whats the minimum size rim that will fit over the ralliart calipers?
ive just realised that the 15" spare, just fits on the rear, so no hope of fitting on the front

16" rim will fit.
AWD's came with 16's std as they came with the same brakes as the Ralliarts

whats the minimum size rim that will fit over the ralliart calipers?
ive just realised that the 15" spare, just fits on the rear, so no hope of fitting on the front

Yep. Mininum of 16". Just grab a cheap 16" steelie from a wrecker.

cheers guys

just dont get falcon steelies or test fit them before buying, The previous owner of my wagon has AU 16's on it and needed 10mm spacers to clear the awd brakes

just had a thought, if i put a 16" on the front with a 20" on the other side, will the rolling diamater difference put the diff in any stress? or have some other adverse affect?

just had a thought, if i put a 16" on the front with a 20" on the other side, will the rolling diamater difference put the diff in any stress? or have some other adverse affect?

Correct, it will alter the differential load (is to do with weight AND diameter). The procedure is actually to swap the rear wheel first and use the 20 on the front.

just had a thought, if i put a 16" on the front with a 20" on the other side, will the rolling diamater difference put the diff in any stress? or have some other adverse affect?

It is not the rim size that matters in the end. It is the overall diameter. As long as that is maintained within a small percentage that is fine. So if the 16" had 215/60R16 than its overall diameter is 664.4mm which means the 20" should have 235/35R20.

On the otherhand the weight difference between a 20" and 16" may cause problems at higher speeds.

Yep, as Dean says avoid whacking the spare on the front if you can, you should always aim for matching rims & tyres on the fronts. Which means if you have a flat/wrecked front tyre and the spare isn't a match (but the rears are) then you should first swap the spare with one of the rears then swap the removed rear for the damaged front. Takes a bit longer but better than wrecking your CV joints or driveshafts or diff or whole trans.

ok cheers guys, looks like i need to jack the rear, put the spare on the rear, then use that 20" and use it to replace the hypothetical flat 20" on the front