245/70R18 Tire Size Guide

The 245/70R18 breaks down into four basic parts. The 245 is the nominal section width in millimeters, 70 is the aspect ratio, meaning the sidewall height is 70 percent of the width, R identifies radial construction, and 18 is the wheel diameter in inches. On this size, the calculated sidewall height is 6.75 inches and the overall diameter is 31.5 inches.

Modern metric sizing like 245/70R18 gives buyers more direct dimensional information than older numeric or alphanumeric formats. You can read width, profile, construction type, and rim diameter right from the code, which makes it easier to compare possible substitutes. What it does not tell you by itself is whether a different tire with similar measurements will clear the vehicle, match the wheel width, or meet the vehicle’s load needs.

The 245/70R18 fits an 18.0-inch wheel, which is 457.2 millimeters at the bead seat. The rim diameter has to match exactly, because the tire bead is built for that specific wheel diameter and will not seat correctly on a different size rim.

Wheel diameter is only one part of fitment. Buyers should also confirm the actual wheel width being used, because the right diameter does not guarantee the correct sidewall profile or adequate support across the tread. If you are replacing tires on an existing vehicle, compare the wheel dimensions, overall tire diameter, and body or suspension clearance before treating the 245/70R18 as a direct replacement.

The 245/70R18 has a nominal section width of 245 millimeters, which converts to 9.65 inches. Section width measures the tire at its widest point from sidewall to sidewall when inflated, not the width of the tread that actually contacts the road.

Clearance questions usually start with section width because that is the dimension most likely to interfere with fender lips, suspension parts, or inner wheelhouse space. Tread width is usually narrower, so relying on tread measurements alone can be misleading. When comparing replacement sizes, use the 9.65-inch section width along with overall diameter and wheel specs rather than judging fitment by appearance alone.

The 245/70R18 has an overall diameter of 31.5 inches, or about 800.1 millimeters. Overall diameter is the full height of the mounted and inflated tire from the ground to the top, measured straight through the center.

Overall diameter affects more than appearance. It changes ride height, wheel-opening fill, and the relationship between road speed and indicated speed on the speedometer. A tire that is noticeably taller or shorter than 31.5 inches can also change how the vehicle feels off the line and at cruising speed. When comparing alternatives, this is one of the most important measurements to keep as close as practical.

The 245/70R18 has a calculated sidewall height of 6.75 inches, or 171.5 millimeters, on each side of the wheel. That measurement comes from applying the 70 aspect ratio to the 245-millimeter section width.

Sidewall height has a direct effect on ride character and visual proportion. A 6.75-inch sidewall generally provides more cushion and a fuller wheel-opening look than a lower-profile tire on the same diameter wheel. It also means more sidewall flex than a shorter sidewall design. Buyers comparing alternate sizes should keep that in mind, especially if they want to preserve the original stance and avoid a harsher ride feel.

The 245/70R18 turns about 640.3 revolutions per mile. That figure is tied to the tire’s circumference, which is 98.96 inches, and it helps show how often the tire rotates to cover a given distance.

Revolutions per mile matter when you compare substitute sizes because a different number changes speedometer and odometer behavior. A tire with fewer revolutions per mile is generally taller, while one with more revolutions per mile is generally shorter. For replacement decisions, this number works best alongside overall diameter and section width rather than as a standalone measurement.

No. Sharing an 18-inch rim diameter only confirms one part of the fitment equation. The 245/70R18 also brings a 245-millimeter section width and a 31.5-inch overall diameter, both of which can affect suspension clearance, fender clearance, steering travel, and the vehicle’s intended tire proportions.

Vehicle fitment should be checked as a system. Compare the existing tire size, wheel dimensions, load requirements, and available space at full lock and full suspension movement. Even when the tire mounts on the wheel, differences in width or height can change stance and rubbing behavior. Buyers replacing a factory-size tire should also review the vehicle placard, owner documentation, and current wheel setup before assuming the size is interchangeable.

