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I'm struggling to remove the cranks from my bike. I have a 2005 or 2006 Trek 2100 road bike with Bontrager Race cranks (triple chainring, marked "9 Speed" and "ISIS Drive"). It appears that the crank bolt is flush with the edge of the crank, with no dust cover. It takes an 8 mm hex wrench.

I've put a good deal of force on both crank arms without it budging. Is it just a matter of putting enough torque on it, or am I missing something? Are either of them reverse threaded?

Right crank arm

Right side crank bolt

Left crank arm

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The crankarm fixing bolts are normal, right hand threaded, so removal is anticlockwise. They do call for significant torque (43-48 N-m, one of your pics show). A simple "L" shaped Allen key used by hand may not provide enough torque to break loose the fixing bolt. Using a ratcheting wrench and a socket that terminates in an 8mm hex head might be the easiest solution. There are several different designs that get a hex head combined with a wrenching tool, and its something along that line that will give you enough power to free the crankarm fixing bolt. You may or may not know that after the fixing bolt is removed, a specialty tool called a "crank puller" will be needed to get the crank arms off the bottom bracket's spindle.

Here is Park Tool's crank puller with an instructional video on its use. If in fact your bottom bracket spindle is ISIS drive splines, you'll use the larger business end in the crank puller to remove the cranks.

Here is a link to a metric hex head socket set as an example of what I'm referring to in the first paragraph. Using these with a ratcheting wrench should allow you to deliver the power necessary to loosen the fixing bolts.

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  • From the look of the of the crank-arm bolts they may well be of the sort with built-in crank-pullers that became popular in the late '90s.
    – Carel
    Sep 8, 2020 at 7:30
  • Thanks for your response! I have an 8mm hex head on order and will try that. I do have a crank puller in case I need that.
    – JMayer
    Sep 8, 2020 at 14:49
  • I was able to remove the bolt with an 8mm hex drive and a big enough wrench. It is an ISIS-splined bottom bracket.
    – JMayer
    Sep 30, 2020 at 0:24
  • @JMayer Excellent. Are you planning on pulling the cranks as well? That referenced crank puller works real slick. Impossible otherwise without creating scrap metal 🤨
    – Jeff
    Oct 1, 2020 at 22:28
  • I pulled the drive side crank to replace my small chainring. It's back on and everything is much smoother now. :)
    – JMayer
    Oct 2, 2020 at 23:05

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