Skipping Chain Questions



N

nick

Guest
So I just bought and installed a brand new SRAM PC-48 to
replace the old, noisy, stretched SRAM PC-48 chain on our
aging Santana Sovereign tandem. The chain rides over Shimano
Deore/XT chainwheels and a Sachs-Maillard FREEWHEEL on
SUZUE sealed hubs.

The brand new chain skips, hops, jumps in most all gears
under pressure. I'm guessing freewheel?? But howcum
the old chain works just fine, just a bit noisy. So for
now the old chain is back on the bike and the new chain
is back in the box.

Further, if I should replace the freewheel (7 speed), where
can I find one?? Neither Performance nor REI lists one. They
list only cassettes.

Help!!!


nick
 
nick <[email protected]> writes:

> So I just bought and installed a brand new SRAM PC-48 to
> replace the old, noisy, stretched SRAM PC-48 chain on our
> aging Santana Sovereign tandem. The chain rides over Shimano
> Deore/XT chainwheels and a Sachs-Maillard FREEWHEEL on
> SUZUE sealed hubs.
>
> The brand new chain skips, hops, jumps in most all gears
> under pressure. I'm guessing freewheel?? But howcum
> the old chain works just fine, just a bit noisy. So for
> now the old chain is back on the bike and the new chain
> is back in the box.
>
> Further, if I should replace the freewheel (7 speed), where
> can I find one?? Neither Performance nor REI lists one. They
> list only cassettes.
>
> Help!!!
>
>
> nick

1. google rec.bicycles.tech faq

2. go to chain section. "Subject: 8d.2 Chain cleaning and lubrication;
wear and skipping" was last edited by Jobst Brandt 5 days ago. Quoting:

Chain Sprockets do not change pitch when they wear, only their tooth
form changes. The number of teeth and base circle remain unchanged on
a worn sprocket. What changes is the diameter at which the lengthened
(worn) chain bears on the sprocket teeth, making wear pockets at a
larger diameter than a new chain requires. In practice, this amounts
to a change of pitch (or pitch circle), because the chain will no
longer ride in the original valleys between the sprocket teeth.

A new chain often will not freely engage a worn rear sprocket under
load even though the sprocket root diameter has the same pitch as the
chain. Under tension, the incoming chain rides in the pockets worn by
an elongated chain that are higher on each tooth (a larger pitch
diameter) than a new in-pitch chain requires. This wear occurs
because a worn chain rides high on the teeth. A new chain with
correct pitch cannot enter into engagement because its rollers ride in
the wear pockets made by a chain with a larger pitch.

3. upshot: you should check your chain length more diligently. I
check my chains every time I remove one for cleaning and err on the
conservitive side for the park chainlength tool

Bill Westphal
 
On 2007-03-18, nick <[email protected]> wrote:
> So I just bought and installed a brand new SRAM PC-48 to
> replace the old, noisy, stretched SRAM PC-48 chain on our
> aging Santana Sovereign tandem. The chain rides over Shimano
> Deore/XT chainwheels and a Sachs-Maillard FREEWHEEL on
> SUZUE sealed hubs.
>
> The brand new chain skips, hops, jumps in most all gears
> under pressure. I'm guessing freewheel?? But howcum
> the old chain works just fine, just a bit noisy.

The old chain has "stretched", and worn the sprockets to match its new
pitch, with the result that it fits them better than the new chain.

If you persist with the new chain it may settle down and work with the
old sprockets after a few hundred miles as they rapidly wear it to fit
them.

But better to get a new freewheel and you might even need new chainrings
too depending on whom you ask.

> So for
> now the old chain is back on the bike and the new chain
> is back in the box.
>
> Further, if I should replace the freewheel (7 speed), where
> can I find one?? Neither Performance nor REI lists one. They
> list only cassettes.

I don't know where/if you can get them. Another option is to get a new
hub, if it will fit or you're OK with making it fit, and convert the
bike to cassettes especially if you do a lot of miles.
 
Ben C? writes:

>> So I just bought and installed a brand new SRAM PC-48 to replace
>> the old, noisy, stretched SRAM PC-48 chain on our aging Santana
>> Sovereign tandem. The chain rides over Shimano Deore/XT
>> chainwheels and a Sachs-Maillard FREEWHEEL on SUZUE sealed hubs.

>> The brand new chain skips, hops, jumps in most all gears under
>> pressure. I'm guessing freewheel?? But how come the old chain
>> works just fine, just a bit noisy.

> The old chain has "stretched", and worn the sprockets to match its
> new pitch, with the result that it fits them better than the new
> chain.

> If you persist with the new chain it may settle down and work with
> the old sprockets after a few hundred miles as they rapidly wear it
> to fit them.

The only thing that can occur is that you light pedal long enough
(1000+miles) until the "new" chain wears to the same elongated pitch
as the old one, meanwhile wearing out the chainwheels as well.

