240/55R390 Tire Size Guide

The 240/55R390 size code breaks down into four parts: 240 is the section width in millimeters, 55 is the aspect ratio, R identifies radial construction, and 390 is the rim diameter in millimeters. Put simply, this is a 240 mm wide radial tire with a sidewall height equal to 55 percent of its width, built for a 390 mm wheel.

Unlike a modern inch-rim P-metric size, the 240/55R390 uses a millimetric wheel diameter rather than a 15-inch or 16-inch bead seat. That difference matters because the code gives you width, profile, construction, and rim diameter, but it does not by itself guarantee interchangeability with another tire that looks close on paper. Buyers still need to confirm the actual wheel system, wheel width, and vehicle clearance before substituting anything.

The 240/55R390 fits a 390 mm wheel, which is about 15.35 inches in diameter. The rim diameter has to match exactly at the bead seat, because tire and wheel interface dimensions are fixed and cannot be improvised by choosing a near-inch equivalent.

Wheel width matters too, and this size is shown on 150 mm, 165 mm, and 195 mm wheel widths. Those measurements are part of the overall fitment picture because tire shape changes with wheel width, which can affect sidewall profile, steering response, and clearance. On a millimetric TRX-style fitment, buyers should confirm both the wheel diameter and the exact wheel width before making any replacement decision.

The 240/55R390 has a section width of 240 millimeters, which converts to about 9.45 inches. Section width is measured at the widest point of the inflated tire from sidewall to sidewall, not across the tread face that contacts the road.

Clearance checks should focus on section width because the sidewall bulge is usually what gets closest to suspension parts, inner wheelhouses, and fender lips. Tread width can be narrower than the published section width, so using tread alone can give a false sense of space. On a classic European fitment, that makes section width one of the first numbers to compare when evaluating replacement options or checking for wheel and body interference.

The sidewall height of the 240/55R390 is about 132.0 millimeters, or 5.2 inches, on one side of the tire. That figure comes from applying the 55 aspect ratio to the 240 millimeter section width, so the sidewall is a little over five inches tall between the wheel seat and the tread edge.

Sidewall height affects more than appearance. It changes how the tire cushions impacts, how much sidewall flex you feel in corners, and how full the tire looks in the wheel opening. A shorter sidewall generally feels more direct, while a taller one tends to look fuller and absorb more road texture. When comparing substitutes, sidewall height is one of the clearest indicators of whether the car’s stance and driving character will change.

The 240/55R390 is normally a tubeless fitment. Even so, tube use is a wheel-and-tire-system question rather than a size question alone, so the final answer should come from the actual tire markings, the wheel design, and the manufacturer’s guidance for the specific combination.

Millimetric wheel systems deserve extra attention because buyers sometimes focus on the size code and overlook the wheel itself. A tubeless tire still depends on the wheel being suitable for tubeless service and in sound condition at the bead area. Before mounting an older wheel or mixing parts from different systems, inspect the rim carefully and confirm compatibility with a qualified tire professional.

The 240/55R390 is best understood as an original-style millimetric radial size used with TRX-style wheel systems on classic European applications. Buyers usually encounter it when preserving the factory wheel format rather than converting the car to a conventional inch-rim setup.

That distinction matters because a tire can match the general width or profile of another size and still be wrong for the wheel. If originality is important, keeping the millimetric wheel system helps preserve the intended proportions and period character. For judged cars, buyers may also want to confirm whether the exact construction and wheel format align with the vehicle’s documented original equipment.

No, the 240/55R390 should not be treated as a regular 15-inch fitment. Its wheel diameter is 390 millimeters, which is a metric bead-seat dimension and not the same as a conventional 15-inch rim standard.

Even though 390 mm converts to roughly 15.35 inches, that does not make it interchangeable with an inch-based wheel. Bead-seat dimensions must match exactly for proper mounting and retention. Anyone replacing tires on a car with this size should first verify whether the vehicle still has its original millimetric wheels or has already been converted to a different rim system.

The 240/55R390 is shown on 150 mm, 165 mm, and 195 mm wheel widths. Those widths define the rim range buyers should compare against the actual wheels on the vehicle before mounting a replacement tire in this size.

Wheel width changes the tire’s installed shape, which can influence steering feel, wheel-opening fill, and clearance to suspension and body panels. A narrower wheel tends to pull the sidewalls inward, while a wider one can flatten the profile. On a lower-profile metric radial like this, confirming the existing wheel width is just as important as confirming the 390 mm diameter.

The 240/55R390 is a radial, so its driving character is generally different from a bias-ply tire. Radial construction usually brings a more stable contact patch, less wandering, and a more settled feel over typical road surfaces, while still preserving the intended proportions of a classic millimetric fitment.

Road feel depends on more than construction alone. Suspension condition, alignment, wheel width, inflation, load, and tire age all influence how the car responds. On a classic European chassis, a radial of this profile often feels more composed than an older bias design, but buyers should still judge the complete vehicle setup rather than expecting the size code by itself to define the result.

A 55-series sidewall makes the 240/55R390 a lower-profile fitment than taller classic touring sizes. With a sidewall height of about 5.2 inches, it balances a relatively direct steering response with enough sidewall depth to avoid looking or feeling excessively short for its original wheel system.

Profile affects both appearance and behavior. A lower-profile tire tends to reduce sidewall flex, which can sharpen turn-in and make the car feel more immediate, while also transmitting more road texture than a taller sidewall would. Buyers comparing substitutes should keep an eye on profile changes because even if width looks close, a taller or shorter sidewall can noticeably alter stance and response.

