The 1958 Armstrong-Siddeley Sapphire came from the final years of a distinguished British luxury-car tradition, blending formal saloon styling with the kind of road manners expected of an upscale touring car of its era. Tire choice on this car is especially important because both a 670-16 bias-ply fitment and a 185R16 radial fitment are used on the same 16-inch wheel diameter. That gives owners a meaningful decision between traditional construction and a later-style radial setup, with blackwall choices from Firestone, Avon, Michelin, and Vredestein. For a restoration-minded Sapphire, the right selection starts with appearance, construction preference, and careful confirmation of the wheel actually on the car.
Which Tire Size Is Right for The 1958 Armstrong-Siddeley Sapphire
The 1958 Armstrong-Siddeley Sapphire uses two primary tire sizes, and the choice depends first on whether the car is being kept in a traditional 670-16 bias-ply setup or fitted with a 185R16 radial. Both sizes use a 16-inch rim, so the key decision is construction, wheel compatibility, and the type of road feel and appearance you want from the car.
670-16 is a numeric bias-ply size, with 670 indicating an approximate 6.70-inch nominal section width and 16 identifying the wheel diameter. For the 1958 Armstrong-Siddeley Sapphire, it represents the traditional bias-ply construction choice and preserves the period-style sizing format associated with mid-century cars. Blackwall options are available from Firestone and Avon in the Firestone Classic Bias Ply and Turbospeed Mk4 series. This size makes sense when maintaining a more traditional presentation matters, but wheel width and the car’s actual current setup should still be confirmed before replacing older tires.
Sub-model fitment is straightforward here because the covered Sapphire 346 Saloon uses the same two 16-inch tire-size paths found at the model level. Checking the exact sub-model still matters so the car can be matched to the intended bias-ply or radial setup before selecting a tire.
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1958 Armstrong-Siddeley Sapphire 346 Saloon
The 1958 Armstrong-Siddeley Sapphire 346 Saloon uses either a 670-16 bias-ply tire or a 185R16 radial, both on 16-inch rims. That gives the owner a clear choice between a more traditional period-style bias-ply presentation and a radial configuration that should be matched carefully to the wheel and vehicle setup.
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 1958 Armstrong-Siddeley Sapphire Tires for Sale
Available 1958 Armstrong-Siddeley Sapphire tire choices cover both 185R16 radial and 670-16 bias-ply fitments, with blackwall options from Michelin, Avon, Vredestein, and Firestone. The product grid is most useful for comparing construction, tire series, rim-width compatibility, and load-related details within the correct size.
These Armstrong-Siddeley Sapphire tire FAQs focus on the two correct 16-inch sizes, the difference between bias-ply and radial fitments, and the practical checks that matter before choosing tires for restoration or regular road use.
Tire Size & Fitment
What tire size fits a 1958 Armstrong-Siddeley Sapphire?
The 1958 Armstrong-Siddeley Sapphire uses two primary tire sizes: 670-16 in bias-ply construction and 185R16 in radial construction. Both sizes are associated with the Sapphire 346 Saloon, so the main fitment question is not model variation but which construction and wheel setup the car is using now.
That distinction matters because a bias-ply size and a radial size should not be treated as the same tire simply because both fit a 16-inch rim. Check the wheel width, the condition of the suspension and steering, and the amount of clearance around the fender and chassis before deciding which size belongs on your particular Sapphire.
What size rim does a 1958 Armstrong-Siddeley Sapphire use?
The tire sizes used on the 1958 Armstrong-Siddeley Sapphire both mount on 16-inch rims. Whether the car is running a 670-16 bias-ply tire or a 185R16 radial, the wheel diameter remains the same, which simplifies one part of the fitment decision.
Rim diameter is only one part of the picture, though. Radial and bias-ply options can call for different wheel-width ranges, so the actual wheel on the car should be measured and inspected before replacement. That is especially important on collector cars that may have had wheels changed at some point in their service life.
Does the 1958 Armstrong-Siddeley Sapphire 346 Saloon use the same tire size?
The 1958 Armstrong-Siddeley Sapphire 346 Saloon uses the same two size pathways as the model overall: 670-16 for bias-ply fitment and 185R16 for radial fitment. In other words, the sub-model does not introduce a separate rim diameter or a different primary size family.
The practical choice is deciding which construction belongs on the car as it sits today. A Sapphire kept in a traditional bias-ply configuration may call for different tire selection priorities than one already set up around radial use, so wheel width and overall vehicle setup should be checked before settling on either size.
Bias-Ply & Radial Options
Is 670-16 a bias-ply or radial tire for the 1958 Armstrong-Siddeley Sapphire?
670-16 is the bias-ply tire size used on the 1958 Armstrong-Siddeley Sapphire. It is a vintage numeric bias-ply format, and available blackwall choices in this size include Firestone and Avon offerings intended for traditional applications.
That matters because 670-16 represents a different construction approach than 185R16, even though both use 16-inch rims. Owners choosing 670-16 are usually focusing on traditional appearance and period-style sizing, while also needing to confirm that the wheel width and the current chassis setup still suit a bias-ply tire.
Should I use bias-ply or radial tires on a 1958 Armstrong-Siddeley Sapphire?
A 1958 Armstrong-Siddeley Sapphire can be fitted with either 670-16 bias-ply tires or 185R16 radial tires. The correct choice depends on whether the car is being kept in a traditional bias-ply configuration or set up for radial use on compatible 16-inch wheels.
