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PostPosted: Sun Nov 21, 2010 10:19 am 
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There was an article a while ago about this issue.

http://www.cyclingtipsblog.com/2010/04/the-big-ring-mechanical-or-psychological-advantage/

For anything other than mild xc MTB use, I would say the issue of clearance rules over the ideal of large rings and sprockets, as well as the weight issues.

:)


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PostPosted: Tue Nov 23, 2010 11:09 am 
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I'm not sure you can get a single 11 unramped sprocket that'll fit on to a regular freehub. The top one off a cassette is stepped, it'll only fit on the end. And a 22 ring will only fit on the inside of a normal crank. Which will mean an epically wonky chainline.


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PostPosted: Tue Nov 23, 2010 11:41 am 
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MikeD wrote:
And a 22 ring will only fit on the inside of a normal crank. Which will mean an epically wonky chainline.


Talking about trials cranks.. seems they all come with a 22T ring, which sucks.

I've kinda given up now.. for the time being, at least ;)


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PostPosted: Tue Nov 23, 2010 5:09 pm 
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djoptix wrote:
I'm going to try out 32/17 on my singlespeed MTB but it will only be for very steep stuff and because I think it's magic for the frame...


You must be a lot stronger than me then - I don't think that 32:17 is especially low for very steep off-road climbing :oops:


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PostPosted: Tue Nov 23, 2010 6:36 pm 
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I need to adjust the chainline a tad but since I changed from Cooks cranks to LX ones the chain is a tad slacker..

What's the chances of correcting the chainline tightening it back up?


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PostPosted: Tue Nov 23, 2010 11:33 pm 
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The other thing is that the smaller the chainring, the higher the chain tension from pedalling. So you get more wear on the rings and chain, and a greater chance of broken chains.


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PostPosted: Wed Nov 24, 2010 8:16 am 
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IDB1 wrote:
I need to adjust the chainline a tad but since I changed from Cooks cranks to LX ones the chain is a tad slacker..

What's the chances of correcting the chainline tightening it back up?

None - as theoretically a perfect chainline will actually make the chain slacker than a chainline that is mis-aligned.


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PostPosted: Wed Nov 24, 2010 9:09 am 
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Is it slacker all the way around? Usually chainrings aren't perfectly round, and/or there's runout between the bolt holes and the teeth, or there's runout between the crank spider and the axle. It can all add up and you get the chain tight at some bits of a crank revolution and slack at others.


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PostPosted: Wed Nov 24, 2010 10:06 am 
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Andy R wrote:
None - as theoretically a perfect chainline will actually make the chain slacker than a chainline that is mis-aligned.


That was my thinking on it but thought this may be one of those times when things defy logic.. .. it's only about 5mm out and it's not that slack that I'll need a tensioner - which is nice.

MikeD wrote:
Is it slacker all the way around? Usually chainrings aren't perfectly round, and/or there's runout between the bolt holes and the teeth, or there's runout between the crank spider and the axle. It can all add up and you get the chain tight at some bits of a crank revolution and slack at others.

Didn't pay too much attention tbh, I'll have a butchers when I get round to moving the rear cog..


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PostPosted: Wed Nov 24, 2010 10:24 am 
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Give it a spin and see. They usually go tight/loose/tight/loose. You can sometimes even it out by slightly loosening the chainring bolts, turning it to a tight spot and tapping the top run of chain downwards with the handle of a screwdriver or something. Rotate to new tight spot, repeat. With any luck the chainring will end up as centred as it'll get on the crank and you can do all the bolts up again. You need to loosen them just enough that the ring will shift when persuaded but doesn't flop about. Then it's a matter of finding a compromise tension where the remaining tight bits aren't too tight and the loose bits aren't too loose.

Is the new chainring more worn than the old one? That could yield a bit of slack if you've not moved the rear wheel to compensate.


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