2018 chorus shifting problem

[Dave]

I've never had a shifting issue that I couldn't fix eventually, but this one has me stymied. I've ridden my new Colnago C-RS about 1200 miles and the shifting seemed to be OK, but it now hesitates or refuses to make reliable shifts to smaller cogs, mainly when in the big ring. Shifting to the smaller cogs when I'm in the little ring is much better.

I've got new cables and housing. Today, I took the whole thing apart to check cable housing ends, put some light lube into the cable housing and even tried switching from the back routed cable position to the the front. I took the RD off and checked the alignment of the hanger and properly adjusted the H screw so the upper pulley is 5-7mm from the largest cog, in the little ring.

Campy's instructional video says nothing about the B screw. I fiddled with it, but it seems to make no difference.

This bike does have internal cable routing, which makes the cabling process a real pain. I have a roll of cable liner, so I replaced the short length that goes under the BB.

The normal answer is that there is a cable friction problem that's causing the cable to not move freely on the shifts to smaller cogs. That's probably the case, but all I can think of to do at this point is trash the cable housing and start over.

[ultraman6970]

Hmm... 3 things...

1 if you check out friction in the cables and you have liner in place aswell then doubt is that...

2nd thing, probably is the lever, not that the lever is bad but happens that if the cable head is not in the cable spooler sit hole thingy right, the cable will get off the spooler and create friction big time.

Remove the lever at fault, and check out the cable spooler, is right there on sight. Look around the spooler itself if the lever has scratches, if you see scratches is because the head of the cable is getting off the cable spooler and messing you out. If you have a problem like that just dremel the head tad more so it fits deeper in the holes.

3rd thing, what if the screw that holds everything together is lose? Remove the lever and check out the center screw, if lose you might have found the problem.

Hope this helps.

[Ralph]

Is this the bike with the Potenza RD? Campy says it's spring is weaker than a regular Chorus.....it's for use with Potenza (Power Shift) shifters.

http://www.velotech-cycling.ltd.uk/c...shtml#comp-mec Scroll down a ways.

[Dave]

Originally Posted by Ralph

Is this the bike with the Potenza RD? Campy says it's spring is weaker than a regular Chorus.....it's for use with Potenza (Power Shift) shifters.

No, this bike has a new Chorus RD. I do get a little of shift hesitation with the Potenza on my old bike, but it's tolerable.

[Joe Remi]

With the caveat that I know nothing about Campy stuff, IMO a shifter or cable problem shouldn't only show up in the big ring. Is there something going on with the tension on the chain in big that is causing it to not want to drop to smaller cogs?

[ChainNoise]

What cassette are you running? Have you tried adjusting the cable tension?

[dddd]

Originally Posted by Joe Remi

With the caveat that I know nothing about Campy stuff, IMO a shifter or cable problem shouldn't only show up in the big ring. Is there something going on with the tension on the chain in big that is causing it to not want to drop to smaller cogs?

Actually, the rear shifting while on the BIG ring is the acid test.

The chain gap is typically larger while the chain is on the big ring, due to the derailer cage offset at the top pulley, so marginal shifting performance may only show up while using the big ring.

I suspect the cabling is suffering from a springy cable bowing between the internal guide features inside of the frame, which introduces unwanted elasticity to the cable force/load path. Any elasticity interacts with the normal, finite amount of friction in the rear-most cabling and derailer itself, leading to hysteresis losses in the transmission of motion from the shifter to the derailer.
Decreasing friction or elasticity will improve matters, since it is effectively like the (friction X elasticity) is the quantitative "problem" parameter.
Note that cables can get crossed inside of the downtube, causing both friction and elasticity. Note also that cable sheaths must not prevent the cable from contacting solidly in the guide grooves, or it might result in elasticity being introduced there.

Depending on the particular frame, I often solve such issues by using thinner 1.1mm cable wire, which is better at forming straight-line tangents between the curves of the frame's internal guiding features.
Shimano's coated cables also seem to help in many situations, though will not fit in the Campagnolo shifter spool.

The choice of lube in today's drivetrain cable housings is very critical imo, I only use cable-specific silicone/Teflon formulations such as Shimano's and SRAM's, as these are specifically made for the metal-on-plastic interface inside of the lined housings.

Lastly, any elasticity resulting from a cable housing not fully seated in the shift lever body would contribute to the problem, and is something that can result from handlebars being taped without there being tension on the cable at the time, or if the housing "springs" out of the hole in the lever body due to the sharp bend along the handlebar.

