1951 Opel Tire Fitment Guide

1951 Opel vehicles use four distinct sizes, divided by model. The Kapitan uses either 185R15 in radial construction or 640-15 in bias-ply construction, while the Olympia uses either 155R15 in radial construction or 560-15 in bias-ply construction. All of those sizes mount on 15-inch rims, but the approved rim-width ranges differ by size and by individual tire design. Examples include 5.00 to 6.50 inches and 4.5 to 6 inches for 185R15 products, 4.00 to 4.50 and 4.50 to 5.00 inches for 640-15 products, 4.00 to 5.50 inches for 155R15 products, and 4.5 or 4.50 to 5.50 inches for 560-15 products.

The practical takeaway is that a buyer should confirm the model first, then choose between that model's radial and bias-ply fitment. Even though every listed size uses a 15-inch wheel, that does not make the Olympia and Kapitan sizes interchangeable. Width, section shape, and intended fitment are different enough that the safer path is to follow the model-specific size range and then verify the actual wheel width before making a final choice.

A 640-15 size on a 1951 Opel is a traditional numeric bias-ply designation. The 6.40 figure is the nominal section width in inches, and the 15 is the wheel diameter in inches. On this year Opel, 640-15 applies to the Kapitan rather than the Olympia, and the available examples are all bias-ply tires with early-1950s-style sidewall treatments such as wide and narrow whitewalls.

That matters because 640-15 is not just an older way of writing a size; it also signals a different construction type and driving feel than a later-style radial. A Kapitan owner choosing 640-15 is usually pursuing the look and road character associated with a period-style restoration. Before finalizing the choice, check the wheel's actual width against the tire's approved rim range, because the available 640-15 products are not all built around the same rim-width window.

185R15 and 155R15 are older Euro-metric radial sizes used on 1951 Opel vehicles, with the first number giving the section width in millimeters and the 15 indicating a 15-inch rim. The R identifies radial construction. In period-style metric sizing like this, the absence of a printed aspect ratio typically means an 80-series profile by convention. On 1951 Opel applications, 185R15 belongs to the Kapitan and 155R15 belongs to the Olympia.

These metric radial sizes help separate the larger Kapitan from the smaller Olympia while still keeping both cars on 15-inch wheels. They also open the door to features not seen across all bias-ply offerings, including higher speed ratings on some Michelin products and, in the 155R15 group, both tube-type and tubeless versions. A buyer comparing them should focus on the correct model first, then the individual product's sidewall style, tube marking, and rim-width range.

No, 1951 Opel models do not use one shared tire size. The Kapitan uses 185R15 or 640-15, while the Olympia uses 155R15 or 560-15. Each model has a radial option and a bias-ply option, but the actual dimensions are different between the two cars. Every listed fitment uses a 15-inch wheel, yet the tire sizes themselves are model-specific.

That distinction is important if a buyer knows the year and make but has not yet identified the model. A 1951 Opel owner who skips that step can easily end up comparing the right construction type but the wrong overall size. Once the model is confirmed, the next decision becomes simpler: choose the radial if your priority is a more modern driving character, or the bias-ply if your priority is preserving an early-1950s appearance and period-correct presentation.

A 1951 Opel owner is usually choosing between two construction paths within the correct model-specific size family. Kapitan owners compare 185R15 radial against 640-15 bias-ply, and Olympia owners compare 155R15 radial against 560-15 bias-ply. The bias-ply sizes align more closely with early-1950s tire construction, while the radial sizes represent a more modern-style alternative within the proper 15-inch fitment.

That makes the decision less about whether the tire will physically mount and more about how the car is meant to be used. A show-focused or restoration-minded car often points a buyer toward the bias-ply size, especially when whitewall appearance is part of the finished look. A car that sees more regular road miles often leads the owner toward the radial option. Keep the comparison within the correct model, because Olympia and Kapitan tires are not the same size.

1951 Opel tires are available in several distinct sidewall styles depending on size. The Kapitan's 185R15 radial offerings include redline, narrow whitewall, and blackwall versions, while the 640-15 bias-ply choices include both wide whitewall and narrow whitewall examples. The Olympia's 155R15 radial products are blackwall, and its 560-15 bias-ply products are offered in both narrow whitewall and wide whitewall form.

For a 1951 Opel restoration, sidewall appearance can matter almost as much as size and construction because it strongly influences the car's finished stance and era impression. Bias-ply whitewalls generally read as more traditionally early-1950s in appearance, while blackwall radials tend to look cleaner and more understated. If the car is being judged or restored to a specific market presentation, check period photos, sales literature, or a marque specialist before settling on a sidewall style.

