Nark: By the looks of the photo in his avitar we can all assume we are talking about the rolla, and lets face it, if its a stock motor there aint no way you gettin those back wheels to spin under power.
rehau: If you want to lock up the rears on a rolla, my mate has the same problem as you, it just wont lock. What he does its puts his foot on the brake pedel and at the same time rip on the handbrake. This should get the arse end out. DONT APPLY FULL PRESSURE TO THE FOOT BRAKE, only use slight pressure.