The 1979 American Motors Spirit arrived during a transitional moment for compact American cars, balancing practical packaging with the individual character that made AMC models stand apart. Spirit buyers could find everything from everyday economy to V8-powered personality in the same basic platform. Tire fitment for the 1979 American Motors Spirit centers on two 14-inch bias-ply sizes, C78-14 and D78-14, so the key decision is confirming which size belongs on the car before choosing a tire style. Modern radial equivalents are available for C78-14, adding another path for owners who want a more contemporary construction while still respecting the car’s proportions and intended use.
Which Tire Size Is Right for The 1979 American Motors Spirit
The 1979 American Motors Spirit uses two primary tire sizes: C78-14 and D78-14. Both are bias-ply fitments on 14-inch rims, and both appear across the covered Spirit sub-models, so the first step is confirming which of the two sizes is on the car now or matches its wheel setup. Once that is settled, the decision shifts to keeping the original bias-ply format or evaluating a radial equivalent where one is available.
C78-14 is a vintage alphanumeric bias-ply size. The letter identifies the tire’s general size class, the 78 designates its profile family, and the 14 corresponds to the wheel diameter. On a 1979 American Motors Spirit, this size suits owners who want to stay with the original-style bias-ply construction and maintain the car’s period presentation. It is also the size with modern radial-equivalent paths available, which makes it especially important for buyers balancing traditional appearance with a possible move to a more modern tire format.
D78-14 is also a vintage alphanumeric bias-ply size, using the same basic naming system of lettered size class, 78-series profile family, and 14-inch wheel diameter. For the 1979 American Motors Spirit, it represents the larger of the two primary fitment codes shown for this vehicle family and remains part of the original bias-ply tire conversation. Choosing this size starts with verifying the car’s wheel and existing fitment, then deciding whether the goal is restoration-oriented authenticity, a traditional driving feel, or simply keeping the Spirit in its proper vintage sizing format.
Tire fitment across the covered 1979 American Motors Spirit sub-models is straightforward in one respect: both the 4 & 6 Cyl. cars and the V8 cars use the same two primary tire sizes. That means the main task is not separating engine groups by tire family, but confirming whether your particular Spirit is set up for C78-14 or D78-14.
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1979 American Motors Spirit 4 & 6 Cyl.
The 1979 American Motors Spirit 4 & 6 Cyl. uses the same two primary 14-inch bias-ply tire sizes found elsewhere in the Spirit range. Tire selection comes down to confirming whether the car takes C78-14 or D78-14, then choosing between a traditional bias-ply replacement path and a radial-equivalent option where available.
The 1979 American Motors Spirit V8 shares the same basic tire-fitment situation as the other covered Spirit sub-models, with two 14-inch bias-ply sizes in play. That makes wheel and existing-tire verification more important than trim differences, especially for owners deciding whether to preserve a period-style setup or consider a radial alternative for C78-14.
Bias-Ply to Radial Tire Conversion for the 1979 American Motors Spirit
For the original C78-14 tire size, three radial-equivalent options are available. 175R14 is the 80-series metric radial equivalent, P185/75R14 is the P-metric 75-series radial equivalent, and P195/70R14 is the P-metric 70-series radial equivalent. These choices follow different sizing conventions and profile families while serving as modern alternatives to the original bias-ply format. The recommended rim-width range is 4 to 6 inches, and any conversion should still be checked against the car’s wheel width, overall setup, and clearance.
Modern Radial Equivalents
175R14
Equivalent 80-series Metric Radial (C78-14)
P185/75R14
Equivalent P-metric 75-series Radial (C78-14)
P195/70R14
Equivalent P-metric 70-series Radial (C78-14)
Important Considerations When Replacing Bias Ply With Radial
Compare overall diameter and section width carefully to ensure proper fit.
Verify recommended rim range (4-6 in) and load needs match your vehicle specifications.
Check fender clearance, steering clearance, and stance before installation.
Consider suspension condition and intended road use when choosing equivalents.
Important Fitment Notes
The tire sizes listed on this page assume factory-standard vehicle configuration. The following modifications may affect tire fitment and are not reflected in this guide:
Suspension changes (lowering, lift kits, spring replacements)
Body alterations (fender modifications, custom bodywork)
If your vehicle has been modified from factory specifications, verify tire clearance before purchase.
