ATV Wheel Size Chart and Fitment Dimensions: How to Read ATV and UTV Tire Sizes

An ATV or UTV tire size such as 25x8-12 gives three dimensions in inches. The tire is about 25 in tall overall and about 8 in wide, and it mounts on a wheel with a 12 in rim diameter. From those three numbers you can calculate sidewall height, circumference and revolutions per mile, and you can compare sizes.

Those numbers describe the tire's nominal geometry. They do not confirm that a tire or wheel will fit your machine. Fitment also depends on the wheel's rim width, bolt pattern, center bore, offset and clearance on the specific vehicle.

How to read the numbers on an ATV tire sidewall

ATV and UTV tire sidewalls carry two kinds of information:

• Dimensions: overall diameter, section width, aspect ratio and rim diameter.
• Construction and performance markings: radial or bias build, ply rating, load index, speed symbol and maximum pressure.

Dimensions tell you the tire's size. Ratings tell you how much load, speed and pressure it is built for.

Inch (flotation) format: 25x8-12

The most common ATV tire size format lists overall diameter x section width - rim diameter, all in inches.

• 25 is the nominal overall diameter (height) of the inflated, unloaded tire, in inches.
• 8 is the nominal section width, the widest point of the tire body, in inches. You may also see it written as 8.00.
• 12 is the rim diameter, meaning the wheel diameter at the bead seat, in inches. The tire fits only a 12 in wheel.

You may see the same size written as 25x8-12, 25x8.00-12, 25x8x12 or AT25x8-12. All of them describe the same nominal dimensions.

Metric format: 205/80R12

Some ATV and UTV tires use a metric format similar to car tires. A size such as 205/80R12 breaks down as follows:

• 205 is the section width in millimeters.
• 80 is the aspect ratio. Sidewall height equals 80% of the 205 mm width.
• R means radial construction.
• 12 is the rim diameter in inches.

Metric sizes mix units: width is in millimeters, but rim diameter is still in inches. Overall diameter is not printed directly in this format, so you have to calculate it. The method is shown below.

Construction letters: R, dash and AT

The letter or symbol before the rim diameter shows how the tire is built:

• R, as in 26x9R14, means radial construction.
• A dash, as in 26x9-14, usually means bias-ply construction.
• AT at the start of a size marks it as an ATV tire. It is not a dimension.

Construction affects how the tire flexes and rides. It does not change the nominal size.

Ply rating, load index, speed symbol and pressure

These markings are performance ratings, not dimensions:

• Ply rating, such as 6PR or 6 ply rated, expresses carcass strength as an equivalent number of plies. It is not necessarily the actual number of layers inside the tire.
• Load index is a number that stands for the maximum load per tire at the specified pressure. For example, load index 50 corresponds to 190 kg and 60 corresponds to 250 kg.
• Speed symbol is a letter that stands for a maximum speed rating. For example, F corresponds to 80 km/h (about 50 mph) and J to 100 km/h (about 62 mph).
• Maximum pressure is the highest inflation the tire is designed for. It is not the recommended riding pressure. ATVs and UTVs usually run far lower pressures, as specified by the vehicle manufacturer.

When comparing two tires, compare dimensions to check size. Compare ratings to confirm each tire suits the vehicle's weight, speed and use.

ATV wheel size chart: calculated dimensions of common tire sizes

The chart below lists common ATV and UTV tire sizes with values calculated from the nominal numbers on the sidewall. The formulas are:

• Sidewall height = (overall diameter − rim diameter) ÷ 2
• Aspect ratio = sidewall height ÷ section width
• Circumference = π × overall diameter
• Revolutions per mile = 63,360 in ÷ circumference

Every value in this chart is geometry calculated from nominal sizes. Measured dimensions of real tires in the same size often differ, as explained further down.

How width, aspect ratio and rim diameter change the tire

Overall diameter is the rim diameter plus two sidewall heights. Change the rim diameter or the sidewall height and the overall diameter changes, unless one change cancels out the other. Width changes the tire's footprint and stance. Width affects diameter only when the aspect ratio stays fixed, as it does in metric sizes.

Sidewall height

The sidewall is the rubber between the rim edge and the tread. In inch sizes you calculate it as (overall diameter − rim diameter) ÷ 2. In metric sizes it is width × aspect ratio.

At the same overall diameter, a taller sidewall usually gives more cushion and flex at low pressure. A shorter sidewall leaves more room for a larger wheel.

Overall diameter and circumference

Overall diameter sets how far the axle sits above the ground. Circumference sets how far the vehicle travels per wheel revolution.

A larger diameter has three main effects:

• Ground clearance under the axle rises by about half the diameter increase.
• Effective gearing becomes taller.
• A speedometer calibrated for the original size reads lower than actual speed.

Worked example: 25x8-12 compared with 27x9-14

1. Sidewall heights: (25 − 12) ÷ 2 = 6.5 in, and (27 − 14) ÷ 2 = 6.5 in. The sidewalls are the same height. The 2 in larger diameter comes entirely from the larger rim.
2. Circumferences: π × 25 = 78.5 in, and π × 27 = 84.8 in. The 27 in tire travels about 8% farther per revolution.
3. Ride height: the radius grows by 1 in, so the axle sits roughly 1 in higher.
4. Speedometer effect: if the speedometer was calibrated for 25 in tires, an indicated 30 mph is about 32.4 mph on 27 in tires.
5. Width: nominal section width grows by 1 in. If the wheel position stays the same, that is about 0.5 in per side.

