The 1966 Sunbeam Imp belongs to the era when small-displacement European cars delivered lively character through light weight, compact dimensions, and clever packaging. For owners today, that makes tire choice especially important because a small car like the Imp responds noticeably to changes in construction and profile. The 1966 Sunbeam Imp uses either a 155R12 radial or a 5.50-12 bias-ply tire, both on 12-inch rims. That opens the door to a more traditional period-style presentation or a more modern radial format within the covered fitments. The right choice depends on how the car is set up, how you want it to look, and how closely you want to follow its vintage driving character.
Which Tire Size Is Right for The 1966 Sunbeam Imp
The 1966 Sunbeam Imp uses two primary tire sizes, and the difference is construction rather than wheel diameter, since both fit a 12-inch rim. The key first step is confirming whether your car is staying with the traditional 5.50-12 bias-ply setup or using the 155R12 radial fitment, because that choice shapes the tire’s appearance, feel, and selection path.
155R12 is a Euro-metric radial size in which 155 identifies the nominal section width in millimeters, R indicates radial construction, and 12 identifies the wheel diameter in inches. On a 1966 Sunbeam Imp, this size represents the radial fitment route for owners who want a more modern tire construction while remaining in the covered 12-inch format. The main decision here is not decoding the size, but confirming wheel condition and overall setup before choosing a radial. It is a useful option for an Imp that is driven regularly and selected with close attention to wheel compatibility and clearance.
5.50-12 is a numeric bias-ply size in which 5.50 refers to the nominal section width in inches and 12 is the wheel diameter. For the 1966 Sunbeam Imp, this is the traditional bias-ply fitment and it suits owners who want a more vintage tire presentation and a setup that stays closer to period construction. Numeric bias-ply sizing is common on compact cars of this era, so the code reflects an older sizing system rather than a modern metric format. It is the size to evaluate when restoration appearance and classic driving character are central to the project.
Fitment is straightforward here because the covered 1966 Sunbeam Imp sub-model shares the same pair of 12-inch tire fitment paths. Checking the exact sub-model still matters so the tire decision stays focused on construction choice rather than assumptions about another Imp configuration.
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1966 Sunbeam Imp Base
The 1966 Sunbeam Imp Base uses the same two covered tire approaches: 155R12 in radial construction and 5.50-12 in bias-ply construction. That makes the selection process less about finding a different size and more about deciding whether the car should retain a traditional bias-ply look or move to a radial setup on the same 12-inch wheel diameter.
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 1966 Sunbeam Imp usually want clarity on its two covered tire sizes, the difference between radial and bias-ply fitment, and what to inspect before putting a light vintage compact back on the road.
Tire Size & Fitment
What tire size fits a 1966 Sunbeam Imp?
A 1966 Sunbeam Imp uses two covered tire sizes: 155R12 in radial construction and 5.50-12 in bias-ply construction. Both sizes fit a 12-inch rim, so the fitment question is less about wheel diameter and more about which construction type matches the way the car is equipped and the kind of driving or presentation you want.
That means the next step is confirming the actual wheel setup on the car and deciding whether you want a traditional bias-ply layout or a radial alternative. If the car has been modified over the years, check wheel width, tire clearance, and overall condition before assuming either size is appropriate for the current setup.
What size rim does a 1966 Sunbeam Imp use?
The covered tire fitments for a 1966 Sunbeam Imp use a 12-inch rim diameter. Both the 155R12 radial and the 5.50-12 bias-ply size are built around that same 12-inch wheel diameter, which keeps the main fitment decision centered on construction rather than moving between different rim diameters.
Rim diameter is only one part of the check, especially on a vintage small car. It is still important to confirm the actual wheels on the vehicle, since older cars are sometimes fitted with replacement wheels that differ in width or profile. A tire can match the wheel diameter and still require closer review for proper compatibility and clearance.
Does the 1966 Sunbeam Imp Base use the same tire size?
Yes. The 1966 Sunbeam Imp Base uses the same covered tire sizes as the model core: 155R12 as a radial option and 5.50-12 as a bias-ply option. Both are 12-inch fitments, so the Base model does not introduce a separate rim diameter or a unique size that changes the basic tire search.
For an owner, that simplifies the process because the real question becomes which construction best suits the car’s current use and appearance goals. It is still wise to inspect the actual wheels and any prior modifications, since an older Imp may no longer be running the same setup it would have used decades ago.
Bias-Ply & Radial Options
Is 5.50-12 a bias-ply or radial tire for the 1966 Sunbeam Imp?
On a 1966 Sunbeam Imp, 5.50-12 is a bias-ply tire size. It uses an older numeric sizing system in which the first number refers to nominal section width and the final number identifies the 12-inch rim diameter. That makes it the traditional construction choice among the covered fitments for this car.
Choosing 5.50-12 usually means keeping a more vintage-style tire presentation and a driving feel associated with bias-ply construction. Before selecting it, confirm that the car is still set up for that type of tire and that wheel condition, suspension condition, and available clearance all support the intended use of the vehicle.
Is 155R12 a bias-ply or radial tire for the 1966 Sunbeam Imp?
For the 1966 Sunbeam Imp, 155R12 is a radial tire size. The 155 denotes nominal section width in millimeters, the R indicates radial construction, and 12 identifies the rim diameter in inches. It is the covered radial fitment path for owners who want to stay with a 12-inch tire while using a more modern construction type.
That difference matters because moving from bias-ply to radial is more than a change in labeling. The car’s wheels, remaining clearance, and overall setup should all be checked before making the switch, especially on a lightweight vintage compact where tire construction can noticeably affect the way the car feels on the road.
