Ghost Shifting Revisited

[drewski]

Originally posted by mre
I haven't had a chance to inspect the housing caps, yet.

don't just look at the housing caps. take them off and look at the end of the actual housings. make sure that the opening is good (open, round, and larger in diameter than the cable) and that the cable slides back-and-forth with little to no friction/effort.

i had NEW shimano cables that came with my DA STI levers with one cable housing end a bit crimped. this was not an end that i cut or shortened so i didn't examine it when doing the original install. shifting was inconsistent until i found the culprit and opened up the end a bit and then reinstalled.

voila.

 

[DesertRider]

Originally posted by drewski
don't just look at the housing caps. take them off and look at the end of the actual housings. make sure that the opening is good (open, round, and larger in diameter than the cable) and that the cable slides back-and-forth with little to no friction/effort.

i had NEW shimano cables that came with my DA STI levers with one cable housing end a bit crimped. this was not an end that i cut or shortened so i didn't examine it when doing the original install. shifting was inconsistent until i found the culprit and opened up the end a bit and then reinstalled.

voila.

This is why factory housings are shi*!

 

[Brizza]

OK I have a different suggestion.

I have suffered this after changing my chain and it can be cause by a stiff link in the chain.

Look over the chain carefully and find the stiff link, most likely the link were the chain was broken or put together originally if it is new. move it round and pay with it until the link moves freely and stops jumping on the cassette.

Brian

 

[el Ingles]

Originally posted by mre
About 150 miles after replacing the RD, the ghost shifting is back. It started innocently enough with chain skipping but no shifting. Yesterday after about 8 miles, full fledged ghost shifting returned. As soon as I got home, I immediately put the bike on a work stand, but could not reproduce the shifting. This must mean something.

What about the chain? The chain is a SRAM PC-69. From the SRAM website, this is a mountain bike chain. The equivalent road chain is the PC-89. Comparing the two chains, the only difference appears to be the weight. According to SRAM, all other characteristics are the same.

Please help.

I know this sounds real dumb but ........Do you have a tight spot on the chain ??????
Often when you fit the chain the joint point can be too tight if not adjusted at the time , could that be why the chain lube helped ?

 

[mre]

A tight link on the chain was the first thing the mechanic suspected. Wiggling the chain had no positive impact on the ghost shifting.

Tonight, I pulled the RD cable out of the housing all the way to the brake lever and checked for anything that could affect smooth action on the cable, including the cable guide below the BB. Everything looked fine. However, one thing that has always bothered me was the length of the cable housing coming from the brake lever. Instead of the cable housing coming out at right angles to the brake lever, the housing actually angled towards the front of the bike. I decided to trim some of the cable and removed about 3 inches. The amount of forward angle is significantly reduced, altho there is still some angle left. I'll let y'all know if the cable housing length had any effect.

Originally posted by el Inglés
I know this sounds real dumb but ........Do you have a tight spot on the chain ??????
Often when you fit the chain the joint point can be too tight if not adjusted at the time , could that be why the chain lube helped ?

 

[drewski]

Originally posted by mre
However, one thing that has always bothered me was the length of the cable housing coming from the brake lever. Instead of the cable housing coming out at right angles to the brake lever, the housing actually angled towards the front of the bike. I decided to trim some of the cable and removed about 3 inches. The amount of forward angle is significantly reduced, altho there is still some angle left. I'll let y'all know if the cable housing length had any effect.

I prefer to have the housings even shorter so they are at "right angles" to the levers. Any forward bend will introduce more friction. You may also try criss-crossing the cables under the down-tube to reduce friction, starting the rear cable on the left side of the downtube cable stop and then crossing under the downtube to the right chainstay.

Also, when you say "everything looked fine" do you mean just that - that it was a visual check? I would try pulling the cable by hand back and forth through each section of housing, as well as the guide under the bottom bracket. You might feel some differences that were not apparent in a quick visual inspection.

 

[el Ingles]

Sorry had the flu ,
ok said it was a stupid question , here´s an other ; have you checked the freewheel isn´t slipping ? I had this type of fault some years ago with a cheap rear wheel ( mtb) and for some reason it would jump , then it failed completley and I took it to the shop , he tried to strip it , couldn´t , and then by mistake dropped it -- which of course fixed it !?!
It worked until I could afford something better , then I lent it to a friend with a busted hub who used it for a year until his wife broke it with a car , hey ho .

 

[mre]

I performed a little cable maintenance this week. 1) I removed both derailleur cables from their housing and shortened the housing so that the cables now sit at right angles to the shifter (brake lever), 2) applied a thin film of grease on the cable only where the cable lies inside the housing, and 3) removed the plastic inner liner from the excess cable housing and placed it on the cable guide under the bottom bracket. This last item prevents any cable to guide contact.

I've only had time for a couple of short rides, but so far, I'm free of ghost shifting. More importantly, the shifting feels more precise.

Thanks to all who offered suggestions. I'm keeping my fingers crossed.

Originally posted by el Inglés
Sorry had the flu ,
ok said it was a stupid question , here´s an other ; have you checked the freewheel isn´t slipping ? I had this type of fault some years ago with a cheap rear wheel ( mtb) and for some reason it would jump , then it failed completley and I took it to the shop , he tried to strip it , couldn´t , and then by mistake dropped it -- which of course fixed it !?!
It worked until I could afford something better , then I lent it to a friend with a busted hub who used it for a year until his wife broke it with a car , hey ho .

 

[Steve Ryan]

Back in November Mike E. asked about Nokon. I just installed their dereailleur cables last night, so here are a few comments.
1) They are expensive.
2) It has the look and feel of a high quality system (I say this after many years as a cyclist and aerospace engineer.)
3) You are asked to drill parts of your bike out to 2.7 mm! Personally, I don't keep metric drill bits around the house, but 7/64" worked okay. Don't try this at home if you don't have some experience drilling metal. I had to drill both downtube cable stops and the cable fitting near the rear derailleur.
4) Sites selling Nokon sometimes say you don't need to lubricate it, but the instructions say "the system must be well-oiled". Unfortunately it doesn't say what type of oil is recommended.
5) On a wind trainer, at least, shifting is great.

 

[mre]

Steve,
Thanks for the comments on Nokon. After much fiddling, I have suffered no instances of ghost shifting since I shortened the cable housing. Therefore, my need for something like Nokon is significantly diminished.

Originally posted by Steve Ryan
Back in November Mike E. asked about Nokon. I just installed their dereailleur cables last night, so here are a few comments.
1) They are expensive.
2) It has the look and feel of a high quality system (I say this after many years as a cyclist and aerospace engineer.)
3) You are asked to drill parts of your bike out to 2.7 mm! Personally, I don't keep metric drill bits around the house, but 7/64" worked okay. Don't try this at home if you don't have some experience drilling metal. I had to drill both downtube cable stops and the cable fitting near the rear derailleur.
4) Sites selling Nokon sometimes say you don't need to lubricate it, but the instructions say "the system must be well-oiled". Unfortunately it doesn't say what type of oil is recommended.
5) On a wind trainer, at least, shifting is great.

 

[Eidetic]

As a footnote, since mre solved his problem, I had a ghost-shifting problem once that turned out to be a bent 12 cog (outermost). Looking at the chain turn on the 12 cog, I could see variation in the inner chain plate to 13 cog spacing during rotation. Since the most of the cogs were also worn, I changed the whole cassette, and the chain, and the ghost-shifting problem went away.