Rear Derailleur won't shift into 2nd smallest cog

[TrackGuy]

Hi guys

 

Okay, I have a little bit of a issue at hand today. The other day I replaced my back wheel's tube and without noticing my shifter was in 7th gear and my front shifter was in 1st but when I reinstalled the back wheel the chain was on the 8th cog, I didn't notice this. So I shifted my shifter into 8th and then when I wanted to shift back into 7th it wouldn't.

 

In a nutshell, my rear derailleur won't go from 8th to 7th but if I go from 8th to 6th it goes and then whilst I am in 6th I can go to 7th and down to 8th. Also when I am in 8th when I shift to 7th the rear derailleur make a little movement, but I think it isn't enough or something.

 

I adjusted the limit screws, this didn't help at all. So what can it be?

 

Thanks a lot

[Maximis]

What rear derailleur do u have?

[TopFuel]

The limit screws are not what control the inter-cog changing. They simply control the upper and lower limit of the derailleur when shifting. The finer details are made by adjusting cable tension using the little barrel adjuster (located either just after the shifter on the cable, or at the derailleur itself).

 

This causes micro-changes in cable tension and thus affects the position of the derailleur with each shift. Considering you've adjusted the limit screw, and thus probably ruined the whole back setup of the gearing, just use this youtube video to start a setup from the beginning:

 

Edit: added link

Edited February 7, 2014 by TopFuel

[chrone]

sounds like you have messed up the limits, Check that the limit screws are correct, once that is done, dial screw in the tension adjuster on the cable all the way, go to the smallest gear at the rear, then change one gear up, pedal hard whilst adjusting the tension until the gear changes. should be fine then

[chrone]

read barrel adjuster

[AngryAustrian]

If you can't fix it with the barrel adjuster take it to your LBS. You can really mess up your shifting if you don't know what you're doing and even end up shifting into your wheel etc which might be bad...

[cfcjim]

Check the cable, make sure the outer casing(s) are all located correctly.

 

This has never happened to me, no not at all, never.. I've never adjusted and cursed a brand new cable and a crappy shifting RD only to find the outer casing was snagged in two positions.

Nope didn't happen...

 

[TopFuel]

If you can't fix it with the barrel adjuster take it to your LBS. You can really mess up your shifting if you don't know what you're doing and even end up shifting into your wheel etc which might be bad...

 

I disagree. It is not a terribly complicated thing to do. Just arm yourself with a bit of information and have an attempt yourself. The likelihood of doing serious damage is negligible to zero. You'll learn a useful skill, save yourself a bit of cash and sort out your bike. Win win win.

[TrackGuy]

I disagree. It is not a terribly complicated thing to do. Just arm yourself with a bit of information and have an attempt yourself. The likelihood of doing serious damage is negligible to zero. You'll learn a useful skill, save yourself a bit of cash and sort out your bike. Win win win.

 

Jip, this is exactly my idea. I am not only passionate about mountain biking and cycling in general but the bikes as well, so this is why I am asking around, looking at videos so that I can learn more and more about the bikes.

 

Well, I got it all sorted and fixed. I readjusted the cable tension and tuned the limit screws, and it was all good. I think the main problem was the cable tension that was a bit low.

[Sniffie]

I disagree. It is not a terribly complicated thing to do. Just arm yourself with a bit of information and have an attempt yourself. The likelihood of doing serious damage is negligible to zero. You'll learn a useful skill, save yourself a bit of cash and sort out your bike. Win win win.

Totally agree with TF. If you want to call yourself a serious mtb'er this is the kind of basic maintenance you should be able to do. Crappy shifting like Ruan are describing here are most likely caused by dirt working its way into the cable housings and causing a lot of extra friction which messes up the shifting.

 

Loosen the cable bolt on the RD, remove cable, clean housings with some alcohol or similar (aerosol can of quick start works the best). Blow the gunk out of the housings with compressed air. Replace housings and if the RD cable looks damaged or frayed replace with new one. You will have crisp gear changing again.