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single-piece crank varients
I want to replace the crank in my daughters single speed BC (drive pin busted off) but I'm finding only triple chainring cranks. Anyone know if there is a difference between 1 and 3 ring cranks? Already read about the different thread sizes. Not really interested in updating to 3 piece. just want to fix it fast and move on to next project. Thx.
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Some shops only carry 3 pc. cranks, you'll need to find a shop that carries 1 pc. cranks. There is a huge difference. Measure the crank arms you have as there are different lengths. If you don't have many shops in your area you can order on-line or any shop can special order one. Price is usually around $20.
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Originally Posted by Insidious C.
(Post 17980167)
I want to replace the crank in my daughters single speed BC (drive pin busted off) but I'm finding only triple chainring cranks. Anyone know if there is a difference between 1 and 3 ring cranks? Already read about the different thread sizes. Not really interested in updating to 3 piece. just want to fix it fast and move on to next project. Thx.
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probaly hit a flea market or thrift store and get a cheap bmx bike for less than buying a new crank. if the sprocket's the wrong size just take both apart and swap it out.
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Thanks everyone. I robbed the crank from an 18 speed Murray that I got for free. The crank turned out to be identical, so I just swapped the triple rings out for the single. All set for camping along the coast!
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Congrats. So I guess both were 3 pc cranks but one had 1 chain ring and the other had 3 chain rings, I think I get it now.
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I think both bikes were 1 piece cranks knowing that the one bike was a Murray. Roger
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Both were one-piece cranks of same width and length. I repaired the single speed beach cruiser, an 80's Murray Monterey, using a crank from a similar vintage 18 speed (three chainrings) Free Spirit. Although the Free Spirit had been repainted there were multiple clues suggesting it was also manufactured by Murray. The Free Spirit is an unusual beast with a Mixte frame design.
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It coulda been. Really there's not too many variables to screw with, when it comes to ashtabula cranks, aside from crank arm length, and sometimes arm diameter, as kids bikes generally have smaller cranks, I mean the 16, and 12 bikes, most bmx, mtb, and cruiser use the same diameter crank, but often have different arm lengths for different BB hieghts. Mtbs usually have the biggest chainrings, especially if it's a double for some reason.
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All one piece Ashtabula cranks
have the same threads for the crank ring and bearings. Regardless of what company made the crank or the brand of bike it is on, they are interchangeable. |
Originally Posted by bicyclridr4life
(Post 18232832)
All one piece Ashtabula cranks
have the same threads for the crank ring and bearings. Regardless of what company made the crank or the brand of bike it is on, they are interchangeable. There are two major types of one-piece crank sets, differentiated by their axle threading. The more common size uses 24 threads per inch, but some bikes, particularly older U.S. made Schwinn and Mongoose models, use 28 threads per inch. No part of the bearing assembly is interchangeable between threadings. 24 TPI cranks use #66 retainers, with 10 5/16" balls. 28 TPI cranks use #64 retainers, with 9 5/16" balls. The pressed-in cups are also a slightly different size internally, though they both fit the same frame bottom brackets. It is usually a good idea to buy a whole set (cones, cups, retainers) if there is serious wear to any of the parts. These are not expensive. Good sets are less than $20. |
Some more arcane info that will be useless for most people. In addition to Schwinn, Columbia and Rollfast made their own bearings and cranks. And while the Rollfast and Columbia cranks are interchangeable with other brands - the cones and lock washers, etc. are not. The main problem is that both of the companies used a dust cover that works specifically with their own bearing assembles, if you try to mix parts with your typical Wald bearing set things won't work quite right. The whole lot has to be swapped together.
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