The 1966 Morgan Plus 4 sits squarely in the tradition of lightweight British sports cars, combining pre-war styling cues with lively postwar road manners that still appeal to drivers who value feel over excess. Tire choice matters here because the car bridges old and newer sizing conventions. Depending on sub-model, the 1966 Morgan Plus 4 uses either 560-15 or 590-15 bias-ply tires, or 155R15 or 165R15 radial tires, all on 15-inch rims. That opens the door to blackwall, narrow whitewall, and wide whitewall presentations across several vintage and classic radial series. The right choice depends on whether the goal is a traditional look, a radial driving setup, or a careful balance of both.
Which Tire Size Is Right for The 1966 Morgan Plus 4
The 1966 Morgan Plus 4 uses four primary tire sizes, and the right one depends first on identifying whether the car is a Base or Plus sub-model. All of the fitments use a 15-inch rim, but they split between bias-ply and radial construction, so the real decision is not just size, but also whether the car is staying with a traditional bias-ply setup or using the radial fitment tied to that sub-model.
155R15 is a Euro-metric radial size in which 155 refers to the tire's nominal section width in millimeters, R indicates radial construction, and 15 is the rim diameter in inches. On the 1966 Morgan Plus 4, this is one of the radial fitments and suits buyers who want a tire built in a more modern radial format while staying within the car's 15-inch wheel setup. Available choices include Firestone, Michelin, Avon, and Vredestein, primarily in blackwall form across series such as F560 Radial, Michelin X, XAS, CR6ZZ, Snow Classic, and Sprint Classic. This size is worth evaluating when the car is set up for the Base-model radial fitment and the goal is a proper radial selection rather than a bias-ply appearance.
560-15 is a numeric bias-ply size in which 5.60 represents the nominal section width in inches and 15 identifies the wheel diameter. For the 1966 Morgan Plus 4, it serves as the traditional bias-ply fitment paired with the same 15-inch rim diameter used by the radial alternatives. Product choices include Firestone, US Royal, Coker Classic, and Pro-Trac, with blackwall, narrow whitewall, and wide whitewall sidewall treatments available across classic bias-ply series. This size makes sense when maintaining a vintage tire presentation is part of the goal and the car's wheel width and overall setup are being kept in line with that bias-ply fitment.
165R15 is a Euro-metric radial size with a 165-millimeter nominal section width, radial construction, and a 15-inch rim diameter. On the 1966 Morgan Plus 4, this radial fitment belongs to the Plus sub-model and gives the buyer a broad range of classic radial choices within the original wheel diameter. Available options include Coker Classic, American Classic, Firestone, BFGoodrich, Michelin, and Vredestein, with blackwall, narrow whitewall, and wide whitewall styles offered across series such as F560 Radial, Silvertown Radial, Michelin XZX, Michelin XAS, Star Series, Snow Classic, and Sprint Classic. This size is the one to evaluate when the car is a Plus-model radial setup and appearance choice matters alongside construction.
590-15 is a numeric bias-ply size where 5.90 indicates nominal section width in inches and 15 names the wheel diameter. For the 1966 Morgan Plus 4, this is the larger of the two primary bias-ply fitments and is associated with the Plus sub-model's 15-inch wheel package. Choices in this size include BFGoodrich and Avon, with blackwall and wide whitewall versions available in classic bias-ply series such as Silvertown Classic Bias Ply and Turbospeed Mk4. This size deserves a close look when the car is being kept on its bias-ply configuration and the buyer wants to match tire construction and visual character to that specific Plus setup.
Sub-model matters on the 1966 Morgan Plus 4 because the Base and Plus do not share the same tire sizes. Both use 15-inch rims, but each sub-model has its own bias-ply and radial fitments, so confirming the exact version of the car is the first step before comparing brands, sidewall styles, or radial alternatives.
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1966 Morgan Plus 4 Base
The 1966 Morgan Plus 4 Base uses the smaller fitment pair, with a choice between a radial setup and a traditional 560-15 bias-ply setup on 15-inch wheels. That means tire selection centers on whether the car is being kept with a vintage bias-ply presentation or matched to the Base-model radial size for road use and product variety.
The 1966 Morgan Plus 4 Plus uses the larger fitment pair, combining a 15-inch radial option with a 590-15 bias-ply alternative. That distinction matters because the Plus opens different product choices and radial-equivalent paths, so the tire decision should follow the car's exact sub-model and current wheel setup.
Bias-Ply to Radial Tire Conversion for the 1966 Morgan Plus 4
The 1966 Morgan Plus 4 has radial-equivalent paths for both primary bias-ply sizes. For 560-15, the available radial equivalents are 155R15 as an 80-series metric radial and 560R15 as a bias-look radial; for 590-15, the equivalents are 165R15 as an 80-series metric radial, P165/75R15 as a 75-series P-metric radial, and P175/70R15 as a 70-series P-metric radial. These options differ by sizing convention and profile approach, with 560R15 offering the most traditional visual format. The stated rim-width range for the bias-ply-to-radial comparison is 4 to 5 inches, and wheel size, dimensions, and clearance should still be checked before conversion.
