The 1978 Chevrolet Monza came from an era when compact domestic cars blended everyday usability with a distinctly sporty look, and that mix still shapes how owners approach tire selection today. Whether preserved as a clean survivor or refreshed for regular cruising, the Monza sits right at the point where bias-ply and radial fitments could both matter depending on configuration. The 1978 Chevrolet Monza uses 13-inch tire sizes that include A78-13, B78-13, BR70-13, and BR78-13. That opens the door to traditional bias-ply choices, later-style radial sizing, and selected modern radial equivalents. The key is matching the exact sub-model and wheel setup before deciding between appearance, construction, and road-use priorities.
Which Tire Size Is Right for The 1978 Chevrolet Monza
The 1978 Chevrolet Monza uses four primary tire sizes, and the right one depends on the exact sub-model rather than rim diameter, since each fitment uses a 13-inch wheel. Some Monza configurations use bias-ply sizing, some use radial sizing, and some were offered with either approach. The first step is confirming whether the car is a 4-cylinder, V6, 8-cylinder, or wagon version before comparing tire style, construction, and equivalent options.
A78-13 is a vintage alphanumeric bias-ply size in which the letter identifies the general size class, the 78 points to its profile family, and 13 is the rim diameter in inches. On the 1978 Chevrolet Monza, this is a traditional bias-ply fitment that suits owners aiming to retain an earlier late-1970s tire character on the appropriate 13-inch wheel. Modern radial equivalents are also available in comparable sizing formats, including metric and P-metric alternatives. This size is worth considering when the car calls for A78-13 and the goal is to keep the tire choice aligned with the Monza's original-era fitment style.
B78-13 is also a vintage alphanumeric bias-ply size, with the letter marking the size class, the 78 identifying the profile family, and the final 13 indicating the wheel diameter. For the 1978 Chevrolet Monza, B78-13 appears on several sub-models and represents a bias-ply fitment that can appeal to restoration-minded owners or those wanting a more traditional look and construction. Radial equivalents for this size include both metric and P-metric options, along with a bias-look radial equivalent. It becomes an important size to evaluate when balancing original-style presentation against a possible move toward radial construction.
BR70-13 uses an alphanumeric radial format, where the letter portion identifies the tire class, the R denotes radial construction, the 70 reflects its profile family, and 13 is the rim diameter. On the 1978 Chevrolet Monza, this size gives the buyer a true radial primary fitment rather than a radial substitute for a bias-ply tire. That matters because the decision shifts away from conversion and toward selecting the right radial presentation for the exact sub-model. This size should be confirmed carefully on 8-cylinder Monza applications so the tire matches the vehicle's intended configuration and 13-inch wheel setup.
Fit(s): V6, V6 w/aluminum wheels, Wagon, and Wagon w/aluminum wheels
Construction: Radial|Rim: 13 in
BR78-13 is an alphanumeric radial size, with the R indicating radial construction, the 78 identifying the profile family, and the 13 showing the wheel diameter in inches. For the 1978 Chevrolet Monza, it serves as a primary radial fitment on certain V6 and wagon applications, making it distinct from the bias-ply sizes used elsewhere in the range. Its role is especially relevant for owners who want to stay with the radial fitment tied to those configurations rather than backtracking to a different construction style. Confirming the exact sub-model remains important before treating BR78-13 as the correct starting point.
Sub-model fitment matters on the 1978 Chevrolet Monza because tire choice is not the same across the full range. Some versions use one construction only, while others can be associated with either bias-ply or radial sizing, so identifying the exact engine and wheel configuration comes first.
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1978 Chevrolet Monza 4 Cyl.
The 1978 Chevrolet Monza 4 Cyl. uses bias-ply sizing, with A78-13 and B78-13 associated with this configuration. That makes the main decision less about rim diameter and more about confirming which of the two bias-ply sizes belongs on the car before considering equivalent radial alternatives.
The 1978 Chevrolet Monza 4 Cyl. w/aluminum wheels follows the same basic pattern, using A78-13 and B78-13 bias-ply sizes. Tire selection still depends on confirming the exact size used on the car now, especially if the wheel setup has changed over time.
The 1978 Chevrolet Monza 8 Cyl. uses BR70-13, a primary radial fitment on a 13-inch rim. For this sub-model, the focus is on staying with the proper radial size and checking that the current wheels match the vehicle's intended configuration.
The 1978 Chevrolet Monza 8 Cyl. w/aluminum wheels also uses BR70-13 as its radial tire size. That keeps fitment straightforward, but wheel confirmation still matters on a car that may have seen aftermarket changes during its life.
The 1978 Chevrolet Monza V6 can be associated with either B78-13 bias-ply or BR78-13 radial sizing. This is one of the Monza configurations where construction choice and the car's present wheel and tire setup should be checked carefully before selecting replacements.
The 1978 Chevrolet Monza V6 w/aluminum wheels shares the same B78-13 bias-ply and BR78-13 radial fitment paths. That means the buyer should verify whether the car is being kept in a bias-ply style or already set up around the radial specification.