Frequently Asked Questions
Common questions for the 1979 American Motors Spirit usually center on choosing between C78-14 and D78-14, understanding vintage bias-ply sizing, and deciding whether a C78-14 radial equivalent makes sense for the car’s wheels, appearance, and road use.
Tire Size & Fitment
What tire size fits a 1979 American Motors Spirit?
The 1979 American Motors Spirit uses two primary tire sizes: C78-14 and D78-14. Both are vintage alphanumeric bias-ply sizes mounted on 14-inch rims, and both appear across the covered Spirit sub-model range, including 4 & 6 Cyl. and V8 versions.
That means the real fitment question is not simply model name, but which size matches the car’s actual wheel and current setup. Checking the existing tire size, wheel diameter, and overall clearance is the safest next step, especially if the Spirit has changed wheels or suspension parts over the years.
What size rim does a 1979 American Motors Spirit use?
The primary tire fitments for the 1979 American Motors Spirit use a 14-inch rim diameter. Both C78-14 and D78-14 are built around that same wheel diameter, so rim diameter stays consistent even though two tire sizes are associated with the vehicle.
Rim diameter is only part of the fitment picture, so it should be confirmed along with wheel width before choosing tires. That matters even more on a collector-era car, because replacement wheels, older aftermarket wheels, or a prior owner’s changes can leave the car wearing a different setup than expected.
What does C78-14 mean on a 1979 American Motors Spirit?
C78-14 is a vintage alphanumeric bias-ply tire size. The letter C identifies the tire’s size class, the 78 refers to its profile family, and the 14 indicates that it fits a 14-inch rim. It is one of the primary tire sizes used on the 1979 American Motors Spirit.
Buyers used to modern metric sizing often need that translation before comparing replacement options. Once the original format is understood, it becomes easier to decide whether to stay with a period-style bias-ply tire or look at a radial equivalent for C78-14 while still checking wheel width and vehicle clearance first.
Bias-Ply & Radial Options
Is C78-14 a bias-ply or radial tire for the 1979 American Motors Spirit?
C78-14 is a bias-ply tire size on the 1979 American Motors Spirit. It uses a vintage alphanumeric sizing format rather than a modern metric radial format, so the original fitment conversation for this size starts with a traditional bias-ply construction on a 14-inch rim.
That distinction matters because a bias-ply tire affects both appearance and setup decisions. Owners keeping a restoration-oriented look may want to remain with the original construction style, while those considering a radial alternative should compare wheel width, overall dimensions, and clearance instead of assuming any modern equivalent is automatically interchangeable.
What radial tire sizes are equivalent to C78-14?
Radial equivalents for C78-14 include 175R14, P185/75R14, and P195/70R14. Those represent three different radial sizing approaches: an 80-series metric radial, a 75-series P-metric radial, and a 70-series P-metric radial. A recommended rim-width range of 4 to 6 inches is also associated with these C78-14 radial alternatives.
These equivalents give Spirit owners more than one path when moving away from a bias-ply tire, but they should still be treated as alternatives rather than guaranteed swaps. Wheel width, tire dimensions, suspension condition, and body clearance all deserve a careful look before a conversion, especially on an older car with unknown changes.
What should I check before converting my 1979 American Motors Spirit from bias-ply to radial tires?
Start by confirming the original tire size on the car, then compare it with the actual radial equivalent available for that size. For C78-14, the radial-equivalent choices are 175R14, P185/75R14, and P195/70R14, with a recommended rim-width range of 4 to 6 inches.
After that, inspect the wheel width, tire-to-fender clearance, steering clearance, and general suspension condition before making the change. A conversion can also alter the car’s appearance and feel, so many Spirit owners decide first whether the priority is preserving a period-style bias-ply presentation or moving toward a more modern tire format.
Choosing the Right Tire
What should I consider when choosing a C78-14 or D78-14 tire for a 1979 American Motors Spirit?
The first consideration is using the correct primary size for the car, since the 1979 American Motors Spirit is associated with both C78-14 and D78-14. After size is confirmed, the next decision is whether to keep the original-style bias-ply construction or, in the case of C78-14, explore one of the available radial equivalents.
Appearance and wheel compatibility also shape the decision. A buyer focused on a restoration-oriented look may prefer the traditional bias-ply route, while a driver-minded owner may want to compare the C78-14 radial alternatives more closely. Either way, verify wheel diameter, wheel width, and clearance before settling on a tire choice.
