1978 American Motors Gremlin Tires

A 1978 American Motors Gremlin uses one of two primary tire sizes: B78-14 or C78-14. Both are vintage alphanumeric bias-ply sizes mounted on 14-inch rims, and the Gremlin Base is associated with both sizes rather than one exclusive fitment.

That means the safest starting point is the car itself. Check the size already on the vehicle, confirm the wheel diameter, and make sure the current setup has not been changed over the years. On an older compact car like a Gremlin, replacement tires should match the actual wheel and space available rather than relying on assumption alone.

The 1978 American Motors Gremlin uses a 14-inch rim with its primary tire fitments. Both B78-14 and C78-14 are tied to that same 14-inch wheel diameter, so the rim diameter stays consistent even though the tire size can vary.

That shared diameter simplifies one part of the search, but it does not make B78-14 and C78-14 interchangeable by default. Wheel width, the tire already fitted to the car, and clearance around the suspension and body still matter. A quick wheel check before ordering helps keep the tire choice aligned with the Gremlin’s actual setup.

The 1978 American Motors Gremlin is associated with two primary sizes because B78-14 and C78-14 were both used on this model year. Both are bias-ply tires for 14-inch rims, but they represent different alphanumeric size classes rather than one single universal fitment.

For an owner, that means the tire decision starts with verification instead of guesswork. Older cars are often found with replacement wheels, earlier substitutions, or long-standing tire changes, so the current wheel-and-tire combination should be checked first. Once that is confirmed, it becomes much easier to stay with the proper bias-ply size or compare the right radial equivalent.

B78-14 is a bias-ply tire size on the 1978 American Motors Gremlin. It uses the vintage alphanumeric sizing system, so the letter and number combination reflects an older bias-ply format rather than a modern metric radial size designation.

That matters because keeping B78-14 preserves the Gremlin’s original-era tire construction and visual character. A buyer considering a change should separate two decisions: whether B78-14 is the correct primary size for the car, and whether to remain with bias-ply construction or move to a radial equivalent. Wheel width and overall clearance should be reviewed before making that switch.

B78-14 has three radial-equivalent sizes: 155R14, P175/75R14, and P185/70R14. C78-14 also has three: 175R14, P185/75R14, and P195/70R14. In each group, the first is an 80-series metric radial, the second is a 75-series P-metric radial, and the third is a 70-series P-metric radial.

Those sizes give a Gremlin owner more than one radial path, but they should be treated as alternatives to evaluate rather than automatic substitutions. The recommended rim-width range is 4-6 inches for both primary sizes, which is a useful checkpoint. Final selection still depends on the wheel actually on the car and the space available around steering and suspension components.

Start by confirming which primary size the car uses, since a 1978 American Motors Gremlin can be set up with either B78-14 or C78-14. Then compare the intended radial equivalent against the car’s 14-inch wheel, keeping the recommended 4-6 inch rim-width range in mind.

A conversion also deserves a close look at clearance and condition. Check the wheel width, inspect steering and fender space, and consider whether the car still has its original-type suspension height or aftermarket changes. On an older vehicle, it is also smart to inspect the wheels themselves before mounting new tires, especially if the car has spent long periods off the road.

The first consideration is choosing the correct primary size for the car, since the 1978 American Motors Gremlin can use either B78-14 or C78-14. After size is confirmed, the next decision is whether the goal is a traditional bias-ply presentation or a radial alternative with a modern sizing format.

That choice usually comes down to how the Gremlin will be used. A restoration-minded owner may want the appearance and construction style of the original-era fitment, while a casual driver may compare radial equivalents more closely. Wheel width, clearance, and the car’s present tire setup should guide the final decision more than appearance alone.

Choosing between B78-14 and C78-14 options starts with the setup already on the car, not with appearance alone. Because both sizes are primary fitments for a 1978 American Motors Gremlin, the better choice is the one that matches the wheel and tire combination the car is actually using.

Once the size is confirmed, compare the kind of result you want from the replacement. Some buyers want a period-style bias-ply tire that keeps the late-1970s look intact, while others are mainly interested in moving toward a radial equivalent. On any older car, checking the wheel before purchase is more useful than assuming one Gremlin size suits every example.

For radial-equivalent sizing tied to the 1978 American Motors Gremlin’s B78-14 and C78-14 fitments, the recommended rim-width range is 4-6 inches. That range helps frame whether a modern equivalent is being considered on a wheel that supports the tire properly.

Rim width becomes especially important when moving away from the original bias-ply sizing format. Even with the correct 14-inch diameter, a wheel that is too narrow or too wide can affect how the tire sits and how much space remains around the car. Measuring the wheel already on the Gremlin is a smart step before committing to any equivalent size.

A period-style 1978 American Motors Gremlin usually starts with the correct primary size in its original-era format, which means B78-14 or C78-14 in bias-ply construction. That keeps the car visually aligned with the late-1970s tire sizing and construction style associated with the model.

The right choice depends on which of the two sizes is actually on the car and what kind of presentation the owner wants to preserve. For a restoration, matching the established wheel-and-tire setup is often more important than simply picking the larger or smaller option. If exact originality matters, marque-specific reference material can help refine that final appearance decision.

Tire construction changes more than just how the size is written on the sidewall. On a restored 1978 American Motors Gremlin, staying with a bias-ply tire keeps the car in a more traditional visual category, while a radial equivalent introduces a more modern sizing convention and presentation.

That difference can matter on a compact AMC where overall proportions are part of the car’s character. Buyers focused on preservation often begin with the bias-ply fitment and then decide whether drivability goals justify a radial alternative. The most satisfying result usually comes from balancing the Gremlin’s visual era, intended use, and the wheel setup already on the car.

Yes, modifications can affect tire fitment on a 1978 American Motors Gremlin even when the tire size itself appears correct. Aftermarket wheels, altered wheel width, suspension changes, or body modifications can all change how a B78-14, C78-14, or a radial equivalent sits on the car.

That is why the actual vehicle should be checked before replacement tires are chosen. A 14-inch rim diameter alone does not tell the whole story, especially on an older car that may have changed hands several times. Looking at wheel width, steering clearance, and fender space helps prevent a fitment choice that looks right on paper but creates issues on the car.

Before driving a 1978 American Motors Gremlin on new tires, inspect the wheels, lug hardware, valve stems, and overall wheel condition, then confirm the tire size matches the setup on the car. It is also wise to check alignment-related wear points and make sure the tires clear properly at full steering lock.

A collector-era compact can sit for long periods, so a broader safety check is worthwhile before regular road use. Look over suspension components, verify tire pressure, and watch for rubbing during the first miles of driving. Even with brand-new tires installed, the Gremlin’s road behavior still depends on the condition of the rest of the wheel-and-suspension system.

B78-14 or C78-14 tires on a collector 1978 American Motors Gremlin should be kept properly inflated, inspected regularly for cracking, cuts, bulges, and uneven wear, and checked for slow air loss if the car is not driven often. Low-use collector cars benefit from more frequent visual inspection than mileage alone might suggest.

Storage conditions matter almost as much as road use on an older vehicle. Keeping the Gremlin away from prolonged sun, heat, moisture, and ozone sources can help protect tire condition over time. It is also helpful to recheck the tires before each driving season so age-related issues are caught early, even when tread still looks usable.