The 1978 Chevrolet Monza Wagon is tied to B78-13 in bias-ply form and BR78-13 in radial form. Choosing correctly here means confirming the tire construction and size already matched to the wagon's 13-inch wheel setup.
The 1978 Chevrolet Monza Wagon w/aluminum wheels also uses either B78-13 bias-ply or BR78-13 radial sizing. That makes it important to inspect the current wheels and tires closely before moving toward either a restoration-style replacement or a radial-based setup.
Bias-Ply to Radial Tire Conversion for the 1978 Chevrolet Monza
A78-13 and B78-13 each have radial-equivalent choices for buyers comparing modern sizing formats to the original bias-ply fitment. For A78-13, the available equivalents are 165R13 as an 80-series metric radial, P165/75R13 as a 75-series P-metric radial, and P175/70R13 as a 70-series P-metric radial. For B78-13, the choices are 175R13, P175/75R13, P185/70R13, and 650R13 as a bias-look radial. Recommended rim widths are 4 to 5 inches for A78-13 equivalents and 4 to 6 inches for B78-13 equivalents, so wheel size and clearance should be checked before changing formats.
Modern Radial Equivalents
165R13
Equivalent 80-series Metric Radial (A78-13)
P165/75R13
Equivalent P-metric 75-series Radial (A78-13)
P175/70R13
Equivalent P-metric 70-series Radial (A78-13)
175R13
Equivalent 80-series Metric Radial (B78-13)
P175/75R13
Equivalent P-metric 75-series Radial (B78-13)
P185/70R13
Equivalent P-metric 70-series Radial (B78-13)
650R13
Bias-look Radial Equivalent (B78-13)
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
Owners of a 1978 Chevrolet Monza usually need to sort out exact tire size, sub-model fitment, and whether the car belongs on bias-ply or radial tires. The questions below focus on 13-inch Monza fitment, radial equivalents, appearance choices, and practical checks before road use.
Tire Size & Fitment
What tire size fits a 1978 Chevrolet Monza?
The 1978 Chevrolet Monza uses four primary tire sizes: A78-13, B78-13, BR70-13, and BR78-13. All of them fit 13-inch rims, but they do not apply across every Monza configuration. A78-13 and B78-13 are bias-ply sizes, while BR70-13 and BR78-13 are radial sizes.
The right choice depends on the exact sub-model. Four-cylinder cars use A78-13 or B78-13, 8-cylinder cars use BR70-13, and V6 and wagon versions can be associated with either B78-13 or BR78-13. Start by confirming the engine and wheel setup on the car, then match the tire size before comparing sidewall style or construction.
What size rim does a 1978 Chevrolet Monza use?
The tire fitments associated with the 1978 Chevrolet Monza use a 13-inch rim diameter. That applies across A78-13, B78-13, BR70-13, and BR78-13, so the wheel diameter remains consistent even though the tire sizes and constructions vary by sub-model.
That consistency helps narrow the search, but it does not mean every 13-inch tire is automatically suitable. The actual tire size still needs to match the Monza's configuration, and wheel width should also be checked before moving from a bias-ply size into one of the radial equivalent sizes tied to A78-13 or B78-13.
Why does the 1978 Chevrolet Monza have more than one tire size?
The 1978 Chevrolet Monza has more than one tire size because fitment varies by sub-model and construction type. Four-cylinder cars use bias-ply sizes, 8-cylinder cars use a radial size, and V6 and wagon versions can be tied to either a bias-ply or radial fitment depending on configuration.
That means the tire decision starts with identifying the exact Monza version rather than choosing by appearance alone. It is also wise to inspect the wheels currently on the car, since a surviving or restored Monza may no longer wear the same tire construction or size family associated with its original configuration.
Bias-Ply & Radial Options
Is A78-13 a bias-ply or radial tire for the 1978 Chevrolet Monza?
A78-13 is a bias-ply tire size on the 1978 Chevrolet Monza. It uses a vintage alphanumeric bias-ply format and appears on certain 4-cylinder Monza configurations rather than across the full model range.
That matters because A78-13 should be treated as a primary bias-ply fitment, not as a radial size. Buyers considering a change in construction can compare the available radial equivalents, but the wheel setup and the car's present clearance should be reviewed first so the alternative remains compatible with the Monza's 13-inch wheel arrangement.
What radial tire sizes are equivalent to A78-13 and B78-13?
A78-13 has three radial equivalents: 165R13, P165/75R13, and P175/70R13. B78-13 has four radial equivalents: 175R13, P175/75R13, P185/70R13, and 650R13, with 650R13 serving as a bias-look radial alternative.
These sizes give Monza owners a range of radial formats, from Euro-metric and P-metric choices to a more traditional-looking radial option in the B78-13 range. Each equivalent should still be checked against wheel width, overall vehicle setup, and available clearance before treating it as an acceptable alternative to the original bias-ply size.
What should I check before converting my 1978 Chevrolet Monza from bias-ply to radial tires?
Start by confirming the Monza's exact original size, current wheel diameter, and wheel width. A78-13 and B78-13 both have radial equivalents available, but the correct equivalent depends on which bias-ply size belongs on the car and whether the existing 13-inch wheels suit the radial option being considered.
