighten them. If you haven't got anything else then use a long allen key/ratchet and just keep pulling until you think your arm is going to pop off. Be carefull that you don't slip though.
  • moorjohn
    moorjohn Posts: 89
    :oops:

    got a 10-inch breaker bar and replaced the allen bolt with a hex bolt.

    progressively tightened the bolt, testing every so often to see if click was gone.

    got to the point where my shoulders were braced under the crossbar (25inch frame you see) and I was giving it a pretty firm push (no blood vessels popping, but, you know).

    !!!!ping!!!!

    damme I've cracked the the crank arm...


    but no - sheared off the bolt.(never done that before+ only a 10inch breaker bar-not a biggie). Now the bbs useless because the bolt hole is filled with a headless bolt!!


    so - off to the bike shop. they put on a new bb and replace the crank. They do use grease/anti-seize. apparently old bb was shot, but they would say that wouldn't they.

    still a tiny tick on the first ride, but better.

    by the end of the second ride, I'm feeling some movement on steep hills + 30-inch gears. Oh Dearrr.

    Tried another go with the 10=inch breaker bar, but haven't had a chance to go out on the bike since. It's not looking good form my stronglight Impact though.

    I'm amazed that I'm getting movement. don't understand where I went wrong. Learning point is probably to get it good + tight first time off, and not to be too gentle...

    :oops:
  • satanas
    satanas Posts: 1,303
    moorjohn wrote:
    Learning point is probably to get it good + tight first time off, and not to be too gentle...
    Exactly!

    A friend of mine had cranks come loose for years because he never did them up tight enough in the first place. OTOH, if they are tight enough, they will never come loose...