Bias-ply tires usually appeal to owners seeking a more period-style presentation, while radial tires often appeal to owners who want a later tire format within the same wheel diameter. The key is to inspect the actual wheels on the car, confirm width compatibility, and make sure the tire choice suits the car’s clearance and intended driving use.
What should I check before converting my 1958 Armstrong-Siddeley Sapphire from bias-ply to radial tires?
A move from 670-16 bias-ply tires to 185R16 radial tires starts with wheel compatibility. Both sizes use 16-inch rims, but radial products in 185R16 can have different rim-width requirements than traditional bias-ply tires, so the wheel itself needs to be measured rather than assumed.
The next step is checking the car around the tire. Steering clearance, fender clearance, suspension condition, and any previous wheel or ride-height changes should all be reviewed before making the switch. A collector car that has been modified over time may need a more careful inspection than one still wearing its long-established wheel setup.
Choosing the Right Tire
What should I consider when choosing a tire for a 1958 Armstrong-Siddeley Sapphire?
Start by deciding whether the car should stay with a 670-16 bias-ply tire or use a 185R16 radial. Both are valid primary fitments for the 1958 Armstrong-Siddeley Sapphire, but they represent different construction types, different sizing systems, and somewhat different selection priorities.
After the size and construction are settled, compare the available tire series, rim-width compatibility, sidewall style, and load-related specifications within that size. It also helps to think about how the car will be used, because a restoration-focused Sapphire and one intended for regular touring may lead the owner toward different tire characteristics.
What brands offer tires for the 1958 Armstrong-Siddeley Sapphire?
Tires for the 1958 Armstrong-Siddeley Sapphire are available from Michelin, Avon, Vredestein, and Firestone. The radial 185R16 fitment includes Michelin, Avon, and Vredestein choices, while the 670-16 bias-ply fitment includes Firestone and Avon options.
Brand alone should not make the decision. The better approach is to narrow the choice by the correct size first, then compare construction type, tire series, wheel-width compatibility, and any load information that matters for the car. That keeps the selection focused on fitment and intended use rather than name recognition by itself.
How do I choose between the available 185R16 and 670-16 tires for a 1958 Armstrong-Siddeley Sapphire?
The simplest way to choose is to separate the decision into two parts: construction first, then product details within that construction. A 670-16 tire keeps the Sapphire in a traditional numeric bias-ply format, while 185R16 places it in a Euro-metric radial format on the same 16-inch rim diameter.
Once that larger decision is made, compare tire series, blackwall presentation, wheel-width range, and load-related figures where they are given. A car being preserved for period-style appearance may point one way, while a Sapphire used more regularly on the road may lead the owner to study the radial options more closely.
Restoration & Appearance
Which tire should I choose for a period-style 1958 Armstrong-Siddeley Sapphire?
For a period-style 1958 Armstrong-Siddeley Sapphire, the 670-16 bias-ply fitment is the more traditional starting point because it preserves the vintage numeric sizing format and bias-ply construction associated with the car’s era. Blackwall options in this size are available from Firestone and Avon.
Appearance goals should still be balanced against the car’s actual wheel setup and intended use. If historical accuracy matters at a very high level, verify the car’s original delivery details through marque references or restoration records. That extra step is worthwhile before treating any modern reproduction tire as an exact original match.
How does tire construction affect the appearance of a restored 1958 Armstrong-Siddeley Sapphire?
Tire construction changes the visual character of a restored 1958 Armstrong-Siddeley Sapphire even when the wheel diameter stays at 16 inches. A 670-16 bias-ply tire presents the car in a more traditional mid-century style, while a 185R16 radial introduces a later tire format with a different sizing convention.
That difference matters on a formal British saloon where stance and presentation are part of the car’s appeal. Owners restoring for touring use may still prefer a radial, but those chasing a more period-minded look usually start by considering the bias-ply size first and then matching that choice carefully to the wheels already on the car.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 1958 Armstrong-Siddeley Sapphire?
Yes, modifications can affect tire fitment on a 1958 Armstrong-Siddeley Sapphire even though both primary tire sizes use 16-inch rims. Changes such as aftermarket wheels, altered wheel width, suspension work, or body and fender repairs can influence how either a 670-16 bias-ply or 185R16 radial sits on the car.
That is why the current vehicle setup matters more than assumptions about a stock car. Measure the wheels, inspect clearances at full steering lock, and look for any signs that ride height or suspension geometry has changed over time. Those checks help prevent choosing a tire simply because the nominal size appears correct.
What should I inspect before driving a 1958 Armstrong-Siddeley Sapphire on new tires?
Before driving a 1958 Armstrong-Siddeley Sapphire on new tires, inspect the wheels for correct diameter and width, make sure the tires are seated properly, and confirm there is no rubbing at the fenders, steering components, or suspension. Tire pressure should also be set appropriately for the tire being used.
A short, careful road check is a smart next step after installation. Pay attention to steering response, any vibration, and whether the car tracks cleanly without unusual pull or noise. On a collector car that may have sat for long periods, it also helps to look over suspension bushings, shocks, and brake components before regular use.
How should tires on a collector 1958 Armstrong-Siddeley Sapphire be maintained?
Tires on a collector 1958 Armstrong-Siddeley Sapphire should be inspected regularly for cracking, bulges, cuts, uneven wear, and gradual air loss, even if the car is driven only occasionally. Low annual mileage does not stop a tire from aging, so condition matters as much as tread depth on a vintage saloon.
Storage habits also make a difference. Keeping the car away from prolonged sunlight, excess heat, moisture, and ozone-producing equipment can help protect the tires between drives. It is also wise to check pressure before every outing and to recheck wheel and tire condition after the car has been parked for a long stretch.
