55 instead of 60 tire sidewalls a problem?

Looking at getting some grippy tires and can pick them up cheap from the track and wondered if going 170/55 on the rear causes any problems vs the stock 170/60? I know going wider makes turning rougher but what does reducing the sidewall do? Plan on keeping the stock 120/70 on the fronts if that means anything.

 

Your speedometer will read faster than you are actually going. Your acceleration will be slightly quicker off the line. Your fuel economy on the highway will be slightly reduced. You will feel the road more because there is less cushioning with a lower profile. Cornering on smooth roads will be tighter. Cornering on rough roads or uneven pavement will be slightly worse.

 

hmm being a bigger rider at 230lbs I don't need to feel the road more. Any experience with going with a skinnier 160 tire? Seems would turn quicker and some tires the 160 is almost as wide as the 170's of a different model.

 

In my opinion, the brand of tire makes just as much a difference as the size. I would recommend going out and getting a set of Pirelli Diablos (Stradas), in stock size. In my experience they are the best DO-IT-ALL sport tire for a DO-IT-ALL sport bike. Exceptional stickyness, reasonable tread life, and light weight. The are confidence inspiring on twisty roads. My chicken strips are down to 1cm.

 

Don't forget as well that the smaller rear tire will provide a (slightly) lower rear ride height and this will slow your steering a little unless you compensate by raising the fork tubes in the triples. Just one more little complication....