I had an emergency and had to put two used tires on my 2001 CRV The tires are a little smaller then the origional. The two tires are on the front. Now I am hearing a strange noise while driving. It is a high pitched wine when I get to about 30mph. Slower I do not hear it. These tires are only on until I can get back to the US and replace all 4. Any clues to what the noise is?

2001 CRV AWD no ABS

 

It's your differential working 100x harder than it should be.

The differential is there so that when you turn, the inner wheel is spinning at a slower speed than the outer wheel. But when one wheel is smaller (how much smaller are we talking about) then the differential has to work constantly to keep the smaller wheel turning faster to keep up with the bigger wheel. Add in RTAWD, it's a big mess waiting to happen. If your car is only FWD, I'd put the two mismatched on the rear, if it's AWD, i'd stop driving, regardless of what the excuse may be, as long as it's not life threatening.