It also helps to inspect steering clearance, fender space, suspension condition, and the tire-to-body relationship at full turn and normal ride height. A Monza that has been modified, lowered, or fitted with different wheels may respond differently than one with a stock-style setup, so conversion should be approached as a fitment check rather than an automatic swap.
Choosing the Right Tire
What should I consider when choosing a tire for a 1978 Chevrolet Monza?
Begin with the exact size and construction tied to the car's sub-model. The 1978 Chevrolet Monza may require a bias-ply size such as A78-13 or B78-13, or a radial size such as BR70-13 or BR78-13, so the first decision is matching the tire to the vehicle's actual configuration.
After size is confirmed, the next considerations are how the car will be used and how closely the tire should reflect a period-style appearance. A restoration-minded owner may stay with bias-ply sizing, while a driver comparing alternatives may look at radial equivalents where available, provided the wheel and clearance checks support the change.
How do I choose between the available A78-13 or B78-13 tires for a 1978 Chevrolet Monza?
Choose between A78-13 and B78-13 by first confirming which size belongs on the specific Monza configuration. Both are bias-ply sizes used on 13-inch rims, but they are not interchangeable simply because they share the same rim diameter.
Once the correct size is established, the decision becomes one of construction strategy and vehicle character. Some owners want to keep the Monza in a traditional bias-ply presentation, while others may compare the radial equivalents tied to that same primary size. Wheel width and the car's existing setup should guide that next step.
What tire series are available for the 1978 Chevrolet Monza?
The 1978 Chevrolet Monza is associated with several distinct tire size families rather than one single tire series. Its fitments span vintage alphanumeric bias-ply sizes like A78-13 and B78-13 as well as alphanumeric radial sizes such as BR70-13 and BR78-13.
For most buyers, that means the useful comparison is not brand hierarchy but size family, construction, and intended appearance. A Monza kept close to its late-1970s character may stay with the primary fitment style, while a car being prepared for more regular road use may lead the owner to compare the available radial equivalent paths.
Restoration & Appearance
Which tire should I choose for a period-style 1978 Chevrolet Monza?
A period-style 1978 Chevrolet Monza usually starts with the primary tire size and construction associated with its exact sub-model. That could mean A78-13 or B78-13 in bias-ply form, or BR70-13 or BR78-13 where a radial fitment is appropriate to the configuration.
The most convincing result comes from matching the tire's size family and overall presentation to the car rather than choosing by wheel diameter alone. Owners pursuing exact restoration detail should compare the car against marque references, period photography, or build-specific documentation before treating any one tire style as the final appearance choice.
How does tire construction affect the appearance of a restored 1978 Chevrolet Monza?
Tire construction changes the visual character of a restored 1978 Chevrolet Monza as much as it changes the driving setup. A bias-ply tire such as A78-13 or B78-13 tends to support a more traditional late-1970s presentation, while BR70-13 and BR78-13 reflect a radial fitment style used on certain Monza configurations.
That distinction matters because a car can look noticeably different even when the rim diameter stays at 13 inches. Owners trying to preserve the Monza's period impression should choose construction only after confirming the sub-model and deciding whether the goal is restoration-oriented authenticity, a later-era road look, or a careful radial alternative.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 1978 Chevrolet Monza?
Yes, modifications can affect tire fitment on a 1978 Chevrolet Monza even when the car still uses a 13-inch wheel. Changes to wheel width, wheel offset, ride height, springs, or suspension parts can alter how an A78-13, B78-13, BR70-13, or BR78-13 tire sits within the fender opening.
That is especially important when the car is being moved from a bias-ply tire to a radial equivalent, since the sizing format may change even if the wheel diameter does not. A careful inspection of steering clearance, suspension travel, and tire-to-body space helps avoid choosing a size that conflicts with the Monza's current setup.
What should I inspect before driving a 1978 Chevrolet Monza on new tires?
Inspect the wheels, lug hardware, valve stems, and the basic condition of the suspension before driving a 1978 Chevrolet Monza on new tires. It is also wise to confirm that the installed tire size matches the car's correct fitment path, since Monza applications vary between bias-ply and radial sizes.
A short walkaround should include checking tire pressure, sidewall condition, tread surface, and visible clearance at the front and rear. Collector cars that see limited use deserve extra attention because age, storage, and long stationary periods can affect both tires and chassis parts even when the tread still appears serviceable.
How should 13-inch tires on a collector 1978 Chevrolet Monza be maintained?
Thirteen-inch tires on a collector 1978 Chevrolet Monza should be kept properly inflated, inspected regularly, and protected from long exposure to sunlight, heat, moisture, and ozone sources. That applies whether the car is running bias-ply sizes like A78-13 or B78-13, or radial sizes such as BR70-13 and BR78-13.
Regular maintenance also means watching for cracking, flat spotting, bulges, cuts, and gradual air loss, especially on a Monza that is driven only occasionally. Seasonal inspections are a smart habit, and any car with older wheels, altered suspension, or long-term storage history deserves another fitment and condition check before extended road use.
