Why does my chain jam all the time?

[Fox McCloud]

Ive an old Pace RC200 MTB, I put new XT cassette, Pace rings, XTR f+r deraillieurs, XT BB and Sedis
chain on it last year,

When shifting from middle ring on front to the small ring, the chain 90% of the time jams inbetween
the small and middle ring. The shifters are XT thumbshifters set to friction and front mech is
adjusted so will

The chain is an 8spd one which I was assured was no narrower than the 7spd it previously had. The
cranks are the original Cooks Bros, would the spacings be slightly narrower these days?

I live overseas miles away from any bike shop who would know what theyre doing, so Ive only used a
couple of times.

Any ideas appreciated.

[Just Zis Guy]

On 27 Dec 2003 06:55:23 -0800, arrowbeau2003@yahoo.co.uk (Fox McCloud)
wrote:

>When shifting from middle ring on front to the small ring, the chain 90% of the time jams inbetween
>the small and middle ring.

Could be chain suck. Have you tried watching it on a workstand?

Guy
===
May contain traces of irony. Contents liable to settle after posting.
http://chapmancentral.demon.co.uk (http://chapmancentral.demon.co.uk/)

[Jon Cooper]

Originally posted by Fox McCloud
Ive an old Pace RC200 MTB, I put new XT cassette, Pace rings, XTR f+r deraillieurs, XT BB and Sedis
chain on it last year,

When shifting from middle ring on front to the small ring, the chain 90% of the time jams inbetween
the small and middle ring. The shifters are XT thumbshifters set to friction and front mech is
adjusted so will

The chain is an 8spd one which I was assured was no narrower than the 7spd it previously had. The
cranks are the original Cooks Bros, would the spacings be slightly narrower these days?

I live overseas miles away from any bike shop who would know what theyre doing, so Ive only used a
couple of times.

Hi Fox

I have the same problem with my Rocky Mountain vertex TO - usually it happens when I have left it a little late to get into the correct gear at the bottom of a hill - then as I switch the old chain suck cuts in.

Try taking a little more time to change down and perhaps that will work - it has reduced the chain suck for me to c 10% - but it is still a wind up...like the sound of the Pace !

Jon
Any ideas appreciated.

[Zog The Undenia]

Fox McCloud wrote:

> Ive an old Pace RC200 MTB, I put new XT cassette, Pace rings, XTR f+r deraillieurs, XT BB and
> Sedis chain on it last year,
>
> When shifting from middle ring on front to the small ring, the chain 90% of the time jams
> inbetween the small and middle ring. The shifters are XT thumbshifters set to friction and front
> mech is adjusted so will
>
> The chain is an 8spd one which I was assured was no narrower than the 7spd it previously had. The
> cranks are the original Cooks Bros, would the spacings be slightly narrower these days?
>
> I live overseas miles away from any bike shop who would know what theyre doing, so Ive only used a
> couple of times.
>
> Any ideas appreciated.

I reckon you got the spacers in the wrong place when changing the rings. Check the rings are at the
same spacing throughout.

[Anthony Campbel]

On 2003-12-27, Just zis Guy, you know? <outlook.bugs@microsoft.com> wrote:
> On 27 Dec 2003 06:55:23 -0800, arrowbeau2003@yahoo.co.uk (Fox McCloud) wrote:
>
>>When shifting from middle ring on front to the small ring, the chain 90% of the time jams
>>inbetween the small and middle ring.
>
> Could be chain suck. Have you tried watching it on a workstand?
>

I experienced this for the first time this summer, when setting up my bike in Greece after a frame
renovation. I'd taken the opportunity to fit a cassette in place of my previous 5-speed block and
this entailed a new chain, which then proceeded to jam in my front inner chain ring (26T). This is a
triple setup.

It took me some time to work out what was happening, and not before coming off and slicing my leg
open with the outer chainring, thus effectively ending my cycling for the rest of the time I was
in Greece.

I couldn't believe that the innermost chainring was at fault, since it had done a relatively low
mileage. However, by watching it carefully I saw that the chain was sticking to the under surface
of the chainring. I happened to have a new one with me, so I replaced it and the problem appeared
to go away. The wear on the original ring is almost invisible but seems to be enough to snag the
new chain.

There is a good discussion of the phenomenon at: http://www.fagan.co.za/Bikes/Csuck/

A.

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[Just Zis Guy]

On 27 Dec 2003 17:09:00 GMT, Anthony Campbell <me@privacy.net> wrote:

[in re chain suck]

>The wear on the original ring is almost invisible but seems to be enough to snag the new chain.

We had it from new on our Me'n'u2 - it wore off after about a thousand miles. Once I knew what that
funny feeling up the back end there was, I learned how to stop it happening (on that bike). It only
happens on the middle ring and you can prevent it by feathering the shifter slightly and spinning
(which is good anyway).