Start with the basics: wheel diameter must be 18 inches, the replacement tire should meet the vehicle’s load needs, and the overall dimensions need to suit the available clearance. Because the 245/70R18 is about 9.65 inches wide and 31.5 inches tall, both width and height should be checked against the current setup.

Replacement decisions are not just about mounting the tire. Buyers should compare the old and new overall diameter, inspect wheel width, and make sure the tire will clear struts, control arms, liners, and outer fenders under real driving movement. On late-model vehicles, it also helps to consider how a change in diameter may affect gearing feel and indicated speed. Careful measurement is more reliable than visual guesswork.

The 245/70R18 is a modern radial format, so it is generally chosen for current replacement use rather than early factory-authentic restoration work. Radial construction can improve everyday drivability, but a vehicle being judged closely on originality may call for a different type of tire, depending on the era and the way the vehicle was originally equipped.

Restoration buyers should separate appearance goals from driving goals. If the vehicle is intended for regular road use, the 245/70R18 may be a practical size when it matches the vehicle’s wheel and clearance needs. If the priority is strict historical authenticity, check the original documentation and the tire format used in that vehicle’s production period before choosing a modern metric radial as a substitute.

The 245/70R18 has a relatively tall 70-series sidewall, so it generally offers more ride compliance than a shorter-profile tire on the same wheel diameter. With 6.75 inches of sidewall, it can absorb road irregularities better than lower-profile alternatives, while still keeping the stability characteristics associated with radial construction.

Ride feel is shaped by more than size alone. Suspension condition, alignment, vehicle weight, inflation, and tire age all influence steering response and harshness. A taller sidewall may feel less abrupt over broken pavement, but it can also introduce a softer response than a shorter sidewall. Buyers trying to preserve factory-like proportions often value that balance when replacing tires on regularly driven vehicles.

A 245/70R18 radial typically emphasizes stable, predictable road manners rather than the especially sharp turn-in associated with very low-profile sizes. Its combination of radial construction, 245-millimeter width, and taller sidewall usually supports a composed steering feel suited to everyday driving and larger vehicle applications.

Steering response can change noticeably if the tire is installed on a wheel that alters the intended profile or if the vehicle has worn suspension components. Wheel width, alignment settings, and the difference between old and new tire diameters can all affect the result. For the most useful comparison, evaluate the tire as part of the whole vehicle setup rather than assuming the size alone determines steering behavior.

Because the 245/70R18 has a 31.5-inch overall diameter and turns about 640.3 revolutions per mile, its height directly influences indicated speed and the way the vehicle feels in motion. A substitute with a meaningfully different diameter will change how far the vehicle travels with each wheel rotation.

Taller tires generally reduce revolutions per mile, while shorter tires increase them, and that shift can affect speedometer readings and cruising feel. Buyers considering alternate sizes should compare overall diameter and revolutions per mile first, then look at width and clearance. On a regularly driven vehicle, staying close to the original rolling diameter usually makes for a more predictable result than focusing on appearance alone.

A good 245/70R18 starts with the right match for the vehicle and its actual use. Buyers should focus on consistent sizing, suitable load capability, sound construction quality, and dimensions that preserve proper clearance and intended ride height. Because this is a modern radial size, everyday drivability and predictable fitment usually matter more than historical appearance.

Quality also shows up in how well the full set works together. Matching construction type, keeping the same size at all four corners when the vehicle requires it, and avoiding mixed tire ages can help the vehicle feel more stable and consistent. When comparing options, review the sidewall markings carefully and make sure the tire’s design intent suits the vehicle rather than choosing only by appearance.

Yes. Even within one size, construction quality influences ride smoothness, uniformity, durability, and how consistently the tire responds on the road. With the 245/70R18, buyers are selecting a radial size, so casing quality and dimensional consistency are important to how the tire behaves once mounted and balanced.

A well-made tire in the correct size still needs the right wheel and proper setup to perform as intended. Uneven wear, vibration, or a vague steering feel can come from wheel condition, alignment, or suspension wear just as easily as from the tire itself. Buyers should think in terms of a complete wheel-and-tire package rather than expecting the size designation alone to guarantee a certain driving result.

