slipping chain at same spot (and only that spot)

[Maurice W]

Chums

I'm perplexed. There's one spot on one of my regular routes, when
having come up a hill and around a bend, it's the right time to slip
up onto the higher of my two chainrings and give it a bit of wellie on
the flat.

This is something I do, of course, quite regularly, and without any
problem on any number of occassions on this route and other routes.
But on this one specific spot, when I do it, the chain slips off.
Always.

Now, of course, the answer is to wait a bit before changing gear, but
I'm intrigued as to why it should just happen on this spot and nowhere
else?

Any ideas? Road surface? Deceptive and still on an upslope?

M

[Pete Biggs]

Maurice W wrote:
> Chums
>
> I'm perplexed. There's one spot on one of my regular routes, when
> having come up a hill and around a bend, it's the right time to slip
> up onto the higher of my two chainrings and give it a bit of wellie on
> the flat.
>
> This is something I do, of course, quite regularly, and without any
> problem on any number of occassions on this route and other routes.
> But on this one specific spot, when I do it, the chain slips off.
> Always.
>
> Now, of course, the answer is to wait a bit before changing gear, but
> I'm intrigued as to why it should just happen on this spot and nowhere
> else?
>
> Any ideas? Road surface? Deceptive and still on an upslope?

For whatever reason, you don't change gear with as much force while
pedalling with that certain cadence and torque elsewhere.

Anyway, your derailleur needs adjusting. I know that's easier said than
done sometimes, but still it should be possible to improve it. Pay
attention to the angle and height as well as the limit screw.

~PB

[M-gineering]

Maurice W wrote:
> Chums
>
> I'm perplexed. There's one spot on one of my regular routes, when
> having come up a hill and around a bend, it's the right time to slip
> up onto the higher of my two chainrings and give it a bit of wellie on
> the flat.
>
> This is something I do, of course, quite regularly, and without any
> problem on any number of occassions on this route and other routes.
> But on this one specific spot, when I do it, the chain slips off.
> Always.
>
> Now, of course, the answer is to wait a bit before changing gear, but
> I'm intrigued as to why it should just happen on this spot and nowhere
> else?
>
> Any ideas? Road surface? Deceptive and still on an upslope?
>
> M

Probably a bump in the road just right to send a horizontal wave in your
chain, at a time when you don't have much tension on it

--
/Marten

info(apestaartje)m-gineering(punt)nl

[Simon Brooke]

in message >, Maurice W
') wrote:

> I'm perplexed. There's one spot on one of my regular routes, when
> having come up a hill and around a bend, it's the right time to slip
> up onto the higher of my two chainrings and give it a bit of wellie on
> the flat.
>
> This is something I do, of course, quite regularly, and without any
> problem on any number of occassions on this route and other routes.
> But on this one specific spot, when I do it, the chain slips off.
> Always.
>
> Now, of course, the answer is to wait a bit before changing gear, but
> I'm intrigued as to why it should just happen on this spot and nowhere
> else?
>
> Any ideas? Road surface? Deceptive and still on an upslope?

What gear are you in at the back at the time? Some setups are a little
intolerant to shifting onto the big ring when already on a small cog at
the back. The answer, of course, is a trimmable front shifter, but on many
Shimano groupsets this isn't available.

And it's also possible to shed a chain with even a well tempered setup if
you shift both shifters at the same time - a thing I tend to do.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

;; Semper in faecibus sumus, sole profundum variat.

[Maurice W]

On Fri, 01 Jun 2007 20:37:00 +0100, Simon Brooke
> wrote:


>
>What gear are you in at the back at the time? Some setups are a little
>intolerant to shifting onto the big ring when already on a small cog at
>the back. The answer, of course, is a trimmable front shifter, but on many
>Shimano groupsets this isn't available.


I'm generally in 5th out of 8, and it's a sweet change the rest of the
time, so I reckon it must be a bump or such in the road, as the other
poster suggested. I'll not change gear next time I'm there,and keep my
eyes peeled, and ******** primed to spot any bumps...

M

[Simon D]

Maurice W pretended :
> Chums
>
> I'm perplexed. There's one spot on one of my regular routes, when
> having come up a hill and around a bend, it's the right time to slip
> up onto the higher of my two chainrings and give it a bit of wellie on
> the flat.
>
> This is something I do, of course, quite regularly, and without any
> problem on any number of occassions on this route and other routes.
> But on this one specific spot, when I do it, the chain slips off.
> Always.
>
> Now, of course, the answer is to wait a bit before changing gear, but
> I'm intrigued as to why it should just happen on this spot and nowhere
> else?
>
> Any ideas? Road surface? Deceptive and still on an upslope?
>

The other replies indicate reasonable possibilities, and I can't add
much else. However, from your new thread (1000 miles in 2007...but...)
it's clear that you're in my area (I live in Castle Hedingham and
commute to Tiptree). Where is the fabled bend on the hill? I'd be
interested to know, and perhaps I might even be able to add some extra
comment!

--
Simon