alexk_il

Trying to tune gears on my old Boardman Hybrid 2013 with Shimano Acera gears.

Did this a few times in the past without any issues, this time can't get the correct cable tension for perfectly smooth gear changes. I can make it perfect either for downshifting or for upshifting, but not both.

It's not really that bad, I can still select all gears with a bit of tension on the lever, but I am a bit annoyed by the hesitation to go either up or down without extra help on my side.

Will a new cable help or should I just forget about it and enjoy the otherwise great bike?

BTinNYC 

I would definitely get new housing and cable, it will make shifting easier, smoother and more consistent.

Not intending to insult, but are you using the barrel adjuster to tune/adjust the shifting?

alexk_il

Not sure if I understand the depth of your question, therefore not insulted. 😁

I am using a plastic cable tensioner thingy positioned where the cable goes into the levers. It rotates with some gentle clicks. Is there another one?

​​​​​​​Thank you for your advice to change the cable and the housing.

BTinNYC 

There is another barrel adjuster on the rear derailleur, but it does the exact same thing.

I'd also get a new chain while you're in maintenance mode.

andrewclaus

I agree your symptoms sound like cable friction. Sometimes that can be fixed with some steel wool and oil. To easily expose the cable, shift into low gear, stop pedaling, then shift into high (smallest rear cog). This will leave slack in the cable. Pull one of the cable housings out of a slotted frame stop, and everything will be loose. Slide each section of housing to expose the cable, clean with steel wool and apply some light oil. If there's any deep corrosion, fraying, or kinking, replace everything.

Some shifting problems are caused by a bent derailleur hanger. If cleaning/replacing the cable doesn't fix the problem, have a shop align the hanger. A special tool is needed.

BCRider

The times I've had this in exactly the way you are describing it turned out to be worn chain AND worn cassette cog teeth. If you check for burrs on the gullets of the most commonly used gears I bet you an E-beer that you can feel burrs on the faces where they meet the tooth gullets. If you are not sure what to look for you can use a toothpick pulled across the edge as shown below to check for burrs. The metal that is burred out is metal that is displaced from the edge of the teeth. This makes it want to hold the chain and require the extra shift.

In the picture below I've placed the tip of a toothpick against a slight burr which is just what I'm describing. I can't see this burr since it's pretty small so far. But as I push the point of the toothpick forward it is feeling a burr. When you can easily see such burrs then that is when it can really start to affect the shifting like you're getting.

Another possible issue is bad wear on the first idler cog in the derailleur cage. Some play is going to be there. But it should be a back and forth float. Not a tilting sort of motion. An older idler that is badly worn so it wobbles instead of floats in a parallel manner can cause the issue you are getting because it doesn't pull the chain as strongly to more than the one side. In essence the side to side float, which you want some of, is increased past the ideal point by the cog's new ability to also lean/tilt. This means you need to "overshift" like you're doing. Often on an older bike all three things, worn chain, worn cassette and worn first idler combine to really mess things up.


Toothpick to test for cog teeth burrs due to wear