How do I choose between the available C78-14 and D78-14 tires for a 1979 American Motors Spirit?
Choosing between the available tire options starts with separating size from construction. C78-14 and D78-14 are both primary bias-ply sizes for the 1979 American Motors Spirit, so the correct choice depends on the car’s existing wheel and fitment rather than simply picking between two close-looking vintage codes.
Once the size is confirmed, think about how the Spirit will be used. A car being kept visually close to its late-1970s presentation may stay with bias-ply construction, while a C78-14-equipped car also opens the door to radial alternatives. That makes wheel width, intended driving use, and visual preference the key comparison points.
What rim-width specifications should I compare when choosing 1979 American Motors Spirit tires?
Rim width becomes especially important when looking beyond the original bias-ply fitment and into radial alternatives. For the C78-14 radial-equivalent group, the recommended rim-width range is 4 to 6 inches. That gives a useful reference point when evaluating whether the wheel on the car is suitable for a modern alternative.
A 14-inch wheel can still vary in width, so matching diameter alone is not enough. Measuring the wheel already on the Spirit helps avoid selecting a tire that falls outside its intended rim-width range, and it also gives a clearer starting point for checking sidewall shape, stance, and clearance around the suspension and fenders.
Restoration & Appearance
Which tire should I choose for a period-style 1979 American Motors Spirit?
A period-style 1979 American Motors Spirit usually starts with one of its original-format bias-ply sizes, C78-14 or D78-14, depending on the car’s actual fitment. Keeping the vintage alphanumeric bias-ply format preserves the visual character most closely associated with the Spirit’s late-1970s tire presentation.
That does not automatically make one exact tire the right answer for every restoration. Some owners want the most traditional look possible, while others are willing to consider a radial equivalent for C78-14 and accept a different presentation. When originality matters at a detailed level, compare the tire choice against marque-specific historical references for the car.
Does correct tire fitment matter for a 1979 American Motors Spirit restoration?
Correct tire fitment matters on a 1979 American Motors Spirit restoration because the tire strongly influences the car’s stance, proportions, and overall period impression. Using the proper primary size family, whether C78-14 or D78-14, helps the finished car look intentional rather than generically fitted with any 14-inch tire.
Fitment accuracy also affects how confidently the restoration comes together around the wheels and body. Even when the goal is not concours-level detail, confirming size, construction type, and wheel compatibility helps avoid a mismatch that can distract from the car’s appearance. It is one of the most visible finishing choices on the vehicle.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 1979 American Motors Spirit?
Yes, modifications can affect tire fitment on a 1979 American Motors Spirit even when the car still uses a 14-inch wheel. Changes such as aftermarket wheels, different wheel widths, altered offsets, suspension work, or body modifications can influence whether C78-14 or D78-14 remains the appropriate starting point.
Older cars often accumulate changes over time, so it helps to inspect the actual setup rather than relying on model name alone. Looking at wheel width, steering travel, fender clearance, and ride height will give a clearer picture before choosing tires, especially if a C78-14 radial equivalent is also under consideration.
What should I inspect before driving a 1979 American Motors Spirit on new tires?
Before driving a 1979 American Motors Spirit on new tires, inspect the wheels for correct diameter and condition, then confirm proper clearance at the fenders, suspension, and steering range. It also helps to look over the brakes, wheel bearings, and alignment condition so the new tires are not being introduced to an unstable setup.
The car’s older chassis components deserve attention too. Worn bushings, sagging springs, or steering play can affect how any new tire sits and behaves on the road. A careful pressure check, lug-nut check, and short low-speed test drive can reveal rubbing, pull, vibration, or other fitment issues before longer use.
How should C78-14 and D78-14 tires on a collector 1979 American Motors Spirit be maintained?
C78-14 and D78-14 tires on a collector 1979 American Motors Spirit should be maintained with regular pressure checks, visual inspections, and careful storage habits. Collector cars often spend long periods parked, so tread condition, sidewall cracking, bulges, cuts, and slow air loss deserve attention even when mileage stays low.
Storage conditions matter almost as much as road use on a lightly driven Spirit. Keeping the car away from prolonged sunlight, excess heat, moisture, and ozone sources can help preserve the tires between drives. Rotating attention back to the wheels before each outing is wise, especially after the car has been sitting for a season.