Modern Radial Equivalents
155R15
Equivalent 80-series Metric Radial (560-15)
560R15
Bias-look Radial Equivalent (560-15)
165R15
Equivalent 80-series Metric Radial (590-15)
P165/75R15
Equivalent P-metric 75-series Radial (590-15)
P175/70R15
Equivalent P-metric 70-series Radial (590-15)
Important Considerations When Replacing Bias Ply With Radial
Compare overall diameter and section width carefully to ensure proper fit.
Verify recommended rim range (4-5 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.
Best 1966 Morgan Plus 4 Tires for Sale
Available 1966 Morgan Plus 4 tires span bias-ply and radial construction across 15-inch fitments from Firestone, Michelin, Avon, Vredestein, BFGoodrich, American Classic, US Royal, Coker Classic, and Pro-Trac. Depending on size, the product grid includes blackwall, narrow whitewall, and wide whitewall choices across several classic tire series.
These 1966 Morgan Plus 4 tire FAQs focus on the Base-versus-Plus size split, 15-inch rim fitment, bias-ply and radial choices, available equivalents, appearance options, and the checks that matter before road use.
Tire Size & Fitment
What tire size fits a 1966 Morgan Plus 4?
A 1966 Morgan Plus 4 can use 155R15, 560-15, 165R15, or 590-15, depending on sub-model and construction choice. The Base uses 155R15 radial or 560-15 bias-ply, while the Plus uses 165R15 radial or 590-15 bias-ply. All of these fitments are built around a 15-inch rim diameter.
The important next step is confirming whether the car is a Base or a Plus before selecting a tire. After that, decide whether the car is staying with a traditional bias-ply setup or using the radial fitment tied to that sub-model, then compare wheel width, sidewall style, and overall tire type against the car's current configuration.
What size rim does a 1966 Morgan Plus 4 use?
The 1966 Morgan Plus 4 uses a 15-inch rim diameter across all of its primary tire fitments. That applies whether the car is running 560-15 or 590-15 bias-ply tires, or 155R15 or 165R15 radial tires.
Even with the same rim diameter, width still matters when comparing specific tires. Some products in these sizes are intended for relatively narrow wheel widths, so a Morgan that has had wheel changes over the years should have the actual rim width confirmed before choosing between the available bias-ply, metric radial, or whitewall options.
Do all 1966 Morgan Plus 4 sub-models use the same tire size?
No. The 1966 Morgan Plus 4 Base and Plus use different tire-size pairings. The Base uses 155R15 radial or 560-15 bias-ply, while the Plus uses 165R15 radial or 590-15 bias-ply.
That difference means tire selection should start with the exact sub-model, not just the year and model name. A buyer looking at a car that has been restored or modified should also verify the current wheel and tire setup, because the presence of a 15-inch rim alone does not tell you which of the two sub-model fitment pairs belongs on the car.
Bias-Ply & Radial Options
Should I use bias-ply or radial tires on a 1966 Morgan Plus 4?
A 1966 Morgan Plus 4 can be found with either bias-ply or radial primary fitments, depending on sub-model. The Base uses 560-15 bias-ply or 155R15 radial, and the Plus uses 590-15 bias-ply or 165R15 radial. That means the construction decision is built into the actual fitment choices for the car.
The better choice depends on what matters most for the car. A restoration-oriented owner may prefer the visual character of a bias-ply tire, while another owner may want to stay with the radial size tied to the same sub-model. Wheel width, clearance, and the current setup should be checked before changing from one construction type to the other.
What radial tire sizes are equivalent to 560-15 and 590-15 on a 1966 Morgan Plus 4?
For 560-15, the radial equivalents are 155R15 as an 80-series metric radial and 560R15 as a bias-look radial. For 590-15, the radial equivalents are 165R15 as an 80-series metric radial, P165/75R15 as a 75-series P-metric radial, and P175/70R15 as a 70-series P-metric radial.
Those equivalent sizes give a 1966 Morgan Plus 4 owner more than one path from a bias-ply format to a radial one, but they are not automatic substitutes. The recommended rim-width range shown for the bias-ply comparisons is 4 to 5 inches, and the final choice should still be checked against actual wheel width, tire dimensions, and body or steering clearance.
Can I use a bias-look radial on a 1966 Morgan Plus 4?
Yes, a bias-look radial equivalent is available for the 560-15 fitment on the 1966 Morgan Plus 4. That equivalent size is 560R15, which gives the buyer a radial construction option in a format intended to preserve a more traditional tire presentation.
This route can be useful when the goal is to keep a vintage visual impression without staying with a true bias-ply tire. It still needs the same careful checks as any other conversion, especially wheel width, overall tire fit within the car's fenders and steering range, and whether the tire's appearance matches the style direction of the particular Morgan.
Choosing the Right Tire
What should I consider when choosing a 1966 Morgan Plus 4 tire?
Start with the exact sub-model and the correct primary size. A 1966 Morgan Plus 4 Base uses 155R15 radial or 560-15 bias-ply, while the Plus uses 165R15 radial or 590-15 bias-ply. After size, the main variables are construction type, wheel-width compatibility, sidewall style, tire series, and the sort of look the car is meant to carry.
