Jumping Down a Gear

meanredspider

Sorry - another rear derailleur question - hopefully save me trial-and-error method of fixing it.

New chain, new jockeys - rear cassette is nearly new.

Problem: Mid range gears on 105 tendancy to jump down a gear (up a cog) - especially in small compact ring. Not an issue top & bottom.

My options:
- cable tension (too tight/loose)
- b-tension
- chain too loose.

I think chain is correct length checking the Shimano guide. B-tension seems slightly odd because it seems to be screwed all the way home. Shimano guide isn't particularly clear on this whole topic. Tension barrel adjuster is also screwed all the way home so, if releasing tension (as seems likely) is the way to go, I can slacken the cable end. Just seems odd that the cable hasn't stretched and needs tensioning.

Anyhow - pointers would be really appreciated until I've built up some experience.

Ben6899

For clarity. Does the chain move to a larger or smaller (physical dimensions) cog? I think this will be a cable tension issue, but too tight or too slack depends on what the precise problem is.

Skipping to larger cog - too tight

Skipping to smaller cog - too slack

cabbage1879

If it's jumping up a cog on it's own then cable tension is too tight, a half turn clockwise should sort it out.

meanredspider

Yup, thanks both - skipping to a larger cog so I'll back the tension off a smidge.