The 1970 American Motors Hornet arrived at a moment when compact American cars were being asked to deliver everyday practicality without giving up distinct styling or brand character. That makes tire choice on a Hornet more than a routine replacement decision, especially when different six-cylinder and V8 configurations used different 14-inch bias-ply sizes. This car can wear 6.45-14, B78-14, C78-14, or D78-14 depending on the exact sub-model. Some sizes also have modern radial equivalents, which adds another layer for owners balancing traditional appearance with road-use preferences. The right starting point is confirming the exact Hornet configuration before comparing construction, sizing format, and replacement style.
Which Tire Size Is Right for The 1970 American Motors Hornet
The 1970 American Motors Hornet uses four primary tire sizes, and the correct one depends on the exact six-cylinder or eight-cylinder configuration. All of them are bias-ply tires built for 14-inch rims, so the first step is identifying the sub-model rather than just matching the year and model name. Once that is settled, the decision shifts to staying with a traditional bias-ply presentation or, where available, considering a radial equivalent for the original size family.
A 6.45-14 tire uses the older numeric bias-ply sizing system, where 6.45 refers to the nominal section width in inches and 14 identifies the wheel diameter. On the 1970 American Motors Hornet, this is a traditional bias-ply fitment used on certain six-cylinder non-air configurations, making it especially relevant for owners keeping an early compact-car look and feel. Its value is less about broad modern interchange and more about preserving the right type of vintage sizing format. Before selecting it, make sure the car still has the wheel setup and sub-model configuration that calls for this narrower bias-ply size.
B78-14 uses the vintage alphanumeric bias-ply system, where the letter identifies the tire's size class, the 78 designates its profile family, and the 14 is the rim diameter in inches. For the 1970 American Motors Hornet, this bias-ply size appears on six-cylinder cars and sits in the range where owners may be weighing a period-style replacement against a radial equivalent. It is a useful size for buyers who want to stay close to the Hornet's original-era tire language while still having alternate sizing paths to consider. The key is confirming whether the car's exact six-cylinder setup calls for B78-14 before moving on to construction and style decisions.
A C78-14 tire follows the same alphanumeric bias-ply convention, with the letter marking the size class, the 78 indicating the profile family, and the 14 naming the wheel diameter. On the 1970 American Motors Hornet, this size is used on certain six-cylinder air-conditioned cars and also appears on eight-cylinder applications, so it spans more than one configuration. That overlap makes it an important size for owners comparing sub-model fitment and evaluating whether a traditional bias-ply or a radial equivalent better suits the car's intended use. Wheel condition, actual wheel width, and the vehicle's current setup should be checked before making that switch.
D78-14 is another vintage alphanumeric bias-ply size, with the letter showing a larger size class than B78 or C78, the 78 indicating the profile family, and the 14 matching a 14-inch rim. For the 1970 American Motors Hornet, this size is tied to certain eight-cylinder cars, making it the larger end of the Hornet's primary fitment range. Its importance is in matching the right V8 configuration rather than simply choosing the largest tire that mounts on a 14-inch wheel. Buyers should verify the car's exact sub-model and wheel setup before treating D78-14 as the proper replacement path.
Sub-model fitment matters on the 1970 American Motors Hornet because tire size changes across the covered six-cylinder and eight-cylinder configurations. The right choice starts with confirming whether the car is a 6 Cyl. Non-Air, 6 Cyl. w/Air, or 8 Cyl., since each uses a different pair of bias-ply size options.
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1970 American Motors Hornet 6 Cyl. Non-Air
The 1970 American Motors Hornet 6 Cyl. Non-Air uses smaller bias-ply fitments in the Hornet range, including 6.45-14 and B78-14. That makes this sub-model especially important to verify before ordering, since moving into larger Hornet sizes changes the sizing family and can alter the period-style presentation.
The 1970 American Motors Hornet 6 Cyl. w/Air falls in the middle of the Hornet fitment spread, using B78-14 or C78-14 bias-ply sizes. Buyers with this configuration may also want to look at radial-equivalent options where they exist, while still confirming the actual wheel setup on the car.
The 1970 American Motors Hornet 8 Cyl. uses the larger C78-14 and D78-14 bias-ply sizes in this fitment group. That makes correct size identification especially important, since the V8 cars move beyond the smaller six-cylinder tire options and may lead owners toward a different replacement strategy.
