Join Date: Apr 2015
Location: Murrysville, PA, USA. A pleasant, wooded suburb of Pittsburgh.
New Rear Tire
My OEM Rosso II was threadbare after 4300 miles (6900km), so I mounted a new Bridgestone S20 Evo on the rear wheel. I am using a 140/70, the same size as all the other (Kawa, Honda, Yam) sub-400cc bikes in the class, which use the same size rim as the 390. This is also the size favored by most of the RC 390 racers. The stock 150/60 does fit on the rim, but has to be pinched such that the profile is distorted and the full contact patch cannot be utilized. Thus, the prevalent "chicken strips". The 390 rim would have to be 1/2 inch wider to fully utilize a 150.
Immediately after fitting the new tire (getting the bead to seat was a bit of challenge), I took the bike for a test drive of about 120 miles on two-lane back roads. The S20 is far smoother in transition and turn-in on curves than the Rosso, but this is not a very fair comparison since the Rosso was badly squared off and down to the wear threads. I can say, however, that the S20EVO is an exceedingly secure-feeling rear tire and seems "natural" on the bike. I do believe that it puts down a bigger contact patch than the distorted OEM Rosso, and seems like a nice upgrade. I am very pleased. The 140/70 is slightly narrower and slightly taller than the Rosso. (The bike now leans at more of an angle on the sidestand and has a little more cornering clearance.)
One unexpected side benefit of the S20 is that it is noticeably more compliant over bumps than the Rosso. Between the new tire and the R6 shock, the bike now passes over the frost heaves that cross the local roads with much less shock and drama than with the Rosso/OEM shock.
Apparently Bridgestone has phased out the S20 EVO in favor of a successor, the S21. The S20 is thus on clearance at many tire dealers and I was able to pick up this tire for $103 on Amazon. It is a lovely, secure and comfortable tire, equal to or better than the stock Rosso II, and certainly sized more appropriately for the rim. How it will wear over distance remains to be seen.
"If you don't know where you're going, you might wind up somewhere else."
2015 390 Duke
1980 Moto Guzzi V50 II (becoming a cafe racer)
1984 Moto Guzzi SP 1000
Last edited by Diploman; 06-18-2016 at 07:47 AM.