Hi, i have recently brought a mountain bike from halfords. it was £130 and just needed it to ride to work (no rough terrain). i can usually get 2 good rides (about 15 minutes each) before something goes wrong. The most common problem i have is that the rear wheel misaligns and starts to rub on the frame work - i then have to walk the rest of my journey. I also suffer from "Gear Slip" i think. i start to pedal - usually up hill and the chain jumps over the cogs? can anyone help resolve these?