Cotter Pin Help

[BADGER.BRAD]

Hello All,

My poor old Fixie is suffering I have too keep tightning the cotter pins at least once a week, it now has got to the point that I have had to fit an extra oversize nut to the threaded end in order to get enough thread to pull on. The cranks seem o.k so I'm thinking the cotter pin must be stretching ! Any ideas what I can do ? How do I size cotter pins Just measure the head or is there more to it than that ?

Many Thanks

Badger Dudley West Midlands

 

[piedwagtail91]

have you got the cotter pins in the right way? when you're pressing down on the pedal the nut should be on top.
other than that ,if i remember correctly, all cotter pins are the same size , you just file the flat until they fit.

 

[BADGER.BRAD]

Hello Piedwagtail,

Never new that ! I will have a look later. Maybe they were already in wrong and I have just copied the way they were.

Many Thanks

Badger in Dudley West Midlands

 

[piedwagtail91]

thats what i was told in the days before cotterless were common.

 

[shimano]

if I may be so bold I was always told to fit them the other way round ie if the crank is towards the front of the bike then the nut should be underneath (it's more natural to fit a pin downwards). Also cotter pins should be fitted as a pair and driven home a little at a time each side then the nuts tightened a little at a time each side - if you file them them you've just wasted the engineering that went into making them.

 

[Saddle bum]

if I may be so bold I was always told to fit them the other way round ie if the crank is towards the front of the bike then the nut should be underneath (it's more natural to fit a pin downwards). Also cotter pins should be fitted as a pair and driven home a little at a time each side then the nuts tightened a little at a time each side - if you file them them you've just wasted the engineering that went into making them.

Sorry, I cannot agree with that. I was told by my LBS in the early 60's that cotters should be fitted nut upwards, crank to the front. They should always be filed to ensure a good fit. This is because thay were made to be filed, the flat produced in manufacture was just a rough cut and not accurate enough to cover all combinations of fit.

Ideally, they only needed the lightest tap with a brass hammer to achieve the perfect fit. If they were wacked in causing metal to be lifted from the cotter flat, they needed to be adjusted more.

 

[Gerry Attrick]

+1 to Saddlebum. Bear in mind that cotter pins date back to the 19th century when engineers were engineers and superb craftsmen fitters to boot. In those days of course, the engineer would make his own cotter pins and obviously file them to suit the application. Move forward to say the early 1900's when every large town had its own cycle and motorcycle manufacturer (no error here, I do mean manufacturer), there was then a good market for batch made small items like clips, washers, split pins, cotter pins and the like. These manufacturers bought in such items made for unspecific machines, and then finished them by hand to suit the intended use. Likewise now, when you buy cotter pins, the same pins will fit a multitude of different applications, but you, dear consumer must be prepared to finish them yourself. (Cycle pedal cotters also fitted the kickstart levers of a number of vintage motorcycles I used to own). I know that may seem old fashioned, quaint and mildly intimidating to younger persons brought up on a diet of ready-to-fit-parts, but treat the exercise as a way of learning a skill, albeit a very basic one. There is a small satisfaction in fettling your own bike by your own leaned skill.

 

[Saddle bum]

+1 to Saddlebum. Bear in mind that cotter pins date back to the 19th century when engineers were engineers and superb craftsmen fitters to boot. In those days of course, the engineer would make his own cotter pins and obviously file them to suit the application. Move forward to say the early 1900's when every large town had its own cycle and motorcycle manufacturer (no error here, I do mean manufacturer), there was then a good market for batch made small items like clips, washers, split pins, cotter pins and the like. These manufacturers bought in such items made for unspecific machines, and then finished them by hand to suit the intended use. Likewise now, when you buy cotter pins, the same pins will fit a multitude of different applications, but you, dear consumer must be prepared to finish them yourself. (Cycle pedal cotters also fitted the kickstart levers of a number of vintage motorcycles I used to own). I know that may seem old fashioned, quaint and mildly intimidating to younger persons brought up on a diet of ready-to-fit-parts, but treat the exercise as a way of learning a skill, albeit a very basic one. There is a small satisfaction in fettling your own bike by your own leaned skill.

Assoluterley.

 

[shimano]

mmmm, yummy, humble pie;

http://www.sheldonbrown.com/cotters.html

another slice please...

 

[Gerry Attrick]

Sorry guys. Didn't mean to go on, but I am an avid admirer of craftsmanship.

 

[campagman]

I was interested in this as my shopping bike needs a new cotter pin and a spare one that I found in the garage wouldn't fit. Anyway Sheldon Brown says that cotter pins can come in 8.5, 9.0, or 9.5 mm dias. No amount of filing is going to work if the pin is the wrong dia.

 

[Gerry Attrick]

I was interested in this as my shopping bike needs a new cotter pin and a spare one that I found in the garage wouldn't fit. Anyway Sheldon Brown says that cotter pins can come in 8.5, 9.0, or 9.5 mm dias. No amount of filing is going to work if the pin is the wrong dia.

Notwithstanding my last post, you guys have no tenacity. With patience and care, cotter pins can be made to fit anything.

 

[BADGER.BRAD]

More cotter pin Hell

Hello All,

Still have problems with the cranks tried new cotters but it killed them on my way to work only 2 1/2 to 3 miles Think I will have to change the crank Although in fairness I can see no damage there ,if anything the hole through the crank arms seems wrong ? If I look through the cotter pin hole from one end to the other I cannot get the two ends of the crank arm to be level with the edges of the flat on the crank at the same time thus I think the crank arm is trying to rock as I pedal. I have measured the holes to see if they are oval with a tape measure (not great I know!) and tried the cotter in there (seems no gap) ?????
How do I know if the cotter pin is fitting ? I tap the thing in put a spanner to the nut and all seems fine not a jot of movement, 3 miles later and all is loose again do I just keep filling until this stops ?

Many thanks for all your help.

http://www.sheldonbrown.com/cotters.html

 

[Gerry Attrick]

When you buy the cotter it will already have a flat filed on it. All you have to do to get the pin to fit your crank is to further file that flat. But, and it is a serious but, you must file it so it is completely flat. i.e. it has no high or low spots on it. If it has, it will tighten up ok, but within a very few revolutions, it will be loose again.

Having said that, the wee beasties do have a tendency to loosen off as they bed in, so first time out, take a spanner with you and check it is reasonably tight at regular intervals. Do not overtighten it as you will eventually get it jammed.

One further bit of advice on filing the flat: File it so that when the nut is tight, the end of the threaded portion of pin is level with the face of the nut. That way you leave enough thread to re-tighten as it it beds in.

Incidentally, the flat of the pin should make contact with the flat on the bottom bracket spindle. If you fit it the wrong way round, you will never get it to tighten properly.

Don't give up, you will get it right!

 

[BADGER.BRAD]

Cotter pin help thanks

Many Thanks Gerry, much appreciated. As brought they are pretty rough so will have a go as soon as it stops raining