Same diameter, different rim: 26x9-12 compared with 26x9-14

Both sizes are 26 in tall and 9 in wide, so their circumference (81.7 in) and revolutions per mile are the same on paper. The difference is the split between wheel and rubber:

• The 12 in wheel leaves a 7.0 in sidewall.
• The 14 in wheel leaves a 6.0 in sidewall.

Moving to a larger wheel diameter at the same tire height reduces sidewall cushion. It does not change gearing or ground clearance.

Same diameter, different width: 25x8-12 compared with 25x10-12

Many ATVs use a narrower front tire and a wider rear tire with the same overall diameter, such as 25x8-12 front and 25x10-12 rear. The extra 2 in of nominal width changes the footprint and stance. The diameter and circumference stay the same, so the front-to-rear relationship is preserved on paper.

Converting a metric size to inches: 205/80R12

1. Sidewall height: 205 mm × 0.80 = 164 mm.
2. Rim diameter in millimeters: 12 in × 25.4 = 304.8 mm.
3. Overall diameter: 304.8 + (2 × 164) = 632.8 mm, which is about 24.9 in.
4. Section width: 205 ÷ 25.4 = about 8.1 in.
5. Circumference: π × 632.8 mm = about 1,988 mm, which is about 78.3 in.

On paper, 205/80R12 is very close to 25x8-12. In a metric size, increasing the width while keeping the same aspect ratio also increases sidewall height and overall diameter.

Why the calculated size differs from the actual tire

Sidewall numbers are nominal. Measured height and width of real ATV and UTV tires can differ from them, sometimes noticeably. Common reasons include:

• Manufacturer and model: two tires labeled 27x9-14 from different brands, or different tread designs, can measure differently.
• Tread depth and lug height: aggressive mud tires often measure taller than less aggressive tires of the same nominal size. Height also drops as the tread wears.
• Rim width: the same tire mounted on a wider rim usually measures slightly wider, and its profile changes.
• Inflation pressure: ATV tires run at low pressure, so small pressure changes noticeably affect shape.
• Load: under the vehicle's weight the tire squats. The loaded radius is smaller than half the unloaded diameter, so the effective rolling circumference is shorter than π × nominal diameter.

If you need real numbers, use the tire manufacturer's published dimensions for that exact model and the approved rim width. Better still, measure the mounted tire at the pressure you will actually run.

Wheel fitment dimensions: what ATV and UTV wheel markings mean

A wheel listed as 14x7 4/137 5+2 describes five things:

• 14 in wheel diameter
• 7 in rim width
• Four studs on a 137 mm bolt circle
• 5 in of backspacing
• 2 in of frontspacing

The tire size has to match the wheel diameter. The wheel itself has to match the vehicle's hub.

How to read backspacing notation such as 5+2 or 4+3

In ATV wheel notation, the first number is roughly how much of the rim sits inboard of the mounting face. The second is how much sits outboard. Together they usually add up to the nominal rim width.

On a 7 in wheel, changing from 5+2 to 4+3 moves the wheel outward by about 1 in on each side. That widens the track by about 2 in in total. It also changes steering geometry and the load on wheel bearings.

How to measure a 4-lug bolt pattern

On a 4-lug hub or wheel, measure from the center of one stud to the center of the stud diagonally opposite it. Small differences matter. A 4/110 wheel and a 4/115 wheel can look alike but do not bolt on interchangeably. Check the vehicle specification rather than relying on a visual estimate.

How to check whether a new tire or wheel size fits your ATV or UTV

A tire fits a vehicle when its wheel matches the hub and the mounted assembly clears the chassis through full suspension and steering travel. The size calculation is only the first step. Work through the checks in this order:

1. Record the original sizes. Note the front and rear tire sizes and wheel sizes from the sidewalls, the wheels or the owner's manual.
2. Confirm the hub specifications. Check bolt pattern, center bore, lug thread and lug seat type. If any one of these does not match, the wheel does not fit.
3. Match the tire to the rim. The tire's rim diameter must equal the wheel diameter. The rim width should fall within the tire manufacturer's approved range for that size.
4. Calculate the dimensional change. Compare overall diameter, circumference and width with the original sizes using the formulas above. Keep in mind that actual measured dimensions may differ.
5. Check clearance on the vehicle. Check at full suspension compression, full droop and full steering lock in both directions. Look for contact with fenders, A-arms, tie rods, shocks, brake calipers and the frame. Also consider how offset changes the wheel's position.
6. Keep front and rear sizes consistent. On four-wheel-drive vehicles, keep the front-to-rear rolling diameter relationship the manufacturer intended. Mismatched circumferences can strain the drivetrain.
7. Confirm the ratings. Make sure the load index, ply rating and speed symbol suit the vehicle's weight, any cargo and the speeds you will ride.
8. Expect secondary effects. A larger diameter makes gearing taller, changes speedometer accuracy and can add weight and rotating mass. Check the vehicle manufacturer's guidance on oversize tires.

What a dimensional difference does and does not tell you

A calculated difference between two ATV tire sizes tells you how nominal geometry changes. It shows changes in sidewall height, overall diameter, circumference, ride height at the axle and approximate speedometer error. On paper, a 2 in increase in diameter means about 1 in more axle height. A 1 in increase in nominal width means about 0.5 in more per side at the same wheel position.

The calculation does not tell you:

• The exact measured size of a specific tire model
• How the tire behaves at your riding pressure and load
• Whether the wheel bolts to your hub
• Whether the tire clears your suspension and bodywork

Use the sidewall numbers and an ATV wheel size chart to narrow your choices. Then confirm them with manufacturer dimensions, the wheel's bolt pattern, center bore and offset, and a clearance check on the vehicle itself.