Perenially loose cottered crank
08-04-05, 02:31 PM
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Perenially loose cottered crank
Hi, I have a 70s road bike that I'm trying to restore and get bike to riding condition. I have everything fixed except the left crank is loose. This is a cottered crank and I have replaced the original cotter pin, installed a new one, and after 5 minutes of riding it would get loose again. Then I would tighten and it would loosen in 5 seconds of riding. Both of these pins had a nice U shaped gash in them on the flat side after I removed them. I put a 3rd one in and didn't tighten it as much as I had the 2nd, and it worked for a day but it is starting to loosen already.
The crank itself looks ok so I'm wondering if anyone has any suggestions. I'm a novice to bike repair but I've enjoyed fixing these problems.
The crank itself looks ok so I'm wondering if anyone has any suggestions. I'm a novice to bike repair but I've enjoyed fixing these problems.
08-04-05, 08:23 PM
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Take it to a bike shop that has a cotter pin press. Most people think they are only for removal, but a press is the best way to get them so tight they won't loosen up.
08-04-05, 08:53 PM
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Originally Posted by theloniouszen
Hi, I have a 70s road bike that I'm trying to restore and get bike to riding condition. I have everything fixed except the left crank is loose. This is a cottered crank and I have replaced the original cotter pin, installed a new one, and after 5 minutes of riding it would get loose again. Then I would tighten and it would loosen in 5 seconds of riding. Both of these pins had a nice U shaped gash in them on the flat side after I removed them. I put a 3rd one in and didn't tighten it as much as I had the 2nd, and it worked for a day but it is starting to loosen already.
The crank itself looks ok so I'm wondering if anyone has any suggestions. I'm a novice to bike repair but I've enjoyed fixing these problems.
The crank itself looks ok so I'm wondering if anyone has any suggestions. I'm a novice to bike repair but I've enjoyed fixing these problems.
08-04-05, 11:14 PM
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Bikes: 1990 Paramount R-90, mustache bars, XC Pro/XTR; Gunner Streetdog fixie, all black; 87 ex-7-11 team Merckx, 753, refin 73 Molteni livery (Cycleart), 8 spd D/A; Gary Yakota hardtail, Tange/Ritchey WCS tubes, heavily modded Judy SL, King, 9 spd XTR
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Cotter pins come in several different diameters, too. Try a larger one...
Also, make sure that your crank and spindle are properly align with each other. The "U shaped gash" may be caused by a misaligment, which would also preclude a proper tightening.
Use a hammer to drive in the pin, too. The bolt and htreaded shaft can easily break if they are used to pull the whole pin in.
good luck...
Also, make sure that your crank and spindle are properly align with each other. The "U shaped gash" may be caused by a misaligment, which would also preclude a proper tightening.
Use a hammer to drive in the pin, too. The bolt and htreaded shaft can easily break if they are used to pull the whole pin in.
good luck...