Several brands cover 1951 Opel fitments, but they are divided by size. The Kapitan's 185R15 radial options come from Coker Classic and Michelin, while its 640-15 bias-ply options come from BFGoodrich and Firestone. The Olympia's 155R15 radial options come from Firestone and Michelin, and its 560-15 bias-ply offerings come from Firestone and US Royal. That means brand choice depends first on the model and then on whether you want the bias-ply or radial size for that model.

Brand selection often ends up being part appearance choice and part specification choice rather than a simple make-or-break fitment issue. Some sizes offer more than one sidewall treatment, while others stay limited to blackwall only. In the radial sizes, Michelin also introduces speed-rating differences within the same nominal size. A smart comparison is to narrow to the correct model and size first, then compare the available brands by sidewall style, tube marking, and rim-width suitability.

Rim-width requirements for 1951 Opel tires depend on the exact size and sometimes on the specific tire within that size. For Kapitan fitments, 185R15 products are shown for 4.5 to 6 inches or 5.00 to 6.50 inches, while 640-15 products are shown for 4.00 to 4.50 inches or 4.50 to 5.00 inches. For Olympia fitments, 155R15 products are shown for 4.00 to 5.50 inches, and 560-15 products are shown either for a 4.5-inch rim or for a 4.50 to 5.50 inch range.

Those ranges show why wheel width should be checked before ordering, even when the wheel diameter is correct. A 15-inch rim is only part of the fitment picture; a tire designed around a narrow wheel can behave differently if mounted on a wider one. If your Opel has replacement wheels or wheels from another model, measure them directly rather than relying on assumption, then match the tire to the wheel that is actually on the car.

Inner-tube requirements on 1951 Opel tires depend on the size and the individual tire selected. The 155R15 radial group for the Olympia includes both tube-type and tubeless products, so tube status varies by product in that size. The 185R15 Michelin radial examples for the Kapitan are marked tubeless, while the listed bias-ply 560-15 and 640-15 products do not show a tube marker in the size line. That means tube use should be confirmed on the exact tire you intend to run, not assumed from the wheel diameter alone.

For a buyer, the important step is to read the sidewall marking of the chosen tire and consider the wheel condition and wheel design at the same time. A product marked TT should be treated differently from one marked TL, and older wheels may have their own practical considerations even when the tire itself is tubeless-rated. If originality matters, tube use may also intersect with restoration practice, so it helps to confirm both the tire marking and the wheel setup together.

All listed 1951 Opel tire sizes use 15-inch rims, so they share the same wheel diameter requirement. That means a correctly sized original 15-inch Opel wheel can be in the right diameter family for either the bias-ply or radial option within a given model. The remaining issue is wheel width, because the approved rim-width ranges differ among 560-15, 640-15, 155R15, and 185R15 tires.

The practical rule is to think in pairs rather than across the whole make. A Kapitan owner can compare the 15-inch radial and 15-inch bias-ply options intended for the Kapitan, and an Olympia owner can do the same within Olympia sizes, but that does not make all four sizes interchangeable. Before mounting a radial on an original wheel, verify that the wheel falls within the selected tire's published rim-width range and that the wheel is structurally sound for service.

A 1951 Opel should be stored in a cool, dry, dark space with the tires kept away from direct sunlight, electric motors, battery chargers, welders, and other ozone-producing equipment. Proper inflation matters during storage, and the car should either be moved periodically or supported in a way that reduces long-term static loading. Bias-ply tires such as 560-15 and 640-15 are generally more prone to flat-spotting during long periods of standing, while any vintage-style tire can suffer from sidewall aging if exposed to heat and ozone.

That storage routine helps preserve both appearance and drivability on a collector Opel that may spend more time parked than driven. If the car sits for months at a time, check pressures before and after storage and inspect the sidewalls for cracking before putting it back into use. Owners running tube-type products should also pay attention to valve stems and slow pressure loss, since a stored car can hide those issues until the next drive.

Tires on a 1951 Opel should be evaluated by age as much as by tread depth, because collector cars often accumulate very little mileage. A common rule is to begin paying close attention around five to seven years of service and to treat around ten years as a serious replacement point regardless of remaining tread. The date code on the tire sidewall is the starting point for that timeline, and the same principle applies whether the car is on a radial or a bias-ply reproduction tire.

A low-mileage tire can still be a poor road tire if the rubber has hardened, cracked, or lost resilience with age. That is especially important on a 1951 Opel, where the rest of the driving experience already comes from an earlier automotive era. If the car is driven infrequently, inspect age and condition before each season rather than assuming a good-looking tread means the tire is still ready for regular road use.

Tires on a 1951 Opel deserve a quick inspection before every drive and a more thorough check before any extended outing. Look for sidewall cracking, cuts, embedded objects, bulges, irregular wear, and signs of pressure loss. If the car uses a tube-type tire, include the valve stem and any signs of tube-related leakage in the check. On a collector car, these inspections matter even more because long idle periods can age the tire without adding mileage.

