Could I get a better explanation? 'Prevents granny gear fromovershifting'

I was popping around looking at some different sites and I found this
thing:

3rd Eye Chain Watcher

* 3rd Eye Chain Watcher Chain Deflector
* Prevents granny gear from overshifting
* Fits 1-1/8" to 1-3/8" round or oval seat tubes

What exactly is overshifting? (I'm going to make sure my guesses of
what the granny gear is on my own.)

What does this thing do, if anything?


Thx in advance,
TBerk

On Apr 16, 6:42*pm, TBerk wrote:
I was popping around looking at some different sites and I found this
thing:

3rd Eye Chain Watcher

* * * 3rd Eye Chain Watcher Chain Deflector
* * * Prevents granny gear from overshifting
* * * Fits 1-1/8" to 1-3/8" round or oval seat tubes

What exactly is overshifting? (I'm going to make sure my guesses of
what the granny gear is on my own.)

What does this thing do, if anything?

Thx in advance,
TBerk

It keeps the chain form falling off the smallest chainring in toward
the frame. This can happen occasionally, and can result in a jammed
chain and/or dirty fingers. It's sort of an insurance policy.

Joseph

"TBerk" wrote in message
...
I was popping around looking at some different sites and I found this
thing:

3rd Eye Chain Watcher

* 3rd Eye Chain Watcher Chain Deflector
* Prevents granny gear from overshifting
* Fits 1-1/8" to 1-3/8" round or oval seat tubes

What exactly is overshifting? (I'm going to make sure my guesses of
what the granny gear is on my own.)

What does this thing do, if anything?


Thx in advance,
TBerk

This and several other similar devices are designed to keep the chain from
falling off of the small inner chainring when down shifting or bouncing on
rough surfaces.

They can help prevent "chain suck" where the chain gets caught between the
crank and chainstays or bottom bracket.

Chas.

TBerk wrote:
I was popping around looking at some different sites and I found this
thing:

3rd Eye Chain Watcher

* 3rd Eye Chain Watcher Chain Deflector
* Prevents granny gear from overshifting
* Fits 1-1/8" to 1-3/8" round or oval seat tubes

What exactly is overshifting? (I'm going to make sure my guesses of
what the granny gear is on my own.)

What does this thing do, if anything?


Thx in advance,
TBerk

Often the chain will fall off when shifting to the granny gear if the
front dérailleur isn't precisely adjusted (as well as depending on which
rear sprocket the chain is on.

It's usually a big drop from the middle front chainwheel to the granny
gear, and the Chain Watcher helps guide the chain onto the granny gear.
I've had one for years on my touring bicycle.

On Wed, 16 Apr 2008 09:42:03 -0700 (PDT), TBerk
wrote:

I was popping around looking at some different sites and I found this
thing:

3rd Eye Chain Watcher

* 3rd Eye Chain Watcher Chain Deflector
* Prevents granny gear from overshifting
* Fits 1-1/8" to 1-3/8" round or oval seat tubes

What exactly is overshifting? (I'm going to make sure my guesses of
what the granny gear is on my own.)

What does this thing do, if anything?

Thx in advance,
TBerk

Dear Berk,

You clamp the chain watcher around your seat post and then turn it
until the small curved plastic arm nearly touches your smallest front
sprocket, just below the chain.

http://i26.tinypic.com/15p63is.jpg

If the chain falls off the smallest front sprocket, it just hangs on
the plastic arm instead of falling down to the bottom bracket. You can
just shift and get the chain back onto the sprocket.

Most bikes at Paris-Roubaix used chain-watchers because bouncing over
cobblestones at speed can bounce chains off.

Cheers,

Carl Fogel

On Apr 16, 7:18*pm, wrote:
On Wed, 16 Apr 2008 09:42:03 -0700 (PDT), TBerk



wrote:
I was popping around looking at some different sites and I found this
thing:

3rd Eye Chain Watcher

* ** 3rd Eye Chain Watcher Chain Deflector
* ** Prevents granny gear from overshifting
* ** Fits 1-1/8" to 1-3/8" round or oval seat tubes

What exactly is overshifting? (I'm going to make sure my guesses of
what the granny gear is on my own.)

What does this thing do, if anything?

Thx in advance,
TBerk

Dear Berk,

You clamp the chain watcher around your seat post and then turn it
until the small curved plastic arm nearly touches your smallest front
sprocket, just below the chain.

*http://i26.tinypic.com/15p63is.jpg

If the chain falls off the smallest front sprocket, it just hangs on
the plastic arm instead of falling down to the bottom bracket. You can
just shift and get the chain back onto the sprocket.

Most bikes at Paris-Roubaix used chain-watchers because bouncing over
cobblestones at speed can bounce chains off.

Cheers,

Carl Fogel

If you mount it a little higher, such that is almost rubs the side of
the chain when it is on the small ring, the chain won't even fall off
enough to hang on the plastic. It will just stay on through all sorts
of abuse. I haven't ridden much pave, though...

Joseph

In article ,
"* * Chas" wrote:

"TBerk" wrote in message
...
I was popping around looking at some different sites and I found this
thing:

3rd Eye Chain Watcher

* 3rd Eye Chain Watcher Chain Deflector
* Prevents granny gear from overshifting
* Fits 1-1/8" to 1-3/8" round or oval seat tubes

What exactly is overshifting? (I'm going to make sure my guesses of
what the granny gear is on my own.)

What does this thing do, if anything?


Thx in advance,
TBerk

This and several other similar devices are designed to keep the chain from
falling off of the small inner chainring when down shifting or bouncing on
rough surfaces.

They can help prevent "chain suck" where the chain gets caught between the
crank and chainstays or bottom bracket.

I suppose they could help with chain suck, but that's usually defined as
what happens when the chain fails to disengage from the ring(s) at the
bottom of the ring and there's a separate device for preventing it:

http://www.bikepro.com/products/chai...nretainer.html

Behold the Ringle Anti Chain Suck Thing.

The difference is simple to remember:

chain drop = cranks spin freely = bike stops, rider falls down
chain suck = cranks lock = bike stops, rider falls down

So basically, if your crotch hits the seat or top tube, it's chain drop,
while if your crotch hits the back of the stem, it's chain suck.

Chain suck is fairly rare outside of mountain biking circles but chain
drop appears in more circumstance. A chain watcher is a reasonable
device for any rider on rough roads, though I'd be reluctant to call it
necessary. I purely forgot to put my old chain watcher on my new CX bike
last year, and I think I actually did drop my chain off the small ring
(compact double setup; letters from purists to the usual address) once
or twice during races.

Cyclocross bikes are somewhat prone to chain drop during dismounts,
remounts, and just as a result of rough and mucky terrain.

--
Ryan Cousineau http://www.wiredcola.com/
"In other newsgroups, they killfile trolls."
"In rec.bicycles.racing, we coach them."

Ryan Cousineau wrote:
[...]
Behold the Ringle Anti Chain Suck Thing.

The difference is simple to remember:

chain drop = cranks spin freely = bike stops, rider falls down
chain suck = cranks lock = bike stops, rider falls down [...]

Or cranks lock, rider stays on bicycle, chain is yanked hard against
chain stay resulting in a nasty gouge. {Been there, done that}

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

On Apr 16, 9:42 am, TBerk wrote:
snip
Thx in advance,TBerk

And Thx to all. Real life experience triumphs again!


TBerk