Campagnolo doesn't use a B-pivot tension adjuster, it's the A-pivot spring tension that must be loosened in order for the top pulley to be moved closer to the cassette. Are all of the cassette cogs tight against each other?

EDIT: I should have also added that any bend or "kink" in the cable wire, no matter how slight, will make the cable wire more elastic in tension, and thus incapable of delivering the crispest shifts. Remember, it is the sum total of all of the elasticity adders that can conspire with normal (or abnormal) friction to make or break acceptable shifting quality.

[zmalwo]

try rotating B screw clock wise, closer derailluer cage = better shifting.

[sib]

Tight cable bends at the handlebars?

[Joxster]

Check the drop out, is it straight and is it tight?

[Joe Remi]

Wow, that was quite a lesson in all the ways cables can go sideways (literally) inside a frame. I've never used internally routed cables, I knew nothing about that stuff.

[ChainNoise]

Originally Posted by zmalwo

try rotating B screw clock wise, closer derailluer cage = better shifting.

Campy doesn't use the B screw to bring the cage closer to the cassette. It uses the Phillips screw in this picture:



Definitely look into the seating of the cable in the shifter. That happened to me once before and stumped me big time until I got fed up and decided to redo the entire cable/housing. Another thing that assisted in poor shifting was chain length. Did you adjust chain length how Campy suggests?

[oldpotatoe]

Originally Posted by Dave

I've never had a shifting issue that I couldn't fix eventually, but this one has me stymied. I've ridden my new Colnago C-RS about 1200 miles and the shifting seemed to be OK, but it now hesitates or refuses to make reliable shifts to smaller cogs, mainly when in the big ring. Shifting to the smaller cogs when I'm in the little ring is much better.

I've got new cables and housing. Today, I took the whole thing apart to check cable housing ends, put some light lube into the cable housing and even tried switching from the back routed cable position to the the front. I took the RD off and checked the alignment of the hanger and properly adjusted the H screw so the upper pulley is 5-7mm from the largest cog, in the little ring.

Campy's instructional video says nothing about the B screw. I fiddled with it, but it seems to make no difference.

This bike does have internal cable routing, which makes the cabling process a real pain. I have a roll of cable liner, so I replaced the short length that goes under the BB.

The normal answer is that there is a cable friction problem that's causing the cable to not move freely on the shifts to smaller cogs. That's probably the case, but all I can think of to do at this point is trash the cable housing and start over.

Yup, no doubt(der hanger straight?)..make sure the wee brass washers are in the lever where the der housing goes in, presses against, make sure they haven't turned 90 degrees(saw that once). Der housing needs to be cut cleanly and at 90 degrees..long enough also. I use 5mm der housing and brass ferrules at the rear der to minimize friction anywhere.

[Mark McM]

Originally Posted by Joe Remi

Wow, that was quite a lesson in all the ways cables can go sideways (literally) inside a frame. I've never used internally routed cables, I knew nothing about that stuff.

The reminds me of a time when I was routing internal cables through an aero road frame. When I threaded the cables through the large down tube, appararently the cables go intertwined somewhere along the line. When in the small chainring, the front derailleur cable was completely slack, allowing the rear derailleur cable to run straight and true, and the rear shifting was excellent. But when shifted int the big chainring, the front derailleur cable was tighter, and the two cables tugged each other laterally, causing the rear shifting to get wonky. I scratched my head for a while about how rear shifting could be so good in the small chainring and so bad in the big chainring, until I discovered that shifting the front derailleur caused the rear derailleur to move, so I realize that the two cables must be interfering with each other.

[Dave]

I got the bike shifting properly this morning. I finally received a 30 foot roll of Shimano housing late yesterday and started over this morning. I used some of that housing with a 1.1mm jagwire cable. With the bolt on cable guide under the BB, you have to at least disconnect the FD cable to work on the RD cable, so I took the opportunity to install the campy inline tension adjuster for the FD cable and replace that cable too.

I didn't find anything specific to be wrong. I did try a shorter cable loop at the RD, but it didn't shift as well, so the longer loop went back on.

One trick I use so I don't loose the cable path through the frame is to use some heat shrink tubing to join a scrap cable to the one I want to pull out, then pull it all the way from front to back. I still manage to lose the pathway occasionally and the only way I've found to get it back is with a 3 foot length of .035 inch welding rod. I can drop that through the upper cable stop hole and eventually get it through the hole at the BB. Then I use the heat shrink tubing to join the end of the new cable to the welding rod and pull it through the down tube.

Having internal cables probably adds two hours to a normally easy task.