I'm a complete novice with bicycle maintenance and have a slight problem. I just picked up a 2nd hand bike as taking part in a charity event this weekend and an unfortunate accident meant my mine was totalled and I couldn't afford to be picky.
The bike is an 04 Giant OCR Zero with Campagnolo groupset. An okish bike and would've been fine as a temporary machine. I wasn't able to test ride as my knee is still battered and when I got home I flipped the bike and ran through the gears.
we have 3 on front and 9spd at the rear. When using the biggest ring at the back and biggest at the front, the tension on the chain is so great that it cannot move. If the rear is in mid position or lower then it transitions ok but not otherwise.
Any help or advice on how to fix is appreciated. I thought changing the chain might solve but the chain on there is a 9 spd and as far I know, it should be fine. replacing it with the same length would just result in the same problem.
Edited to add pics and info. Apologies for incorrect use of tension. I've taken a few pics(hopefully they've attached ok) showing the different states of the rear mech as I transition through the gears. There is a lot of crud but no slack on the chain at all