The 1979 Jaguar XJ12C stands apart as a refined grand touring coupe from Jaguar’s late-classic era, blending long-hood elegance with the smooth, high-speed character expected of a V12 British luxury car. Its presence is very different from a stripped-down sports car, and tire choice plays a major role in preserving that composed, substantial feel on the road. This exact model uses an ER70-15 radial tire on a 15-inch rim. With one primary fitment shared across the covered configurations, the main decision centers on selecting the right tire within that size while keeping wheel compatibility, intended use, and the car’s period-style appearance in mind.
Which Tire Size Is Right for The 1979 Jaguar XJ12C
The 1979 Jaguar XJ12C uses one primary tire size: ER70-15, a radial fitment for a 15-inch rim. That same size is used across the covered Base and Base w/alloy wheels configurations, so the question is less about multiple fitments and more about choosing the right ER70-15 tire for the car’s appearance, wheel setup, and road-going use.
ER70-15 is an alphanumeric radial size in which the letter code identifies the tire’s size class, the 70 designates its profile family, and the 15 refers to the wheel diameter in inches. On the 1979 Jaguar XJ12C, this is the primary radial fitment and suits the car’s late-1970s luxury-performance character better than an earlier bias-ply sizing system would. For buyers, the real comparison point is not decoding multiple factory sizes, but choosing an ER70-15 that matches the car’s intended presentation and confirming that the existing 15-inch wheels remain the correct ones on the vehicle.
Tire fitment is straightforward across the covered 1979 Jaguar XJ12C sub-models because both use the same ER70-15 radial size. Checking the exact sub-model still matters, especially when verifying that the car remains on the proper 15-inch wheel setup.
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1979 Jaguar XJ12C Base
The 1979 Jaguar XJ12C Base uses the ER70-15 radial tire size. That keeps selection focused on finding the right tire within that fitment and confirming wheel condition, overall presentation, and intended road use before installation.
The 1979 Jaguar XJ12C Base w/alloy wheels also uses the ER70-15 radial tire size. Even with the same fitment, alloy-wheel cars still deserve a careful check of actual wheel diameter and width before replacing older tires or evaluating different tire designs in the same size.
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 Jaguar XJ12C usually center on the ER70-15 tire size, 15-inch rim fitment, radial construction, period-style tire selection, and the checks worth making before putting a collector Jaguar back on the road.
Tire Size & Fitment
What tire size fits a 1979 Jaguar XJ12C?
The 1979 Jaguar XJ12C uses ER70-15 tires. This is a radial tire size for a 15-inch wheel, and it is the primary fitment for the covered configurations of this model, including the Base and Base w/alloy wheels versions.
That makes fitment selection fairly straightforward, but the car should still be checked carefully before replacement. A collector Jaguar may have had wheels changed over the years, so confirming the actual wheel diameter and overall setup is still important before choosing a new ER70-15 tire.
What size rim does a 1979 Jaguar XJ12C use?
The 1979 Jaguar XJ12C uses a 15-inch rim with its ER70-15 tire fitment. The 15 at the end of the tire size designates the wheel diameter, and that same 15-inch rim diameter applies across the covered sub-models for this vehicle.
Rim diameter is the first item to confirm on any older car that may have seen wheel changes, restoration work, or aftermarket upgrades. Even when the tire size is known, the wheel still needs to match that diameter, and wheel width and overall condition should also be inspected before mounting new tires.
Do all 1979 Jaguar XJ12C sub-models use the same tire size?
Yes. The covered 1979 Jaguar XJ12C sub-models use the same ER70-15 radial tire size. That includes both the Base model and the Base w/alloy wheels configuration, so there is no split fitment among the sub-models shown here.
Shared sizing simplifies the search, but it does not remove the need to inspect the car itself. Alloy wheels, replacement wheels, or older restorations can change what is actually on the vehicle, so it is still smart to verify the present wheel setup before selecting a replacement ER70-15 tire.
Choosing the Right Tire
What should I consider when choosing a ER70-15 tire for a 1979 Jaguar XJ12C?
Start with the correct size and construction. The 1979 Jaguar XJ12C uses an ER70-15 radial on a 15-inch rim, so the first priority is staying within that fitment and selecting a tire that suits the car’s touring-oriented, late-1970s character.
