Shimano RSX front derailleur -- too much tension?



D

Doug McLaren

Guest
I recently picked up a Trek 2000 Alpha SL bike used, and I've been
fixing it up. I don't know the year, but from what I was told I'm
guessing late 1990s.

It's got Shimano RSX components.

So, the first thing broken was the left/front shifter (it's a three
speed brifter.) Would shift up but not down. Cleaned it up with
WD-40 and it did start working, though it sounds like there's still
grit in there.

However, it could barely shift the gear -- I have to really crank down
on it. The right shifter/rear derailleur is much easier. The
derailleur itself seems fine, the cables are fine (and the routing is
correct), so I found a replacement brifter, and put it in. Same
problem.

Upon closer investigation, to move the front derailleur from the
loosest position by pulling the cable manually away from the frame
between the two braze-ons on the bottom tube requires a lot more
effort than my other bike.

Removing the derailleur, it seems fine, but it requires a _lot_ of
effort to move it. It's not stuck -- it slides freely, and it
requires just as much effort to `compress' it as it does to keep it
from uncompressing. It's like they put a big honking spring in there,
far larger than I'd think was needed. I've certainly never heard of a
spring failing in such a way to *increase* the tension, so I'm quite
confused by this -- it's like it was designed this way, but it just
doesn't seem right.

To be fair, I don't have a lot of experience fixing bikes -- I sort of
know what I'm doing, and have books to refer to, but don't have the
experience to tell me what sort of tension to expect here -- but it
seems way too high, like 2-3x as high as it ought to be.

Looks like it's a FD-A417 Chainstay angle 63-66 degrees. Looking
carefully at the spring while it's moved, it looks like the entire
spring is working and is clean and not rusted and such.

Thoughts?

--
Doug McLaren, [email protected]
`The chief obstacle to the progress of the human race is the human race.'
- Don Marquis.
 
On May 16, 11:31 am, "Doug McLaren" <dougmc
[email protected]> wrote:
> I recently picked up a Trek 2000 Alpha SL bike used, and I've been
> fixing it up.  I don't know the year, but from what I was told I'm
> guessing late 1990s.
>
> It's got Shimano RSX components.
>
> So, the first thing broken was the left/front shifter (it's a three
> speed brifter.)  Would shift up but not down.  Cleaned it up with
> WD-40 and it did start working, though it sounds like there's still
> grit in there.
>
> However, it could barely shift the gear -- I have to really crank down
> on it.  The right shifter/rear derailleur is much easier.  The
> derailleur itself seems fine, the cables are fine (and the routing is
> correct), so I found a replacement brifter, and put it in.  Same
> problem.
>
> Upon closer investigation, to move the front derailleur from the
> loosest position by pulling the cable manually away from the frame
> between the two braze-ons on the bottom tube requires a lot more
> effort than my other bike.
>
> Removing the derailleur, it seems fine, but it requires a _lot_ of
> effort to move it.  It's not stuck -- it slides freely, and it
> requires just as much effort to `compress' it as it does to keep it
> from uncompressing.  It's like they put a big honking spring in there,
> far larger than I'd think was needed.  I've certainly never heard of a
> spring failing in such a way to *increase* the tension, so I'm quite
> confused by this -- it's like it was designed this way, but it just
> doesn't seem right.
>
> To be fair, I don't have a lot of experience fixing bikes -- I sort of
> know what I'm doing, and have books to refer to, but don't have the
> experience to tell me what sort of tension to expect here -- but it
> seems way too high, like 2-3x as high as it ought to be.
>
> Looks like it's a FD-A417 Chainstay angle 63-66 degrees.  Looking
> carefully at the spring while it's moved, it looks like the entire
> spring is working and is clean and not rusted and such.
>
> Thoughts?
>
> --
> Doug McLaren, [email protected]
> `The chief obstacle to the progress of the human race is the human race.'
>  - Don Marquis.


Shifting front STI is often harder than rears. That said, they're can
be really hard if the cable's under the tab (by the pinch bolt)
instead of over it. Not enough leverage. Check and maybe move the
cable so it passes by the tab on the "inboard" side (of the bicycle)
then over the top of the pinch bolt.
 
D

Doug McLaren

Guest
In article <[email protected]>,
[email protected] <[email protected]> wrote:

| Shifting front STI is often harder than rears. That said, they're can
| be really hard if the cable's under the tab (by the pinch bolt)
| instead of over it. Not enough leverage. Check and maybe move the
| cable so it passes by the tab on the "inboard" side (of the bicycle)
| then over the top of the pinch bolt.

Thanks -- your second suggestion nailed it.

It wasn't quite clear what you meant at first, but I looked at my
other bike and realized that the the derailleur was almost identical
-- but the cable was connected to the derailleur differently, and when
I made my new bike match, things got much easier. And now that I look
back at your post, that's what you suggested. It doesn't look right,
but it does give it more leverage, and while it doesn't look like
much, it made a huge difference.

Thanks again!

--
Doug McLaren, [email protected] Yow! Everybody out of the gene pool!