BB Replacement: Is My Head in the Right Place?
06-03-13, 03:35 PM
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BB Replacement: Is My Head in the Right Place?
Greetings folks.
I'm cleaning/rebuilding a Trek 728. It came with a Sugino AT half-step+granny crankset and an asymetric 124mm loose bearing Sugino BB. I'd like to swap it out for a cartridge BB so I don't have to worry about regreasing the darn thing. Besides, both cups are starting to become pitted.
I checked sheldonbrown.com, and he said that a 130mm cartridge unit would get the cranks/chainline straight, but would push the left crank out away from the bike. If my math is right, it would push the left crank arm out ~6mm, not a big deal, but possibly enough to annoy me, aeshetically if nothing else. Mainly just because I'd know the left side was a whole entire 1/4 inch off!
My question, could I arrive at the same (or close) DS crank/chainline position with a 127.5mm BB and a 1-2mm spacer on the DS, without pushing the NDS crank as far out?
I'd like to keep the crankset on there (I think), and honestly having the left side off that little bit off isn't a big deal, but would the shorter spindle and a spacer be an alternative?
Thanks in advance.
I'm cleaning/rebuilding a Trek 728. It came with a Sugino AT half-step+granny crankset and an asymetric 124mm loose bearing Sugino BB. I'd like to swap it out for a cartridge BB so I don't have to worry about regreasing the darn thing. Besides, both cups are starting to become pitted.
I checked sheldonbrown.com, and he said that a 130mm cartridge unit would get the cranks/chainline straight, but would push the left crank out away from the bike. If my math is right, it would push the left crank arm out ~6mm, not a big deal, but possibly enough to annoy me, aeshetically if nothing else. Mainly just because I'd know the left side was a whole entire 1/4 inch off!
My question, could I arrive at the same (or close) DS crank/chainline position with a 127.5mm BB and a 1-2mm spacer on the DS, without pushing the NDS crank as far out?
I'd like to keep the crankset on there (I think), and honestly having the left side off that little bit off isn't a big deal, but would the shorter spindle and a spacer be an alternative?
Thanks in advance.
06-03-13, 04:26 PM
#2
Mechanic/Tourist
I checked sheldonbrown.com, and he said that a 130mm cartridge unit would get the cranks/chainline straight, but would push the left crank out away from the bike. If my math is right, it would push the left crank arm out ~6mm, not a big deal, but possibly enough to annoy me, aeshetically if nothing else. Mainly just because I'd know the left side was a whole entire 1/4 inch off!
My question, could I arrive at the same (or close) DS crank/chainline position with a 127.5mm BB and a 1-2mm spacer on the DS, without pushing the NDS crank as far out?
My question, could I arrive at the same (or close) DS crank/chainline position with a 127.5mm BB and a 1-2mm spacer on the DS, without pushing the NDS crank as far out?
06-03-13, 06:06 PM
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Sorry, spindle code is "3U" (124.5mm). Symmetric conversion chart at the top of that page says use a 133 (forgot the last 3, sorry). That's where I got that number.
I was under the impression (wrongly apparently) that the list you pointed out was for OEM parts used with that model.
So I guess I was right in my thinking. Thanks for the clarification.
I was under the impression (wrongly apparently) that the list you pointed out was for OEM parts used with that model.
So I guess I was right in my thinking. Thanks for the clarification.
