I get a sound from my crank as if something were about to break to pieces when I stand and pedal hard.

  • What kind of crankset do you have? That noise generally means a loose crankbolt in older 3 piece cranks. – Fred the Magic Wonder Dog Dec 9 '14 at 14:59
  • it is a Shimano, 3-cog crankset – user14633 Dec 9 '14 at 15:03
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    difficult to guess from what little you say, could be the cranks themselves, could be the bottom bracket..... Treat it as potentially serious (i.e. you could damage yourself if something did break mid-ride) and have someone look at it as a matter of urgency. This is one of those situations where the web is probably not the best means of diagnosing what's wrong – PeteH Dec 9 '14 at 15:04
  • If you use clipless pedals, consider also the cleats on your shoes. Mine tend to creak a bit if the bolts aren't very tight. – Carey Gregory Dec 9 '14 at 15:40
  • The possibility that would be most concerning is that the crank arm is loose on the spindle. This can wreck the arm and spindle if not corrected immediately. Beyond that there are a dozen different possibilities -- bad pedal bearing, bottom bracket cartridge shifting between the cups, loose chainrings, a slightly bent tooth on a chainring, "frozen" chain links, etc. – Daniel R Hicks Dec 10 '14 at 3:02

The fault turned out to be a crippled ratchet in my rear hub. I got it replaced but am thinking of replacing my old bike now, it served me 10000Km in every season, every road in 2 years plus 3000Km in 3 years, a good service.

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    Although you found the problem, I'll comment that it also could be the wheel bearings. That is for those who have similar problem. – Alexander Dec 14 '14 at 12:49

You should have this checked by a mechanic immediately. There are at least 4 possibilities:

  1. One of the crank arms is loose or cracked. This is the most dangerous, since a failure at the wrong time could cause you to lose control of the bike.
  2. A bearing is loose or worn out in either the bottom bracket or one of your pedals. A pedal could also fail catastrophically, though it's unusual.
  3. The chainring bolts might be loose.
  4. The bike's frame might be cracked. Unlikely, and worth checking only after other possibilities have been eliminated.

The most common cause tends to be a worn out bottom bracket bearing or loose crank arm.

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