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Topic: big chainring with small cog vs small chainring with big cog

Posted on: 2nd May 2015 8:54 PM    Quote and Reply

what's your default choice? 
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Posted on: 3rd May 2015 1:21 AM    Quote and Reply


2nd choice, reason is look at the DH bikes or trail bikes or fatbikes, all small chain ring with 9 or 10 speed cog. do u see the reverse?

1st choice, speed very fast, scceleration is fast. but depends on bike weight and leg power, if bike is too heavy, cannot maintain speed. Climbing is a nightmare

2nd choice, speed slow, acceleration slow, can maintain speed. easy on leg power, climbing is no problem

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Posted on: 3rd May 2015 7:00 AM    Quote and Reply


For commuting along flat route, I believe gain ratio of 5 to 6 adequate for most of us. Can check against Shelton Brown's gear calculator, what you got there.

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Posted on: 3rd May 2015 12:26 PM    Quote and Reply


Sorry, originally wanted to compare big chainring with big cog vs small chainring with small cog. Any advice?

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Posted on: 3rd May 2015 12:55 PM    Quote and Reply


It's more efficient with bigger cogs to a point. The slight increase in rotational mass is more than offset by the fact that chain doesn't have to deflect as much round the rear sprocket. I have a bike with a Roholff IGH and having tried various combinations I find 36/16 or 40/16 are the most efficient 11 and 12 on the back were noticeably more draggy - it isn't quite as noticeable with dérailleur gears on my road bike but the drive train feels stiffer better to me running on the 52 ring and a bigger sprocket than the 39 and a small one.

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Posted on: 4th May 2015 3:49 AM    Quote and Reply


Quote:
"Formerly posted by Zappadeedoohdah: It's more efficient with bigger cogs to a point. The slight increase in rotational mass is more than offset by the fact that chain doesn't have to deflect as much round the rear sprocket. I have a bike with a Roholff IGH and having tried various combinations I find 36/16 or 40/16 are the most efficient 11 and 12 on the back were noticeably more draggy - it isn't quite as noticeable with dérailleur gears on my road bike but the drive train feels stiffer better to me running on the 52 ring and a bigger sprocket than the 39 and a small one."
Puzzled: Any optimising of drive train done? It reads to me like Keong81 is musing optimising drivetrain.

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Posted on: 4th May 2015 4:13 AM    Quote and Reply


Quote:
"Formerly posted by keong81: Sorry, originally wanted to compare big chainring with big cog vs small chainring with small cog. Any advice?"
Now there is this 1X11-speed drivetrain available. So it should be easier to optimise your drivetrain. In theory, the lighter rotating components would help. I have yet to do some time trials with optimised drivetrains to appreciate the differences. Perhaps you may want to try out those MTB with triple chainrings, if it helps you decide. Select the two extreme chainrings to compare the performances. 

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Posted on: 4th May 2015 8:12 PM    Quote and Reply


Thank you everyone for sharing

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