The 1978 Dodge Magnum XE came at a moment when Chrysler’s personal luxury coupes blended long-hood styling, formal trim, and big American road-car presence with a distinctly late-1970s feel. For owners restoring one or getting a driver back on the road, tire choice is closely tied to the car’s exact engine configuration. The 1978 Dodge Magnum XE uses 15-inch radial fitments in FR78-15, GR78-15, or HR78-15 depending on sub-model. That means the decision is less about bias-ply versus radial and more about confirming the right alphanumeric radial size, then selecting a tire that suits the car’s stance, appearance, and intended road use.
Which Tire Size Is Right for The 1978 Dodge Magnum XE
Three primary tire sizes apply to the 1978 Dodge Magnum XE, and all of them are radial fitments for 15-inch wheels. The key step is identifying the exact engine-based sub-model first, since tire size varies across the covered configurations. Once that is confirmed, the real choice becomes selecting the right alphanumeric radial size for the car’s existing wheel setup and desired period-style presentation.
FR78-15 is a vintage alphanumeric radial size in which the lettered prefix identifies the tire’s size class, the R marks radial construction, the 78 refers to the profile family, and 15 is the rim diameter in inches. On the 1978 Dodge Magnum XE, this size belongs to certain 318 and 360 engine configurations rather than every version of the car. Because it is already a radial-format fitment, the focus stays on preserving the proper size and overall look. FR78-15 is worth considering when the car’s specific setup calls for the narrower of the Magnum XE fitments.
GR78-15 follows the same vintage alphanumeric radial system, with the letter showing the size class, R identifying radial construction, the 78 marking the profile family, and 15 indicating the wheel diameter. This size appears across both covered Magnum XE sub-model groupings, making it the overlap fitment within the 1978 range. For buyers, that makes GR78-15 an important size to confirm before moving into product selection or appearance preferences. It suits owners who want to stay with the middle fitment used on multiple engine-based configurations of the Magnum XE.
HR78-15 is also a vintage alphanumeric radial, using the letter to indicate size class, R for radial construction, 78 for the profile family, and 15 for the rim diameter. On the 1978 Dodge Magnum XE, this size is associated with the 400-engine configuration rather than the smaller-engine versions. That makes exact sub-model identification especially important before choosing a tire in this size. HR78-15 is the fitment to evaluate when the car carries the larger-engine setup and the goal is to maintain the proper 15-inch radial specification for that configuration.
Sub-model fitment matters on the 1978 Dodge Magnum XE because tire size changes with engine configuration, even though all versions use 15-inch radial tires. Confirming whether the car is a 318 and 360 engine model or a 400 engine model is the first step before choosing among the applicable alphanumeric radial sizes.
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1978 Dodge Magnum XE w/318 & 360 Eng.
The 1978 Dodge Magnum XE w/318 & 360 Eng. uses radial fitments in FR78-15 or GR78-15 on 15-inch wheels. That means tire selection starts with confirming which of those two sizes matches the car’s actual wheel and fitment setup before comparing period-style replacement choices.
The 1978 Dodge Magnum XE w/400 Eng. uses 15-inch radial fitments in GR78-15 or HR78-15. For this sub-model, the important step is verifying which of those two sizes is on the car now, then choosing a tire that maintains the correct late-1970s radial format and overall fitment.
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 1978 Dodge Magnum XE usually center on which of the three 15-inch radial sizes belongs on a specific engine configuration, how vintage alphanumeric sizing works, and what to inspect before putting a restored or long-stored car back on the road.
Tire Size & Fitment
What tire size fits a 1978 Dodge Magnum XE?
The 1978 Dodge Magnum XE uses one of three primary tire sizes: FR78-15, GR78-15, or HR78-15. All three are radial fitments for 15-inch wheels, but they do not apply to every version of the car. The 318 and 360 engine configuration uses FR78-15 or GR78-15, while the 400 engine configuration uses GR78-15 or HR78-15.
The first step is confirming the exact engine-based sub-model and then checking what size is actually on the car now. On a collector car, wheel changes over the years are common, so the sidewall size, wheel diameter, and overall clearance should all be verified before choosing a replacement tire.
What size rim does a 1978 Dodge Magnum XE use?
The covered tire fitments for a 1978 Dodge Magnum XE all use a 15-inch rim diameter. FR78-15, GR78-15, and HR78-15 each mount on a 15-inch wheel, which keeps rim diameter simple even though the car has more than one possible tire size depending on engine configuration.
That does not mean every 15-inch wheel is automatically the right wheel for every Magnum XE tire size. Width, previous wheel changes, and the tire size already fitted to the car should still be checked, especially on restored cars or examples that may have had aftermarket wheels installed at some point.
Why does the 1978 Dodge Magnum XE have more than one tire size?
The 1978 Dodge Magnum XE has more than one tire size because fitment varies by engine-based sub-model. The 318 and 360 engine version uses FR78-15 or GR78-15, while the 400 engine version uses GR78-15 or HR78-15. GR78-15 overlaps both configurations, but the smaller and larger companion sizes differ.
