Is it viable to use cottered cranks?

Question

I'm restoring a Bianchi Sprint (~1975).

It has a cottered crankset/bb. I was originally planning on replacing them, because we all know that cottered cranksets are junk, right? Well, they have a great Q-factor and the rings I want (52-42, because it's got DT shifters), so I'm looking at trying to make them work.

I know cottered cranks are gone now because square taper is a better, lower maintenance, more foolproof system. But that doesn't mean that cottered cranks can't work well, right?

Is it going to be an ongoing nightmare trying to keep these cranks working smoothly and silently? This bike would be used heavily (~100 miles/week).

Answer 1

Give them a try.

The main reasons they used to fail, if my boyhood memories are accurate, was incorrect installation.

When installed firmly they would last for years.

The important thing is proper support for the bike and pedal arm while installing the cotter pins. The pins must be hammered in firmly, without transmitting any of the hammer impact to the BB bearings. Destroying the bearings was common. After installing the pins firmly the nut on each should be tightened to hold them firm.

If you have a source of the correct cotter pins then trying will not cost much. If you find them to be too much trouble then you can always such to plan B: a square taper BB.

The Spirit crank and chain rings were integrated, so you'd need new rings of you replace the BB.

Answer 2

Cotter less cranks are much easier to maintain and if you can find some that aesthetically suit your bike then that is a better option.

However, if you want to use cottered cranks then that's OK - they have been used for over a century, but follow the rules below and pray to the bicycle gods.

1) always get the correct diameter cotter pin. I believe they used to make a variety of angles, but these days you usually need to file the pin to get it to fit snugly. When doing so, make sure the final surface is even and flat.

2) replace the pins in pairs

3) A cotter pin press is the best tool for removing and tightening the pins.

4) If you do not have a press, then study up on the correct techniques for hammering the pin before you start (e.g. never hammer the pin on an unsupported crank, do not tap lightly, and there are more). Poor technique in the beginning of the removal, or when fitting the pin, can literally add hours to removing a pin.