Bikesmith is out of stock on all the high grade cotters, im looking for the sort with ground flats as opposed to smashed ones. Anyone have a source to share? 9.5mm dia. is what im after. Would rather not take a gamble on ebay specials.

wow jayjay1976 -

this is a most excellent question. afaik they have been unavailable for decades. recall the beautifully polished ones that came on italian machines back in the day with their false acorns whose inserts came in various colours to match the bicycle's finish.

looking forward to the responses...

Mark Stonich--Bike Smith Design:

Bicycle Crank Cotters

I think he just mentioned that Bikesmith was out of stock...

I saw some 9.5mm on ebay yesterday. In lieu of not having anything else, I would buy a set and press them into place and put the bike back on the road- all the while looking for the real thing. If the new ones fit OK, you could always take one to a machinist and see if he could make up a set... if you don't feel bad about paying $100 or so for them...

If Mark Stonich can't get them for you, it might be difficult to get them yourself.

I've had good luck with the el-cheapo cotters though. I think the key is to file them very accurately and this requires a very steady hand and a good quality mill file. I always make sure I have some spares though, for when I mess up with filing the flat.

+1. Buy a bunch and get filing!

You may want to stop in a local bike shop that you know hoards bike parts. I know of two in the NYC metro area. You may want to ask Steve Willis of The Bike Stand in Scotch Plains, NJ. He likes cotters.

I think I might have a few new cotters in that size--I'll have a look in the morning and get back to you.

I just use the cheap ones. I find they are good enough. My only complaint is the threaded part is too thin and is easy to bend or crush when removing them.

jayjay1976, I did find a pair of good-quality 9.5 mm cotters in my box o' junk. It looks like you don't have enough posts to send a private message, but email your mailing address to me at jon@redclovercomponents.com and I'll drop them in the mail to you.

Thanks for the informative link.

I also agree with Noglider in finding a shop with a large assortment. Learned the hard way when I ordered two different pairs for an Italian crankset. My hope was that at least one of the two pair would work. Not so and didn't want to fuss with trial and error grinding. Was lucky to find a shop with a very large and variety of pins. My guess there were at least six different type of tapers.

IMHO, makes a difference in getting a pin precision close and use a good grease. The arms set nicely and its easier to take apart for future service.

If you use cheap cotters a cotter press is mandatory. Otherwise you will strip the nut trying to get it tight enough. A properly installed cotter will not loosen up over time, contrary to comments I have read elsewhere. I have Nervar, Stonglight and Chater Lea cranksets, the the Bikesmith press works on all three.

Agreed--hail Mark Stonich and the Bikesmith cotter press! It's money very well spent if you have even one bike with a cottered crank.

the "grade " is less important .. they have to be softer than the BB spindle, anyhow.

Back in the day.. there was a cotter holding clamp to go in the bench vise to use while filing the taper ..

That's interesting. Do you have a visual of what this tool looked like?

It had rounded jaws to hold the round cotter.


Pictures of everything Ive seen in 68 years, most before the digital camera was invented or the Web?


Im not Google. help your self to their services..

I get cotters from my LBS, but I expect they are "the cheap ones" and probably not unlike what you'd buy on ebay. I'm curious about these "good" cotters. How do you tell a good one from the rest? My dad had a cottered crank on his bike when I was a kid, but I never had one until a few years ago. I don't recall how cotter pins were different before. These 9.5mm cotter pins have a nice vintage-looking nut and file marked: New Cotter Pin for Crankset 9 5 mm 43 mm Vintage Bike Old Bicycle French | eBay Would you consider these "good ones"?

+1 to the Bikesmith press. A great investment if you expect to work on cottered cranks, or, like me, enjoy excuses to buy a new tool.

You can't tell the good ones visually. It's about the hardness of the steel.

Try Wayne at Velo Classique. He probably has cases of them around the place since Velo Classique is essentially the storefront for Mel Pinto.

Actually, you can tell the good ones by looking at them. The cheap ones are not domed on the ends like the higher grade cotters.

I got one of his presses a few years ago and it's one of the best investments I've made. A benefit of using a press for cotters installation and removal is that the cotters are usually reusable.

Thanks for all the informative replies!

In my understanding, 'high-grade' cotters are made from a harder steel and have flats and threads that are machined or ground as opposed to the lower grade type with stamped features. Those are made out of a softer steel to allow stamp-forming the flat, and roll-forming the threads, and are made from a slightly undersized rod (9.2mm vs. true 9.5mm) so that the stamping operation doesn't cause them to expand beyond 9.5mm which would cause fit issues.

From a mechanical design standpoint, a tight-fitting cotter leaves less of a gap for material spread when the cotter is deformed either from insertion or the dynamic loads generated while pedaling. Also, a cotter closely matched to its bore gives a better distribution of stresses.

jonwvara hooked me up with a set and I have a good mill file to tune the flats, then I'll be using one of these to press them in $16 Cotter Press

I'll report back with the outcome!

I was chasing a problem with the BB of my 72 Raleigh Superbe and had the cotter out of the crank 10-15 times (the problem turned out to be a casting issue with the crank arm). That same cotter is in the crank today. I likely ride that bike more than my performance stuff as it has racks, saddlebags and a locking front fork- its very convenient and good for commuting. I would not have been able to do that without a cotter press.

I think cotters have received a bad rap mostly due to the skill needed to fit and service them. Square tapers, on the other hand, can be fitted correctly by the layperson which makes them cheaper to manufactre, repair, and replace, all of which benefit the bike industry. The cottered crank technology is just as sound today as it was in the 1880's, so i dont see the need to fetishize its obsolescence, its just good, proven engineering. Ive had far more issues with creaking from square tapers than i ever have from cotters, so they seem to me a superior method of power transmission.

BTW in this particular case I'm fitting a pair of stronglight cranks off a raleigh to a german made Thompson BB, to get it back close to the original configuration. The frame is a late-60s touring model by Victoria-Werke out of Nuremberg. Nothing particularly rare or valuable, but the love of my cycling life because of the places she's taken me.