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Help with converting a 3x8 to 1x8: chainlines & bottom brackets

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Help with converting a 3x8 to 1x8: chainlines & bottom brackets

Old 09-11-19, 08:56 PM
  #26  
Kapusta
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I have not read this whole thread or even make it through your epic length original post, so forgive me if this has already been asked.....

Can’t you just take the big and small rings off the triple and just run a single ring in the middle position? I’ve done this many times. I am currently running a 1x7, 1x8, and 1x11 all using converted triples.

If you want to dress it up a little, get a bash ring for the outer ring position. . Check out BBG Bash Guards for a whole mess of options for around $20.

Last edited by Kapusta; 09-11-19 at 09:06 PM.
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Old 09-12-19, 12:23 AM
  #27  
le mans
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Originally Posted by the sci guy
I'm not 100% sure. It's a R300 triple. page 53 here: https://vintagecannondale.com/year/1999/1999V2.pdf
specs are page 91.
That has good bottom stay clearance, i think you should just go ahead an order that nice crank for it, preferably the Sram coz it has the light weight BB unit built in. Going single chainring lightens the bike up..might as well go all the way, imo
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Old 09-12-19, 08:22 AM
  #28  
adipe
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you need a chainring that is not meant for shifting, otherwise the chain will fall off too easily.
be sure you have it so or you'll have to stop once in a while to put it back on;

the chainring can be very close to the chainstay - if it's just 1mm close there's no danger of the chain messing the chainstay.
it is a good thing to have it so close for different reasons.

i would advise looking for a crankset that has less than 170mm if you are less than 1.75m height... unless you are climbing hills very often.
smaller crank arm with clipless pedals is very nice. and i'm about 1.76m height.
and it is very important to have as low q factor as possible... for different reasons. the first is to be able to use with good efficiency lower than usual cadence or higher. the least important reason is aerodynamics.

i ran 46:19 with 165mm on the last road-ish bike. it was a singlespeed setup and i never felt too low gear ratio. i was able to climb hills quite alright by anticipating them (knowing the route) and having a bit less effort before the climb and just mashing.

i prefer a large chainring so there's less chain wear. i used a 46t because the frame was with vertical dropouts and i had to "magic gear" it - no tensioners.
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Old 09-12-19, 01:32 PM
  #29  
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The Sugino crank has an JIS square taper, and a 110 mm bottom bracket will put the chainline where you want it if you buy that crank. Any Shimano bottom bracket is going to have the JIS square taper you want.

If you somehow wind up with a ISO tapered bottom bracket, and put an JIS tapered crank on it, you'll have joined a pretty big club. Nothing happens, except maybe a real bike snob will make fun of you someday.

I agree with many others here -- just buy your identical bottom bracket if it's worn out, and put a narrow wide chainring on your existing crankset in the middle position. Turn the outside chainring into a chain guard, or replace it with one. Abandon the front derailleur, granny ring and left shifter.
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