Thinking of buying another old Raleigh Grand Prix that looks like a time capsule. I would ride it on a pretty regular basis. I think it's a 74-75'? It has cottered cranks but the bike was barely ever ridden. A brief search here on Bikeforums has me worried about them slipping or worse yet removing them. Then there's the threading issues I've read about if I need to switch the bottom bracket, maintaining the width and chainline, etc? I'm not sure I want to get into crank upgrades along with wheel upgrades, adding a Brooks, etc. I don't want to invest $500 into a $150 bike.

The question is how much of a problem are cottered cranks that presumably are aligned properly and have little wear on them and are like new. I know they are heavy as heck but didn't they rule for years without slipping and injuring the world?

Cottered cranks get loose but they don't slip unless the cotter falls out. You can learn everything you need to know about cottered cranks and everything else bike related by reading Sheldon Brown. The bearings in your bottom bracket require regular maintenance and that requires that someone who knows how to work on a cottered crank take it apart and put it back together. You can become that person by doing some reading. Otherwise, just take it to a shop and pay them to do it.

They are probably frozen on to the point that slippage is NOT an issue.
Removal might be though.

They should be fine.

Give the top of the cotterpin a gentle tap with a hammer and tighten the nut snug but don't overdo it. The taper holds the crank on, the nut holds the cotterpin in. They can't go anywhere unless unusually loose.

Removing them is not usually a big deal, but many times requires new cotters, and the taper has to be filed to fit.

After that, the bottom bracket services like any other cup, spindle and bearings one, requiring somewhat specialized tools.

Cotterred crankset that were assembled right, such as on the old Raleigh sport and superbe 3-speeds, were not known to slip, at least by me and my childhood riding buddies. Such cranks could slip if they were disassembled and not re-assembled using the right tools to fit and set the pins. I saw a lot of this in college, when fellow students who did not know the risks took their bikes apart and couldn't always get them back together. I couldn't help them, because I didn't have the tools for cottered BB work.

I have cottered cranks on my Sports. I put them on crudely but correctly and I don't have any problems. I weigh 230 lbs and tow the kids up hills in the bike trailer (another 90-100 lbs). if you don't mind the weight or the PITA it is to take them apart for bearing service they will be cool.

I ride an old cottered miyata and I've never had a problem with slippage, wear, or breakage. Depending on your local bike shops, the only problem will be finding replacement cotters that FIT. My LBS happened to have a drawer of pins they let me sift through for free, but they were all too small. Don't bother - no matter how hard you tap it in there, it will slip eventually. Your shop might not have any, but good news -

https://harriscyclery.net/itemlist.cf...dsearch=cotter

Buy in bulk - if you are doing regular BB service (as you should) chances are you are going to need two new pins every time you take your cranks off. The pins are pretty soft, so once they've been ridden for a while they will take a couple off good hits with a hammer to get knocked loose - this usually mushrooms the threaded head of your pin making it near impossible to get a nut back on it.

As mentioned above, some filing might be needed to get the threaded end of the pin all the way through your cranks for a good fit, but this can be done without any hassle in a couple of minutes. Also (I believe Sheldon mentions this) - once your pins have been ridden for a good number of miles it is wise to tap them even further into the cranks and retighten your nuts. A WORD OF CAUTION - It's very easy to strip the nuts that come with these pins (in my experience anyway) when you're trying to get a tight fit - The sawzall takes the place of the hammer in such cases. Use a drop of locktite on your nuts and you should be fine.


My miyata originally did not come with any type of internal BB sleeve so I was servicing more often than i wanted to - so invest in one of these if you don't already have one.

https://harriscyclery.net/itemdetails.cfm?id=1073

With the correctly sized pin you won't have anything to worry about.

EDIT -

On such an old bike, removal of the original pins could be a problem (it was on my miyata). One side popped out after pounding on it for a couple of minutes. On the other side, the threaded head broke off and i had to use a hammer and a punch to get it out - pretty stubborn pins but it can be done.

sheldon has more information on these things :

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

Get the right tool and it becomes a simple task:

https://www.bikesmithdesign.com/CotterPress/

I have one bike with a cottered crank. Now that I have the tool I wish I had more.

I can't think of any other specialized tools required. I use VAR lockring pliers, but I made do with a hammer and a soft drift punch made from copper water pipe for years.

Cottered cranks are pretty indestructible and very very reliable. The system is a pain to disassemble but frankly they are less likely to have problems than alloy square taper cranks. I've taken apart and assembled a number of them and never had any problem. I don't have the nice press, I've made do with a brass punch for removal and a wooden mallet for insertion. Ruined a cotter during removal that way once, but it was on a Peugeot and I have a bag of cotter pins so I just put another one in.

In any case, it would be really hard for them to slip. Even installed horribly, as long as you can see that the cotter has the nut screwed on there's just not much to worry about.

Cheers,
Karl

Don't fear the cotter. I find it extremely theraputic to work on a bike with a hammer.

One note on the replacement pins, the originals are better made than the replacements.

I agree with Dirtdrop on this one - they're no problem to ride, do not have more reliability issues than cotterless, and if you have the right tool (just the one) are easy to maintain as well. Get a Bikesmith Designs cotter press, as Dirtdrop linked, and you'll have no trouble:

I love good tools, and this is one of the best.

However--I've only had occasion to service a bike with cottered cranks. I followed the directions at sheldonbrown.com to the letter and as a result removing and reinstalling the cotter pins was a piece of cake. Really. Don't be afraid. Sheldonbrown.com is your friend. Trust him.

I think you are referring to a swaged-on spider slipping with respect to the cranks. This can be dangerous, and it can happen with any cheap cottered crankset, but it is probably far more likely on a cheap cotterless set. Listen for creaks and groans, and perioidically check the integrity of the crank-to-spider junction. Better yet, find an Agrati crankset with an integral spider.

I have owned several bikes with cottered cranks, and the only failure I ever experienced was a left crank fracture at the spindle/cotter eye during a strong downstroke. My left foot lurched downward about an inch or so, but I maintained my balance and rode home with my cranks in a 160-degree / 200-degree orientation, i.e., with the left crank timing advanced by about 20 degrees. The outcome was far better than when I snapped an aluminum crank at the pedal eye during an out-of-saddle climb ...

As regular readers know, my red-with-white Capo has updated components, but I am keeping its white-with-red stablemate as original as possible, including the cottered crankset and balky Campagnolo Gran Sport derailleurs.

I have ridden one cottered cranked bike over 15,000 miles with no issues. And ridden many others on a regular basis without problem. As long as the cotters are tight and of the correct size I say ride on

Aaron

May I toss out a home remedy... A c clamp & a wrench socket
or a brass drift
or hammer & sturdy peice of wood between cotter & the hammer (support from below)
used these at various times on the '70 Raleigh Record bought new.
The threads on the cotters wore away from years & years of servicing it.

The only time I had a problem with crushing cotter pins was with a Gitane Tandem that we had sold at the LBS back in the day. Once assembled, my boss and I took it out for a test. One of the cotters flattened and allowed the crank set to twist forward. I wish I could recall what we did to remedy the problem, probably just new non-French cotter pins.