from google search:
"Putting just two snow tires on your car is a bad idea. If you have a front-wheel-drive car and put snow tires on the front only, the back wheels won't have anywhere near as much grip as the front wheels. This will make the car much more likely to spin out while braking or cornering. Likewise, if you put snow tires on the just back wheels of a rear-wheel-drive car, the wheels that do the steering won't grip as well as those that provide the power, so the car may not respond when the steering wheel is turned -- it will simply plow straight ahead. Always install snow tires as a full set of four"
My local dealer once showed me a vid of the effects of swapping rears to the front of a FWD and contrary to what I'd always told it's not advised as the lack of rear grip will make the car quite unstable under heavy braking conditions and cornering.
I feel your pain on the tyre prices as I was planning on fitting 4x Nokian WrG2's to mine until the prices went up 20% last month, had been told prices would have dropped by now as the market gets flooded with winter tyres but so far not the case.
