Re: How can you tell when a chainring is worn?
On Mon, 10 Jan 2005 17:54:13 GMT,firstname.lastname@example.org
>Carl Fogel writes:
>>>> I'm looking at this one I just bought (used) and it looks
>>>> great. The chain and the cassette are new and 10 speed so I'm
>>>> concerned and don't want to wear them out quickly. Is there
>>>> something I could measure?
>>> Yes, measure the chain, not the sprockets. Sprockets take care of
>>> themselves. They either mesh effectively or skip under load.
>>> Chainwheels just keeps on working until teeth break off. I have
>>> never seen a chainwheel that won't drive a new or worn chain but I
>>> have seen plenty of rear sprockets over which the chain skips under
>>> load. A worn (elongated) chain is what wears out sprockets.
>> About a year ago, I replaced my chain and rear cluster.
>> The new chain came off my worn front 53-tooth chain ring the moment
>> that I pushed down on the pedal to roll out the driveway.
>> The new chain came off the worn chain ring twice more, despite the
>> derailleur being apparently sitting in the right place.
>> The new chain worked fine on the 39-tooth chain ring, which is used
>> on only about 15% of my daily ride, so I replaced the big chain
>I don't know what sort of chain ring you have or what other effects
>were involved, but I have ridden chainrings until there was barely any
>width and length of full height teeth left. I'll let the thing run
>until it fails. I can always use the other CW to ride home, it not
>I think bicycle shops can attest to there being no need to replace a
>chainwheel until the teeth are gone. In what manner did your chain
>"come off". I can't visualize how the chain did not stay on the
>sprocket. Was the chain in a strong cross-over angle, left CW of
>three to rightmost rear sprocket of 10? I think this needs some
>qualification. Of course since I ride with two CW's and a 6-speed FW,
>I may be better off.
>> The new front chain ring worked fine.
>> No broken teeth on the old chain ring, just badly worn teeth when
>> compared in profile to a new chain ring. I rotated them to match
>> the irregular factory tooth shaping.
>> Maybe this was a fluke? If rear cogs can wear out enough to skip,
>> shouldn't front cogs be able to do the same?
>I would invest in a bit of repeatability before buying a new CW.
I can't think of anything odd, beyond the new chain
stripping off the worn front 53-tooth repeatedly as soon as
I stepped on the pedal to roll down the driveway into the
The chain was sitting on the usual start-out gear of #4 on a
new 7-cog Shimano 11 x 28--I'd just replaced both chain and
Same sram pc48 chain, same number of links, same quick
connect link--hell, front wheel lined up on the same crack
as always in the driveway.
The new chain just stripped off the front 53-tooth and out
onto the pedal side of things, not down onto the smaller
ring. I can't think of much else to describe it.
It happened three times as soon as I stepped onto the pedal
to start off.
I tried the chain on the 39-tooth and it worked fine, so I
put a new 53-tooth on and rode off without any problem.
Here's a picture of some of the teeth:http://home.comcast.net/~carlfogel/d.../wornteeth.jpg
None of the others are broken. I figured that cahin ring was
just worn out, but I admit that I can't see why a worn chain
ring would fine the previous day with the worn chain and
then strip off so reliably with a new chain fifteen miles
later the next day.