1978 Mazda Tire Fitment Guide

1978 Mazda vehicles use eight sizes across five model lines: 6.00-14 for the B1600 & 1800, 185/70R14 for the Cosmo, 155R13 plus 6.15-13 plus 175/70R13 for the GLC, 155R13 plus 560-13 for the RX-3, and 195/70R13 plus BR70-13 for the RX-4. Rim diameter varies by application, with 14-inch fitments on the B1600 & 1800 and Cosmo, and 13-inch fitments on the GLC, RX-3, and RX-4.

That means year and make alone are not enough to choose a tire for a 1978 Mazda. Start by confirming the exact model, then match the correct rim diameter, and only after that compare construction type, sidewall style, and use case. On models with more than one size path, the right choice often comes down to whether the car is being restored with an original-type appearance in mind or driven in a way that favors a later radial feel.

On a 1978 Mazda, 560-13 is a numeric bias-ply size. The 5.60 figure is the nominal section width in inches, expressed without a decimal point in modern style, and the 13 identifies the wheel diameter in inches. For 1978 Mazda fitment, that size belongs to the RX-3.

Numeric sizes like 560-13 read differently from modern metric radials, so they are easy to misinterpret if you are used to later tire markings. The important takeaway is that this is a 13-inch bias-ply application with a distinctly vintage format. If an RX-3 owner is comparing 560-13 to 155R13, the difference is not just the code on the sidewall but the construction style and overall character of the tire.

On a 1978 Mazda, BR70-13 is an alphanumeric radial size. The lettered prefix identifies the general size range, the R confirms radial construction, and the 13 is the wheel diameter in inches. Within the 1978 Mazda range, BR70-13 is associated with the RX-4.

That format was common during the transition from earlier domestic-style sizing to more modern metric labeling, so it has a distinctly late-1970s look. For an RX-4 owner, BR70-13 and 195/70R13 both point toward radial construction, but they present the fitment in different period-correct naming conventions. If authenticity matters, it is worth deciding whether you want the sidewall to reflect that era-specific alphanumeric style.

For a 1978 Mazda RX-3, 155R13 and 560-13 represent two different directions. The 155R13 is a radial size shared with the GLC, while the 560-13 is a numeric bias-ply size specific to the RX-3. The radial option comes in blackwall form from Michelin and Dunlop, while the bias-ply option is available from BFGoodrich and Firestone with narrow or wide whitewall styling.

An RX-3 built around factory-era presentation usually leans naturally toward the bias-ply size, especially if the rest of the car follows an original-style look. A driver-oriented car often points toward the radial because the construction itself changes the feel more than the sidewall code does. Before choosing either one, confirm which wheel is on the car and whether the goal is restoration appearance, casual weekend driving, or a blend of both.

Sidewall treatment varies quite a bit across 1978 Mazda sizes. The 185/70R14 used on the Cosmo is available in blackwall and wide whitewall form, 155R13 and 175/70R13 are available as blackwalls, 560-13 for the RX-3 comes in narrow whitewall and wide whitewall versions, and 195/70R13 for the RX-4 appears as a narrow whitewall radial. That gives the year a mix of sporty blackwall choices and more formal whitewall presentations.

A sidewall choice can change the look of the car even when the size stays the same. Smaller economy and sporty Mazda applications generally look most natural with blackwalls, while the Cosmo and some vintage-styled RX-3 builds can support a whitewall treatment more convincingly. If show authenticity matters, use the car’s market, trim character, and restoration theme as the final guide rather than choosing solely by brand or tread pattern.

1978 Mazda fitments are covered by BFGoodrich, Avon, Dunlop, Michelin, and Firestone across the available sizes. The Cosmo’s 185/70R14 size is especially broad, with choices from BFGoodrich, Avon, Dunlop, and Michelin. The 155R13 size comes from Michelin and Dunlop, the 560-13 from BFGoodrich and Firestone, the 175/70R13 from Avon, and the 195/70R13 from BFGoodrich.

That spread gives buyers room to prioritize different things within the same size, whether that is sidewall appearance, a familiar vintage name, or a particular radial series. It also means brand choice depends heavily on the model and size rather than the Mazda badge alone. The most efficient path is to confirm the car’s correct size first, then compare the brands that actually exist within that size rather than shopping brand-first.

