I've used lynch pins, nails, bailing wire, safety wire, piano wire, ... . Most anything that will go through the hole will do. What matters is how resistant is the part to falling out on the trail. Not much of an issue on the road. Clip-style retaining pin? Hairpin cotter?

 

I'm not sure why you should discard the cotter pin every time you remove it. Treated with some modicum of care they can be re-bent innumerable times, inserted repeatedly etc. They are cheap as dirt and need not be spread to the maximum to stay in so maybe you just need to have more faith in your old one. Maybe this is my farm heritage coming out, but almost every cotter pen I've removed was suitable for reuse unless I broke it completely. Tom

 

I'm not sure why you should discard the cotter pin every time you remove it. Treated with some modicum of care they can be re-bent innumerable times, inserted repeatedly etc. They are cheap as dirt and need not be spread to the maximum to stay in so maybe you just need to have more faith in your old one. Maybe this is my farm heritage coming out, but almost every cotter pen I've removed was suitable for reuse unless I broke it completely. Tom

 

The castellated nut is more secure by nature. All you really need to do is pin it against rotation as insurance.



All I do is spread only the LONG leg of a properly fitting cotter pin sufficiently to keep it snugly in the hole, and leave it at a length where it is easily straightened for removal. I can dangnear remove them by hand, yet they're secure enough to stay put.

 

Would it be easier or should I say better to just install the Teflon nuts that the newer bikes have? Why did they switch? I'm not sure! I have an 2005 and noticed I don't have castle nuts and often wonder if I would be better off the old way!