SOLVED
Zombie, thanks for all the hard work in trying to help, I do appreciate it but, as you can tell, I verify things for myself and thankfully I did because you were wrong. Generally you'd be right with your 'don't overinflate over max psi' logic but not in this case. For others using a search engine for an answer to this, here is the bottom line on this tire:
Re: Michelin City Grip 150/70-14 66S Tire
General Notes from a 20 minute conversation with the heads of Michelin Motorcycle Tire Support Group:
First off, this 150/17-14 66s is NOT a small/medium scooter tire. This tire is a purposely built tire for a Maxi scooter and though it's not a radial tire it is used on Kymco Xciting 500s, Piaggio X9 500s and a lot of Burgman 650s around the world without problems. In fact most who use them (including me) prefer them over Avon, Pirelli and Metzler. The confusion arises because 33 Max PSI is clearly listed on the sidewall yet, in the Xciting's case, 36psi is listed as the rear pressure by Kymco, Piaggio wants the X9 500 to be at 37psi in the rear when riding two up, and the Burgman 650 even higher. So what should we do???
Short answer from Michelin re: this City Grip -- ALWAYS RUN AT THE MANUFACTURER RECOMMENDED PRESSURE. PERIOD.
But that seems counterintuitive as 33 max psi is listed on the sidewall? It is stupid and Michelin should probably change that in the 150/70-14 66Ss case but they haven't so run the tires at the pressure your bike recommends, NOT LOWER!
FWIW, here's why Michelin lists the 33psi on City Grips: As Zombie originally pointed out, MOST of the City Grip sizes are made for smaller or medium size scooters. Almost all of these scooters probably have a 32psi or lower recommendation for the rear tire. Michelin has found that a lot of owners just look at the sidewall and use the max psi as the number they inflate to and then jump on the bike. So what Michelin does in the City Grip's case (not all tires) is show a Max PSI on the sidewall that is closest to what most manufacturers will recommend for the bikes they will fit on. If they had listed the max psi as a lot higher these riders would be in trouble. So 33 max psi works great for all sizes in the City Grip line EXCEPT for the 150/70-14. What is the real max psi for the 150/70-14 probably much, much higher but if they listed it on all City Grips, a lot of folks might run at this on smaller bikes so they would have a liability. Regardless, I've been told by Michelin corporate to run this specific 150/70-14 66S at 36psi like Kymco suggests. Which makes sense as I have run them at 36psi for 9 months and 5,000 miles without issue. What spooked me was Zombie's response and thankfully, in this case though well intentioned he was wrong. No harm no foul, it was a great education. Hopefully this will help others who are confused about THIS PARTICULAR TIRE and SIZE. Please do not read this and think that the above answer from Michelin relates to any other tire in their line, it may or may not, I only asked about one tire, the 150/70-14 66S.
Peace, out.
