Tractor Tire Size: Find the Right Tire for Your Antique Tractor
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Things to keep in mind about tire sizes for antique tractors
It also should be noted that the tire industry adopted a more aggressive tread pattern about the time the first size change went into effect. And, you must remember that rear tractor tires evolved from existing sizes used on aircraft, so there may have been a slight increase in physical size when molds were developed exclusively for tractors.
Most restorers are aware of the second change, but few are aware of the first change. They go to the original owner’s manual, look under “tires,” see “13.5-28,” and purchase a set of 14.9-28s, thinking they have the proper original size.
They do not realize the 1927 13.5-28 is now an 18.4-28. And if this seems a big jump, you must remember the 18.4-28 has a recommended rim width of 16 inches, double the width of the original rim used for this tire in 1937. If you squeeze those beads together by 8 inches, the tread shoulders probably will come in that inch and a half. Remember, the first two sizes are based on tread width; the last is based on overall carcass width.
I hope I have shed some light on rear tractor tire sizes and their evolution over 65 or so years. If you thought some tractors at shows looked not-quite-right because their rear tires seemed small or odd, you probably were right. The restorers used the best information they had, and should not be faulted for this common mistake. Based on this assessment, however, if a tire looks small or odd, restorers may be justified in using a larger-sized tire without feeling they are not putting an “original” size on a tractor.
I am no “expert,” but I am very familiar with the rear tire industry and have come to the above conclusions after studying the sizes of old tires for a number of years.
Happy restorations. FCTed Buisker may be reached at Sue-Ted US Farm, 8744 E. Pleasant View Rd., Davis, IL 61019, (815) 865-5797.
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