Using a consistent set of 245/70R18 tires helps preserve balanced handling, uniform ride height, and predictable wear behavior. Mixing different constructions, noticeably different ages, or substitute sizes on the same vehicle can change the way the vehicle reacts during steering, braking, and everyday road use.

For most buyers, consistency matters more than chasing small differences in appearance. Matching the size, confirming comparable overall diameter, and keeping load capability aligned with the vehicle’s needs will usually produce a more satisfying result. If one tire must be replaced separately, compare the remaining tire dimensions and condition closely before assuming any 245/70R18 will behave the same as the others.

The service life of the 245/70R18 depends on use, alignment, inflation maintenance, road conditions, and how evenly the vehicle loads the tires. Tread depth is only part of the picture. A tire can still need replacement because of age, cracking, impact damage, irregular wear, or repeated air-loss issues even if the remaining tread looks usable.

Routine inspection matters most on vehicles that are driven often. Check for cuts, bulges, sidewall cracking, exposed cords, and unusual wear patterns across the tread. A regularly used vehicle also benefits from periodic pressure checks and prompt correction of alignment or suspension problems that can shorten tire life. Time and condition should be weighed alongside mileage when deciding whether to keep using the tire.

The 245/70R18 is normally a tubeless fitment. Even so, tube use is really a wheel-and-tire-system question rather than something the size alone settles, so the final answer should be confirmed against the actual wheel and the specific tire being installed.

Wheel condition and wheel design matter here. A tire that is commonly run tubeless still depends on a sound bead seat, a proper valve setup, and a wheel intended for that kind of service. If there is any doubt about the wheel’s design, previous repairs, or sealing surface condition, have the assembly checked by a qualified tire professional before putting the vehicle into regular road use.

The most useful routine checks for the 245/70R18 are inflation, tread wear pattern, visible damage, and air retention. On a regularly driven vehicle, uneven shoulder wear, center wear, or cupping can point to pressure, alignment, or suspension issues long before the tire is fully worn out.

Drivers should also inspect the tire before longer trips, especially if the vehicle carries passengers or cargo. Look for nails, cuts, bulges, weather checking, and anything unusual at the bead or sidewall. Keeping the tire in serviceable condition is not only about preserving tread life; it also helps maintain the ride quality and road manners expected from a modern radial size in daily use.

The 245/70R18 should be replaced when inspection shows cracking, bulges, cuts, exposed cords, chronic air loss, or wear severe enough to compromise traction and stability. Age also matters. A tire that has acceptable tread depth can still be unfit for continued road use if time, heat, sunlight, or storage conditions have degraded the casing.

Replacement timing should be based on condition as well as mileage. Buyers should inspect all four tires, including the sidewalls and inner side, and consider whether the vehicle is used for highway trips, heavy passenger loads, or long periods between inspections. If condition is questionable, a qualified tire professional should evaluate the tire before the vehicle is driven at normal road speeds.

The 245/70R18 is a modern radial size, which makes it a format commonly used in current road-going applications. Still, suitability for any specific vehicle depends on more than the size code. Buyers should confirm the tire’s condition, load capability, wheel compatibility, and whether the overall dimensions are appropriate for the vehicle’s suspension and body clearances.

Road use expectations should be grounded in the complete tire and wheel setup. A fresh tire in the correct size can still perform poorly if the wheel is damaged, the alignment is off, or the suspension is worn. Before interstate travel or long trips, inspect the tires carefully and verify that all sidewall markings and service characteristics match the vehicle’s needs.

Buyers should review the current sidewall markings on the actual tire, confirm the vehicle’s required service characteristics, and make sure the 245/70R18 matches the wheel diameter exactly. Local rules, inspection standards, and equipment expectations can vary, so it is wise to verify that the complete wheel-and-tire setup is appropriate before road use.

Fitment checks should include wheel specifications, tire age, visible condition, and clearance at both static ride height and steering lock. If the vehicle has been modified, those checks become even more important because a correct size code does not guarantee proper real-world clearance. Careful confirmation before installation is the best way to avoid avoidable fitment or roadworthiness problems.