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Trouble with 105 shifting

Old 02-24-20, 02:06 PM
  #1  
Razorrock
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Trouble with 105 shifting

I have a drop bar bike with Shimano 105 ST-RS505 shifters. In the last year it has gotten progressively worse shifting. here is the problem. I can adjust (turn the adjuster at rear derailleur) to shift into the largest cog 32 tooth (11-32) on rear. but when I do the other gears are slow shifting getting worse the smaller the gear. ie I shift up and pedal a rotation or so then it shifts. Or I can adjust it so it shifts smoothly into all of the other gears but wont shift into largest cog 32 tooth. I am on the largest cog on the crank (50/34) I realize this is cross chaining but should shift into gear.

The shifter lever (ST-RS505) feels like it is hitting a stop when I am shifting into the largest cog on rear. It isn't the rear derailleur stop because It will shift into it when adjusted but makes all other shifts worse. Is there a stop limiter in the shifter?

Any advice on what is causing my problem. It is almost like the indexing is off. I can choose to adjust to shift into bottom gears or top gears just not both?
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Old 02-24-20, 02:19 PM
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caloso
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How many miles on the chain and cassette? When's the last time you replaced the cables?
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Old 02-24-20, 03:07 PM
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Wilfred Laurier
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Your description of the problem sounds like a bent derailleur hanger. Bike shops have a tool to accurately align the hanger with the wheel.

https://www.parktool.com/product/der...e%20%26%20Fork
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Old 02-24-20, 03:20 PM
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Razorrock
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New Chain. 4,300 miles on bike.

Replaced chain within last 500 miles. no change in shifting.
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Old 02-24-20, 03:37 PM
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deacon mark
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This seems too easy to diagnose you need new cables and housing. If it does not shift back down this tells me that cable is getting friction and this is the obvious problem. The biggest culprit is the rear derailleur loop on the end going to the RD. Get good housing and good cables. Then report back.
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Old 02-24-20, 04:06 PM
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Cables run on the outside bottom of the BB shell? Turn you bike over an make sure they haven't started sawing into the guide and binding. My 1990 era bike just ran bare cable under the BB without a guide and when I started having shifing issues I found the rear DR cable had almost sawed through the thickness of the shell.

Frayed cable can be an issue too. Look up inside the shifter.

Last edited by Iride01; 02-24-20 at 04:10 PM.
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