Farm Tractor Tire Guide & Size Conversion Chart

April 25, 2021

Keeping your tires in good shape will improve your productivity and reduce your fuel consumption.

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How do I maximize the life of my tractor tires?

Tires over time will age and wear down. The following tips will help you get the most out of your tires:

  1. Check tire pressure: Properly inflating your tires is very important to maximize service life. When a tire is underinflated it can cause excessive wear on the tire. Follow manufacturer specifications and ensure your tire pressure is in line with guidelines. Check your tire pressure on a regular basis since changing temperatures can raise and lower tire pressure naturally.
  2. Regular inspections: Check the sidewalls and treads on a monthly basis to monitor overall condition. Look for cracks, discoloration, bulges, wear or additional unnatural blemish. You might be able to catch issues early.
  3. Store your tractor indoors: Exposure to sunlight UV will damage your tire over time and shorten its lifespan.
  4. Clean your tires: Clean and wash your tires after use. You can use a light dish soap in the water without causing an issue.
  5. Avoid harsh chemicals: Petroleum-based products may degrade your tire, so read labels of any products you use.
  6. Avoid overloading: Follow manufacturer guidelines and avoid operating with excessive weight for prolonged terms.

When should I replace my tractor tires?

As tractor tires wear down you may notice performance and productivity declines. This can result in higher fuel consumption and lost time because energy is lost when the tire slips or loses traction. When your slip starts to increase then it is often a sign you should consider replacing your tractor tires.

The frequency at which you should replace your tires depends on your local climate. Wetter regions tend to require more frequent tractor tire replacement than dryer regions.

If you start to see cords, then the tire needs to be replaced immediately. Sometimes damaged tires can be repaired — if your tire was damaged you might be able to save money by having it repaired rather than replacing it. Each instance is different, so it is best to speak with a qualified service person.

Who makes farm tractor tires?

The largest manufacturers of farm tractor tires include Goodyear, Titan, Carlisle, and Advance. Titan International is one the largest off highway tire manufacturers, selling tires under the Titan and Goodyear brand names.

How do I read my tractor tire size?

Tractor tires come in many shapes and sizes. When you change your tires you should check your existing tires and make sure your new tires will fit properly. Tractor tires use three different formats: Standard, Radial and Metric.

An example of tractor tire size expressed in Standard format would be “20.8-42”. The “20.8” means the tire is 20.8 inches wide and the “42” indicates the tire fits a 42-inch diameter wheel. The dash “-” indicates the tire construction is bias-ply (an "R" would be used if the tire were radial).

Tractor tire sizes are stated in Standard (Imperial measurement, inches), Radial, and Metric (millimeters) Sizes. You should first establish which measurement your tire uses, then you can use the chart below to reference the tire size you need.

Tractor tire size conversion chart for Standard, Radial and Metric

We have included a basic tire conversion chart below. To convert from metric to imperial (millimeters to inches) you can divide the number by 25.4 to get the inches equivalent. To convert from imperial to metric you can multiple by 25.4 to get millimeter equivalent.

Standard Size Radial Size Metric Size
11.2X20 11.2R20 280/85R20
12.4X20 12.4R20 320/85R20
9.5X24 9.5R24 250/85R24
11.2X24 11.2R24 280/85R24
12.4X24 12.4R24 320/85R24
13.6X24 13.6R24 340/85R24
14.9X24 14.9R24 380/85R24
16.9X24 16.9R24 420/85R24
18.4X26 18.4R26 420/85R26
11.2X28 11.2R28 280/85R28
12.4X28 12.4R28 320/85R28
13.6X28 13.6R28 340/85R28
14.9X28 14.9R28 380/85R28
16.9X28 16.9R28 420/85R28
14.9X30 14.9R30 380/85R30
16.9X30 16.9R30 420/85R30
420/90R30
18.4X30 18.4R30 460/85R30
12.4X32 12.4R32 320/85R32
12.4X34 12.4R34 320/85R34
14.9X34 14.9R34 380/85R34
16.9X34 16.9R34 420/85R34
18.4X34 18.4R34 460/85R34
20.8X34 20.8R34 520/85R34
12.4X36 12.4R36 320/85R36
13.6X36 13.6R36 340/85R36
13.6X38 13.6R38 340/85R38
14.9X38 14.9R38 380/85R38
16.9X38 16.9R38 420/85R38
18.4X38 18.4R38 460/85R38
20.8X38 20.8R38 520/85R38
18.4X42 18.4R42 460/85R42
20.8X42 20.8R42 520/85R42
20.8X46 20.8R46 520/85R46

Source: Ken Jones Tires

Resources

Tractor tire tread options

Preventing tire dry rot

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