Won't change up, now won't change down...aaaaaaah

[Thomk]

Been having a problem changing from the small to big ring for a few weeks (worked sometimes, sometimes not). Seemed to get better this week on its own. Coming back from work today I couldn't change from the big to small ring. I discovered this just before getting to the biggest drag on my commute (gulp). Anyway, what is going on. I haven't fiddled with anything for the past week.
BTW It's a 9 spd sora compact

 

[Davidc]

Check the cable.

 

[TonyEnjoyD]

Make sure it's grit free and well lubed.

 

[Pauluk]

Sounds like a cable tension problem. If the fault is coming and going it could be a poor/clogged cable.

 

[lordloveaduck]

Are you sure your not riding a fixie

 

[fossyant]

New cables. Simple.

 

[rusty bearing]

I suspect the inner has got frayed somewhere along the line and is just jammed up. The answer as everyone rightly says is new inner and possibly outer depending on their condition

 

[sidevalve]

99% as above cables but do just check the front mech can move ok.

 

[gwhite]

This is more likely to be the FD being bunged up with grit than the cable in my opinion. Try lubing all the pivots and then, with the gear lever in the Low position, pull the gear cable away from the frame a number of times, moving the FD over its whole arc of travel to ensure it's free.

 

[boydj]

I'd suspect a cable that's frayed inside the shifter - that's where they tend to break.

 

[Thomk]

I've cleaned everything I can think of and lubed the cable and FD, taken the chain off and cleaned it and it now seems to work well on the stand. I won't have a ride until tomorrow so will see for sure then. BTW the cables as far as I could see looked in good condition.