Several 1978 Mazda sizes have clear rim-width guidance. The 185/70R14 fits rims from 4.5 to 6.5 inches wide depending on the tire, the 155R13 fits 4.00 to 5.50 inches, the 175/70R13 fits 4.5 to 6.0 inches, the 560-13 fits 3.50 to 4.50 inches depending on brand, and the 195/70R13 fits 5.00 to 6.50 inches. Those ranges are size-specific and should not be carried over from one size to another.

Rim width matters because it affects the tire’s section shape and how correctly it seats and carries load. A 13-inch tire can still be wrong for a 13-inch wheel if the wheel is too narrow or too wide for that particular casing. Before mounting a replacement on any 1978 Mazda, measure the actual wheel or verify its width through the car’s wheel markings or a trusted workshop reference.

Inner-tube requirements vary by size and sometimes by product on 1978 Mazda applications. The 155R13 radial products are tubeless, and Michelin’s 185/70R14 XAS is also marked tubeless. Other sizes do not carry a uniform tube marking across every available product, so tube use should be confirmed on the exact tire being considered rather than assumed from the size code alone.

That matters most on collector cars that may still wear original-style wheels, because wheel design and condition influence whether a tubeless tire is appropriate. If a wheel has rivets, pitting, prior repairs, or an older profile, discuss tube use with the tire maker or a restorer familiar with vintage wheels. Matching the tire and wheel correctly is more important than trying to apply one tube rule across the entire 1978 Mazda range.

Original 1978 Mazda wheels cannot be treated as universal across all models because the lineup uses both 13-inch and 14-inch rim diameters, and the tire widths vary substantially by application. A B1600 & 1800 or Cosmo wheel will not automatically interchange with a GLC, RX-3, or RX-4 setup just because the cars came from the same make and year. Even within the 13-inch group, rim-width requirements differ by size.

The practical approach is to verify the wheel already on the car before comparing tires. If the wheel diameter is correct and the width falls inside the tire’s accepted range, you can move on to construction and sidewall style. If the wheel has been changed during the car’s life, the model’s original fitment may no longer tell the whole story, so checking the wheel itself prevents expensive mistakes.

A stored 1978 Mazda should be kept out of direct sunlight and away from ozone sources such as electric motors, battery chargers, welders, and some compressors. Clean, dry concrete is preferable to dirt or damp surfaces, and maintaining proper inflation helps the casing keep its shape. Bias-ply tires such as 6.00-14, 6.15-13, and 560-13 are generally more prone to flat-spotting during long static storage than the radial fitments used elsewhere in the 1978 Mazda range.

If the car will sit for extended periods, move it periodically or place it on stands in a way that follows safe chassis support practices. A breathable cover and stable indoor temperatures help preserve both rubber and the car itself. Collector vehicles often age tires by time and environment more than by mileage, so good storage conditions are one of the most important steps in protecting a fresh set.

Tires on a 1978 Mazda should be evaluated by age as much as by tread depth. A sound collector-car rule is to begin looking closely at tires around five to seven years old and to give serious replacement consideration at around ten years, even if the tread still looks usable. The DOT date code on the tire sidewall is the key reference for age, not the number of miles the car has traveled.

That age-based approach matters because many vintage Mazdas are lightly driven, and low use can hide hardening, internal aging, or sidewall cracking that tread alone will not reveal. A car that only goes to shows or weekend events can still out-age its tires long before it wears them out. If you have just acquired a 1978 Mazda, checking tire age is one of the first maintenance steps worth taking.

Tires on a 1978 Mazda deserve a quick inspection before every drive and a more thorough inspection before any longer outing. Look for sidewall cracking, weather checking, tread separation signs, punctures, bulges, irregular wear, and pressure loss. On tube-type or possibly tube-equipped applications, valve stems and any signs of slow leakage deserve extra attention because the assembly may rely on more than the outer casing alone.

Vintage cars often spend more time parked than moving, and that can allow problems to develop slowly and quietly. A five-minute check in the garage is far easier than dealing with a roadside failure on an older chassis. If the car has been dormant for months, inspect the spare as well, since it may be the only backup available if a period-size tire is damaged on a trip.

