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In the last 6 months I have been getting really bad noises, creaks, clunks, etc coming from somewhere around the spindle connecting to the crankshaft. Every time I put pressure down on the left hand pedal, either it or the spindle attaching to the pedal creaks, clunks real loud and then the pedal works itself loose. I have tightened it up every time and after a couple of days it becomes loose and almost falls off again. Can anyone help explain why and how I may fix it myself?

Sorry actually being a bit clearer it is the square taper crank arm that comes away from the spindle. The pedal actually is fine. The bike is an Dawes XC 2.2 and the crank arm has "Truvativ" Powered by SRAM on it.

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  • Can you tell us a bit more about what band/model components you have? For the life of me, I can't imagine how this is happening since cranks are threaded in a way that the pedal tightens as it is used.
    – Greg
    Commented May 27, 2012 at 1:13
  • If this has been going on for 6 months then the crank arm, and possibly the shaft, is toast.
    – Daniel R Hicks
    Commented May 27, 2012 at 1:22
  • @Greg -- The crank bolts are the same direction on both sides. It's the pedals that are right-hand on the right side and left-hand on the left side.
    – Daniel R Hicks
    Commented May 27, 2012 at 1:35
  • What is actually coming out? If it's the pedal, what do the threads look like? and does the pedal spin (i.e. are the bearings inside the pedal shaft still good)?
    – Ken Hiatt
    Commented May 27, 2012 at 6:06
  • Sorry actually being a bit clearer it is the square taper crank arm that comes away from the spindle. The pedal actually is fine. The bike is an Dawes XC 2.2 and the crank arm has "Truvativ" Powered by SRAM on it.
    – Matt
    Commented May 27, 2012 at 11:20

2 Answers 2

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Like I said, by now the crank arm is toast. Originally the problem was just that the crank bolt was loose (they need to be REALLY tight -- ideally set with a torque wrench).

But running with a loose crank has deformed the socket on the end of the crank to where it no longer fits, and it rocks and works the bolt loose as you pedal. And by now the crank shaft (which is steel vs the aluminum crank arm) may also be deformed.

There is a vague possibility that a clever person could make the existing crank arm work fairly well with a shim cut from a beer can, but it takes some mechanical aptitude.

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You have worn threads on the crank bolt. Over time older softer bolts can have threads that separate, and make it easier for the bolt to work loose. Try a new steel or Ti bolt with some thread lock.

Usually the problem is the bolt.

Secondarily, but you may have oversized the hole in the crack where the bottom bracket spindle goes, making the issue worse. Any crank arm rocking with a snug bolt will add to the speed at which the whole side comes loose. If this is the case the crank arm and the BB should probably be replaced.

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  • When you say Crank Bolt do you mean the actual screw that keeps the crank arm attached to the spindle or do I need a new spindle as well? What do you mean BB? Sorry for my inexperinced this the first time I have looked at fixing my own bike.
    – Matt
    Commented May 27, 2012 at 13:52
  • What could be making the really loud clunking and creaking. It almost sounds like it will shear off.
    – Matt
    Commented May 27, 2012 at 14:13
  • Correct. the crank arm is held to the square spindle by a single bolt. The bottom bracket is the spindle and all the bearings are a single unit called a bottom bracket. Its a $12 part. the crank arm is the more expensive part. Yes, the creaking and clunking is the crank arm moving on the spindle.
    – Matt Adams
    Commented May 27, 2012 at 14:51
  • The origial problem was from failing to properly torque the bolt. But once the crank arm has rattled around on the spindle a bit it no longer seats well, and then the bolt will work loose no matter what you do.
    – Daniel R Hicks
    Commented May 27, 2012 at 18:28
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    @Matt -- "BB" is short for "bottom bracket", which technically refers to the entire assembly, but is usually taken to mean the bearing and crank shaft assembly which may be individual components or (more often) a "cartridge".
    – Daniel R Hicks
    Commented May 27, 2012 at 18:31

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