QuestionIs the S rating on tires important? I haven't heard anything about it before now, when my wife was trying to buy tires for our Camry wagon - the store had 195/70 R14 tires in stock that matched all numbers except for the S91; they only had S90 in stock. Does that S number really matter???
Thanks for your response.
Jon
Answerjon,
The 3 digits after the tire size are called the Service Description. The Service Description has 2 parts - the Load Index and the Speed Rating - and takes the form NNL - where N = a number and L = a letter.
The Load Index (LI) is a code for the load carrying capacity of the tire. It is important to use the same or higher Load Index as originally came on the vehicle.
The Speed Rating is an indication of the maximum speed potential of the tire. You should use tires that have at least the same speed rating as the original tires.
On every vehicle sold in the US, there is a sticker - commonly called the placard - that will list the original tire size and the proper pressure for that size. The placard is usually located on a doorpost or in the glove box, but sometimes it is located in the trunk or on the fuel filler door.
So if your car's placard shows that the original tire was a P195/70R14 90S, the you should choose a tire with at least a 90 LI and an S speed rating.
In your case, a difference of one LI is not significant and the difference could be the result of rounding between the English system of units (pounds, feet, etc.) and the metric system.
If you want to read up a bit more on the subject:
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35