That makes the sub-model and the car’s present wheel-and-tire setup more important than the year and model name alone. A Magnum XE that has been restored, modified, or simply re-tired over time may no longer wear its expected size, so checking the existing sidewall marking and wheel diameter helps prevent ordering the wrong fitment.
Choosing the Right Tire
What should I consider when choosing a FR78-15, GR78-15, or HR78-15 tire for a 1978 Dodge Magnum XE?
Start with the exact tire size that belongs on the car’s engine-based configuration, since a 1978 Dodge Magnum XE does not use one universal fitment. FR78-15, GR78-15, and HR78-15 are all 15-inch radial sizes, but each serves a different place within the Magnum XE range.
After size is confirmed, focus on whether the tire suits the car’s intended use and appearance. A restoration-minded owner may want a tire that preserves a late-1970s radial look, while a regular driver may be more concerned with keeping the correct size on the correct wheel and maintaining proper clearance around fenders and suspension parts.
How do I choose between the available FR78-15, GR78-15, and HR78-15 tires for a 1978 Dodge Magnum XE?
The main choice is not between three interchangeable sizes, but between the one or two sizes that apply to the car’s specific sub-model. A 318 and 360 engine Magnum XE uses FR78-15 or GR78-15, while a 400 engine car uses GR78-15 or HR78-15, so the car’s configuration narrows the decision first.
Once the correct fitment range is clear, compare the tire already on the car with the wheel diameter and available space in the wheel opening. That helps keep the selection grounded in the actual setup, which is especially useful if the car has seen wheel changes, suspension work, or long-term storage between tire replacements.
What tire series are available for the 1978 Dodge Magnum XE?
The 1978 Dodge Magnum XE uses vintage alphanumeric radial sizes, so the relevant tire series question starts with matching FR78-15, GR78-15, or HR78-15 to the car’s exact configuration. The important distinction on this page is the size family and construction type rather than a mix of unrelated modern sizing systems.
For most Magnum XE owners, series selection matters only after the correct size has been established. A tire that visually suits a formal late-1970s personal luxury coupe can be the right direction, but the tire still needs to match the proper 15-inch radial fitment and the actual wheel setup already on the vehicle.
Restoration & Appearance
Which tire should I choose for a period-style 1978 Dodge Magnum XE?
A period-style choice for a 1978 Dodge Magnum XE starts with the correct alphanumeric radial size for the car’s engine-based configuration: FR78-15, GR78-15, or HR78-15. Staying within that late-1970s radial sizing format helps preserve the visual character the Magnum XE would typically carry as a personal luxury coupe of its era.
Appearance should follow fitment, not replace it. Once the proper size is confirmed, look for a tire whose tread and sidewall presentation complement the car’s overall restoration direction, while keeping in mind that exact originality claims should be checked against marque references, historical photos, or other vehicle-specific documentation.
Does correct tire fitment matter for a 1978 Dodge Magnum XE restoration?
Correct tire fitment matters because tire size strongly affects how a restored 1978 Dodge Magnum XE sits and presents. Using the proper FR78-15, GR78-15, or HR78-15 radial size for the right engine-based configuration helps maintain the car’s intended proportions and avoids a visibly mismatched look at the wheel openings.
Fitment also matters mechanically, especially on older restorations that may no longer have their original wheels. Even when the wheel is still 15 inches in diameter, the wrong size choice can complicate clearance and overall stance, so the existing setup should be checked carefully before a new tire is selected for the restoration.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 1978 Dodge Magnum XE?
Yes. Even though the 1978 Dodge Magnum XE uses 15-inch radial fitments, modifications can change whether FR78-15, GR78-15, or HR78-15 remains appropriate for the car’s current setup. Aftermarket wheels, altered ride height, suspension work, or body changes can all affect clearance and the space available around the tire.
A modified Magnum XE should be checked at the wheel itself rather than relying only on the original fitment range. Wheel diameter, wheel width, steering clearance, and fender clearance are all worth confirming before replacement, particularly if the car has been lowered, has non-stock wheels, or has seen previous restoration changes.
What should I inspect before driving a 1978 Dodge Magnum XE on new tires?
Before road use, inspect the wheels for damage, confirm the wheel diameter matches the intended 15-inch fitment, and make sure the selected tire size matches the car’s actual configuration. On the vehicle itself, look for adequate clearance at the fenders, steering components, and suspension so the new tires are not crowded anywhere in travel.
A broader safety check is just as important on a long-stored collector car. Tire pressure, lug hardware, brake condition, alignment behavior, and any signs of rubbing during a short test drive should all be reviewed, since a fresh set of tires cannot compensate for worn suspension parts or wheel issues already present.
How should FR78-15, GR78-15, or HR78-15 tires on a collector 1978 Dodge Magnum XE be maintained?
Collector-car tires should be inspected regularly even if the 1978 Dodge Magnum XE is driven only occasionally. Check pressure, tread condition, cuts, bulges, cracking, and any air loss, and keep an eye on how evenly the tires wear across the tread, since unusual wear can point to alignment or suspension issues.
Storage habits matter almost as much as mileage on a low-use car. Keeping the Magnum XE away from prolonged sunlight, moisture, excessive heat, and ozone sources can help protect the tires between drives, while periodic movement and routine visual checks make it easier to catch age-related problems before a longer trip.