Sometimes a good clean and a change of lubricant can work, going from a sticky Teflon lube to wax or
vice-versa. And sometimes you're just stuck with it, especially on very small rings, according to my
friends in the local CTC.

Guy
===
May contain traces of irony. Contents liable to settle after posting.
http://chapmancentral.demon.co.uk (http://chapmancentral.demon.co.uk/)

[Tony Raven]

Just zis Guy, you know? wrote:
> On 27 Dec 2003 17:09:00 GMT, Anthony Campbell <me@privacy.net> wrote:
>
> [in re chain suck]
>
>> The wear on the original ring is almost invisible but seems to be enough to snag the new chain.
>
> We had it from new on our Me'n'u2 - it wore off after about a thousand miles. Once I knew what
> that funny feeling up the back end there was, I learned how to stop it happening (on that bike).
> It only happens on the middle ring and you can prevent it by feathering the shifter slightly and
> spinning (which is good anyway).
>
> Sometimes a good clean and a change of lubricant can work, going from a sticky Teflon lube to wax
> or vice-versa. And sometimes you're just stuck with it, especially on very small rings, according
> to my friends in the local CTC.
>

If I read the original post correctly it is not chain suck that is the problem
i.e. the chain sticks to the teeth of the small chain ring and gets carried round until it jams on
the chainstay. It seems to be the chain falling in between the two chainrings and getting stuck
between them. I had this happen on a Pace inner chain ring and I'm wracking my brains to try to
remember what the cause and solution was. I remember it wasn't the spacers being wrong but it
may have been as simple as turning the ring round to mount the other side facing inwards. If I
remember I'll post.

As an aside I found the Pace inner ring to be made of butter and within relatively few miles it had
raised ridges on either side of the teeth where the metal had deformed.

Tony

[Just Zis Guy]

On Sat, 27 Dec 2003 18:13:21 -0000, "Tony Raven"
<junk@raven-family.com> wrote:

>If I read the original post correctly it is not chain suck that is the problem

I read it as possibly either, hence the original request for clarification.

Guy
===
May contain traces of irony. Contents liable to settle after posting.
http://chapmancentral.demon.co.uk (http://chapmancentral.demon.co.uk/)

[Fox McCloud]

Zog The Undeniable <ggg@hhh.net> wrote in message news:<bskic9

> Fox McCloud wrote:
>
> > Ive an old Pace RC200 MTB, I put new XT cassette, Pace rings, XTR f+r deraillieurs, XT BB and
> > Sedis chain on it last year,
> >
> > When shifting from middle ring on front to the small ring, the chain 90% of the time jams
> > inbetween the small and middle ring. The shifters are XT thumbshifters set to friction and front
> > mech is adjusted so
>
> I reckon you got the spacers in the wrong place when changing the rings. Check the rings are at
> the same spacing throughout.

To clarify the problem, the chain is dropping down inbetween the small ring and the middle ring
when downshifting, and jamming solid, making me think that modern 8spd chains are narrower than the
old 7 spd XT chain (although when I bought all the new XTR gear last year I was assured this wasnt
the case).

The cranks / rings have never had any spacers fitted from new. It originally had Pace rings and I
just replaced them with the same (24,36,48). Is it possible to get very thin spacers for chain
rings? However if I was to space out the middle ring slightly so it was nearer the small ring then
would the problem reoccur between the large and middle ring in view of the increased gap?

Thanks

[Pete Biggs]

Fox McCloud wrote:
> To clarify the problem, the chain is dropping down inbetween the small ring and the middle ring
> when downshifting, and jamming solid, making me think that modern 8spd chains are narrower than
> the old 7 spd XT chain

Chain outside width can vary from model to model - even with the same speed. Any difference will
most likely be only a fraction of one milimeter but I suppose that could be enough to make the
difference between jamming and not jamming sometimes.

Width specs are hard to find but see the following for some examples for a start:
http://tinyurl.com/3eo3k

> (although when I bought all the new XTR gear last year I was assured this wasnt the case).

They may have been thinking of internal width or believed that any difference would be
inconsequential.

> The cranks / rings have never had any spacers fitted from new. It originally had Pace rings and
> I just replaced them with the same (24,36,48). Is it possible to get very thin spacers for
> chain rings?

Some special spacers are available for some chainsets. Sorry I don't know more about them.

> However if I was to space out the middle ring slightly so it was nearer the small ring then would
> the problem reoccur between the large and middle ring in view of the increased gap?

I would have thought so too.

How about a different inner chainring? Another brand might be thicker or have more of an offset.

~PB

[Pete Biggs]

I wrote:
> How about a different inner chainring? Another brand might be thicker or have more of an offset.

Correction: A *thinner* ring might solve the problem.

~PB