Why Does it matter what speed rating my tires are?
"After all, I never speed, I don't even drive fast... honest"
With all the different makes & models of cars available, their tire's "speed rating" is critical to the handling & performance of each model & even some sub-models. Tire Code is written on the sidewall of every DOT approved tire & is where to look to get data that corresponds with the engineering & manufacture of that particular tire.
The load index is also recorded right there with the speed rating & is also important to the engineering of the tire in relation to the car's weight carrying capacity. The tire is designed to work with the suspension system to give the car a safe & responsive feel when you, the driver, need it most... on the road, at speed, in traffic.
Here is a handy chart to use if you would like to know how much load your tires are capable of handling safely. Also on the chart are some speed ratings that correspond with the ratings on the tire's sidewall.