[b3lha]

I'm no gearbox expert, but I reckon mismatched tyres on the same axle is asking for trouble.

I recently had two punctures on my green SVX. I swapped on two wheels from another SVX. But when driving it I could hear an unusual whirring noise from either the trans or the front diff. So I put the undamaged originals on the back and bought two new ones for the front and the noise went away.

As Harvey said, you should swap them around and put the new ones on the front. Then we can tease you about two of your wheels being on backwards.