The short version
- Imperial format is height × width – rim, all in inches:
27×11R14is 27″ tall, 11″ wide, radial, 14″ wheel. - Ply rating is a strength grade, not a ply count. 6PR is the sweet spot for most trail riding.
- Bias flexes and resists punctures; radial rides better and lasts longer. Terrain decides.
- Pressures are tiny — 4–8 psi on ATVs. A car gauge is the wrong tool.
Reading the size: two formats, one tire
Imperial (the common one)
Roughly three quarters of the ATV and UTV market uses the imperial format. Its virtue is that the first number is the actual overall diameter — no arithmetic required.
| Element | Meaning | Value |
|---|---|---|
27 | Overall diameter of the mounted, inflated tire | 27 inches |
11 | Section width at the widest point | 11 inches |
R | Construction — R = radial, – (hyphen) = bias ply | Radial |
14 | Rim diameter | 14-inch wheel |
So 25×10-12 is a 25-inch-tall, 10-inch-wide bias tire on a 12-inch wheel. That single-character difference between - and R is the most commonly missed detail on a spec sheet.
Metric (mostly European and some sport quads)
The metric string works exactly like a car tire, with one trap: the rim diameter is still in inches.
| Element | Meaning | Value |
|---|---|---|
255 | Section width in millimetres | 255 mm ≈ 10.0″ |
80 | Aspect ratio: sidewall height as % of width | 204 mm sidewall |
R | Radial construction | Radial |
14 | Rim diameter — inches, not mm | 14″ = 355.6 mm |
M/C | Motorcycle-class designation | — |
Overall diameter (inches) = (widthmm × aspect ÷ 100 × 2 ÷ 25.4) + rimin
For 255/80R14: (255 × 0.80 × 2 ÷ 25.4) + 14 = 16.06 + 14 = 30.1 inches. So that tire is effectively a 30×10R14. Our size comparison calculator handles both formats.
Ply rating: a number that stopped counting plies
“6-ply” is a historical unit. It originally meant six literal layers of cotton fabric in the casing. Modern nylon, polyester and aramid cords are so much stronger that a tire rated 6PR usually contains only two or three actual plies. The rating survives as a strength-equivalence grade, and manufacturers increasingly write it as “6 Star” or a load range letter to make that clearer.
| Ply rating | Casing character | Best for |
|---|---|---|
| 2PR | Very light, flexible, cheap | Youth quads, light sport ATVs, OEM fitment |
| 4PR | Light recreational | Groomed trails, grass, occasional use |
| 6PR | The mainstream choice | Mixed trail, rocks, roots, most utility ATVs |
| 8PR | Heavy, stiff, puncture-resistant | UTVs, rock crawling, loaded work machines |
| 10PR+ | Very heavy, harsh ride unloaded | Heavy hauling, towing, commercial and agricultural |
Higher is not automatically better. Every extra ply adds unsprung weight, stiffens the casing, and reduces the tire's ability to conform to terrain at low pressure — which is precisely where off-road traction comes from. Going from 6PR to 8PR on a light trail quad typically buys puncture resistance you may not need and costs you ride quality you will notice on every ride.
Bias vs radial
| Bias ply (“–”) | Radial (“R”) | |
|---|---|---|
| Cord angle | Crossed diagonally at 30–40° | 90° to travel direction, plus belts |
| Sidewall | Stiff — resists sharp rock cuts | Flexible — conforms and floats |
| Contact patch under load | Distorts, loses area | Stays flat and consistent |
| Tread life | Baseline | Typically ~50% longer |
| Ride comfort | Harsher, more feedback | Noticeably smoother |
| Heat build-up at speed | Higher | Lower |
| Cost | Lower | 15–40% more |
| Best fit | Sharp rock, low speed, tight budget, heavy loads | Fast trail, dunes, long rides, UTVs |
Bias and radial tires distort differently under load. Mixing them on one axle produces asymmetric traction and unpredictable handling. If you replace only two tires, replace an axle pair with matching construction, and ideally match all four on any machine with a locked or limited-slip driveline.
