The letter code in the tire size and rating column is also on the sidewall of the tire and the tire label; tires are the same size, but compound and construction will vary to suit the weight, horsepower and handling characteristics of the model for which each tire was designed
TT type is tube-type
S-rated for speeds up to 112 mph, H-rated for speeds up to 130 mph, V-rated for speeds up to 149 mph, W-rated for speeds up to 168 mph