Rear tire size question.

[Speedfrog]

Tire/Rim size fitment recommendation:

180/55-17 => 5.50-6.00

170/60-17 => 4.25-5.50

These 2 tire sizes have different aspect ratio and although you could go either way on the 5.5" rim that came with the later models, mounting a 180/55 falls on the lower side of the recommended rim width where the 170/60 is on the higher side.

The 170/60 will definetly sit a bit flatter on a 5.5" rim but the 180/55 with a smaller recommended rim size span would be just right. 

In fact, next tire size up, 190/55-17 will only properly fit on a 6.0-6.5" rim.

There are so many other factors to handling performance not only with tires of different brands - even between models within the same brand - with different actual size and shape but also tire pressure, carried weight, ergonomics, etc. and most importantly suspension setup that it all comes down to personal experience with your own setup when it comes to tire choice.

Don't forget that motorcycle tires have come a long way in the last 20 years and the 180/55 - 5.5" rim combo is pretty much today's standard for most sport/sport touring liter bikes.

I personally favor that combo on my bike - it looks right and it feels right - again just a personal choice... YMMV