Tire Tech 101 What is a tire made of. What percent of a tire is rubber? What is a pneumatic tire? What is the difference between radial & bias ply tires ? Why are tires black? Actual components that go into a tire. Raw Rubber Carbon Black Steel Synthetic Rubber Nylon Fiberglass Polyester Aramid Rayon Brass Aramid: A synthetic fabric used in some tires that is (pound-for-pound) stronger than steel. What percent of a tire is rubber? By weight, give or take 30% By volume, quite a bite more. Rubber 30 20 Steel Nylon Synthetic Rubber 10 Carbon Black Rayon 0 Tire compontents What Is Pneumatic Tire? Filled by air, especially compressed air: a pneumatic tire (dictionary definition). All tires manufactured today are considered Pneumatic tires. Who Invented The First Tire? It was invented in 1888, by John Dunlop. This would be the end of the solid tire. Why are Tires Black? To protect the rubber from the harmful UV rays. A common type of UV stabilizer called a competitive absorber is added to capture and absorb these harmful UV light wave energy. Bias Ply Tire A bias ply tire has plies running at an angle from bead to bead. The cord angle is also reversed from ply to ply. Tread is bonded directly to the top ply. Belted Bias Tire Is a bias tire with belts added to increase tread stiffness. These belts are also ran at a different angle. These belts only lie on the tread area and not on the side walls, like cords. Radial Ply Tire Has plies running straight across from bead to bead with stabilizer belts lying directly beneath the tread. This results in the radial having flexible side wall, but a stiff tread. Michelin developed it in 1955! 50 years ago! – Sears imported them in the 1970s Tire Cutaway Tire Cutaway Cooper Tire Cutaway Tire Cutaway Tire Sidewall Tire Sidewall Tire Sidewall Tire Size LT = Light Truck Tire Size If you switch tire size on a car you can mess up the speedometer to figure out how close you are do the math to figure out the diameter. For a 205/75R15 tire it would look like this 205 X .75 x 2 ÷ 25.4 + 15= 27.106 Tire size X Aspect ratio X 2 ÷ 25.4 + Rim size 100 Aspect Ratio Percentage of tires height in relation to it’s width A 60 series tire height will be 60% of the width. The aspect ratio can be a 40,50, 60,65,70,75,78 These are some of the most common ones. Aspect Ratio So if we have a P205/60R15 tire. The width is 205 millimeters and the height is 60% of the width. That means 205 x .6 = 123 millimeters. That tire should be 123 millimeters tall. You can raise or lower your car by changing the height of the side wall. SERVICE DESCRIPTION On most tires, you will notice some additional numbers and letters located at the end of the tire size. For Example: P185/70R14 92S In this example the 92S is called the SERVICE DESCRIPTION. The Service Description consists of two parts, LOAD INDEX (the numbers) and SPEED RATING(the letter). The SPEED RATING is a letter which designates the rating achieved on indoor wheel testing. The LOAD INDEX is a number ranging from 0 to 279 and covers load capacities from the smallest motorcycle tires to those for the largest earth mover tires. In passenger car tires, the load index typically ranges from 75 to 100. As in aspect ratio where the operative word was ratio, in load index the operative word here is index. An index is a point of reference or a chart to refer to find information. All tire guides used by retail tire stores have them and they have load index charts in them. By referring to the load index chart in the Tire Guide you can determine the maximum load carrying capacity of a tire size from using the load index number at the end of the P-Metric size. For Example: Load Index Max Load (lbs.) 91 1356 92 1389 Load Index 93 1433 Load Index For a complete listing of load index ratings go to this web site Load Index Speed Rating from Michelin Tyres 2003 Speed Rating Thanks To Tire Guides. Com Effects of speed on a tire Tires are tested under Laboratory conditions they are not worn out, are properly inflated, not over loaded, damaged or altered. Just because the tire is rated at these speeds does not mean the car is safe or legal to drive at those speeds. TIRE GRADING Uniform Tire Quality Grading System Code UTQGS TREAD WEAR: Tire life expectations 100 is base line, 150 will give you 50% more wear then one ranked 100 (100 = 30,000 miles TRACTION:Braking capabilities – AA, A, B, C (AA