1 Tire Fundamentals R. Bortignon

2 Tire Function  provide traction (friction) with the road surface  provide a cushion between the road and the metal wheel

3 Tire Size  Letter designates tire type: “P” Passenger tire “P” Passenger tire “LT” Light truck tire “LT” Light truck tire “C” Commercial tire “C” Commercial tire “T” Temporary/spare tire “T” Temporary/spare tire

4 Tire Width  tread width in millimetres  this tire’s width would be 235 mm

5 Aspect Ratio  tire height-to-width ratio  aspect ratio = 75  sidewall height is 75% of the tire width  aspect ratio of this tire is 235mm X 75% = 176mm tall sidewall

6 Construction  “R” designates the tire is a radial tire  radial tires plies go from bead to bead

7 Rim Diameter  rim diameter is given in inches  13 = 13”  14 = 14”  15 = 15” etc.

8 Treadwear Rating  treadwear is given as a number  the higher the number, the longer the tire will last  100 = baseline  more than 100 = better  less than 100 = poorer

9 Traction Rating  traction (wet braking test) is given as an A, B, or C rating AA = best tractionAA = best traction A = intermediate tractionA = intermediate traction B = acceptable tractionB = acceptable traction C = poor traction ratingC = poor traction rating

10 Temperature Rating  temperature is also given as an A, B, or C rating  A = best  B = intermediate  C = acceptable  the higher the rating the more resistant to temperature build-up  the more a tire heats up, the quicker it wears

11 Inflation & Wear Problems under inflated: excessive wear on outer treadunder inflated: excessive wear on outer tread over inflated: excessive wear in middle of treadover inflated: excessive wear in middle of tread Wear bars flush with tread? Tire needs replacing!

12 Tire Rotation  ensures maximum tire life  evens out tire wear  tires should be rotated every 10,000 kms  check with owners manual or Mitchell for specific rotation pattern  this diagram is just one example

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14 Load Index  2-digit # that determines the tire’s maximum load carrying capacity  82 Load Index = 1047 lbs

15 Maximum Load Rating  the weight a tire can carry at the recommended air pressure  e.g lbs  ask your self, are the tires needed for a minivan or delivery van?  Don’t do what this person did!

16 Speed Rating  maximum allowable speed a tire can safely withstand without failure  letter system  for example “H” speed rating = 130 mph

17 Mud and Snow Rating  M+S stands for mud and snow (used on all-season tires)  good all-weather performance  generally not be suitable in heavy snow  Driving in snow? tire should have the mountain snowflake symbol  meets severe snow standards set out by RMA

18 Split Rims used on many ¾ ton pick-ups into the early 70’sused on many ¾ ton pick-ups into the early 70’s DO NOT demount, inflate or install in our shop!DO NOT demount, inflate or install in our shop!

19 Wheel Balance wheel tramp wheel shimmy imbalance causes vibration in the vehicle or a steering wheel that shakes wheel balancers correct this imbalance in the wheel/tire assembly