Pat, you sent me off in a search to straighten out my confusion after your post on Z ratings. I thought WTF that's not what I know. So after finding some "old" info on the web that was the same as the old info in my head I found the latest:
L 75 mph 120 km/h Off-Road & Light Truck Tires
M 81 mph 130 km/h Temporary Spare Tires
N 87 mph 140km/h
P 93 mph 150 km/h
Q 99 mph 160 km/h Studless & Studdable Winter Tires
R 106 mph 170 km/h H.D. Light Truck Tires
S 112 mph 180 km/h Family Sedans & Vans
T 118 mph 190 km/h Family Sedans & Vans
U 124 mph 200 km/h
H 130 mph 210 km/h Sport Sedans & Coupes
V 149 mph 240 km/h Sport Sedans, Coupes & Sports Cars
W 168 mph 270 km/h Exotic Sports Cars
Y 186 mph 300 km/h Exotic Sports Cars
(99Y) in excess of 186 mph, 300 km/h
when the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35&bPostID=post-id-87555290-bf13-4eed-8a0a-f2ecf721438d&Now there is also a (xxW), when the W-speed rating indicated in a service description is enclosed in parentheses the top speed of the tire has been tested in excess of 168 mph, 270 km/h
http://en.wikipedia.org/wiki/Tire_codeLooks like I will need to keep my towing speed down.
Geo