Highest rating) Traction Grades Asphalt g Force Concrete g Force AA Above .54 .41 A Above .47 .35 B Above .38 .26 C Less than .38 .26 TIRE GRADING TEMPERATURE: Ability to withstand extreme heat - A, B, C Tire pressure Tire pressure should be check monthly Tire pressure should be checked cold For every 10° Fahrenheit change in air temperature, your tire's inflation pressure will change by about 1 psi The air pressure in the tire supports the car, make sure that it is the right amount. If you check the air pressure inside the shop at a temperature of 70° will the tires be the right pressure when it goes outside at 0°? Tire Pressure The EPA says your mileage drops 1% for every 2 pounds under the recommended tire pressure. Tire pressure Use the tire pressure recommended in your vehicle's owner's manual or tire information placard Tire Placard Driver’s door pillar Glove box door or Center Consol lid Trunk lid or Gas door Tire pressure This is the Maximum pressure for the tire not the normal pressure, use only if car is fully loaded. Thanks to Michelin for the picture Tread Patterns Competition Passenger Touring Performance Performance Snow Grand Touring Rain All Season High Performance Passenger Net to Gross Ratio – The amount of rubber hitting the road. 35 psi sitting still in water Effects of Tire pressure and Speed on wet traction 35 psi at 60 mph 30 psi at 60 mph 25 psi at 60 mph Nitrogen in tires Nitrogen is a dry inert gas. That means moisture free. Nitrogen leaks out of the sidewall three times slower then oxygen. Oxygen oxidizes the rubber in the sidewall. Plus the moisture in the air will rust the steel rims. Effects of tire pressure Over inflation Wide tires that are under inflated can also wear in the center Effects of tire pressure Under inflation Tire Defects Separations Weather cracking Bulges Breaks in sidewall/tread sidewall separations Excessive radial runout – diameter tread tearing, Excessive lateral runout chunking – width shoulder cracking Conicity Sidewall cracking – not level across tread cone shaped Tire Wear Cupping Tire Defects Bulge Tire Defects Chunk Outs Tire Defects Cracks Tire Defects, Foreign Objects Tire Wear Side Wear & Feathering Tire Pull Defective/damaged tires Bent wheel (rim) Excessive shoulder wear Excessive feathering Tire Defects Tire Wear Tire Wear Tire Wear Tire Rotation Tires should be rotated between 5,000 and 7,500 miles see charts on how to rotate Thanks to Michelin for the picture Tire Rotation Effects of Mismatched Tires Different Manufactures Different sizes New and/or used tires Effects on speedometer Effects on ABS/Traction Control Systems Effects on vehicle handling Tire Replacement One problem with replacing just one tire on FWD, AWD or 4X4’s is that you have a different size tire when you measure the circumference this creates a problems with the transaxles and drive trains. It also cause’s problems with traction control and ABS stopping. Tires need to be rotated at least every 7500 miles and if one tire is damaged on one of these cars all 4, count them FOUR tires need to be changed. Tread depth should be maintained within 4/32 of each tire. For more info go to Wheels steel \ cast Off set Bump steer Scrub Radius – note pages C 311- 313 How to measure a rim You need to measure from bead seat to bead seat. But you cannot measure from the inside with a tape measure take a good guess where it is on the outside. This one is 14 inch’s. How to measure a rim To find the diameter you measure the circumference (C) and divide it by Pi (3.14) ( C ÷ Pi = Diameter ) 44 ÷ 3.14 = 14.0127 So it is really a 14 inch rim That math class is important. Wheel Balance Improper balance causes the tire to vibrate several types of balancers, Bubble balancers, on car balancers and off car balancers shown. Some are hand spun and some are powered Static balance C 77 Equals wheel tramp or hop weight not even around the tire must add weight to other side to equal it out. Dynamic balance C- 78 equals wobble side to side weights not equal Wheel Balance Make sure when you balance a tire to use the right adapter some wheels are Hub centric or lug centric that means does it center on the Hub or the lugs most cars from the factory are Hub centric but some after marker wheels are lug centric If you think that your balancer is not working right or the wheel is off check the balance rotate it 180 degrees and rebalance it.