Service Description
The service description provides two important facts about the tire. First, the number designation is it's load index. Second, the letter designation indicates the tire's speed rating. The rating will appear with the load index following the size designation in the Service Description

STREET CHARTS

Index Rating
LI	lbs.	LI	lbs.	LI	lbs.	LI	lbs.	LI	lbs.
20	176	33	254	46	375	59	536	72	783
21	182	34	260	47	386	60	551	73	805
22	187	35	267	48	397	61	567	74	827
23	193	36	276	49	408	62	584	75	853
24	198	37	282	50	419	63	600	76	882
25	204	38	291	51	430	64	617	77	908
26	209	39	300	52	441	65	639	78	937
27	215	40	309	53	454	66	661	79	963
28	220	41	320	54	467	67	677	80	992
29	227	42	331	55	481	68	694	81	1019
30	234	43	342	56	494	69	716	82	1047
31	240	44	353	57	507	70	736	83	1074
32	247	45	364	58	520	71	761	84	1102
Load Rating - A numerical code which corresponds to the total load carrying capacity at the speed indicated by the speed symbol.