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Old 03-30-04, 01:08 AM
  #17  
shecky
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Originally Posted by OneTinSloth
i think there's a little more force acting on the sprocket and crankarm pin when you're trying to resist on a fixed gear than there is when you're engaging a coaster brake. if it's anything like any of the other one-piece arrangements that i've seen and taken apart, that pin is the ONLY thing keeping the sprocket from spinning freely around the crank spindle, and it's probably being held in place laterally by some spacers.
I'm not sure I'm buying this notion that the crank pin is vulnerable to failure on a fixie. Certainly, reverse pedal forces are greater on a fixie than on a coaster brake. However, it seems unlikely that reverse pedal forces on a fixie will exceed forward pedal forces on a coaster, fixie or just about any bike for that matter. And one piece crank pins just don't seem prone to breaking. Interestingly, lots of the high end ultra tough 3 piece BMX cranks use the same system.

Originally Posted by OneTinSloth
i'd rather have that force spread out over five arms going to the crank than one pin. if you're gonna be using at least a front brake, go for it. having seen a lot of snapped and bent one-piece cranks (one set was brand new and was bent by the end of a 4 hour bmx ride where the kid using them was taking it easy). use brakes. one-piecers are maybe about as trustworthy as old-style cottered cranks on a fixed gear on the street.
Having seen lots of snapped three piece cranks, I think anyone capable of busting a typical forged cromo 1 piece crank will almost certainly destroy a typical three piece aluminum road crank without to much trouble. Perhaps the only real alternative for such a gorilla would be one of the cromo 3piece BMX cranks with Ti spindle.

Of course, these are blanket statements that probably don't always apply. 1piece cranks come in a variety of qualities, and I've seen them bend and break, too. Same goes for cottered three piece cranks, which are all over the map as far as quality is concerned. I'd have no trouble trusting a old Raleigh cottered crank (in fact I do on a nearly daily basis). The cast steel Indian cottered cranks, on the other hand, seem worth their weight at the scrap metal yard.

Unfortunately, I can't vouch for the quality of the cranks on a old Murray. However, the cranks on old Schwinns are practially indestructable, unles you're doing some hard BMX stuff.

The greatest tesitmonial to the 1 piece crank comes from a guy named Chalo Colina, a 6' 5", 350 lb bike destroyer and frequent contributor to rec.bicycles.tech, who has sung the praises of the one piece for durability and simplicity. And surprisingly never managed to break one. And of course, myself, who to this day owns the "real" Ashtabula 7.5" crank that survived my BMX and early MTB days. (Can't figure out how I used to ride those things... they kill my knees these days.)
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