> But better to get a new freewheel and you might even need new
> chainrings too depending on whom you ask.

If you find sprockets for your freewheel, get some extras if you want
to continue using it. This will occur again if you leave the chain on
too long. This is a common problem even with slight chain elongation.

>> So for now the old chain is back on the bike and the new chain is
>> back in the box.

>> Further, if I should replace the freewheel (7 speed), where can I
>> find one? Neither Performance nor REI lists one. They list only
>> cassettes.

It may be time to change to a seven speed cassette hub anyway.

> I don't know where/if you can get them. Another option is to get a
> new hub, if it will fit or you're OK with making it fit, and convert
> the bike to cassettes especially if you do a lot of miles.

I'm for it!

Jobst Brandt
 
On 18 Mar, 20:18, nick <[email protected]> wrote:

> Further, if I should replace the freewheel (7 speed), where
> can I find one??

I bet Andrew Muzi, of Yellowjersey, carries them.

Sergio
Pisa
 
On Sun, 18 Mar 2007 19:18:14 GMT, nick <[email protected]> wrote:

>So I just bought and installed a brand new SRAM PC-48 to
>replace the old, noisy, stretched SRAM PC-48 chain on our
>aging Santana Sovereign tandem. The chain rides over Shimano
>Deore/XT chainwheels and a Sachs-Maillard FREEWHEEL on
>SUZUE sealed hubs.
>
>The brand new chain skips, hops, jumps in most all gears
>under pressure. I'm guessing freewheel?? But howcum
>the old chain works just fine, just a bit noisy. So for
>now the old chain is back on the bike and the new chain
>is back in the box.
>
>Further, if I should replace the freewheel (7 speed), where
>can I find one?? Neither Performance nor REI lists one. They
>list only cassettes.
>

You need a new freewheel and you local shop can get you one w/o
problem. I am surprised that Nashbar no longer has. Also, if you can
find an old shop, they might have a cog board and be able to replace
the cogs on the freewheel. This is doubtful.
 
nick wrote:
> So I just bought and installed a brand new SRAM PC-48 to
> replace the old, noisy, stretched SRAM PC-48 chain on our
> aging Santana Sovereign tandem. The chain rides over Shimano
> Deore/XT chainwheels and a Sachs-Maillard FREEWHEEL on
> SUZUE sealed hubs.
>
> The brand new chain skips, hops, jumps in most all gears
> under pressure. I'm guessing freewheel??

Good guess.

> But howcum
> the old chain works just fine, just a bit noisy.

The freewheel is worn to (sort of) fit the dimensions of the worn chain.
There is a myth that you are supposed to change the freewheel and
chain together, because of this. Reality is that, if you change the
chain when it begins to wear (so that the distance between 12 full links
is 12 +1/16 inches), your freewheel will last through several chains.
Even freewheels are more expensive than chains, and harder to find.

> Further, if I should replace the freewheel (7 speed), where
> can I find one?? Neither Performance nor REI lists one. They
> list only cassettes.

Try Loose Screws, or Harris Cyclery. I've got a couple of 8-speed Sachs
freewheels I'd be willing to part with for the right offer, but maybe
you don't want 8-speed, and maybe you don't want the close-ratio
freewheels that these are.

--

David L. Johnson

"Business!" cried the Ghost. "Mankind was my business. The common
welfare was my business; charity, mercy, forbearance, and
benevolence, were, all, my business. The dealings of my trade were but
a drop of water in the comprehensive ocean of my business!" --Dickens,
 
Paul Kopit wrote:
>
> You need a new freewheel and you local shop can get you one w/o
> problem. I am surprised that Nashbar no longer has. Also, if you can
> find an old shop, they might have a cog board and be able to replace
> the cogs on the freewheel. This is doubtful.

I think the days of availability of freewheel cogs are over. Even
single cassette cogs are so expensive as to discourage their sale. The
cost of two sprockets is essentially the same as a new cassette.

--

David L. Johnson

"Business!" cried the Ghost. "Mankind was my business. The common
welfare was my business; charity, mercy, forbearance, and
benevolence, were, all, my business. The dealings of my trade were but
a drop of water in the comprehensive ocean of my business!" --Dickens,
 
nick wrote:
> So I just bought and installed a brand new SRAM PC-48 to
> replace the old, noisy, stretched SRAM PC-48 chain on our
> aging Santana Sovereign tandem. The chain rides over Shimano
> Deore/XT chainwheels and a Sachs-Maillard FREEWHEEL on
> SUZUE sealed hubs.
>
> The brand new chain skips, hops, jumps in most all gears
> under pressure. I'm guessing freewheel?? But howcum
> the old chain works just fine, just a bit noisy. So for
> now the old chain is back on the bike and the new chain
> is back in the box.
>
> Further, if I should replace the freewheel (7 speed), where
> can I find one?? Neither Performance nor REI lists one. They
> list only cassettes.

