Tire Ratings

According to Hondo 03ST:

When "ZR" appears in the size designation with the service description, the maximum speed is as indicated by the service description.

Tire Designation	Maximum Speed
120/70ZR18 59W	270 km/h (168 mph)
120/70ZR18 59Y	300 km/h (186 mph)

For tires having a maximum speed capability above 240 km/h (149 mph), a "ZR" may appear in the size designation. For tires having a maximum speed capability above 300 km/h (186 mph), a "ZR" must appear in the size designation. The actual speed rating is specifically identified by the alpha character on the end (in the example above it's the "W" or the "Y". See the chart below to decode. Of course the tire manufacturers data should be checked to see what the tires actual rated max speed is.

Full List of Speed Ratings

Rating	Speed km/h	Speed mph
A1	5	3
A2	10	6
A3	15	9
A4	20	12
A5	25	16
A6	30	19
A7	35	22
A8	40	25
B	50	31
C	60	37
D	65	40
E	70	43
F	80	50
G	90	56
J	100	62
K	110	68
L	120	75
M	130	81
N	150	87
P	150	94
Q	160	100
R	170	106
S	180	112
T	190	118
U	200	124
H	210	130
Unlimited V	210+	130+
V	240	149
W	270	168
Y	300	186
ZR	300+	186+

Source: http://groups.msn.com/st1300us/general.msnw?action=get_message&mview=0&ID_Message=67125

Partial List of Load Ratings

Index	Weight (lbs)
54	467
55	481
56	494
57	507
58	520
59	536
60	551
61	567
62	584
63	600
64	617
65	639
66	661
67	677
68	694
69	716
70	736
71	761
72	783
72	783
73	805
74	827
75	853
76	882
77	908
78	937
79	963
80	992

Source: http://www.st-owners.com/forums/showpost.php?p=857274&postcount=2

-- MarkFeit - 19 Jul 2005