Should I use bias-ply or radial tires on a 1966 Sunbeam Imp?
A 1966 Sunbeam Imp can be approached either with the 5.50-12 bias-ply fitment or the 155R12 radial fitment. Bias-ply usually appeals to owners aiming for a more traditional period-style presentation, while the radial option appeals to owners who want a modern tire construction within the covered 12-inch size range.
The better choice depends on the car’s mission rather than a blanket rule. A restoration-oriented Imp may lean toward the bias-ply route, while a regularly driven car may lead you toward the radial path. Either way, confirm wheel compatibility, inspect suspension and steering components, and check clearances before committing to one construction.
Choosing the Right Tire
What should I consider when choosing a tire for a 1966 Sunbeam Imp?
Start with the two covered fitments for the 1966 Sunbeam Imp: 155R12 radial and 5.50-12 bias-ply. The main decision is which construction suits the car’s current setup, intended road use, and visual character. Since both sizes use a 12-inch rim, the choice is driven more by tire type and presentation than by wheel diameter.
After that, focus on the condition of the actual wheels and the way the car will be used. A restoration-minded Imp may favor the bias-ply route, while a driver-oriented car may point toward radial construction. It also helps to inspect suspension condition and confirm that no prior wheel changes altered the fitment requirements.
How do I choose between the available 155R12 and 5.50-12 tires for a 1966 Sunbeam Imp?
The first step is deciding whether the car should stay with 5.50-12 bias-ply construction or use the 155R12 radial fitment. Those sizes reflect two different tire formats, so the choice is not simply one label versus another. It affects how the Imp presents visually and how closely the tire setup follows a more traditional vintage layout.
Once construction is settled, compare the actual wheel setup on the car and think about how often the Imp will be driven. A car built around period-style restoration goals may call for the bias-ply size, while a regularly used road car may justify the radial route. Clearance, wheel condition, and suspension health should all be reviewed before final selection.
What matters most when selecting a 12-inch tire for a 1966 Sunbeam Imp?
What matters most is matching the tire to the car’s intended setup, not simply matching the 12-inch rim diameter. The 1966 Sunbeam Imp uses two covered 12-inch sizes, but one is a radial metric fitment and the other is a traditional numeric bias-ply size. That makes construction type the central selection factor.
A careful choice starts by deciding whether the Imp is meant to preserve a period-style feel or serve as a more frequent road car. From there, inspect the wheels for condition and verify that any past changes to wheels, ride height, or suspension have not altered the clearances needed for the selected tire size and construction.
Restoration & Appearance
Which tire should I choose for a period-style 1966 Sunbeam Imp?
For a period-style 1966 Sunbeam Imp, the 5.50-12 bias-ply fitment is the natural starting point because it uses the traditional numeric sizing and bias-ply construction associated with many compact cars of the era. It gives the restoration process a more vintage tire format than the metric radial alternative.
That does not automatically make every 5.50-12 tire the right historical answer for every project. Owners pursuing a highly exact restoration should compare tire details against marque references, period photography, or other vehicle-specific history. For many drivers, though, the bias-ply size is the clearest route to a traditional visual presentation.
Does correct tire fitment matter for a 1966 Sunbeam Imp restoration?
Yes, correct tire fitment matters on a 1966 Sunbeam Imp restoration because the tire has a strong effect on stance, visual balance, and the overall character of a small vintage car. Staying with the covered 12-inch fitments and choosing the appropriate construction helps keep the finished car aligned with its era and intended look.
It also matters mechanically, since restoration work often brings old wheels, suspension parts, and body clearances back into focus. Even if the goal is mainly appearance, the tire still needs to suit the actual wheel and vehicle setup. A careful fitment check helps avoid spoiling the restoration with a tire choice that looks or fits out of place.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 1966 Sunbeam Imp?
Yes. Modifications can change tire fitment on a 1966 Sunbeam Imp even when the tire still uses a 12-inch rim diameter. Replacement wheels, altered wheel widths, suspension changes, and body or fender work can all affect how a 155R12 radial or 5.50-12 bias-ply tire sits on the car and whether it has adequate clearance.
That is especially important on a compact vintage vehicle where available space can be tight. If the Imp has aftermarket wheels or a changed ride height, check steering clearance, fender clearance, and wheel condition before selecting tires. Small differences in setup can matter, so the car should be evaluated as it sits now, not as it left the factory.
What should I inspect before driving a 1966 Sunbeam Imp on new tires?
Before driving a 1966 Sunbeam Imp on new tires, inspect the wheels for damage or corrosion, make sure the tire size and construction match the intended setup, and check for adequate clearance at the fenders and steering components. It is also wise to confirm that suspension and steering parts are in sound condition before regular road use resumes.
A vintage small car can feel very sensitive to neglected chassis parts, so tires should not be treated as the only item needing attention. Look over tread seating, watch for air loss after installation, and verify inflation is appropriate for the tires being used. A short test drive followed by a second inspection helps catch issues early.
How should tires on a collector 1966 Sunbeam Imp be maintained?
Tires on a collector 1966 Sunbeam Imp should be checked regularly for inflation, tread condition, sidewall cracking, bulges, cuts, and any signs of air loss. Cars that spend long periods parked deserve extra attention because age and storage conditions can affect the tire even when tread wear remains low.
Good storage habits help preserve both radial and bias-ply tires on a lightly used Imp. Keep the car away from prolonged sunlight, heat, moisture, and ozone sources, and inspect the tires before every meaningful drive rather than assuming they are fine because the mileage is low. Older collector cars reward routine visual checks and cautious road preparation.
