I am a student for automotive and have a print out of the conversion chart for tires. it says I can go from 215/70r15 to 244/55r16 and only lose 1mph on speedometer, but found some 245/50r16 will that be a too much of a conversion?
245/50r16 tyres are 30mm (just over 1") wider than 215/70r15. More of a difference is the diameter - 215/70r15 gives 26.85" or 682 mm, 245/50r16 is 25.65" or 651mm - just over 1", or 4.5% smaller - your speedometer will over-read by nearly 5%.
Also bear in mind that you'll need new wheels for the 16" tyres (though that might be the whole reason you're asking?), so make sure they will fit correctly - check the offset and PCD (bolt pattern) of the new wheels before buying.