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.