need help

[quicky106]

can any one help me ive put new wheels on my 318ti is got 225/45/17 on the front and 205/40/17 on the back (gona put 205s on front when the 225s need replacing ) used to drive fine put these wheels on and when i drive now i get to a certan speed and the traction conrol light starts flashing and cuts power i have to drive with it of to go over 10mph
any ideas all i can think is that it doesnt like having smaller tyres on the rear

[teetime4one]

Put the smaller tyres on the front.

[quicky106]

yer going to get 205s for front but was tring to get as much life out of the 225s first