8/4/15 2:12 PM

I'm fixing up a Raleigh Grand Prix mixte, probably 1975. I'd like to replace the cottered crankset with a '90s base model Trek square taper cotterless. I haven't taken it apart but it sounds like the BB is not stock English, but a fine thread.

Phil Wood makes a BB for the job. Of course that will quadruple the investment. I'd rather invest in brakes, wheels and lunch, kwim.

Suggestions?

8/4/15 2:16 PM

I have just replaced the axle from cottered to square taper a few times with success. Keeping existing the cups threaded into the frame, last one being a french threaded frame. New axle, bearings and a lube and roll..

8/4/15 3:01 PM

My first bike 10 speed was a '72 Gran Prix. That was the only bike I've owned that I have sold, but I currently I have a '57 Bianchi and '65 Cinelli Mod B with cottered cranks. Granted I don't use them much but the cottered cranks work fine. If you're not going to put big miles on the bike I don't see the problem. And the steel cranks are freakin' aero! I'd put the $ elsewhere.

8/4/15 6:05 PM

Speaking if which, I have a skip tooth cottered setup on craigslist locally. Pulled off a project bike:

"Magistroni/Charter-LEA vintage Skiptooth 170mm crankset/BB" add title.

New Ukrainian made I think BB. ;)

8/5/15 5:40 AM

Back when I was in the bike biz, I hated cottered cranks with a passion. Until you've spent time pounding and/or drilling out mangled cotter pins, you can't appreciate what a horrible design it is.

8/5/15 9:11 AM

Cottered is cool?? I'm with you, Brian.

Sure, they work fine on the bike. But removal for maintenance? No way, at least not no more. I replaced a few, and went through that mess of pounding out pins, and grinding the new ones to fit. Never again. Now, if I get an old bike I want to fix up, and I have a "cotterless" crankset to put on it, the cottered cranks come off the easy way: a hacksaw through the arm parallel to the cotter, a tap of a cold chisel, and that cotter falls right out. Not reversible, obviously. I smile when I throw the the destroyed cranks in the trash.

None of these I'm working on are as nice as the ones you're saving, Dan.

8/5/15 9:15 AM

When I was 15 and bought a Schwinn World Voyager it had a forged crank sans cotters. Even then I wanted no part of them. ;) Mostly because my bike idol had an all campy chrome bike with sewups. My next bike was a chrome 531 custom that was made for someone else I got 'on sale' due to a chrome blem, with sewups. Made by Andres or Francisco Cuevas, I forget which in the basement of the home of Paris Sport bicycles. ;0 But no cottered cranks. ;)

8/5/15 10:05 AM

But if the cotter pin is kept tight the crank will work.

And:

(a) how much money and effort do you want to put into upgrading a '75 Gran Prix? I had a '72, they are gas pipe specials and came with cheap components all around.

(b) how many miles is someone going to put on a '75 Gran Prix? How often is it going to need maintenance?

You could probably get a better bike for the cost of the replacement crank.

Hey, it it's worth it to you, go ahead and upgrade the bb.

8/5/15 10:25 AM

I think seeing all the non maintained bikes with failures early on had me squarely in the junk camp. Of course, just keeping them tight is a good thing. But a lot of ham fisted folks after a cotter would loosen or the nut fall off would do more harm that good to the system overdoing trying to get it not to happen again. that seemed to be what I saw, or remember mostly.... ;)

8/5/15 10:25 AM

Just chase the threads with a 24x1.37 tap

8/5/15 2:29 PM

Cotters actually have several advantages, with adjustable chainline being just one of them.
I made a cotter press tool for about $10 using a motorcycle chain tool.
The biggest problem with cotter cranks occurs ONLY if you have damaged the original cotters, as the good hardened one's are nowhere to be found, and have to be precisely sized to the particular crank/nationality.
Since my Steyr had adequate crank gearing for the intended 5s freewheel ratios, I just rebuilt the bb with Gr25 balls which really smoothed it out. The original cups and spindle were nicely hardened and will last many thousands of miles.

8/5/15 7:33 PM

Okay, keep the crank for now. I've got a Bianchi engraved Super Record to replace it with after I chase the threads, forget the used Trek crank. What was that I read about the BB shell diameter being oversize?

Another thing that burns me about the bike is the seat tube must be 25.35, as in, put it in a vise and use a see-saw for leverage to pull the out 25.4 seat post.

But I'm sure she's going to look nice having fun riding it. With the new saddle, handlebars and mostly replacement drivetrain it will be better than new. And if after a few hundred miles when the bug has bitten, well it won't be the first story like that written on this forum.

So how high do I set my torque wrench for the cotter pin?

8/5/15 8:06 PM

My first decent ride was a cottered Raleigh. And I had a similar bike in the mid-'90s when I got back into cycling.

I hate cotters. I used to carry a wrench.

If you're dealing with a non-standard frame, I'd probably try one of these. Pricey, but effective:

http://store.velo-orange.com/index.php/components/bottom-brackets/grand-cru-threadless-bottom-brackets.html

8/5/15 9:02 PM

Seems reasonable considering what it can do for you. Especially if it is of better quality etc.

8/7/15 11:16 AM

"So how high do I set my torque wrench for the cotter pin?"

I think that a torque wrench is worthless for this application.

What you want to do is to apply and maintain(!) torque to a short box-ended wrench whilst tapping on the head of the cotter. Note that the wrench will yield in response to the tapping, then at some point the yielding will level off.
The torque level can be modest, as seems appropriate to the threaded diameter of the cotter, which varies (factory cotter threadings are usually thicker and with finer threads than modern replacements).
The hammer tapping also need not be heavy, use common sense is all I can say.
The cotters must be well-settled, wedged in, or movement and damage to the flats might result!

Is there a real reason to replace the cottered crankset? I've found them to last practically forever (steel chainrings last much longer), they exude that vintage style and never creak. I now have over 3k miles of intense riding on the Steyr, here in the hilly foothills.
Installed as I have described, the nuts should never loosen, but if concerned, just use a drop of Loctite on the cotter threads.

8/7/15 2:22 PM

quote:

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Is there a real reason to replace the cottered crankset?

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8/8/15 2:51 AM

When talking about cotters, we often are starting with a cheap bike, so likely not wanting to put much additional money into it in most cases.

But with a cotter press tool, maintenance is about as easy as with cotterless.
Hammering on the wonderful original, hardened cotters to remove them is a sin.
Ruining one is a disaster!
And one could change to sealed cups if riding in bad weather or really high mileage were anticipated. I expect to ride to 5k before my next cottered bb overhaul, no seals but I did use a good grease and chromium balls last time.