345/35R18 Tire Size Guide

The 345/35R18 size code identifies a tire that is 345 millimeters wide, has a sidewall height equal to 35 percent of that width, uses radial construction, and fits an 18-inch wheel. In dimensional terms, that works out to about 13.58 inches of section width, a 4.75-inch sidewall, and roughly 27.51 inches of overall diameter.

Unlike older numeric or alphanumeric vintage sizes, the 345/35R18 code directly gives you width, profile, construction, and wheel diameter in one line. What it does not tell you by itself is tread width, load capacity, sidewall style, or whether a tube is needed, because those details depend on the specific tire and wheel combination being used.

The 345/35R18 fits an 18-inch wheel, which is 457.2 millimeters in diameter. That bead-seat diameter must match exactly, so this tire cannot be mounted correctly on a 17-inch or 19-inch rim even if other dimensions seem close.

Wheel width matters almost as much as wheel diameter on a size this wide. In this case, the tire is set up around a 13.00-inch wheel width, so buyers should confirm that the actual wheel matches the tire's intended profile and that the combination clears the body, suspension, and inner wheelhouse under real driving movement.

The 345/35R18 has a section width of 345 millimeters, which converts to about 13.58 inches. Section width is measured at the widest point of the inflated tire from sidewall to sidewall, not across the tread face.

Clearance planning should start with section width because the sidewall bulge is often what reaches the fender lip, frame rail, or suspension first. Tread width can be narrower than the section measurement, so using tread numbers alone can give a false sense of space when you are trying to fit a very wide tire under a tight wheel opening.

The 345/35R18 has an overall diameter of about 27.51 inches, or roughly 698.75 millimeters. That is the full mounted-and-inflated height of the tire measured straight through the center from ground to top.

Overall diameter affects more than appearance. A change in tire height can alter wheel-opening fill, effective gearing, and speedometer reading, so buyers comparing this size to another should look closely at total diameter rather than wheel diameter alone. On a low-profile fitment, even a modest height change can be noticeable in stance and clearance.

The 345/35R18 has a sidewall height of about 4.75 inches, which is approximately 120.65 millimeters. That measurement runs from the wheel's bead seat to the outer edge of the tread on one side of the tire.

A 35-series sidewall is short relative to the tire's width, which is why this size has a low-profile look. That shorter sidewall usually sharpens the visual stance and can reduce the cushioned feel associated with taller sidewalls, so buyers should think about ride character, wheel protection, and how much sidewall they want showing in the wheel opening.

The 345/35R18 turns about 733.1 revolutions per mile. That figure comes from the tire's overall circumference of roughly 86.43 inches and represents how many complete rotations it makes over one mile of travel.

Revolutions per mile become useful when you are comparing substitute sizes. A noticeable change in that number can affect speedometer and odometer readings, and it can also hint at a change in effective gearing. On a performance-oriented setup, those differences may show up in both highway rpm and the way the tire visually fills the rear of the car.

The 345/35R18 is most closely associated with performance and low-profile passenger car use, so it usually appeals to builders looking for a wide, modern rear tire with substantial footprint and short sidewall proportions. Its dimensions make it a specialized fitment rather than a general replacement size.

Fitment depends on more than the size code alone. Buyers should verify wheel width, suspension travel, inner-fender room, and outer clearance at ride height and under compression. On very wide sizes like this one, backspacing, axle location, and body tolerances can matter as much as the nominal tire dimensions.

The 345/35R18 shown here is matched to a 13.00-inch wheel width. That width supports the tire's intended profile and helps the sidewall and tread sit in the shape the tire was designed to have.

Using a wheel that differs from that width can change the way the tire stands, spreads, and clears nearby components. A narrower wheel can pull the sidewalls inward, while a wider wheel can flatten the profile and alter the contact patch shape. On a size this aggressive, wheel width should be treated as a core fitment requirement, not an afterthought.

The 345/35R18 can make sense when a build calls for a modern, wide, low-profile look and the drivability characteristics of a radial tire. It is not the kind of size normally chosen when the goal is an original tall-sidewall appearance from an earlier factory era.

For a judged restoration, buyers should compare the intended visual result against original documentation and period wheel proportions before moving to a size this modern. If the project is more restomod or pro-touring in spirit, the size may suit the build better, provided the wheel package and body clearance have been carefully measured.

The 345/35R18 combines radial construction with a very short 35-series sidewall, so the road feel is usually more immediate than what drivers expect from older tall-sidewall sizes. Its low-profile proportions tend to emphasize steering response and a firmer, more direct character rather than a soft, floaty ride.

Ride quality still depends on the full vehicle setup. Suspension tuning, alignment, wheel width, inflation, and the tire's actual age all influence how this size behaves. On a well-sorted performance car, the result can feel precise; on a poorly aligned or overly stiff setup, the same size may feel harsher and less forgiving over rough pavement.

A 4.75-inch sidewall is relatively short for such a wide tire, and that changes both the look and the behavior. The tire presents a lower-profile stance, and there is less sidewall height available to absorb impacts and flex the way a taller profile tire would.