For a 1978 Mazda GLC, both bias-ply and radial directions appear within the model’s fitment range, including 6.15-13, 155R13, and 175/70R13 depending on the exact application. By 1978, radial adoption was well established on many small imported cars, but bias-ply fitments still remained part of the period on some applications and replacement pathways. That means original-equipment expectations can vary with body style, market, and how the car was delivered.

A restorer should treat the size range as a strong starting point and then confirm the exact car through factory literature, surviving labels, or a Mazda marque specialist. If the goal is strict originality, construction type matters just as much as section width or rim diameter. Choosing between the GLC’s 13-inch options is often less about what physically fits and more about what best matches the car’s specific restoration brief.

Correct tire fitment matters a great deal when a 1978 Mazda is judged for authenticity. Judges and knowledgeable enthusiasts often notice whether the car carries the right size family, the right construction type for its intended restoration level, and a sidewall treatment that suits the era and market character. A modern-looking radial where a period-style bias-ply is expected, or an out-of-place whitewall on a sporty model, can change the visual accuracy of the whole car.

That does not mean every show car must wear the same tire, because some 1978 Mazda models legitimately straddle bias-ply and radial territory. It does mean the owner should be able to explain why a particular choice was made. For event-specific standards, the best reference is the relevant Mazda club or the judging manual used by the organization hosting the show.

On the 1978 Mazda Cosmo’s 185/70R14 size, BFGoodrich Silvertown Radial and Michelin XAS take different approaches. The BFGoodrich version uses a wide whitewall presentation, fits 5.00 to 6.50-inch rims, and carries a maximum load of 1,201 pounds at 35 psi. The Michelin XAS appears as a blackwall tubeless radial, fits 4.50 to 6.00-inch rims, and is marked with a V speed rating to 149 mph in 185/70VR14 form.

That comparison is useful because it shows how two tires in the same size can target different visual and driving priorities without changing the basic fitment. One leans more toward an American-style classic appearance, while the other carries a more European sporting flavor in both sidewall presentation and speed marking. Cosmo owners should decide whether the car’s restoration theme is formal, understated, or performance-oriented before picking between them.

Many 1978 Mazda tire choices are suitable for normal highway use when they are correctly fitted, properly inflated, and in sound condition. Several radial sizes carry H speed ratings to 130 mph, and the Michelin 185/70VR14 carries a V rating to 149 mph. Bias-ply sizes such as 6.00-14, 6.15-13, and 560-13 should be approached with period-appropriate expectations, since construction type affects the way an older vehicle feels and responds even when the tire itself is in good shape.

In real-world collector driving, the condition of the car often matters as much as the speed symbol on the sidewall. A 1978 Mazda’s brakes, steering, suspension, wheel bearings, alignment, and age of the rubber all influence safety on the road. Highway use is far less about chasing a tire’s theoretical maximum speed and far more about having the correct tire, the correct pressure, and a mechanically sound car beneath it.

Inflation pressure on a 1978 Mazda should follow the vehicle’s factory recommendation first, then be checked against the tire maker’s specifications for the exact product. Some available tires include load-and-pressure figures, such as 185/70R14 examples at 35 psi, 560-13 examples at 30 psi, and the 195/70R13 at 35 psi, but those figures are tied to that tire’s rated load and are not a blanket inflation recommendation for every 1978 Mazda.

Pressure should never be borrowed from one size and applied casually to another just because the cars are from the same year and make. A GLC, Cosmo, RX-3, and pickup have different weight distribution, suspension tuning, and intended use. Start with the factory vehicle guidance if it is available, then adjust only within the tire maker’s acceptable range after confirming the exact size and product mounted on the car.

Before a longer drive in a 1978 Mazda, inspect all four tires and the spare for cracking, cuts, bulges, uneven wear, and proper cold inflation pressure. Check valve stems closely, especially on any assembly that may involve tubes, and make sure lug nuts are secure and wheels show no obvious damage. A collector-car trip check should also include fluid levels, belts, hoses, lights, and basic brake feel, since tire safety is only one part of the car’s readiness.

That routine is especially important on a vintage Mazda because many of these cars are used intermittently rather than daily. A tire that looked fine at the last event may have aged, lost pressure, or developed a slow leak since then. Giving the car a careful once-over before heading out reduces the chance that a manageable garage issue becomes a roadside problem far from home.