Bias-Ply to Radial Tire Conversion for the 1970 American Motors Hornet
B78-14 and C78-14 each have three radial-equivalent options available. For B78-14, the choices are 155R14 as an 80-series metric radial, P175/75R14 as a 75-series P-metric radial, and P185/70R14 as a 70-series P-metric radial; the recommended rim-width range is 4 to 6 inches. For C78-14, the equivalents are 175R14, P185/75R14, and P195/70R14 in the same progression, also with a 4 to 6 inch rim-width range. These alternatives should be checked against wheel width, overall fitment, and vehicle clearance before conversion.
Modern Radial Equivalents
155R14
Equivalent 80-series Metric Radial (B78-14)
P175/75R14
Equivalent P-metric 75-series Radial (B78-14)
P185/70R14
Equivalent P-metric 70-series Radial (B78-14)
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
Hornet owners usually need to sort out the exact tire size first, then decide whether to stay with bias-ply construction or consider one of the available radial equivalents. The questions below focus on sub-model fitment, 14-inch rim compatibility, appearance choices, and the checks worth making before road use.
Tire Size & Fitment
What tire size fits a 1970 American Motors Hornet?
A 1970 American Motors Hornet can use 6.45-14, B78-14, C78-14, or D78-14, depending on the exact sub-model. The 6 Cyl. Non-Air uses 6.45-14 or B78-14, the 6 Cyl. w/Air uses B78-14 or C78-14, and the 8 Cyl. uses C78-14 or D78-14. All of these are bias-ply sizes for 14-inch rims.
That means the model name alone is not enough to choose the correct tire. The practical first step is confirming whether the Hornet is a six-cylinder non-air, six-cylinder with air, or eight-cylinder car, then matching the tire to the wheel setup that is actually on the vehicle today.
What size rim does a 1970 American Motors Hornet use?
The tire sizes used on the 1970 American Motors Hornet are built around a 14-inch rim diameter. That applies across the Hornet fitment range here, including 6.45-14, B78-14, C78-14, and D78-14, even though the overall tire sizing families differ between numeric and alphanumeric bias-ply formats.
Rim diameter is only one part of the fitment picture, so a 14-inch wheel should not be treated as automatic confirmation by itself. It still helps to verify the sub-model, wheel width, and whether the car has replacement wheels, since those factors affect whether a specific Hornet tire size remains the right choice.
Why does the 1970 American Motors Hornet have more than one tire size?
The 1970 American Motors Hornet has more than one tire size because fitment changes with the covered sub-models. Six-cylinder non-air cars use 6.45-14 or B78-14, six-cylinder air-conditioned cars use B78-14 or C78-14, and eight-cylinder cars use C78-14 or D78-14. The shared 14-inch rim diameter stays the same, but the size class changes.
That variation matters because a tire that belongs to one Hornet configuration may not be the best match for another. A buyer should identify the exact engine and air-conditioning configuration first, then compare the tire size family, appearance goals, and any wheel changes made during the car's life.
Bias-Ply & Radial Options
Is B78-14 a bias-ply or radial tire for the 1970 American Motors Hornet?
B78-14 is a bias-ply tire size on the 1970 American Motors Hornet. It uses the vintage alphanumeric sizing system rather than a modern metric radial format, and it appears on certain six-cylinder Hornet configurations as a primary fitment within the original 14-inch wheel family.
That distinction matters because a buyer deciding on B78-14 is also deciding whether to keep a traditional bias-ply construction or evaluate a radial equivalent. If a conversion is being considered, the wheel width, tire dimensions, and clearance around the fenders and suspension should all be checked before making the change.
What radial tire sizes are equivalent to B78-14 and C78-14?
For B78-14, radial equivalents include 155R14, P175/75R14, and P185/70R14. For C78-14, radial equivalents include 175R14, P185/75R14, and P195/70R14. Those options cover an 80-series metric radial, a 75-series P-metric radial, and a 70-series P-metric radial for each original bias-ply size family.
The choice among them is not just about finding a radial in the same rim diameter. Each equivalent should be checked against the Hornet's actual wheel width, the car's current stance and clearance, and the owner's preference for a more traditional tire profile versus a more modern sizing convention.
What should I check before converting my 1970 American Motors Hornet from bias-ply to radial tires?
A 1970 American Motors Hornet owner considering a bias-ply to radial conversion should start by matching the original size family to the correct equivalent. B78-14 and C78-14 each have radial equivalents, and both of those equivalent groups call for a recommended rim-width range of 4 to 6 inches.
The next checks are practical ones: confirm the wheel width, compare the actual tire dimensions of the radial being considered, and inspect clearance at the fenders and suspension. A Hornet with replacement wheels or previous suspension changes deserves extra attention before treating any radial equivalent as a suitable alternative.
Choosing the Right Tire
What should I consider when choosing a B78-14 or C78-14 tire for a 1970 American Motors Hornet?