Drivers often notice that change in steering sharpness, impact response, and wheel-opening appearance. On smooth roads, the shorter sidewall can support a more controlled feel. On broken pavement, it may transmit more road texture into the chassis. Buyers should balance the visual payoff against the ride comfort they expect from the vehicle.

They matter quite a bit because the 345/35R18 stands about 27.51 inches tall and turns roughly 733.1 revolutions per mile. Those numbers help you compare how another size may change ride height, speedometer reading, and the way the tire fills the wheel opening.

A substitute that is much taller or shorter can alter effective gearing and visual stance even if the wheel diameter stays the same. Buyers considering a different size should compare section width as well, since a similarly tall tire may still create clearance issues if it grows wider in the sidewall area.

The 345/35R18 is available here from M&H Racemaster. In a specialized size like this, brand choice can be narrower than it is in more common street sizes, so buyers usually focus first on the tire's intended use, construction, and dimensions rather than expecting a broad brand spread.

When comparing any tire in this size, look closely at how the tire is meant to be used, the wheel width it expects, and whether the load rating matches the vehicle. A specialized performance fitment should also be evaluated as part of a full set strategy so the rear tire's dimensions and behavior make sense with the rest of the chassis.

Quality in the 345/35R18 comes down to choosing a tire that matches the job it is being asked to do. Construction type, dimensional consistency, wheel-width suitability, and a load rating appropriate for the vehicle all matter more than general assumptions based on size alone.

A careful buyer should also consider how the tire fits the project's goals. On a modern performance build, road manners and wheel-opening fill may carry the most weight. On a show-oriented car, sidewall appearance and overall stance can matter just as much. The strongest choice is usually the one that matches the full vehicle setup, not just the rim diameter.

Yes, sidewall style can matter because it changes the visual effect of a tire this large and visible. The example shown in 345/35R18 uses a blackwall sidewall, which tends to suit modern performance, drag-oriented, and understated custom builds better than a more decorative vintage-style treatment would.

Appearance should still be weighed alongside fitment and function. A dramatic rear tire can dominate the look of the vehicle, so buyers often choose a sidewall style that complements the wheel design and the era they are trying to suggest. Consistency across the full set also helps the car look intentional rather than mismatched.

The 345/35R18 should be inspected regularly for cracking, cuts, bulges, punctures, uneven wear, and air loss, especially because a wide low-profile tire can be sensitive to alignment and clearance issues. Frequent checks are smart before longer drives and after any contact with road debris, potholes, or rubbing points inside the wheelhouse.

Wear patterns can reveal problems long before a failure occurs. Outer-edge wear, inner-edge wear, or polished areas on the sidewall may point to alignment trouble or interference with nearby suspension and body parts. On a performance-oriented fitment, catching those signs early helps protect both the tire and the wheel.

The 345/35R18 is normally a tubeless fitment. Even so, tube use is a wheel-and-tire-system question rather than a size question, so the final decision should be confirmed against the actual tire and wheel combination being used.

Modern one-piece tubeless wheels are often the starting point for this kind of radial size, but condition still matters. Damaged bead seats, unusual wheel designs, or specialty applications can change the setup requirements. Buyers who are unsure should inspect the wheel carefully and confirm the intended arrangement before mounting and use.

The 345/35R18 should be stored away from direct sunlight, heat sources, moisture, and ozone-producing equipment if the vehicle sits for long periods. Even when tread wear is low, time and environment still age the rubber and can shorten useful service life.

Seasonal storage matters most when a car is used intermittently, but it also helps to move the vehicle occasionally and keep the tires clean and properly maintained. Flat spotting, surface checking, and hidden age-related deterioration are all easier to prevent than to correct once the tire has been left stationary in poor conditions.

The 345/35R18 should be replaced when inspection shows cracking, bulges, cuts, impact damage, repeated air loss, or other signs of structural decline, even if tread depth still looks usable. Tire condition matters as much as tread because age, storage, heat, and use can all affect roadworthiness.

Before any long trip, inspect the full tire carefully, including inner sidewalls that are harder to see when mounted. A very wide low-profile tire can also show evidence of rubbing or alignment problems that shorten service life. If condition, age, or prior damage is in doubt, a qualified tire professional should evaluate it before continued road use.

Load rating is critical because each tire must be able to support its share of the vehicle's actual weight. In this 345/35R18 example, the tire is rated at 1,700 pounds at 35 psi, and that figure should be checked against the vehicle's weight distribution and intended use.

A very wide tire can look substantial, but appearance alone does not confirm suitability. Buyers should compare the tire's stated load capability with real vehicle requirements, especially on heavy, high-horsepower, or luggage-carrying applications. Matching the wheel, the tire, and the use case as a system is the safest way to approach a specialized size.

No, radial construction alone does not automatically settle the question. The 345/35R18 uses a modern radial layout, which can support more contemporary driving manners, but actual suitability still depends on the tire's condition, age, load match, wheel compatibility, and the way the vehicle is set up.

Buyers should also review current sidewall markings and confirm that the tire's intended use aligns with how the vehicle will be driven. A specialized performance tire demands the same basic checks as any other tire: sound wheel condition, proper clearance, regular inspection, and a realistic understanding of the vehicle's weight and usage.