soz if this is a silly question..
i ride roughly 80 - 82 inches....
when i started in fixies i bought a 17 and 18 tooth cog (and a 15) but then i settled on 16 (which gave me that magic 81 inches).
so i just don't wanna waste those big cogs and i am currently building a new fixie and i thought maybe i should get a bigger crank so i can use some of those idle cogs...
so is there any reason to buy a smaller crank and a smaller cog rather than a bigger crank and a bigger cog?
crank sizes
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Postby rustychisel » Thu Aug 28, 2008 9:39 pm
none.
It can be aesthetic, but mostly it's about the donor cranks. Most [many] people on a budget use one ring of a road double so that means a 40 or 42 ring, commonly.
You might find you need a track crank with a 144mm BCD to find reasonable rings to give you the gear you want.
80~82in is quite high for a road fixed gear BTW, I hope you and your knees know what you're doing.
It can be aesthetic, but mostly it's about the donor cranks. Most [many] people on a budget use one ring of a road double so that means a 40 or 42 ring, commonly.
You might find you need a track crank with a 144mm BCD to find reasonable rings to give you the gear you want.
80~82in is quite high for a road fixed gear BTW, I hope you and your knees know what you're doing.
- mikesbytes
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Postby mikesbytes » Thu Aug 28, 2008 11:58 pm
What you need to look at is gain ratio's, which will help you match gear to crank length.
If the R-1 rule is broken, what happens to N+1?
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Postby HappyHumber » Fri Aug 29, 2008 12:14 am
I think the OPs talking number of teeth, rather than crank length. Assuming his crank arms are staying the same.mikesbytes wrote:What you need to look at is gain ratio's, which will help you match gear to crank length.
I remember reading some theory somewhere that given a similar ratio between two different chainring/cog combinations eg 53x19 (75.3") 44x16(74.2") and 36x13(74.8") - you gotta remember you're acheiving the same sort of speed & power over less teeth on the smaller sized combos - thereby not spreading the wear as much. Thus smaller combos may wear out quicker?
Dunno how much water this holds.. but it stuck in my head for some reason when I read it.
Kym
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Postby winona_rider » Fri Aug 29, 2008 9:57 am
no - i think i got mixed up...i *was* at 81, now i'm at 75 ish.
which is pretty sweet.
but yeah...the crank arms will probably stay at 165...(just cause apparently it makes leaning into turns better)
so yeah - it's crank (and cog) teeth i am wondering about.
please post pics of your fave cranks!
i like the look of the soma hellyer available at some stores at $150 US
linky
which is pretty sweet.
but yeah...the crank arms will probably stay at 165...(just cause apparently it makes leaning into turns better)
so yeah - it's crank (and cog) teeth i am wondering about.
please post pics of your fave cranks!
i like the look of the soma hellyer available at some stores at $150 US
linky
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Postby il padrone » Fri Aug 29, 2008 11:15 am
Oh yeah! Smaller sprockets and chainrings wear out quicker.
You'll know that if you run a 22t 'granny' ring on a touring/MTB triple. Back in the 80s we used to use alloy rings, and they'd wear out in just 6 months of touring. Nowadays most smaller chainrings are steel, for longer life.
You'll know that if you run a 22t 'granny' ring on a touring/MTB triple. Back in the 80s we used to use alloy rings, and they'd wear out in just 6 months of touring. Nowadays most smaller chainrings are steel, for longer life.
Mandatory helmet law?
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Postby mikesbytes » Fri Aug 29, 2008 1:40 pm
I did the maths on gain ratio on my track bike and to move from 165mm cranks to 170mm cranks it required one extra tooth on the ring, taking it to 49t.
If the R-1 rule is broken, what happens to N+1?
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Postby prawza » Tue Sep 02, 2008 9:18 pm
Yes. However the advantages of either are quite limited.so is there any reason to buy a smaller crank and a smaller cog rather than a bigger crank and a bigger cog?
For a fixed gear, the smaller crank will reduce the chance of pedal strike when turning, it would add to a very small reduction in weight as well, although i ride with 170mm cranks and have yet had pedal strike *touch wood*. Other than that, the bigger cog would mean less wear and would last longer than a smaller cog/chainring combo.
hope that makes sense.
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