When I ordered new tires to replace my low-mileage but old & deeply cracking
OEM tires, I was feeling experimental. I bought IRC Road Winners again, but
messed with the sizing a bit. This was some months ago, so I've ridden quite
a bit with the replacements.
The rear tire: Replaced stock 140/80 with 130/80.
I have used skinnier than stock rear tires on bikes in the past and
have always been happier, felt that the bike turned better, had a sharper
feeling from the rear tire. That is how I feel about this switch. GOOD.
The front tire: Replaced stock 110/80 with 110/70.
I was having trouble finding a front tire in the stock size.
Some bad googling or something was going on, because I was
able to easily find the correct OEM size about a day after I had ordered.
With past bikes, going for a LARGER than stock aspect ratio was the
hot ticket. But here I went with a SMALLER than stock aspect ratio.
Result? Feedback was sharper, but not good. Front tire now feels as though
it is much more easily deflected when hitting bumps. So I am definitely
cornering less aggressively than I would with an OEM front. BAD.
I hope this helps.