1970 Subaru Tire Fitment Guide

1970 Subaru fitment centers on the FF-1, which uses two sizes: 155R13 and 6.15-13. Both sizes mount on 13-inch wheels. The 155R13 radial has a confirmed rim-width range of 4.00 to 5.50 inches, while 6.15-13 is the period bias-ply size associated with the same model.

That means the first decision is not which Subaru model you have, since only the FF-1 appears here, but which tire construction you want on your car. If your goal is a more factory-era look, the numeric bias-ply size is the natural starting point. If you want a radial in the same wheel diameter, 155R13 is the size to confirm against your actual wheel before moving forward.

On a 1970 Subaru, 155R13 is a metric radial size. The 155 identifies nominal section width in millimeters, the R denotes radial construction, and the 13 is the wheel diameter in inches. In this older metric format, the aspect ratio is not written into the size code and is conventionally treated as an 80-series profile.

For an FF-1 owner, that decoding matters because 155R13 is not just a different label for the same tire as 6.15-13. It points you toward a radial tire with a different construction style and a modernized driving character compared with a bias-ply tire. It also means you should verify wheel width, since the radial options are intended for a 4.00- to 5.50-inch rim range.

On a 1970 Subaru, 6.15-13 is a numeric bias-ply size. The 6.15 refers to nominal section width, and the 13 indicates the wheel diameter in inches. Unlike a metric radial code, there is no R in the size, and the format reflects the older bias-ply sizing conventions common during the period.

That makes 6.15-13 especially relevant if you are trying to preserve the visual character of a 1970 FF-1. Numeric bias-ply sizes tend to be chosen for originality-focused restorations, while owners who prioritize a later radial-style road feel often move toward 155R13. The key is to match the size code to the construction you actually want, rather than assuming the two sizes are interchangeable in every respect.

For a 1970 Subaru FF-1, the choice between 6.15-13 and 155R13 is mainly a choice between bias-ply and radial construction. The 6.15-13 size is the traditional numeric bias-ply format associated with the era, while 155R13 is the radial alternative in the same 13-inch wheel diameter. That puts appearance, driving feel, and restoration goals ahead of simple year-and-make matching.

Owners building a factory-style presentation usually start with the bias-ply route because the construction and sizing language look right for the period. Owners who plan to drive their FF-1 more often commonly prefer the radial option because it aligns with later tire design practice while staying in a correct 13-inch format. Make the choice at the size level first, then confirm wheel width and the exact sidewall marking of the product you want.

The current 155R13 radial choices for 1970 Subaru come in blackwall form. That presentation fits the straightforward, compact-car character of the FF-1 and avoids the visual heaviness that a wide whitewall would introduce on a small import from this period. No alternate sidewall treatment appears within the available 155R13 products.

For many restorations, blackwall is the cleanest visual match because it suits the late-1960s and early-1970s small-import look. If your Subaru is being judged for authenticity, sidewall appearance matters alongside size and construction, so it is worth comparing your tire choice to original photos, brochures, and marque-club guidance. Even when the wheel diameter is correct, an off-era sidewall style can change the whole stance of the car.

The 155R13 radial size for 1970 Subaru is available from Michelin and Dunlop. Michelin offers the XAS-FF in 155HR13 form, while Dunlop offers the SP Sport Aquajet in 155R13 form. Both are blackwall radial options in the FF-1’s 13-inch wheel diameter.

That gives FF-1 owners a choice between two historically familiar tire names from the era when imported compacts were increasingly moving toward radial construction. Brand selection at this level is less about chasing a universal answer and more about choosing the product character and sidewall marking that best fit your car’s intended use. Once you narrow the size to 155R13, compare the exact construction details and service markings on the tire itself.

For 1970 Subaru fitment in 155R13, the radial tire options fit a rim-width range of 4.00 to 5.50 inches on a 13-inch wheel. That range applies to the radial size used on the FF-1. The wheel diameter is shared with 6.15-13, but the most important setup point is still matching the tire to the actual wheel on the car.

Older imported cars are often restored, repaired, or modified over time, so it is smart to measure the wheel before committing to a tire. If the wheel is outside the radial’s approved width range, a different approach may be needed even though the diameter is correct. Confirming width first helps avoid mounting a tire on a wheel that does not support its intended profile or footprint.

Inner-tube requirements for 1970 Subaru tires depend on the exact tire and wheel combination. The Michelin 155HR13 carries a TL marking, indicating tubeless construction, while the Dunlop 155R13 does not present the same tube marking in the same way. Tube use can therefore vary by product and by the condition and design of the wheel itself.

That is why tube fitment should be confirmed at the product level instead of assumed from the size alone. A tubeless-marked tire still needs a wheel capable of sealing properly, and an older wheel may need closer inspection around the bead seat and valve area before being used without a tube. When in doubt, check both the tire sidewall marking and the wheel condition before final assembly.

Both 155R13 and 6.15-13 use a 13-inch rim diameter on the 1970 Subaru FF-1, so the original wheel diameter is compatible with either size in principle. That shared diameter is what allows owners to compare a bias-ply and a radial option without changing to a different wheel diameter. Diameter compatibility, however, is only the first part of the fitment question.

Wheel width and wheel condition still need to be checked before switching between constructions. The 155R13 radial has a confirmed 4.00- to 5.50-inch rim-width range, and the actual wheel on the car should fall within that span if you choose the radial route. On a decades-old Subaru, it is also worth checking that the wheels are true, free of heavy corrosion, and suitable for the way the tire will be mounted.

A 1970 Subaru should be stored in a cool, dry space away from direct sunlight, electric motors, welders, battery chargers, and other ozone-producing equipment. Tire pressure should stay near the recommended service level during storage, and the car should be rolled periodically so one part of the tread does not carry the load for months at a time. Bias-ply tires are generally more prone to flat-spotting during long static storage than radials.

