Hi all

I'm having a major problem with the back rail of my bike not turnng over, the gears just are not responding!

the gears hav e been slipping quite a bit lately but intensified when I reinstalled my back wheel after a tyre change. First of the front gears would rub against the rail so I tightened the front cable, then I tried to tweek the rear high low screws and cable but it's made things a whole worse, so much so that the rear gears won't even change!

Got a 54 mile bike ride ( London to brighton ) this weekend fir charity and I'm desperate to do it for the first time. Any help or advice would be greatly appreciated