Matching tread pattern to terrain
| Type | Lug depth | Strengths | Weaknesses |
|---|---|---|---|
| All-terrain | 12–19 mm | Best single-set compromise; predictable on 80% of trails | Clogs in deep mud; vague in soft sand |
| Mud | 25–50 mm | Deep V-lugs self-clean and paddle through slop | Loud, harsh, quick-wearing on hardpack; heavy |
| Sand / paddle | Paddle blades | Enormous float and thrust in dunes | Rear-only; illegal or destructive elsewhere; useless on hard ground |
| Rock crawling | 15–20 mm dense | Large contact area, reinforced sidewall, superb pinch-flat resistance | Poor in mud; heavy |
| Hardpack / trail | 8–12 mm | Long life, quiet, good on-road manners | Loses traction the moment the ground softens |
| Utility / work | 15–25 mm | High lug-to-void ratio, high load rating, durable | Ride harshness, mediocre in deep mud |
Fitment reference chart
| Machine class | Common sizes | Ply | Max psi | Diameter |
|---|---|---|---|---|
| Youth / small ATV | 20×7-8, 22×10-9 | 2–4PR | 5–7 | 20–22″ |
| Sport ATV | 25×8-12, 25×10-12 | 4–6PR | 7–18 | 25″ |
| Large ATV / light UTV | 26×9R14, 26×11R14 | 6–8PR | 18–22 | 26–27″ |
| Mid UTV | 27×9R14, 27×11R14 | 8PR | 22 | 27″ |
| Heavy UTV | 30×10R14, 30×10R15 | 8PR | 18–22 | 30″ |
| Big-bore / lifted UTV | 32×10R14, 35×10R15 | 8–10PR | 18–22 | 32–38″ |
Pressure: the number most people get wrong
ATV tires operate at pressures that would look like a flat on a car. Typical figures are 4–8 psi for ATVs and 12–22 psi for UTVs. The maximum pressure moulded on the sidewall is a structural limit for seating the bead, not a recommendation.
A standard 0–60 psi car gauge is typically accurate to about ±2 psi. At a 5 psi target that is a 40% error. Buy a dedicated 0–15 psi powersports gauge; it is the cheapest meaningful upgrade you can make to a quad. Running 3 psi instead of 5 dramatically raises the risk of debeading in a hard corner.
Lower pressure lengthens the contact patch and improves traction and ride quality on soft ground. Higher pressure protects against pinch flats on rock and reduces rolling resistance and squirm on hard ground. Adjust by terrain within the machine's stated range, and always set pressures cold.
Going bigger: what it actually costs
Oversizing is the most popular ATV modification and the least understood. Every inch of added diameter has consequences:
- Effective gearing changes. Adding 2″ of diameter to a 26″ tire is roughly an 8% taller gear — noticeably slower acceleration and more clutch heat on a CVT machine.
- Driveline stress rises. Bigger tires apply more leverage to axles, CV joints and the differential. Failures cluster after tire upsizes.
- Unsprung weight rises steeply. A 30″ mud tire can weigh twice a 26″ all-terrain, which degrades suspension response and braking.
- Clearance disappears at the extremes. Check at full steering lock and full suspension compression together, not one at a time.
- Speedometer reads low. On machines with a speedometer, the error scales with diameter change.
Practical guidance: most stock machines accept +1″ to +2″ of diameter without a lift. Beyond that, plan on a lift kit, clutch recalibration and — on heavily loaded UTVs — upgraded axles. Check the diameter delta with the size comparison tool before ordering.
A five-step buying checklist
- Confirm your current size and construction from the sidewall, and note whether it is
Ror a hyphen. - Be honest about terrain. If 70% of your riding is trail, an all-terrain tire will beat a mud tire even on your muddy 30%, because it will be better everywhere else.
- Pick a ply rating from consequences, not bravado. Sharp rock and heavy loads justify 8PR; grass and gravel do not.
- Check total diameter change and clearance before ordering.
- Weigh the tire. Manufacturers publish it and it is one of the best single predictors of how a machine will feel afterwards.
Frequently asked questions
What does 27x11R14 mean?
27 inches tall, 11 inches wide, radial construction, on a 14-inch wheel. A hyphen instead of the R would mean bias-ply.
Does a 6-ply tire have six plies?
No. It is a strength equivalence. Modern nylon and aramid cords let manufacturers hit a 6-ply rating with two or three physical plies.
How much bigger can I go on stock suspension?
Usually one to two inches of diameter. Past that, expect rubbing at full lock and compression, plus meaningful driveline stress and CVT heat.
What pressure should I run?
4–8 psi for most ATVs, 12–22 psi for most UTVs, set cold, following the machine placard rather than the sidewall maximum. Use a 0–15 psi gauge for accuracy.
Can I run ATV tires on the road?
Legally it depends entirely on your jurisdiction and whether the machine is street-legal. Mechanically, aggressive off-road treads wear extremely quickly on asphalt, generate heat, and offer poor wet braking. If you ride significant pavement, choose a hardpack or DOT-approved pattern.