All will be revealed in the 'chain' section here:
http://draco.acs.uci.edu/rbfaq/FAQ/index.html

Seven freewheels are neither rare nor expensive and your rings are also
not difficult to replace.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
 
Luns Tee wrote:

> The key isn't with a 'hook' getting in the way, per se. Under
> normal operation, a chain engages the sprocket with rollers
> making initial contact on the leading edge of a tooth. As it
> progresses around the sprocket, the roller then rolls down to
> the root circle (the bottom between teeth), and then up the
> trailing edge of the neighbouring tooth until it disengages.
> Wear on the sprocket is on this trailing edge, not on the
> leading edge where the roller normally engages.

If I've understood you, I beg to differ, and argue that the hook
simply _does_ get in the way. Below is a reworked version of I
post I made here in January 2004.

Here's my attempt at a ASCII diagram of the area where the chain
is trying to mesh with a worn tooth. View with a fixed font
for this to make any sense.

\ /
| |
| |
| \
| |
| /
\___/

/|\ /|\
| |
A B

"A" represents the line taken by the bushing on a new chain
trying to mesh with a worn sprocket tooth as it's fed onto it.
And "B" represents the line of the corresponding part on a worn
chain. We're looking at a tooth on the bottom of the sprocket,
rotating clockwise (ie, towards the left).

The reason the new chain is committed to line "A" is that it's
sitting in the pockets of the teeth it's already engaged with
(having been pulled into those pockets by peddling pressure).
And it doesn't have enough slackness to follow line "B".

That the hook (the unworn material towards the head of the
tooth) is the problem is easily demonstrated by removing it (on
all teeth of that sprocket) with a grinder. The skipping
disappears.

As Jobst pointed out in reply to my earlier post, this is a
temporary repair, as the case-hardening is gone.

John
 
[email protected] wrote:
> > Secondary rule for myself, be very slow to swap the chain.
>
> I don't understand, please explain.

No doubt you can replace the chain quickly and keep the freewheel
through several chains. The question is how many miles you get on
a freewheel, not how many chains.

I keep the same chain for a little less than a year (always being forced
to swap it _just before_ road salt season ends, damn the luck), which
is nearly 8k miles. So I get 8k miles on a freewheel too.

The penalty is chainwheel wear. They last a couple years, the
clue for swapping being that the chain pops off them under load,
the teeth having been worn down to nubs. (Interesting that the
wear patterns on cogs and chainwheels are nearly opposite, driven
vs. driving chain entry and all.)
--
Ron Hardin
[email protected]

On the internet, nobody knows you're a jerk.
 
On Mar 18, 1:18 pm, nick <[email protected]> wrote:
> So I just bought and installed a brand new SRAM PC-48 to
> replace the old, noisy, stretched SRAM PC-48 chain on our
> aging Santana Sovereign tandem. The chain rides over Shimano
> Deore/XT chainwheels and a Sachs-Maillard FREEWHEEL on
> SUZUE sealed hubs.
>
> The brand new chain skips, hops, jumps in most all gears
> under pressure. I'm guessing freewheel?? But howcum
> the old chain works just fine, just a bit noisy. So for
> now the old chain is back on the bike and the new chain
> is back in the box.

Chains wear the freewheel with them, get longer. New chain, engages
fewer teeth of a given cog-skips-

I and many others like Andy Muzi of Yellow jersey have freewheels...MO
and REI do not the bike indistry make.
>
> Further, if I should replace the freewheel (7 speed), where
> can I find one?? Neither Performance nor REI lists one. They
> list only cassettes.
>
> Help!!!
>
> nick
 
Sergio Servadio writes:

> On Mar 19, 6:05 am, A Muzi <[email protected]> wrote:

>> All will be revealed in the 'chain' section here:

http://draco.acs.uci.edu/rbfaq/FAQ/index.html

> I went in there and read a bit of the section about touring Europe.
> Soon I suspected I knew who was the writer. Went back to the
> beginning and there he is: Bruce Hindenbrand. Anyone knows his
> whereabouts?

Palo Alto CA

Bruce Hildenbrand <[email protected]>

Jobst Brandt
 
> On Mar 19, 6:05 am, A Muzi <[email protected]> wrote:
>> All will be revealed in the 'chain' section here:http://draco.acs.uci.edu/rbfaq/FAQ/index.html

sergio wrote:
> I went in there and read a bit of the section about touring Europe.
> Soon I suspected I knew who was the writer.
> Went back to the beginning and there he is: Bruce Hindenbrand.
> Anyone knows his whereabouts?


Bruce Hildebrand, a.k.a. "Rock Climber", no longer in Madison . . .
somewhere in Boulder - maybe Peter knows?

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
 
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