Andy's Tire Service
"Our service goes a long way!"
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Andy's Tire Service "Our service goes a long way!" |
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Sizes - Load Capacity Air Pressure
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Agricultural Farm Tractors, Combines, Grain Buggies, Balers, Pickers, Plows, and other Implements Agricultural tires should not be used at high speeds, i.e. no more than 20 mph. The casing construction and the rubber compound are not designed to tolerate and dissipate the heat produced during high speed operation. There is one exception to this we will discuss later. Some tread designs will wear prematurely if used on hard surfaces such as gravel or pavement. Ag tires are engineered for specific applications and may not perform well outside of that intended use. The same size of tire may fit different machines. As an example, a turf tread would be almost useless in a rice or cane operation. Likewise, an implement tire is not tough enough for a backhoe. Most ag tires have a feature known as "rim shield". This is simply the sidewall of the tire extending flush with the outside of the rim flange. This prevents mud, sticks and stubble from pushing in between the tire and wheel. Foreign objects between the tire and wheel can cause an air leak on tubeless tires or can puncture or chafe an inner tube. What do all the letters and numbers mean on the sidewall of a tire? Size We'll look at a rear tractor tire. The size might read 12.4-28. We'll take the easy part first; the last number means the tire fits a 28 inch diameter wheel. Well, not really. The 28 inch refers to the diameter of the ledge where the tire bead sits. The overall diameter of the wheel might measure 31 inches or so. The first number is the nominal width of the tire from sidewall to sidewall. This will vary with the width of the rim the tire is mounted on. The original pneumatic tires had a cross-section of a circle; height and width were the same. The original designations were 9, 10, 11, 12 and so on. As tire manufacturing progressed, engineers figured out they could get more traction by making that cross-section a little wider and keeping the same height. Thus, the cross-section became an oval rather than a circle. So now, the 10 inch wide tire is 11.2 inches wide; the 11 is 12.4 and so on. Ply Rating The first pneumatic tires were constructed of layers of cotton canvas. This canvas contained the air pressure and gave the tire its shape. A layer of canvas would only stand a certain amount of pressure before it ripped. To withstand more pressure in order to carry heavier loads, more layers of canvas were added. These became known as plies. They were always added in pairs because the threads in the canvas were oriented at a angle to each other. Thus, a 4 ply was stronger than a 2 ply and a 6 was stronger than a 4. The number of plies became the indicator of carrying capacity. A major jump in technology came when layers of individual cords replaced the canvas plies. Then some manufacturer discovered they could use larger cord and fewer plies. The new 4 ply tire could have the same strength as a 6 ply. To avoid confusion, the ply rating system was developed. A tire was given a ply rating, indicating it had the same carrying capacity as a tire of the old ply system. An extreme example is a steel radial where one ply of steel equals the strength of a 12 ply tire. Position and use We see another bit of information on the sidewall of our tire; R-1. The "R" means it is for the drive axle of a tractor. The number is the intended use. In this case, a "1" means it is for general field use. The tread design would be the traditional chevron lug. An R-2 indicates the tire is for use in wet soil conditions, such a rice or cane fields. The tread lugs are about twice as deep as the R-1. And to confuse things further, there is an R-1W that is for less wet soil than the R-2 but more than the R-1. The lugs are about 25 percent deeper. The R-3 and R-4 are special use designs. The R-3 is a diamond tread tire for use on turf such as golf courses or landscaping machines. The R-4 has beefier lugs that are more closely spaced. It is for industrial use on backhoes and loaders where more wheel spin is expected when pushing a loader bucket into a pile of dirt or debris.
R-1, R-1W, R-3 and R-4 above. We haven't even mentioned radial farm tires. The users of radial tires are generally more sophisticated, experienced farmers. We'll delve into radials once we have covered the basics. Click here for information on implement and front farm tires.
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