Re: Derailleur rattling?

On Wed, 14 May 2025 14:35:43 -0500, AMuzi <am@yellowjersey.org> wrote:

On 5/14/2025 1:47 PM, Mark J cleary wrote:

Guy brings me a bike to check out. A Specialized Sirrus from
about 2014 8 speed DT. Says the derailleur was rattling and
shifting on its own at times. I put in on the stand and it
seemed to shift ok really/ He need the back wheel trued also
and was really a wobble.
 
I ask him if he did anything and he said he did go home and
clean and lubed the chain. The chain look pretty clean too.
So I managed to get the wheel trued and it is pretty decent
not like truing a precise road machine with expensive wheels
but it is fine.
 
I then cleaned the chain good again and adjust the back V
brakes. Was a bit off but now they are even on both side. I
lubed some point of contact in the brakes at the frame and
then clean the rear derailleur. I then drop some lube at the
pivots on the RD.
 
I made absolutely no adjustment to the RD. I did make a very
small FD adjustment to take out some rub on the big cog in
front in the middle ring when in the small rear.
 
Right now on the stand the bike shifts perfectly in all
combinations and quite good I might add. So do you think
what this guts problem was all along a dirty non-lubed
chain? I know if things not lubed it will shift funny is
ghost shifting a product of dry chain? In the end ghost
shifting suggest to me much more problems but frankly I had
this back working in 20 minutes.

>
V brakes do not move on the frame post. The pivot is inside
the arm. Some models can be lubricated easily and some cannot.
>
Did you check that the cassette sprockets are tight on the
body? A loose cassette lockring will give randomly sloppy
shifts.
>
Is the rear changer straight? Get your head behind it and
sight the chainrings.  A vertical line through the pulleys
should match one through the chainrings.
>
Did you ride it?  There are some things which are not
obvious in mid air.

+1 to that last one. Making changes on the work stand is often
followed by a stop a mile or two out on the next ride to get things
right.

--
C'est bon
Soloman