155-400 Tire Size Guide

The 155-400 size identifies a classic Euro-metric radial format. In this code, 155 is the section width in millimeters, while 400 is the wheel diameter in millimeters for the millimetric rim the tire is built to fit.

Unlike a modern P-metric code, the 155-400 format does not show an aspect ratio in the size itself. That matters because you can read the tire's width and wheel system directly, but you cannot assume it matches a common inch-rim or modern passenger-car size just because the numbers seem close. Buyers should read the full size marking carefully and confirm that both the tire and the wheel belong to the same metric-rim family before treating the code as a replacement guide.

The 155-400 tire fits a 400-millimeter wheel, which converts to about 15.75 inches. The wheel diameter must match the tire exactly at the bead seat, so a 400-millimeter tire is not intended for a 15-inch or 16-inch rim.

Millimetric rim sizes are one of the biggest points of confusion with older European fitments. Even when the overall dimensions seem close to an inch-based size, the bead seat diameter is different, and that difference determines whether the tire can mount correctly. If you are replacing an older set, inspect the wheel markings and confirm that the rim itself is the correct metric type before considering any tire in the 155-400 size.

The 155-400 tire has a section width of 155 millimeters, which is about 6.1 inches. Section width measures the tire at its widest inflated point from sidewall to sidewall rather than across the tread face.

Clearance questions usually start with section width because that is the part of the tire most likely to come close to fenders, suspension parts, or inner wheel housings. The tread that touches the road is narrower than the section width, so buyers should not use tread appearance alone when checking fit. On a vintage European car with tight wheel openings, the sidewall bulge can matter just as much as the contact patch.

Yes, 155-400 and 155400 are two ways of writing the same tire size. The spacing or punctuation changes, but the meaning stays the same: a 155-millimeter-wide tire for a 400-millimeter wheel.

Catalogs, sidewall markings, and old service literature do not always use the same notation style, especially with older European and millimetric sizes. A version written as 155 400 also points to the same format. Even so, buyers should still confirm the rest of the tire and wheel details, because matching the shorthand alone does not answer questions about construction, clearance, or whether the wheel itself is truly a millimetric rim.

The 155-400 is normally a tubeless fitment. Tube use is still a wheel-and-tire-system question rather than a size question, so the final decision should be confirmed against the actual wheel and tire being used.

Older vehicles can introduce extra variables such as wheel condition, bead-seat design, and prior modifications, all of which matter more than the size code alone. A buyer replacing tires on original metric wheels should inspect for corrosion, damage, or sealing issues before assuming a tubeless setup is ready for service. When there is any doubt, compare the markings on the actual tire and wheel and get a qualified tire professional involved before mounting.

The 155-400 size is associated with classic European passenger-car applications and appears on examples from the late 1940s through 1960. It is most closely tied to vehicles built around millimetric wheel systems rather than the inch-rim standards more familiar to many U.S. collectors.

Fitment should be treated as an application clue, not a blanket rule. Original documentation, surviving wheel markings, and the physical tire-to-body clearance on the car all matter before a replacement is chosen. A vintage European sedan that still carries its original wheel type is a stronger candidate for the 155-400 than a car that has already been converted to inch-based rims at some point in its life.

The 155-400 should not be treated as an inch-rim tire because its wheel diameter is metric, not nominal inch sizing. A 400-millimeter rim is about 15.75 inches, which is close enough to confuse buyers but not close enough to make bead fit interchangeable.

Using an inch-rim tire in place of the 155-400 only makes sense if the wheel itself is changed to the correct inch-diameter type. Without that wheel change, the basic tire-to-rim interface is wrong, no matter how similar the proportions might look on paper. Buyers should verify the actual wheel system first, then compare overall package dimensions and clearance before considering any substitute path.

The 155-400 is well suited to restorations of classic European cars that originally used this millimetric radial format. It preserves the correct wheel system and the narrow, original-looking proportions that help an older car sit and present the way it was intended.

Judged originality can still require checking what was fitted to a specific car when new, because some restorations are evaluated very closely on construction type and exact size family. Radial construction can improve day-to-day drivability, but authenticity standards vary by vehicle and event. When originality matters, compare the tire choice against factory literature, wheel markings, and the restoration goals for the car rather than assuming any vintage-looking replacement is automatically correct.

The 155-400 uses radial construction, which generally gives a more settled, predictable feel than older bias-ply designs on similar vintage vehicles. Its relatively narrow width also tends to preserve light steering effort and the original, less aggressive road feel expected from small classic European cars.

Driving impressions depend on more than construction alone. Suspension wear, alignment settings, wheel condition, and the age of the tire all influence how the car tracks, responds, and absorbs road texture. On a properly sorted vehicle, the 155-400 size usually supports the modest, balanced handling character these cars were designed around rather than forcing a wider or lower-profile look that changes the way the car behaves.

A radial 155-400 can offer more familiar road manners for drivers who use a classic European car regularly, especially in terms of tracking and general composure. That does not mean every car should automatically move away from its original construction, but it does explain why some owners prefer a radial in real driving.

Restoration goals should guide the choice. A car being preserved for judged authenticity may call for closer review of what construction type best matches its original specification, while a car driven more often may benefit from the behavior many owners associate with radial tires. Vehicle condition still matters just as much, so steering components, alignment, and wheel trueness should be sorted before expecting any tire change to transform the car.

