You'll be just fine with the 50 series. I can't tell the difference on the streets. The only difference is the 55 raises the rear slightly and it changes the gear ratio slightly. I can tell a slight difference at the track when I'm throwing it into a corner. But it is a "Slight" difference. I"m not particular on street tires and race tires never come in 50 series!
Your biggest improvement is getting off the PP's and onto Q2's!
Rick, If I were riding for Grip (track), the Q2's are an awesome tire and you can find some GREAT deals ($200/set) at times. However, if riding street as you predominatly are, I'd recommend Avon Storm 2's. Good enough street grip for Pashnit, but a lot better mileage....
Thanks guys, Your opinions are much appreciated. Dont feel like buying the tire twice to get the right one for my riding style.
thanks again, Rick