Help: Installation square taper crank
 

I am working on an older hybrid bike. The crank is bent. I removed it using a crank puller. I thought that would be the hard part but it was easy, using a Park Tool video. I now am installing the new crank/chain wheel. I can't figure out how. The instructions that came with the Shimano FC-M171 say use the crank puller to install the new chainwheel. What? How would you do that? It seems to me that you would put the new chainwheel over the square spindle and then tighten the nut to the right torque. Am I wrong?

The attachment is by a simple nut on the threaded spindle. The same as figure 7 in this Park Tool page: http://www.parktool.com/blog/repair-...e-spindle-type

Specifically:

http://www.parktool.com/uploads/imag...p/crank101.jpg

I think you have misread the installation instructions and/or they are not from Shimano. Yes, you just place the new crank over the square taper on the spindle, add the washer if there is one (most don't have one), thread in the fixing bolt or nut and tighten it to the recommended torque. The only "trick" is to be sure you install the other side 180° from the first arm. :)

The tool being used on the Shimano instruction page is a Shimano compact crank tool. Unlike the more common Park tool with a handle, the Shimano tool has no handle. On one side is the extractor mechanism and on the other side is a 14mm socket. Hense they are telling you to use the 14mm socket to install the crank.

http://bikeforums.net/attachment.php...hmentid=266995

Thanks so much! I cannot believe how misleadingly terse the instructions were that came with the crank. They should just have said use a 14mm socket to install the crank if you have a 14mm bolt. :)

Anyway, crank is on!

Funny, I have that exact crank puller and have never used its built in 14 mm socket to reinstall any crank so I forgot it was even there. I always use a plain 3/8"-square drive socket so I can use my torque wrench.

Op you are ok... as for the torque, pretty much just put grease in the threads of the bolt and tight the heck out of it. You dont want that to get lose in the middle of a ride.

I like to recheck a new square taper crank a couple times,they can come loose until they bed in sometimes.

Thanks for the tip Boog.

You don't want to do this. If you torque the cranks properly to spec the first time they should never come loose. However, if you check them some time later you will indeed find the bolt or nut turns a bit more if you apply full torque again. That's normal and has a good mechanical reason why it should happen. It does not mean the crank is coming loose. However, if you persist in applying full torque periodically, you will "chase" the crank up the taper and eventually crack it. Torque it to spec once and leave it alone until you remove it again.

IMHO your wrong here. The whole idea of using a torque wrench is to properly tighten a bolt (or some other threaded item). The danger of chasing the crank up the taper comes from those that pull out a wrench and check the tightness without a torque wrench. According to your theory, the crank bolt will loosen with use, but you should not tighten it. One can regularly check the toque of any bolt as long as you use a torque wrench and don't exceed the proper torque setting.

I tighten the crank bolts, after a few rides double check torque,if everything is ok. I remove the bolt, clean bolt and hole and bolt apply Blue loctite and retorque to specs. It should never work itself loose afterwards.