elbowging

Hello fantastic people of bikeforums,

I have a Raleigh cottered crank question. My daily rider (70s era sports) is having an issue whereby the crank arm "migrates" over time until it's so close to the adjustable cup that it rubs when I pedal. This first started happening somewhat recently. I repacked the BB and in doing so, broke the threaded part off my cotter pin when taking it out.... I cursed, got a new cotter pin, and finished up. Fast forward a couple of months, I notice a noise while pedaling, and it's the crank arm making contact with the adjustable cup. So, I get out the cotter press and re-do it, making sure to leave more clearance than I had the first time, making sure it's good and tight... today I notice the crank arm has migrated again! (easy to see since there's more spindle sticking out..). It's not yet rubbing but I'm sure it will soon.

I'm not sure what the deal is - should I try a new cotter (maybe try to find a better quality one)? Is it the spindle? I've been riding this bike for over 2 years now without a problem. Well, who am I kidding, of course there have been problem, but not with the crank arm moving!

Thanks in advance!

Bianchi84

If it is moving that much, I would look at not only the condition of the pin, but of the spindle-"flats" that the pin locks into; chances are that it is worn also if there was that much movement. I'm assuming it is the correct pin length and diameter (?) if it was tight for 2 years.

lostarchitect 

Yeah, I agree with the above. Also sometimes you need to file the pins somewhat to get a really good fit.

clubman 

Somethings off if it's possible for you to 'leave more clearance than the first time'. You can't do that if the pin is the right diameter, it fixes the crank in one position only.

Since there's apparently no stupid questions and you do have the correct 9.5 mm cotter pin oriented properly, are you sure your BB repack included the requisite number of 1/4" balls? Has the fixed cup worked itself loose?

rhm

I assume this is with a three speed hub? If so, how's the chain line? Perhaps you can shift spacers around and move the cog to the right, so it doesn't pull the chain ring to the left.

Hoopdriver

A couple of more posts and you will be allowed to post pictures, which will be of some help.

I have had many cottered crank bikes over the years and have never seen what you describe. I suspect that it is a problem with the way that your cotter registers with the spindle flat. Cotters must first be the correct diameter for the pin hole (9.5 mm for Raleighs). Secondly, they must have the correct taper, which also must be of the proper length for your set up. If the taper is not long enough, the cotter will not go in all the way. If too long, it may not exert enough pressure on the spindle to lock the crank into place. I have had to file almost ever cotter I've installed to get it to fit just right.

Unfortunately since cottered cranks are not a significant part of the market these days, the availability of quality replacement cotters is poor indeed. I recommend those sold by BikeSmith Design.

Good luck and let us know how you get on.

elbowging

Thanks all. I'm going to take things apart in a couple of days and will check the spindle for wear as well as the cotters themselves...I think I have another spindle somewhere in case I need to replace it. The BB repack went fine, no missing bearings. The cotter was the correct 9.5 mm. I didn't file it but it went in all the way and seemed to have a tight fit - that's why this issue is so surprising. I didn't think it was possible for the pin to move laterally on the flat. I have access to a very good home-built cotter press so that wasn't a problem...

I'll revisit this and see what happens when I have everything apart and can examine more closely!

elbowging

I have an update! Not only was the cotter itself a poor fit (when I pulled it out it was quite mooshed), but it turns out the crank arm was slightly misshapen at the end - oval hole rather than round. It was not sitting snugly on the spindle anymore.

​​​​​​I replaced the crank arm with a spare, and popped in a new cotter. I ended up ordering some cotters from bikesmith as was recommended above, so the next time I encounter a cotter-related failure mode, I'll have a good quality replacement ready to go. This is my daily rider so I didn't want to have it out of commission while I waited on my order.

Thank you all for the advice!

RobbieTunes

A workable solution to the crank migration problem. Practical and not destructive. America needs you.