SRAM rear mech; can't get into largest cog

Having trouble with a new SRAM Force rear mech. Was fitted by shop and all shifts are nice and smooth but it won't stay in the largest cog/smallest gear. Same issue in either the large or small ring on the front. It's not an issue with the limiting screw; even letting the screw out so that the mech just brushes the spokes when the lever is fully pushed in, when you release the lever the mech returns one position back onto the second cog.

Any ideas? I'm sure the shop would sort it since they fitted it but if I'm missing something obvious I'd like to think my limited mechanical skills should be able to sort it.

Cheers.

Have you tried tightening the cable a bit using the barrel adjuster? Is it an old cassette/chain combo? What shifters are you using?

I should have mentioned that it's an entire new Force group incl. shifters, chain and cassette, on a brand new Novatec hub, so shouldn't be any problems due to other equipment. Wheel alignment fine, etc.

I was reluctant to fiddle with the cable since all the other shifts are so smooth and clean, but I think I'll have to. Thanks for your help. :)

Now I may be wrong as this is the internet .. but like Hovis I think you've got some slack/stretch in your cable as the cables have settled since the shop initially set the bike up. Also have a look at this, if you haven't done so

http://www.bikeradar.com/gear/article/workshop-how-to-set-up-sram-force-25902/

Very useful link...

"In effect a mis-shift override, SRAM include an extra index point, past the first gear position (largest cog), which allows the paddle to be pushed beyond the release click without dropping out of gear..."

That makes sense. I'll have a fiddle this evening, see what I can do. Thanks again.

Thanks guys, it was indeed just a slack cable. A bit of yanking and all's good.

Great stuff .. if only more bike problems where that easy!

Another success story, Lfgss strikes again.