Chain Length



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P

Paul

Guest
I recently had the chain on my bike changed at my LBS and immediately noticed much smoother shifting
and a all-round general drive chain improvement.

I've ridden a few hundred miles on it since the change over without problems.

Today, whilst cleaning and lubing the chain, I moved through all the gears just to check general
shifting and found that when I shifted onto the largest sprocket whilst on the largest chainring the
derailleur seems overstretch and the chain is extremly taught with no give at all. The pedals will
rotate but the whole thing grinds terribly. It seems as if the chain is a link or two too short.

Since largest sprocket, largest chainring is not a gear combination that is ever used is this
something I need worry about, all other gear combos are fine and, as I have mentioned, the whole
drivetrain seems to function much better with this chain.

I'm pretty inexperienced and new to cycling (as you might guess from the fact that I got the LBS to
change the chain!) so I'm not sure whether I need to do anything. The mechanic at the shop is very
experienced so I doubt whether it's a mistake.

I have an 8 speed drivechain with 28,38,48 chainrings and a cheap 11-34 tooth Shimano Megarange
cassette, the new chain is a SRAM PC58.

Thanks in advance for any thoughts,

Paul.
 
K

Ken

Guest
"Paul" <[email protected]> wrote in news:[email protected]:
> Since largest sprocket, largest chainring is not a gear combination that is ever used is this
> something I need worry about, all other gear combos are fine and, as I have mentioned, the whole
> drivetrain seems to function much better with this chain.

If your old chain was worn, your drive train is going to function better with a new chain.

One popular rule of thumb is that you should thread your chain over the largest cog and
largest chainwheel without going through the rear derailleur. Cut your chain to fit with one
extra link (2 pins).

You want to be able to shift into the large-large combination without destroying your rear
derailleur, just in case. If you're using a triple crankset, you may not be able to use some of the
small-small combinations, but those don't damage your derailleur.

Ken
 
P

Paul

Guest
Thanks for the information, I've tried the two suggested tests. Shifting up the gears whilst in
the largest chainring without binding is fine. Shifting up from the middle to largest chainring
whilst on the largest sprocket also works although it does take a little bit of extra pressure on
the shifter.

In the largest chainring, largest sprocket combination the chain is extremly taught and the
derailleur does look over stretched although I can lift it a couple of millimetres higher before it
stops. Also, if I back pedal in this comb. the chain drops down a couple of sprockets (but it did
this with the old chain too, I don't know whether the megarange cassette makes a difference, there
is a jump from 26 tooth to 34 tooth when shifting from 2 to 1). On closer inspection most of the
noise seems to be coming from the chain dragging across the front derailleur, it's at quite an
accute angle.

So I'm guessing that this is ok? Certainly the chain doesn't bind.

Thanks for the help.

Kind Regards, Paul.
 
M

Mike Jacoubowsk

Guest
If your chain passes the following tests (and it must pass *both*)-

#1: With the chain already in the largest front chainring, can you shift up
through the rear gears to the largest rear cog without it binding?

#2: With the chain already in the largest rear cog, can you shift the chain
up from the middle chainring without it binding?

It's got to be long enough to do both, or you could have serious trouble. If it doesn't, you need to
add some links to the chain. Don't let them tell you "Don't worry, those aren't gears you ride in."
Sometimes you're tired, the hill got steeper, and you just reach for that next-lower gear, not
realizing you're already in the large front. And bang, you're derailleur rips out of the hanger,
possibly tossing into the rear wheel and potentially wrecking a wheel and frame.

But if it does manage both of those tests, it's probably OK.

--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com

"Paul" <[email protected]> wrote in message
news:[email protected]...
> I recently had the chain on my bike changed at my LBS and immediately noticed much smoother
> shifting and a all-round general drive chain improvement.
>
> I've ridden a few hundred miles on it since the change over without problems.
>
> Today, whilst cleaning and lubing the chain, I moved through all the gears just to check general
> shifting and found that when I shifted onto the largest sprocket whilst on the largest chainring
> the derailleur seems overstretch and the chain is extremly taught with no give at all. The
pedals
> will rotate but the whole thing grinds terribly. It seems as if the chain
is
> a link or two too short.
>
> Since largest sprocket, largest chainring is not a gear combination that
is
> ever used is this something I need worry about, all other gear combos are fine and, as I have
> mentioned, the whole drivetrain seems to function much better with this chain.
>
> I'm pretty inexperienced and new to cycling (as you might guess from the fact that I got the LBS
> to change the chain!) so I'm not sure whether I
need
> to do anything. The mechanic at the shop is very experienced so I doubt whether it's a mistake.
>
> I have an 8 speed drivechain with 28,38,48 chainrings and a cheap 11-34 tooth Shimano Megarange
> cassette, the new chain is a SRAM PC58.
>
> Thanks in advance for any thoughts,
>
> Paul.
 
M

Mike Jacoubowsk

Guest
> So I'm guessing that this is ok? Certainly the chain doesn't bind.

Sounds like you're OK. Don't worry about it dropping off when you back pedal; that's normal. Time
to ride it!

--Mike-- Chain Reaction Bicycles http://www.ChainReaction.com

"Paul" <[email protected]> wrote in message
news:[email protected]...
> Thanks for the information, I've tried the two suggested tests. Shifting
up
> the gears whilst in the largest chainring without binding is fine.
Shifting
> up from the middle to largest chainring whilst on the largest sprocket
also
> works although it does take a little bit of extra pressure on the shifter.
>
> In the largest chainring, largest sprocket combination the chain is
extremly
> taught and the derailleur does look over stretched although I can lift it
a
> couple of millimetres higher before it stops. Also, if I back pedal in
this
> comb. the chain drops down a couple of sprockets (but it did this with the old chain too, I don't
> know whether the megarange cassette makes a difference, there is a jump from 26 tooth to 34 tooth
> when shifting from 2 to 1). On closer inspection most of the noise seems to be coming from the
> chain dragging across the front derailleur, it's at quite an accute angle.
>
> So I'm guessing that this is ok? Certainly the chain doesn't bind.
>
> Thanks for the help.
>
> Kind Regards, Paul.
 
D

David L. Johnso

Guest
On Mon, 24 Feb 2003 12:24:18 -0500, Paul wrote:

> Thanks for the information, I've tried the two suggested tests. Shifting up the gears whilst in
> the largest chainring without binding is fine. Shifting up from the middle to largest chainring
> whilst on the largest sprocket also works although it does take a little bit of extra pressure on
> the shifter.
>
Well, then you probably won't break anything, and that is OK. You don't plan to use such a gear, but
you might accidentally shift into it. It's those accidents that you have to worry about, but your
chain is (barely) long enough.

The back-pedalling thing is due to the poor chainline. Don't backpedal unless your chainline is
pretty good.

--

David L. Johnson

__o | Some people used to claim that, if enough monkeys sat in front _`\(,_ | of enough
typewriters and typed long enough, eventually one of (_)/ (_) | them would reproduce the
collected works of Shakespeare. The internet has proven this not to be the case.
 
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