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Chain Ring Diameters



 
 
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  #1  
Old March 6th 07, 08:26 PM posted to rec.bicycles.tech
James Fitch
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Posts: 41
Default Chain Ring Diameters

Does anyone know, offhand, what the outside diameters are of 53, 52, 51, 50
tooth chain rings? I'm fine tuning a derailleur fit. I'd like to get the
tail of the derailleur dropped a couple of mm to keep the chain from
dragging one rear cog smaller than it does now (currently 53 on the front).

-Jim



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  #2  
Old March 6th 07, 08:49 PM posted to rec.bicycles.tech
Dan Connelly
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Posts: 451
Default Chain Ring Diameters

James Fitch wrote:
Does anyone know, offhand, what the outside diameters are of 53, 52, 51, 50
tooth chain rings? I'm fine tuning a derailleur fit. I'd like to get the
tail of the derailleur dropped a couple of mm to keep the chain from
dragging one rear cog smaller than it does now (currently 53 on the front).

-Jim


Each tooth is a half-inch. Diameter = circumference / pi.

Dan
  #3  
Old March 6th 07, 09:27 PM posted to rec.bicycles.tech
JeffWills
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Posts: 409
Default Chain Ring Diameters

On Mar 6, 12:49 pm, Dan Connelly
wrote:
James Fitch wrote:
Does anyone know, offhand, what the outside diameters are of 53, 52, 51, 50
tooth chain rings? I'm fine tuning a derailleur fit. I'd like to get the
tail of the derailleur dropped a couple of mm to keep the chain from
dragging one rear cog smaller than it does now (currently 53 on the front).


-Jim


Each tooth is a half-inch. Diameter = circumference / pi.

Dan


Plus a skosh for the points of the teeth. The formula you posted
describes the diameter through the pins of the chain- the chainrings'
actual diameter is a little larger than that.

In my experience, fine-tuning front derailleur fit is best done once
the bike is completely assembled. If you need a front derailleur with
a longer cage, maybe you should indicate what kind of frame and front
derailleur you have currently.

Jeff

  #4  
Old March 7th 07, 02:41 AM posted to rec.bicycles.tech
James Fitch
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Posts: 41
Default Chain Ring Diameters


"JeffWills" wrote in message
oups.com...
On Mar 6, 12:49 pm, Dan Connelly
wrote:
James Fitch wrote:
Does anyone know, offhand, what the outside diameters are of 53, 52,
51, 50
tooth chain rings? I'm fine tuning a derailleur fit. I'd like to get
the
tail of the derailleur dropped a couple of mm to keep the chain from
dragging one rear cog smaller than it does now (currently 53 on the
front).


-Jim


Each tooth is a half-inch. Diameter = circumference / pi.

Dan


Plus a skosh for the points of the teeth. The formula you posted
describes the diameter through the pins of the chain- the chainrings'
actual diameter is a little larger than that.

In my experience, fine-tuning front derailleur fit is best done once
the bike is completely assembled. If you need a front derailleur with
a longer cage, maybe you should indicate what kind of frame and front
derailleur you have currently.

Jeff


Its on a long-assembled bike with a Campy triple front derailleur. I
recently put on a smaller inner chain ring, which caused the dragging when
on the 5th cog. I'd like the lower gears more than the higher ones, so the
simplest solution seemed to be to simply put on a smaller large chain ring
and lower the derailleur. A longer derailleur cage would work, too. Dan's
formula (and I'm a little irked I didn't think of it myself) is probably
accurate enough to tell me what I need to know.

-Jim



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