It’s easy to forget about the parts that connect you directly to the bike but every time you grind against a gradient or push a gear, it’s your cranks and pedals that you’re relying on. Most of the time they do the job just fine but occasionally they’ll let you down.
The most common problem, which applies to all types of crank, is the crank bolts working loose so that the crank then begins to move on the axle. On a square taper, ISIS or Octalink crank, this can result in the crank bolt becoming so loose it actually falls out, allowing the crank to fall off completely. If you’re using clipless pedals you’ll find yourself with one foot attached to the bike and another with a useless crank and pedal dangling off the end! On a two-piece crank, you’re less likely to lose the crank completely as the preload cap will hold it in place but you can damage the shallow splines inside the crank if you stamp down on the pedals whilst the pinch bolts are loose.
Both situations are likely to damage the cranks irreparably a square taper, ISIS or Octalink crank will be deformed enough by the slight but persistent movement between axle and crank to never be properly tight again, whilst a stripped spline will never stay put. Keep your crank bolts tight to avoid having to solve the problem in the first place but if the worst happens, then there are a couple of things you can do to get yourself home.
If you have a square taper, ISIS or Octalink crank and have been lucky enough to notice the looseness before the bolt disappears, then tighten it as much as possible and make your escape, stopping to re-tighten the bolt every twenty minutes or when you feel the crank loosening again. If you don’t have the necessary 8mm Allen key in your toolkit, then a stand-in made by using two 4mm, 5mm and 3mm, or 6mm and 2mm Allen keys wedged together in the bolt head is surprisingly effective. You can attempt the same fix with a two-piece crank, returning the lefthand crank to its correct position on the axle and tightening the two 5mm pinch bolts as much as possible.
If this course of action fails then your best bet is to remove the loose crank, stash it in your pack rather than hurling it into the near distance in frustration and head for home prepared to push up descents, pedal one-legged on the flat (as long as it’s not the driveside crank that’s made its bid for freedom!) and coast the descents with one foot on the pedal and the other on the exposed end of the axle – it’s surprisingly hard to balance on a bike one-legged.
“Remove the loose crank, stash it in your pack rather than hurling it into the near distance in frustration and head for home”
Securing your crank
If you have a way to go to get home, a little bit of time spent securing your crank will pay off. Even if you can’t find the original bolt, you still have a spare – it’s holding your other crank on. Remove the right-hand crank bolt and use this to tighten your lefthand cranks as firmly as possible onto the axle. Remove it again and refit it back onto the right-hand crank. Chainsets are more expensive than cranks and so are not worth sacrificing. An emergency crank bolt will help keep the crank in place. If you can carve a short stub out of a handy-sized branch, then
screw it into the end of the axle. Cut off any wood that protrudes out of the crank though – it will be in just the right position to take chunks out of your ankle. Pedal gingerly!
Pedals can also seize, break or suffer crash damage. If the body of the pedal falls off leaving the axle in the crank, just use the axle as a pedal to get you home. It’s not particularly comfortable but it will get you there, though you may have a hard time removing a redundant clipless pedal body from the bottom of your shoe without the leverage of the axle to remove it.
Occasionally, the whole pedal will tear out of the crank usually as a result of failing to tighten the pedal up firmly in the first place. In which case, you have two choices: either jam the pedal back into the crank (the chances are the thread was stripped as the pedal worked its way out, so the crank will be going straight in the bin when you get home anyway), or fabricate an ‘axle’ from a handy stick. It only needs to be long enough to balance the ball of your foot onto and won’t take much pressure but should be enough to enable you to balance successfully and help the pedal through the bottom of the downstroke. Stay in a low gear, spin as much as possible and don’t expect the stick to hold your weight if you stand up on the pedals.
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES