All gears shift smoothly, but won’t shift into 1st gear/large cog. Help?

Question

So I was tuning my newly acquired bike today and working with all 8 gears on the rear derailleur. I managed to properly set the high limit screw as well as cable tension so all gears shift smoothly from 2-7. However, when I try to shift to 1st gear, the derailleur won’t move and neither will the shifter. The cable tension is too tight. I also tried manually pushing the derailleur by hand and I can jusssssttttttt get it to shift into first, but it requires a lot of pressure. The only effect adjusting the low limit screw has had is that if it is too loose, it won’t shift from 3rd to 2nd. Tightening it anymore doesn’t shift it from 2nd to first.

I briefly inspected for alignment and from eyeballing it things look OK, but I am not too sure.

What are some things I can do or try and what should I be looking at if something needs fixing?

Thank you guys for your help.

Answer 1

From what you describe, it seems that pushing the derailleur inwards manually to get it onto the largest sprocket was tightening the shifter cable - that is suspicious, it should have loosened the cable.

First thing to do is disconnect the shift cable from the derailleur and check three things:

1. The derailleur will swing through its full range
2. The shifter will click through all gears.
3. The cable travels freely. You should be able to get hold of the shifter and derailleur ends of the cable and pull it back and forth.

If anything is hanging up or jamming, that is where you need to look for problems. I'd also check the shifter cable routing and make sure there are no cable and housing are where they should be and there are no kinks.

Answer 2

You need to either loosen the hard-stop screw for the high limit or the low limit depending on if it won't go into the biggest cog or the smallest cog.

I would loosen the screw one-turn and see if it helps. Fine tune the adjustment from there. The screws are easy to turn if you move the derailleur slightly away from the stop.

You might also experience not being able to drop into the smallest cog if your cable is too tight. If this is the case, then loosen the cable by turning the barrel-adjuster on the cable in.

Here's a decent tutorial: http://www.madegood.org/bikes/repair/set-a-limit-screw-on-a-rear-derailleur/

Answer 3

First off:

Your description "The cable tension is too tight." is ambiguous. Do you mean that loosening the cable would allow the derailer to move sufficiently? (And that it does so if you disconnect the cable?) Or do you mean (and that's what I suppose) that it is very tight despite the derailer not moving? (I know this should be a comment to the question, but I seem not allowed to do so. If anyone else can, feel free to move.)

To your question:

Given that the cable is really tight and the derailer is not moving nonetheless, it is most likely blocked and most likely by the teeth of the biggest sprocket. Look carefully, comparing how the pulleys align with the smaller sprockets. To remedy, carefully hold the derailer and twist it clockwise around the mounting bolt. If it moves, you found the culprit. Other possible causes include:

• your hanger is bent. Try to check whether the pulleys are parallel to each other and to the sprockets.
• the derailer is blocked by other means. There could be debris, twigs or such inside it.
• your chain is too short. (Did you switch to the smallest chainring?)
• the cassette is mounted too far inside. Since you are talking about an 8-speed cassette, that should hardly be possible, however. (Also, the derailer should be able to move all the way to the spokes.)