The 155-400 is a vintage-size tire, so longer-trip behavior depends heavily on the condition of the tire, the wheel system, and the vehicle itself. Radial construction can help the car feel more composed than an older bias-ply setup, but trip readiness should never be judged by size code alone.

Before sustained road use, inspect for cracking, air loss, bulges, uneven wear, and any signs that the millimetric wheels are damaged or poorly sealing. Classic European cars in this size were designed around modest power and period suspension geometry, so expectations should stay realistic even with a fresh tire. A careful pre-trip inspection matters more than assuming a vintage-size radial is automatically ready for every modern-road situation.

A good 155-400 tire starts with accurate sizing, proper compatibility with a 400-millimeter wheel, and construction that suits the way the car is actually used. Because this is a specialty classic European size, precision in bead fit and overall proportions matters at least as much as general brand reputation.

Buyers should compare the tire against the car's restoration goals, driving habits, and existing wheel setup. A matched set with consistent dimensions and the correct millimetric fitment is usually more important than chasing cosmetic differences alone. If the car is used on the road regularly, construction quality and fresh manufacturing matter; if originality is central, the tire should also preserve the narrow profile and visual character expected on the vehicle.

Yes, construction type is a major part of the decision with the 155-400 because this size is a radial fitment tied to classic European applications. Radial construction influences how the tire flexes, tracks, and feels on the road, so it affects both drivability and the car's overall character.

Owners should choose with purpose rather than treating all vintage tires as interchangeable. A radial can be the practical choice for a driver-focused car, while a highly judged restoration may call for closer review of what is authentic for that specific vehicle. Either way, the tire should match the correct wheel system first, because a well-made tire in the wrong rim format is still the wrong fitment.

Using a matched set of 155-400 tires helps keep the car's stance, steering response, and visual balance consistent from corner to corner. On smaller classic European cars, even subtle differences in casing shape or overall proportions can become noticeable in both appearance and road feel.

Mixed constructions, mixed ages, or mixed interpretations of a specialty size can make the vehicle behave unevenly, especially if one tire sits taller or has a different sidewall character than the others. Consistency is also helpful when diagnosing handling issues, because it reduces the number of variables in the tire package. Buyers restoring a car or preserving its original look usually benefit from replacing the set together rather than one tire at a time.

The 155-400 should be inspected regularly for cracking, cuts, bulges, uneven wear, and air loss, especially on older cars that may not be driven daily. A visual check before longer trips is wise, and a more thorough inspection should include the sidewalls, tread area, valve hardware, and the condition of the millimetric wheel.

Vintage-size tires can age out before they wear out, particularly on collector vehicles that spend long periods parked. Heat, sunlight, ozone exposure, and infrequent use all contribute to deterioration even when tread depth still looks acceptable. Owners should also pay attention to changes in steering feel or vibration, because those can point to tire or wheel issues that are not obvious at a glance.

Low mileage does not guarantee long service life for the 155-400. A tire on a lightly used collector car can still deteriorate with age as rubber compounds harden and the structure is affected by time, temperature swings, sunlight, and ozone.

Storage conditions make a real difference. Keep the car in a cool, dry area away from direct sun, electric motors, and other ozone sources, and move it occasionally so the tires do not sit in one loaded position for long periods. Even when the tread looks healthy, an aging specialty-size tire deserves careful inspection before road use, because calendar age and storage history matter as much as accumulated miles.

The 155-400 is normally a tubeless fitment, but tube use should always be confirmed from the actual wheel and tire combination. The size alone does not override the condition, design, or sealing quality of the wheel it is being mounted on.

Original wheels on older European cars may have corrosion, surface damage, or prior repairs that affect whether a tubeless setup will hold air properly. A sound decision comes from inspecting the rim, checking the tire's own markings, and following manufacturer guidance for the specific components in use. When there is any uncertainty, a qualified tire professional should evaluate the wheel-and-tire system before the tire goes into service.

The 155-400 can be used on modern roads only when the tire is in sound condition, the wheel is the correct 400-millimeter type, and the vehicle's overall setup is in proper order. Safety depends on the complete wheel-and-tire system, not simply on the size designation or the fact that the tire is radial.

Buyers should inspect for age-related cracking, air retention problems, impact damage, and uneven wear before regular road use. The millimetric rim system is especially important here because an incorrect inch-based wheel choice creates a basic compatibility problem before the vehicle even moves. For any car that sees regular driving, periodic inspection and confirmation of load requirements are just as important as selecting the right size.

The 155-400 should be replaced when it shows cracking, bulges, persistent air loss, impact damage, or other signs of structural aging, even if tread depth still appears usable. Collector-car tires often age by time and storage conditions long before they wear out through mileage alone.

A tire can look acceptable from a distance and still be past its best service life. Older European cars may spend years parked, which adds flat spotting, compound hardening, and hidden sidewall stress to the equation. Before any extended drive, evaluate the full tire condition rather than relying on tread alone. If there is doubt about age, internal condition, or roadworthiness, replacement is the safer course.

One of the biggest mistakes with the 155-400 is assuming the metric wheel size is close enough to an inch-rim size to interchange. The tire is designed for a 400-millimeter rim, and that bead-seat diameter must match exactly for proper mounting and service.

Another common error is focusing only on the size code while overlooking tire age and wheel condition. A correct 155-400 on a damaged, corroded, or mismatched wheel is still not a sound setup. Buyers should confirm the actual wheel markings, inspect the rim carefully, and review current tire sidewall markings before road use. If the car's wheel history is unclear, getting the assembly checked by a qualified professional is a smart step.