After that, focus on the actual vehicle in front of you. Check that the wheels are still the correct diameter, inspect their condition, and think about whether the goal is a restoration-oriented appearance or regular road use. On an older grand touring coupe, appearance, wheel compatibility, and overall condition matter as much as the size itself.
How do I choose between the available ER70-15 tires for a 1979 Jaguar XJ12C?
Selection within ER70-15 comes down to how the tire supports the way the 1979 Jaguar XJ12C will be used and presented. Since there is one primary size, the comparison is usually about construction details, visual style, and whether the tire suits a preservation-minded car or a driver-oriented car.
A careful buyer should also look beyond the sidewall. Check wheel condition, confirm the car has not been altered in a way that changes fitment needs, and inspect suspension and steering components if the Jaguar has been sitting. A tire that is correct in size still needs to make sense for the vehicle’s actual setup.
What rim-fitment details should I compare when choosing 1979 Jaguar XJ12C tires?
The most important rim-fitment detail is wheel diameter. A 1979 Jaguar XJ12C uses an ER70-15 tire on a 15-inch rim, so any replacement tire must match that wheel diameter before anything else is considered.
Wheel width and overall wheel condition also deserve attention, especially on a car that may have had previous restoration or aftermarket work. Corrosion, bent rims, or non-original wheels can affect how a new tire seats and performs, so measuring and inspecting the actual wheels is a smart step before purchase.
Restoration & Appearance
Which tire should I choose for a period-style 1979 Jaguar XJ12C?
A period-style 1979 Jaguar XJ12C should begin with the correct ER70-15 radial fitment. Using the proper size helps preserve the car’s late-1970s grand touring stance and keeps the overall presentation closer to what buyers expect from a well-sorted XJ12C.
Beyond the size itself, the right choice depends on how exact the restoration needs to be. Some owners want a broadly era-appropriate appearance, while others want the closest possible visual match to their car’s original delivery configuration. When originality matters at a high level, marque references and restoration records are worth consulting.
Does correct tire fitment matter for a 1979 Jaguar XJ12C restoration?
Yes, correct tire fitment matters because tires influence both the appearance and the attitude of the 1979 Jaguar XJ12C. An ER70-15 radial helps maintain the proper visual balance for this large Jaguar coupe and keeps the restoration grounded in the right sizing format for the model.
Fitment also affects how believable the finished car looks to knowledgeable enthusiasts. A wheel or tire choice that drifts too far from the proper size can change the stance and distract from an otherwise careful restoration, so checking the actual wheels and keeping the overall presentation consistent is worthwhile.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 1979 Jaguar XJ12C?
Yes. Even though the 1979 Jaguar XJ12C uses ER70-15 tires on 15-inch rims, modifications can change what actually fits the car today. Aftermarket wheels, altered suspension height, brake changes, or body repairs can all affect clearance and wheel compatibility.
That is why the actual car should be inspected rather than relying only on model-year fitment. A modified XJ12C may need extra attention around wheel width, steering clearance, and fender room, especially if the car has been restored in stages or updated long after it left the factory.
What should I inspect before driving a 1979 Jaguar XJ12C on new tires?
Start with the basics: confirm the wheels are the correct 15-inch diameter, inspect them for damage or corrosion, and make sure the new ER70-15 tires are mounted and balanced properly. Then look at valve stems, lug hardware, and overall tire condition after installation.
A car like the 1979 Jaguar XJ12C also benefits from a broader road-readiness check. Suspension bushings, steering components, alignment, and brake condition all influence how the car feels on fresh tires. On a collector vehicle that has seen limited use, these surrounding systems deserve as much attention as the tires themselves.
How should ER70-15 tires on a collector 1979 Jaguar XJ12C be maintained?
ER70-15 tires on a collector 1979 Jaguar XJ12C should be inspected regularly for cracking, cuts, bulges, uneven wear, and signs of air loss. Tire pressure should be checked consistently, especially on a car that spends long periods parked between drives.
Storage conditions matter too. Keeping the car away from prolonged sunlight, excess heat, moisture, and ozone sources helps protect tire condition over time. A low-mileage collector Jaguar can still have aging tires, so visual inspection and periodic professional evaluation are important even when tread wear appears minimal.