The 240/55R390 was built around a radial design and classic European road use, so many buyers consider it when keeping a car on its original-style wheel system for normal fair-weather driving. Actual road behavior still depends on tire age, condition, wheel integrity, alignment, and whether the car is being driven within its intended load and speed range.

Before longer trips, inspect the sidewalls and tread for cracking, bulges, cuts, and uneven wear, and make sure the wheels are in proper condition for tubeless service. Classic cars can feel very different from modern vehicles even on correct tires, so drivers should account for older steering, brakes, and suspension geometry rather than assuming modern-road behavior from construction type alone.

Michelin is the brand shown in the 240/55R390 size. For buyers trying to keep a millimetric TRX-style fitment intact, that matters because this is a specialized classic European radial size rather than a broad modern replacement category.

Brand choice in a niche size should be weighed alongside wheel-system correctness, construction type, and consistency across the full set. On a car that uses four matching millimetric tires, buyers usually want the same brand, same size designation, and similar age across all corners so steering feel and appearance stay uniform. The wheel format is specialized enough that fitment accuracy matters as much as brand familiarity.

In the 240/55R390 size, quality starts with correct millimetric fit, proper radial construction, and clear sidewall markings that match the intended application. A good choice in this category should preserve the wheel-system compatibility and overall proportions the car was designed around, not merely approximate the width.

Buyers should also pay attention to full-set consistency, including matching size codes, matching construction, and similar age across all four tires. Because this size is tied to a specialized rim format, dimensional accuracy and proper bead fit are especially important. If the goal includes authenticity, keeping the original-style millimetric setup often matters as much as the brand itself.

The 240/55R390 can serve both goals because it is a radial size associated with classic European millimetric applications. For many owners, it preserves the intended wheel system and proportions while still offering the road manners expected from radial construction.

The right priority depends on the car and the owner. A vehicle being preserved close to factory specification may benefit from staying with the original-style millimetric format, while a driver-focused car may place more emphasis on tire condition, matched construction, and predictable road behavior. When authenticity matters, check original documentation and the car’s current wheel setup before making a change.

The 240/55R390 should be inspected regularly for air loss, sidewall cracking, cuts, bulges, and uneven wear, especially if the car sees normal road use. A classic vehicle with a specialized millimetric wheel system benefits from frequent visual checks because wheel condition and bead sealing are part of the overall tire system.

Monthly pressure checks and pre-trip inspections are sensible habits for a car driven more than occasionally. Uneven wear can point to alignment issues, worn suspension parts, or wheel problems rather than a problem with the size itself. On an older vehicle, catching those issues early helps preserve both the tire and the original-style wheel setup.

Yes, the 240/55R390 can age out even when tread depth still appears usable. Rubber hardens over time, and cracking, loss of flexibility, or internal deterioration can develop from age, heat, sunlight, ozone exposure, and long periods of inactivity.

Collector cars often accumulate fewer miles than daily drivers, so tread wear alone is not a complete guide to serviceability. Review the tire’s age markings, inspect the sidewalls and tread carefully, and consider how the car has been stored and driven. If there is any doubt about condition, especially before highway use, a qualified tire professional should inspect the tire and wheel assembly.

The 240/55R390 should be stored away from direct sunlight, moisture, high heat, and ozone sources such as electric motors or battery chargers when the car is parked for extended periods. Clean, dry storage helps slow the aging process and protects both the tire and the specialized millimetric wheel system.

If the vehicle sits seasonally, move it occasionally or support it in a way that reduces long-term flat spotting and prolonged loading in one position. Before returning the car to service, inspect the tires for cracks, deformation, and air loss. Storage care does not stop aging, but it can help the tire remain in better condition over time.

The 240/55R390 can be used on modern roads when the tire is in sound condition, mounted on the correct 390 mm wheel, and matched to the vehicle’s real load and use requirements. Safe road use depends on the complete tire-and-wheel system, not the size code alone.

Millimetric fitments deserve careful attention because an incorrect wheel match can create a serious mounting problem even when the tire appears close in size to an inch-based option. Before regular road use, inspect the tire thoroughly, confirm wheel compatibility, and review the current sidewall markings for service description and intended application. Classic-car braking, steering, and suspension condition also affect roadworthiness.

The 240/55R390 should be replaced when it shows cracking, bulges, repeated air loss, exposed cords, impact damage, severe uneven wear, or age-related hardening that compromises serviceability. Replacement timing is based on condition as much as tread depth, especially on classic cars that may not accumulate many miles.

Pre-trip inspections matter even more with a specialized millimetric size because wheel condition and bead sealing are part of the decision. If the tire has spent long periods parked, inspect for flat spotting and sidewall deterioration before driving at speed. Buyers should also make sure any replacement remains correct for the 390 mm wheel system rather than assuming a near-size inch-rim tire is acceptable.

Yes, the biggest safety concern with the 240/55R390 is that it uses a metric or millimetric TRX-style rim system. It should not be substituted with an inch-rim tire unless the wheel is changed, because bead-seat dimensions must match the tire exactly.

That warning is central to this size, not a minor detail. A tire that looks close in diameter or width can still be wrong at the bead if it is built for a different rim standard. Before mounting, confirm that the wheel is truly the correct millimetric type, inspect the rim condition carefully, and have any uncertainty reviewed by a qualified tire professional.