A careful choice balances fitment and character. Some owners want blackwall radials for a classic sports-car presentation, while others want bias-ply tires or whitewalls to support a more traditional restoration theme. Since many Morgans have seen wheel changes over time, confirming the actual rim width and current setup is just as important as choosing the correct nominal tire size.
What sidewall styles are available for 1966 Morgan Plus 4 tires?
The available sidewall styles for 1966 Morgan Plus 4 tires include blackwall, narrow whitewall, and wide whitewall, depending on the size and tire series. Radial options are mostly blackwall in 155R15, while 165R15 opens blackwall plus both narrow and wide whitewall choices. The bias-ply sizes also include blackwall and whitewall variations.
Sidewall style affects the car's visual impression as much as the construction choice does. A blackwall usually keeps the look understated and sporting, while narrow or wide whitewalls shift the car toward a more formal vintage presentation. The right approach depends on the sub-model, the period look being pursued, and whether the tire is part of a fresh restoration or a road-focused setup.
What brands offer tires for the 1966 Morgan Plus 4?
Brands available for the 1966 Morgan Plus 4 include Firestone, Michelin, Avon, Vredestein, BFGoodrich, American Classic, US Royal, Coker Classic, and Pro-Trac. Brand availability changes by size, with the broadest radial selection in 165R15 and a more focused set of offerings in the two bias-ply sizes.
Brand choice should follow fitment and tire type first, then visual and specification details. Some sizes emphasize blackwall sport-oriented radial series, while others include classic bias-ply and whitewall options better suited to a traditional presentation. Once the correct sub-model size is confirmed, compare the brands within that size for rim-width compatibility, sidewall treatment, and series character.
Restoration & Appearance
Which tire should I choose for a period-style 1966 Morgan Plus 4?
A period-style 1966 Morgan Plus 4 usually starts with choosing the correct sub-model size and then deciding whether the car should present as a bias-ply or radial-equipped example. The Base uses 560-15 bias-ply or 155R15 radial, while the Plus uses 590-15 bias-ply or 165R15 radial, so the period-style decision begins with the car's exact fitment path.
Bias-ply tires generally deliver the most traditional visual impression, especially when paired with blackwall or whitewall treatments that suit the car's presentation. A radial can still look very much at home on a Morgan, particularly in classic Euro-metric sizing. When exact originality matters, compare the tire choice with marque references and the individual car's restoration goals before settling on a final setup.
How does tire construction affect the appearance of a restored 1966 Morgan Plus 4?
On a restored 1966 Morgan Plus 4, tire construction changes the car's visual tone as well as its fitment language. A 560-15 or 590-15 bias-ply gives the car a more traditional vintage presentation, while a 155R15 or 165R15 radial reflects the classic metric-radial look that also suits the era and shape of the Morgan.
Sidewall treatment then sharpens that look. Blackwalls keep the appearance simple and sporting, while narrow or wide whitewalls create a more decorative, restoration-oriented effect in the sizes that offer them. The most convincing result usually comes from keeping the construction, sidewall, and wheel setup in visual agreement rather than mixing styles that pull the car in different directions.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 1966 Morgan Plus 4?
Yes. A 1966 Morgan Plus 4 may still use its original-style 15-inch wheel layout, but aftermarket wheels, suspension changes, altered ride height, or bodywork differences can all affect how a tire sits and clears. That matters whether the car is using a bias-ply size such as 560-15 or 590-15, or a radial size such as 155R15 or 165R15.
Even small changes can alter wheel-width suitability or tire clearance at full steering lock and suspension movement. A Morgan that has been modified should have the actual wheel diameter and width checked first, then the buyer should compare the intended tire against the car's current stance and available space rather than assuming every correct-size 15-inch tire will behave the same way.
What should I inspect before driving a 1966 Morgan Plus 4 on new tires?
Before driving a 1966 Morgan Plus 4 on new tires, inspect the wheels for condition and correct size, confirm proper inflation, and check that the tires seat correctly and clear the body and steering range. It is also wise to look over suspension and steering components, especially on a lightly used collector car that may have sat for long periods.
A road test should begin gently so any rubbing, pull, vibration, or pressure loss can be caught early. The first miles are a good time to recheck inflation and make sure wheel hardware remains secure. On a narrow-bodied sports car like a Morgan, basic clearance and setup checks matter just as much as choosing the right nominal tire size.
How should tires on a collector 1966 Morgan Plus 4 be maintained?
Tires on a collector 1966 Morgan Plus 4 should be inspected regularly for cracking, cuts, bulges, uneven wear, and air loss, even if the car is driven only occasionally. Both bias-ply and radial tires benefit from correct inflation and periodic movement, since long stationary periods can be hard on tires that spend more time stored than driven.
Storage conditions make a real difference on a classic sports car. Keeping the Morgan away from prolonged sunlight, excess heat, moisture, and ozone-producing equipment helps preserve tire condition over time. A pre-drive inspection is especially important before tours or longer runs, because age and storage history can matter as much as tread depth on low-mileage collector vehicles.
