Originally Posted by
Mos6502
The cotter can wear out. The cranks can wear out. The cotter can wear out, causing the cranks to wear out, ruining the cotter and the cranks. They're usually heavy. They're usually on the cheapest bikes (unless you go waaayyy back into the 1950s, then they were on the best bikes too).
When they're in good condition, they work. When they're in bad condition they wobble, have slop, make noise, etc. In my opinion, worse than one piece ashtabula cranks - unless you happen across cranks in excellent pristine condition.
In defense of cottered cranks....
Cottered cranks are old-fashioned, and they are (usually) steel, but they are not necessarily bad, or cheap.
As you said, once upon a time they were found even on the best bikes. Telling people to avoid all cottered cranks is just bad advice. Good advice would be more specific, such as: avoid any 'ten speed' bike with a cottered crank made after 1975 or so. Excellent three speed bikes still had cottered cranks well into the 80's
Cranks, by which I mean crank arms, do not wear out. Bearings wear out. Chain rings wear out, and aluminum ones wear out faster than steel.
If a crank arm and chain ring are swaged together, and the chain ring wears out, then the crank is worn out. It doesn't matter whether said crank is cottered and cotterless.
The advantage of Ashtabula cranks is that the crank arms and the spindle are made from a single piece of metal, and therefore cannot move relative to one another. On three-piece cranks, whether cottered or cotterless, there is a possibility that crank arms will move relative to the spindle if not attached properly, and in such cases the movement in question will damage the crank arms. It is a question of installation; and I have seen more cotterless cranks ruined by bad installation than cottered ones.
Certainly it is true that a lot of cheap nasty bicycles came with cottered cranks, and these are bikes to avoid. But the same can be said of bikes with cotterless cranks.