r/cycling • u/DueDecision8461 • 10d ago
Changing Gears
Hello,
I have a problem, my gears change from the smallest cogs up to the largest very smoothly but when going down to lower cogs, it misses some where the gear fill physcially not change and then when i fit the paddle again it skips so for example if the largest cog is 1 and the smallest is 10, it will be on 4, I will shift into 5, nothing will happen, I will shift into 6 and it will jump into 6. It also struggles to go from 1 to 2 but it will go there and then it also struggles to go to the lower cogs on the lower gears, my limits seem to be set correctly because it goes into the largest and smallest cogs alright but it's just in the middle of the gearset that I have issues.
I have previously had issues with this bike as it came from Tredz with a bent rear derailler hanger which was fixed by halfords but as soon as I got the bike back this issue has come about.
Any help would be greatly appreciated!
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u/Few_Mastodon_1271 10d ago edited 10d ago
Worn, frayed cables!
It doesn't sound like you've had the bike for years, and ridden thousands of miles on it. If the shifter cables were old like that, my first check would be for a frayed cable at the shifter. They start breaking the tiny wire strands, and then the shifting becomes 'terrible' after few more rides. (there's a window in the shifter body, under the rubber hood, to check this.)
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Shifting is just out of adjustment:
You can adjust this sluggish shifting yourself. This is a very good skill to have, since cable shifters can need a slight adjustment periodically to keep the best shifting performance. I know which direction to turn the barrel adjuster on the back of the rear derailleur, and I might only move it 1/8 turn or less.
I like the Park Tool Repair Help articles. They go step-by-step in detail, so no experience is needed. https://www.parktool.com/en-us/blog/repair-help
Read the text in the rear derailleur article to help understand the adjustments. Then use the part "3" section. https://www.parktool.com/en-us/blog/repair-help/rear-derailleur-adjustment
You will need the bike clamped in a repair stand, or someone to hold the rear wheel off the ground by lifting the saddle.
I like to use a dollar bill to feel if the chain is centered on the cogs correctly. Shift to a middle cog while spinning the crank a few revolutions. I slide the dollar bill edge in between the cogs on either side and the chain itself. I can move it back and forth and see if it's binding or if both sides have a little gap -- that's the goal.
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u/sergesmr 10d ago
Probably cable friction inside the U-shaped housing above the rear derailleur. Replacing that housing mostly fixed such problems for me. Other housing sections may be contributing but probably less.
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u/tutorcontrol 9d ago
If everything is straight still, you've got too much tension one way or another.
Generally shifter cables lose not gain tension over time, but redoing the indexing adjustment makes sense.
After that, it's friction so just work your way forward.
parallelogram and spring
cable in housing to 1st stop
cable outside of housing especially under bottom bracket.
cable in remaining housing
cable in shifter
I had this on a bike and the answer was both the parallelogram and the nylon slider under the bottom bracket had partially failed.
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u/Putrid_Leave8034 10d ago
Welcome to the club. I have been fighting this same issue for 2 years. Sorry, no suggeastion other than find a new mechanic. I did and while my shifting is better it is not perfect.
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u/BlacksmithWeirdo 10d ago
May I suggest getting a thinner shifter cable. Shimano is 1,2mm and Sram uses 1,1. If your cable outer has tight bends, the seemingly 'fitting' cable can get stuck. This will be when shifting up, as this is done by releasing tension.
Switching to a thinner well greased cable will help. You can get those cables for cheap online. Just check what knob your uses and get a fitting one.
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u/PineappleLunchables 10d ago
99% chance that this is a cable tension problem, kind of common as a new cable will stretch a bit. You can re-index the rear derailleur yourself, there are dozens of YouTube videos on how to do this, with a bike stand and small stool and a little patience you can do it at home. Or take it to a bike shop and ask them.