How to Read OTR Tire Sizes: 7 Simple Rules for Buyers
How to read OTR tire sizes in 7 simple rules: width, rim, radial or bias, ply and star ratings. A clear guide for tire buyers and importers worldwide.
Knowing how to read OTR tire sizes saves money on every order. A wrong digit on a purchase order can mean a container of tires that will not fit your loader. Here are the seven rules our sales team explains to new buyers almost every week.
Rule 1: The First Number Is Width
In a size such as 23.5R25 or 23.5-25, the first number is the section width in inches. A 23.5 tire is about 600 mm wide when inflated on the correct rim.
Rule 2: The Letter Tells You the Construction
An R means radial, with steel belts under the tread. A dash means bias, built from crossed nylon plies. The two are not mixed on the same axle.
Rule 3: The Last Number Is the Rim
The final figure is the rim diameter in inches. Loader and dozer sizes mostly sit on 25-inch rims, while graders use 24-inch rims and large haul trucks use 33 to 63-inch rims.
Rule 4: Wide-Base Sizes Use Millimetres
Sizes such as 750/65R25 give width in millimetres and the aspect ratio, so the sidewall is 65 percent as tall as the tire is wide. These fit the same rim diameter but need a wider rim.
Rule 5: Ply Rating Is About Strength, Not Layers
On bias tires, 16PR or 20PR shows the load strength. It no longer counts real plies. Higher ratings carry more load at higher pressure.
Rule 6: Radials Use Stars
Radial OTR tires show one, two or three stars. Two-star tires suit most loaders. Three-star tires carry more load and are common on haul trucks.
Rule 7: Check the TRA Code
Codes such as E-3, L-3 or G-2 describe the job the tread is built for. Always match the code to the machine, not only the size.
How to Read OTR Tire Sizes Before You Order
Write down the full sidewall marking, take a photo, and send both with your enquiry. The official standards are published by the Tire and Rim Association and the ETRTO, and the tire code article is a helpful summary. You can also browse common sizes such as 23.5R25 tires, 17.5R25 tires and 20.5-25 tires.
Get Expert Help With How to read OTR tire sizes
Our export team has answered questions like this for buyers in Asia, Africa, the Middle East, Australia and the Americas for many years. Send your machine list, sizes and destination port, and we will reply with options, prices and freight within 24 hours. You can also browse the full tire catalogue or compare tire brands before you write.
OTR TIRE (THAILAND) CO., LTD. ships mixed containers from Laem Chabang to ports worldwide. Message us on WhatsApp +66 640 130 805 or email info@orttirethai.shop.