If the FF-1 sits for a season at a time, moving it a short distance every few weeks can help reduce localized stress in the casing. Some owners also use stands to reduce long-term weight on the tires, but the suspension should still be supported correctly. A simple storage routine preserves both the tire shape and the visual quality of the sidewalls on a lightly used collector Subaru.

Tires on a 1970 Subaru should be judged more by age and condition than by mileage. A collector car tire often deserves careful evaluation once it reaches roughly five to seven years of age, and replacement enters the conversation around the ten-year mark even if tread depth still looks good. The DOT date code, sidewall condition, and how the car has been stored all matter more than odometer use alone.

That age-based approach is especially important on a low-mileage FF-1 because old rubber can look serviceable while losing flexibility and stability. A Subaru that comes out only for fair-weather drives can still be riding on tires that are too old for dependable road use. If there is any doubt, inspect the date code, look for cracking or hardening, and treat age as a core service factor rather than a secondary concern.

Tires on a 1970 Subaru should be checked before every drive and more thoroughly before any longer outing. Look for sidewall cracking, cuts, bulges, uneven wear, and pressure loss, and make sure the tire still holds air consistently between uses. If your setup uses tubes or older valve hardware, inspect the valve stems and surrounding wheel area as part of the same routine.

Regular inspection matters on a seldom-driven car because problems often appear during storage rather than during use. An FF-1 that has been parked for months can develop low pressure, weather checking, or age-related stiffness that is easy to miss until the car is back on the road. A few minutes in the garage before each drive can prevent the most common tire-related surprises on vintage imported cars.

A 1970 Subaru FF-1 would have been associated with period sizing in the 13-inch range, and bias-ply construction was still part of the factory-era tire picture for many compact cars of that time. Within this fitment range, 6.15-13 represents the period-style bias-ply direction, while 155R13 reflects the radial alternative that became increasingly relevant in imported-car circles. Original-market details can vary by destination and specification.

For a restoration, that means the safest approach is to start with size and construction rather than chase an assumed original brand. If your car is being restored to a strict factory presentation, marque-club archives, road tests, and original sales literature are the right next step for market-specific confirmation. For many owners, the key authenticity decision is whether the car should wear an era-correct bias-ply look or a radial that still respects the FF-1’s 13-inch fitment.

Correct tire fitment absolutely matters when a 1970 Subaru is judged in a restoration or concours setting. Size, construction type, sidewall appearance, and overall stance all influence whether the car looks appropriate for its year. On an FF-1, a numeric bias-ply format communicates a different restoration intent than a metric radial, even when both fit the same 13-inch wheel diameter.

That distinction is important because judges and knowledgeable enthusiasts often notice tires immediately, especially on smaller cars where the sidewall is a visible part of the vehicle’s character. A radial may be fully appropriate for touring or preservation use, but an originality-focused event may favor period construction and era-correct presentation. If the car is being prepared for show, compare your choice with event rules and consult Subaru marque specialists before finalizing the tire setup.

For the 1970 Subaru FF-1, both the Michelin XAS-FF and Dunlop SP Sport Aquajet are 155R13 blackwall radial choices in the same 13-inch diameter, and both carry H speed ratings. The Michelin appears as 155HR13 78H TL and has a confirmed 4.00- to 5.50-inch rim-width range, while the Dunlop appears as 155R13 78H and carries a 937-pound maximum load figure. Each weighs 20 pounds.

Those details make the two tires similar in overall format but different in the exact service markings and supplemental published specifications attached to them. If you are comparing them for a specific FF-1, the practical next step is to match the tire to your wheel width, confirm whether you want a clearly marked tubeless product, and decide which sidewall marking best suits the way you want the car to present.

1970 Subaru tires can be suitable for highway driving when they are the correct size, in sound condition, and used within their service markings. The available 155R13 radial products carry H speed ratings, which correspond to a 130 mph ceiling. In real-world use, an FF-1’s age, braking system, suspension condition, alignment, and overall mechanical state are usually more limiting factors than the tire’s nominal speed rating at normal highway speeds.

Safety on a vintage Subaru comes from the whole package working together, not from a tire rating in isolation. A fresh, correctly mounted tire still needs proper pressure, a straight wheel, and a chassis that is ready for sustained road use. Before any highway trip, confirm condition first, then drive the car at speeds that respect both the tire and the mechanical realities of a compact early-1970s import.

Inflation pressure for a 1970 Subaru should follow the vehicle manufacturer’s recommendation for the car, while also respecting the tire maker’s service markings and rated limits. In the 155R13 range, one radial carries a 937-pound maximum load figure, but that number does not automatically translate into the running pressure your FF-1 should use every day. Pressure should never be copied from a different size or construction without checking the application.

The best approach is to start with the original owner’s manual or factory placard if it is still present, then compare that recommendation with the sidewall information on the tire you choose. A bias-ply setup and a radial setup may not respond the same way to pressure changes, even on the same car. Use the factory guidance as the baseline, then fine-tune only within the limits appropriate for the exact tire on the wheel.

Before a longer drive in a 1970 Subaru, inspect each tire for cracking, cuts, bulges, uneven wear, and proper inflation, and make sure the spare is usable as well. Check valve stems closely, especially if the car uses older wheel hardware or tube-equipped assemblies. Tire condition should be part of a wider pre-drive review that also includes brakes, wheel bearings, steering play, and fluid condition.

A longer trip asks more from an FF-1 than a short local outing, so small age-related issues can become real problems once heat and speed build over time. If the car has been sitting, give the tires a close look after the first few miles as well, since flat-spotting or pressure loss may only become obvious once the car is back in motion. Good preparation is what turns an old Subaru into a pleasant road car instead of a roadside project.