Start with the exact sub-model, because B78-14 and C78-14 are not universal across the 1970 American Motors Hornet range. B78-14 belongs to six-cylinder applications, while C78-14 appears on six-cylinder w/Air and eight-cylinder cars. Both are bias-ply primary sizes, and both also have radial-equivalent paths for buyers comparing construction choices.
Once the size is confirmed, the selection decision becomes more specific: maintain a traditional bias-ply presentation or consider a radial equivalent in the same size family. Wheel width, intended use, and the car's current wheel and suspension setup all deserve attention before settling on one direction.
How do I choose between the available 1970 American Motors Hornet tire sizes?
The right way to choose among 6.45-14, B78-14, C78-14, and D78-14 is to treat them as configuration-specific fitments rather than preference-based alternatives. Each size belongs to a particular Hornet setup, with the smaller sizes appearing on certain six-cylinder cars and the larger sizes moving into the eight-cylinder range.
After the proper size family is established, then appearance and construction become the real comparison points. Owners should look at whether the car remains on its original-type wheel setup, whether a radial equivalent is even available for that size, and whether the goal is restoration-oriented presentation or regular road use.
What rim-width specifications should I compare when choosing 1970 American Motors Hornet tires?
Rim width becomes especially important when a 1970 American Motors Hornet owner is considering radial equivalents for the original bias-ply sizes. The equivalent groups for both B78-14 and C78-14 use a recommended rim-width range of 4 to 6 inches, which gives a practical benchmark for checking wheel compatibility.
That check matters even though the Hornet uses a 14-inch rim diameter across all listed sizes. A car with aftermarket wheels may still have the right diameter but the wrong width for the intended tire, so measuring the wheel before final selection helps avoid an appearance or clearance mismatch.
Restoration & Appearance
Which tire should I choose for a period-style 1970 American Motors Hornet?
For a period-style 1970 American Motors Hornet, the starting point is the original bias-ply size family that matches the car's exact sub-model. That means choosing from 6.45-14, B78-14, C78-14, or D78-14 as appropriate, rather than simply selecting any 14-inch tire that looks close enough.
Bias-ply construction usually keeps the tire presentation closer to what a compact American car of this era would have worn. Owners seeking exact restoration accuracy should still compare the vehicle against marque references or historical documentation, especially if the car has been altered or its wheel history is uncertain.
How does tire construction affect the appearance of a restored 1970 American Motors Hornet?
Tire construction changes the visual character of a restored 1970 American Motors Hornet even when the wheel diameter stays the same. A bias-ply tire preserves the older sizing language and traditional profile associated with the Hornet's original-era fitment, while a radial equivalent introduces a more modern sizing convention and look.
That does not make one approach automatically right for every restoration. A buyer should decide whether the priority is maintaining a vintage presentation, improving everyday drivability with an equivalent radial where available, or balancing both while keeping the car within the proper size family for its configuration.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 1970 American Motors Hornet?
Yes, modifications can affect tire fitment on a 1970 American Motors Hornet even when the car still uses a 14-inch wheel. Aftermarket wheels, changes in wheel width, suspension work, ride-height changes, or body repairs can all alter how a 6.45-14, B78-14, C78-14, or D78-14 tire sits in the car.
That is especially important when moving between original bias-ply sizing and a radial equivalent. A Hornet that has been lowered, widened, or fitted with non-original wheels should have steering clearance, fender space, and wheel measurements checked carefully before a tire is chosen on size code alone.
What should I inspect before driving a 1970 American Motors Hornet on new tires?
Before driving a 1970 American Motors Hornet on new tires, inspect the wheels for damage, make sure the tire size matches the car's exact configuration, and confirm that inflation is set appropriately for the tires being installed. It also helps to look over the suspension and steering components so the new tires are not being asked to compensate for worn hardware.
A short clearance check is worth doing before regular road use. Turn the steering from lock to lock, look for contact around the inner fenders, and recheck air pressure after the first few drives, especially if the Hornet has sat for long periods or recently received wheel or suspension work.
How should 1970 American Motors Hornet tires be maintained on a collector car?
Tires on a collector 1970 American Motors Hornet should be inspected regularly even if the car is driven only occasionally. Check for sidewall cracking, cuts, bulges, uneven wear, and slow air loss, and keep the tires properly inflated so a stored Hornet does not spend long periods resting on underinflated tires.
Storage conditions matter as much as mileage on an older collector car. Keeping the Hornet away from prolonged sunlight, excess heat, moisture, and ozone sources helps protect the tires, and a brief inspection before each outing is a smart habit whether the car remains on bias-ply tires or has been converted to radials.
