trek caliber 8 gear problem

[m3jappa]

My wife has just got me the above as a birthday present

testing it out today i find that when going into the 12th gear the chain keeps slipping back into 11th then 12th then 11th and so on.

Why would this be? is there some adjustment issue?

[Justin S]

If you are talking about the smallest sprocket and one up from there, maybe the rear mech needs the lower screw adjusting of the cable needs loosening off on the adjuster.
If you re meaning the largest sprocket to one below it, might need the other adjustment screw on the rear mech adjusting or cable tensioning a bit. Be careful with this adjustment as if you go too far, it will just the gear cassette and jam between it and the spokes and makes a mess.

[m3jappa]

thank you, i have been reading and then had a proper look, i think it was slightly bent as it didn't look square iykwim, so i gave it a little tug and its perfect now, just took it out for a quick ride.
must have been where it was shipped and it was all cable tied together i reckon.