Bicycle Mechanics - Help with Rapid Fire Shift Return

I have just put together a bike and am having a problem shifting. Sorry if this has been covered in the forum, but I searched to no avail. I may just not know what to search for.

Anyway... The bike has Shimano Acera Rapid Fire shifters. What is happening is that the big shifter (the one you do with you thumb) is not returning to its orignal position. I have to manually pull it back. The other little shifter seems to be working fine.

Both front and back are doing the same thing, just the big thumb shifter does not return on its own.

Any suggestions would be GREATLY appreciated!

Thanks,

Phillip

I'm guessing that it's the cables. Worn, dirty and causing too much friction.

If a dragging shift cable is not the problem then it is most likely the shifter. Acera uses a lot of plastic parts. The the returns spring in the shifter could have been damaged.

Guys, thanks for the reply. I took your suggestions and was looking at the cables and the shifters in detail. The bike and shifters are brand new.

As I was looking carefully, I noticed that the very top of the thumb shifter was sllightly dragging the rubber "rim" of the grip! These are the grips that came with the bike. So, I little trimming and all is well.

OK, I feel like an idiot. Thanks for the help.

Phillip

I know you fixed it, but i had that happen once because the shifter was slighlt on the downcurve of the handlebar. As soon as it was moved over it was fine. The angle was throwing something off big time.