On 7/31/2020 10:05 PM, Mark J. wrote:
On 7/31/2020 5:26 PM, John B. wrote:
On Fri, 31 Jul 2020 12:10:15 -0400, Frank Krygowski
wrote:

On 7/31/2020 2:34 AM, wrote:
On Thursday, July 30, 2020 at 4:52:38 PM UTC-5, Lou
Holtman wrote:
On Thursday, July 30, 2020 at 11:14:59 PM UTC+2,
wrote:
On Wednesday, July 29, 2020 at 5:53:08 PM UTC-5, John
B. Slocomb wrote:
On Wed, 29 Jul 2020 15:39:48 -0700 (PDT),
"
wrote:

On Tuesday, July 28, 2020 at 4:09:31 PM UTC-5, AK
wrote:
What do you think of a gravel bike?

Does anyone have one?

https://www.youtube.com/watch?v=XC_xFpg_UmA

Andy

I've done a few rides recently on gravel roads.
They were fun with the group. Not sure
riding them by myself would be any fun. I used a
Nashbar cyclocross
bike. Heavy steel. 38mm tires. STI ten speed.
Cantilever. Shimano
105 rear derailleur died at the end of one ride and
had to be
replaced. So I'm not sure gravel riding is good or
not. Not sure
what a gravel bike means. I've ridden many different
bikes on gravel
roads just fine. Most gravel roads have two or three
perfectly smooth
strips on them that you ride on. Much smoother than
many potholed
roads. Less wear and tear on the bike. But you do
have to run over
loose rocks when making turns. Those are the rough
pothole portions
of gravel roads. Pros ride the cobblestone classics
each year on road
racing bikes converted to gravel by putting huge 28mm
tires on them.
They ride 150 miles at 30 mph.

Out of curiosity "Shimano 105 rear derailleur died"
What actually
happened?

Cheers,
John B.

It stopped shifting with the STI levers. I replaced
it with another new 105 long cage rear derailleur and
the shifting works perfectly again. It happened a few
months ago so I cannot remember exactly what
happened. But shifting was bad, not precise, move the
STI one click and the derailleur did not shift the
chain. Move it two or three clicks and it would sort
of move the chain. Everything imprecise. New
derailleur, no change to cable, and everything shifts
perfectly again. So I am pretty sure it was the
derailleur, not the cable or shifters. Perfect
shifting for several years before the one gravel
ride. End of gravel ride bad shifting. New
derailleur perfect shifting again with no other
changes. So I assume the 20 miles of gravel riding
killed the derailleur somehow.

A RD being a spring loaded lever, what can possibly
went wrong. What could have happened is a cracked
pulley cage plate (inner or outer). My brother had that
once causing also weird shifting. Replacing the cracked
outer cage plate was less than 10 euro:
https://www.bike-components.de/en/Sh...8-grey-GS-type


Lou

I went down to the basement and cleaned up, looked at
the bad Shimano 105 rear derailleur. I took the plate
and pulleys off. No broken cage/plate. Pulleys and
their bushings looked OK. About the only thing that
might be wrong is the spring to pull the cage backwards
was not really consistent over the whole travel. Can't
remember if all rear derailleurs have that varying
spring tension for pulling the pulley cage backwards.
The side to side spring in the derailleur was strong and
consistent. No problem with it. Everything looks OK on
the derailleur. It still looks new. And it sort of is
new. But it died on me at the end of the gravel ride.
Would not shift. And the new 105 long cage derailleur I
installed now works perfectly. So...

Odd.

I had a rear derailleur whose jockey pulley spring
failed. But IIRC the
symptom was no takeup of chain slack. The shift cable
still moved the
derailleur side to side, so that main part of shifting
action worked.

When I disassembled, the jockey pulley's torsion spring
had broken at
its end. It was a close wound helical spring made of
square wire, ending
in a short axial tang that plugged into a hole or slot.
The tang had
broken off at the 90 degree angle to the main coil. I
just bent a few
millimeters of the coil out to make a new tang, and all
was well.

That pivot motion should be smooth and consistent, AFAIK.
I wonder if
gravel dust, etc. jammed that pivot? Would cleaning and
lubricating fix it?


I have seen a rear derailer that the spring that moves the
cage
sideways was weak and the bike shifted normally when the
cable was
pulling the derailer and didn't shift as well when the
shifter moved
under spring power. But, if I recollect that was a no name
7 speed
derailer on a $100 bike.
--
Cheers,

John B.

Yes, I had the same - a SunTour Cyclone GT (i.e. the
long-cage, original cyclone version). The parallelogram
return spring did, um, /something/. I never figured out if
part of it had broken off or if it had just gone soft -
neither of which really make sense to me. Even with the
derailleur taken completely off the bike it was clear that
the return spring just didn't have the oomph required to do
its job.

I believe it was a coil spring with ends that extended out
from the coil, wrapped around one of the parallelogram
pivots; the ends pushed against adjacent sides of the
parallelogram. Couldn't really see it clearly without
pushing out the press-fit pivot, so I never did figure out
how it "failed."

Mark J.

Nothing smaller than 'body assembly'[1] is shown in the
drawing and I can't recall the body return spring format for
those. However similar designs of the era can bind when
smacked and sometimes respond well to working the two end
castings a bit until the roll pins are freed up. It's more
likely that than an actual spring failure IME.

[1]Same body for both long & short models

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