Chainwheels are worn out when ?

someone to shy to reveal his name writes:

So, when are chainwheels actually "worn out" ?

When the chain no longer is driven by them. With more than one
chainwheel, this is no problem unless racing. Just use the other one
to return home when the other actually fails.

I'm familiar with the symptoms of worn clusters - skipping, poor
shifting, etc - do shark teeth chainwheels do the same thing ?

No, but you can get chain suck if the previous chain was badly
elongated and the chainwheel is smaller than ~39t.

Jobst Brandt

On Fri, 22 Oct 2004 02:06:37 +0000, jobst.brandt wrote:

I'm familiar with the symptoms of worn clusters - skipping, poor
shifting, etc - do shark teeth chainwheels do the same thing ?

No, but you can get chain suck if the previous chain was badly elongated
and the chainwheel is smaller than ~39t.

Actually, I have experienced skipping on a chainring. It was a small one,
either 30 or 32 teeth, but the skipping was essentially the same as with a
rear sprocket. It was badly shark-toothed. Also, when the teeth are so
shark-shaped that they bend over or develop burrs, you will have shifting
problems.

--

David L. Johnson

__o | If all economists were laid end to end, they would not reach a
_`\(,_ | conclusion. -- George Bernard Shaw
(_)/ (_) |

On Fri, 22 Oct 2004 00:47:19 -0400, "David L. Johnson"
wrote:

On Fri, 22 Oct 2004 02:06:37 +0000, jobst.brandt wrote:

I'm familiar with the symptoms of worn clusters - skipping, poor
shifting, etc - do shark teeth chainwheels do the same thing ?

No, but you can get chain suck if the previous chain was badly elongated
and the chainwheel is smaller than ~39t.

Actually, I have experienced skipping on a chainring. It was a small one,
either 30 or 32 teeth, but the skipping was essentially the same as with a
rear sprocket. It was badly shark-toothed. Also, when the teeth are so
shark-shaped that they bend over or develop burrs, you will have shifting
problems.

Dear David,

Twice, I've replaced badly worn chains, installed new rear
gear clusters, and had the new chains skip badly on a worn
53-tooth chain-ring.

The first time, the new chain just skipped when I pedalled
hard on the flats in high gear. New front chain ring, no
more skipping.

The second time, several years later, I put on the new rear
cluster and the new chain and figured that I'd just take it
easy if the front was too worn and started skipping. The new
chain came off the front 53-tooth on the first downstroke as
I set off.

Startled, I flipped the bike upside down, pulled the chain
back onto the sprocket, ran front and rear derailleurs up
and down while cranking the pedals with one hand, and saw no
obvious problem. I set the chain back onto the 53-tooth
front and one of the middle gears on the back, set the bike
right side up, started off again, and--presto!--chain off
the front sprocket. I replaced the worn 53-tooth, everything
began to work normally.

At a rough guess, both chain rings had over 20,000 miles on
them. They may have worn more than usual or in an odd
pattern due to shamefully worn chains.

Carl Fogel

The chain pops off the chainwheel under heavy load, say when starting
up hard to cross a busy intersection.

The load it takes to do that then starts to decline until it's
such a pain that you replace the whole drive train.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

At a rough guess, both chain rings had over 20,000 miles on
them. They may have worn more than usual or in an odd
pattern due to shamefully worn chains.

Carl Fogel

Carl: I get about 15,000 miles out of Ultegra (and possibly a bit more from
DuraAce) chainrings before I notice a significant decline in shifting
performance and change them. Rear cassettes go for about 10,000 miles, but
chains, for my weight and the hills I ride, get only about 1800-2000 miles
before they're toast. By toast I mean significantly reduced shifting
performance. By the classic wear standards, I'm replacing them just before
Jobst would say I need to. That's OK; if spending a few more dollars on
chains means things shift better, I'll spend the $$$.

For what it's worth, I've never worn a chainring to the point that the chain
skipped over it, but I've seen quite a few customers whose bikes have done
that. It's tougher to diagnose than a skipping rear cassette; you really
don't believe it's happening at the front. Sometimes I'll even have someone
ride it in the parking lot while I watch what's happening.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com


wrote in message
...
On Fri, 22 Oct 2004 00:47:19 -0400, "David L. Johnson"
wrote:

On Fri, 22 Oct 2004 02:06:37 +0000, jobst.brandt wrote:

I'm familiar with the symptoms of worn clusters - skipping, poor
shifting, etc - do shark teeth chainwheels do the same thing ?

No, but you can get chain suck if the previous chain was badly elongated
and the chainwheel is smaller than ~39t.

Actually, I have experienced skipping on a chainring. It was a small one,
either 30 or 32 teeth, but the skipping was essentially the same as with a
rear sprocket. It was badly shark-toothed. Also, when the teeth are so
shark-shaped that they bend over or develop burrs, you will have shifting
problems.

Dear David,

Twice, I've replaced badly worn chains, installed new rear
gear clusters, and had the new chains skip badly on a worn
53-tooth chain-ring.

The first time, the new chain just skipped when I pedalled
hard on the flats in high gear. New front chain ring, no
more skipping.

The second time, several years later, I put on the new rear
cluster and the new chain and figured that I'd just take it
easy if the front was too worn and started skipping. The new
chain came off the front 53-tooth on the first downstroke as
I set off.

Startled, I flipped the bike upside down, pulled the chain
back onto the sprocket, ran front and rear derailleurs up
and down while cranking the pedals with one hand, and saw no
obvious problem. I set the chain back onto the 53-tooth
front and one of the middle gears on the back, set the bike
right side up, started off again, and--presto!--chain off
the front sprocket. I replaced the worn 53-tooth, everything
began to work normally.

At a rough guess, both chain rings had over 20,000 miles on
them. They may have worn more than usual or in an odd
pattern due to shamefully worn chains.

Carl Fogel

On Fri, 22 Oct 2004 06:28:33 GMT, "Mike Jacoubowsky"
wrote:

[snip]

For what it's worth, I've never worn a chainring to the point that the chain
skipped over it, but I've seen quite a few customers whose bikes have done
that. It's tougher to diagnose than a skipping rear cassette; you really
don't believe it's happening at the front. Sometimes I'll even have someone
ride it in the parking lot while I watch what's happening.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

Dear Mike,

Diagnosis is extremely simple if you're extremely
simple-minded.

Something skips under heavy pedalling in high gear.

Okay, time to replace the rear cluster. I wear out high gear
cogs now and then. (But far less often after I switched from
Sachs Aris 12-tooth cogs to Shimano 11-tooth cogs--Shimano
must be better metal.)

Sometimes, something still skips.

Okay, replace the chain. I wear out chains, too.

Damn! No question now what's skipping! As Ron put it
elsewhere in this thread, the chain "pops off" the front
sprocket. Replace the front sprocket.

There, that fixed it!

One day, I fear, something will still skip. When it does, I
plan to look at the frame to see if it's cracked.

Carl Fogel

Wrote:
someone to shy to reveal his name writes:

So, when are chainwheels actually "worn out" ?

When the chain no longer is driven by them. With more than one
chainwheel, this is no problem unless racing. Just use the other one
to return home when the other actually fails.

I'm familiar with the symptoms of worn clusters - skipping, poor
shifting, etc - do shark teeth chainwheels do the same thing ?

No, but you can get chain suck if the previous chain was badly
elongated and the chainwheel is smaller than ~39t.

Jobst Brandt


a very helpful tool is the HG/IG check from rohloff.

http://www.rohloff.de/index.php?p=PRODUKTE/HG-IG-CHECK


--
fixit