A routine walk-around catches problems early and reduces the chance of discovering them on the roadside. Pay special attention after the car has been stored, after wheel work, or after a long highway run, since those are times when weakness may first show up. If steering suddenly feels different, the car develops a pull, or a tire begins losing pressure faster than usual, stop and inspect before continuing.

A 1951 Opel Kapitan would have been associated with bias-ply construction in its original era, and the period-style fitment listed here is 640-15. The available radial alternative, 185R15, is useful for owners who want a different driving character, but it is not the original early-1950s construction type. No specific original-equipment brand should be assumed without market-specific factory literature, because postwar European production and distribution could vary by destination and replacement history.

For a restoration-minded Kapitan owner, the most authentic starting point is usually the 640-15 size in a sidewall style that matches the way the car is being presented. If the goal is concours judging, verify details through Opel club resources, factory brochures, and event rules, because judges may look at size, construction type, and sidewall appearance together. That extra step matters more on a formal restoration than on a driver-quality car.

Correct tire fitment can matter quite a bit when showing a 1951 Opel, especially in classes that reward period accuracy. Judges and knowledgeable enthusiasts often notice whether the size suits the model, whether the construction matches the era, and whether the sidewall treatment fits the car's intended presentation. A radial in place of a period bias-ply tire, or a sidewall style that looks out of character for the restoration, can change how authentic the finished car appears.

That does not mean every show car must avoid radial tires, but it does mean the owner should be clear about the standard the car is being held to. A local driver-oriented event may be far more relaxed than a marque or concours class focused on originality. Before final judging, compare your Opel's tires against period images and ask the sponsoring club what it considers acceptable for size, construction, and sidewall appearance.

A 1951 Opel Olympia would have been rooted in bias-ply practice for its original period, and the period-style size listed for that model is 560-15. The 155R15 radial is the alternate fitment available today, but it reflects a different construction approach from what an early-1950s family Opel would have started with. As with the Kapitan, the exact brand originally supplied new should be confirmed through marque-specific references rather than assumed from current replacement offerings.

An Olympia owner chasing authenticity will usually begin with the 560-15 size and then narrow the sidewall treatment to match the intended restoration theme. That is especially helpful if the car is being finished to a stock visual standard rather than a touring-driver standard. If originality is the priority, it is worth comparing your chosen tire to period Opel imagery and asking a knowledgeable club member whether your sidewall style looks right for the market and presentation you want.

1951 Opel tires can be suitable for highway use when the size, condition, inflation, and construction are all appropriate, but the answer varies by product. In the radial range, 155R15 examples include T-rated tires up to 118 mph and H-rated tires up to 130 mph, while 185R15 examples include H-rated choices up to 130 mph and V-rated choices up to 149 mph. The listed bias-ply sizes do not carry the same speed-letter examples here, so they should be approached with the expectations of a vintage-style tire rather than a modern high-speed touring tire.

On a 1951 Opel, real-world highway confidence usually depends as much on the car's brakes, steering, suspension, and overall mechanical condition as on the tire itself. A sound radial setup may suit more frequent road use, while a bias-ply setup may be better matched to moderate speeds and period-style driving. Whatever the construction, no old or poorly stored tire should be trusted simply because the size is correct.

Inflation pressure on 1951 Opel tires should be set by the specific tire and the vehicle's factory guidance, not guessed across all sizes. Several listed products include rated load-and-pressure figures such as 1355 pounds at 35 psi for one 185R15 radial, 1190 pounds at 32 psi for several 640-15 bias-ply options, 1045 pounds at 44 psi for one 155R15 radial, and 970 pounds at 32 psi for the listed 560-15 products and one narrower 640-15 version. Those figures describe the tire's rated load point, not a universal Opel inflation recommendation.

The best approach is to start with the original Opel handbook or period pressure guidance for your exact model, then confirm that your chosen reproduction tire's rating and use pattern make sense together. A pressure figure from a Kapitan tire should not be transferred to an Olympia tire, and a radial's needs should not be assumed to match a bias-ply's. Recheck pressures cold, because even a correctly sized vintage tire will drive poorly if inflation is inconsistent.

Before a longer drive in a 1951 Opel, inspect every tire for cracking, cuts, bulges, punctures, abnormal wear, and correct cold inflation. Check the spare as well, since a trunk-mounted spare that has been ignored for years may be the oldest tire on the car. If your chosen tire is tube-type, inspect the valve stems closely and be alert for any signs of slow leakage. On radial products, confirm the sidewall marking and overall condition just as carefully, especially after long storage.

Tires are only one part of the preparation, but they are one of the quickest ways to turn a pleasant drive into an avoidable problem. A 1951 Opel heading out for distance should also have its brakes, wheel bearings, steering, and suspension checked as part of the same pre-drive routine. Starting with fresh pressure readings and a close visual inspection gives you the best chance of catching age-related issues before the car is on the road.