1959 Armstrong-Siddeley Tire Fitment Guide

1959 Armstrong-Siddeley vehicles in this guide use two tire sizes, both for the Sapphire: 185R16 and 670-16. Both sizes fit 16-inch wheels, but they are different constructions. The 185R16 products listed are radial tires, while the 670-16 products listed are bias-ply. Rim-width guidance appears within the available products, with 185R16 examples covering 4.50 to 6.50 inches depending on tire, and 670-16 examples covering 4.50 to 5.00 inches where that range is specified.

That means a 1959 Armstrong-Siddeley owner usually starts by deciding what kind of driving experience and restoration character they want, then confirms wheel width before choosing a specific tire. If your Sapphire still wears its original-style narrow wheel, that can influence which tire within the 16-inch family is the better match. Treat size and construction as separate decisions, even though the rim diameter is shared.

On a 1959 Armstrong-Siddeley, 670-16 is a classic numeric bias-ply size. The 6.70 figure refers to the tire's nominal section width in inches, and the 16 refers to the wheel diameter in inches. It does not indicate a radial construction, and it does not carry the modern slash-format dimensions seen on later metric tires. In the available selections for the Sapphire, 670-16 is offered as a bias-ply blackwall size.

That makes 670-16 the size most closely aligned with late-1950s tire practice and visual presentation. If your goal is an authentic period look, this is usually the first size to consider, especially for a show-focused restoration. Before final selection, compare the wheel width on your car to the listed rim-width guidance for the specific tire rather than assuming every 16-inch wheel is equally suitable.

On a 1959 Armstrong-Siddeley, 185R16 is a euro-metric radial size. The 185 is the nominal section width in millimeters, the R identifies radial construction, and the 16 is the wheel diameter in inches. Because no aspect ratio is written into the size itself, it follows the older euro-metric convention commonly associated with classic radial sizing. In the available Sapphire fitments, this size appears only as a blackwall radial.

That makes 185R16 a logical choice for owners who want a radial tire while staying in a size family appropriate to a vintage British saloon. It is still essential to check the individual tire's details, because the available 185R16 products do not all share the same tube notation, rim-width range, or speed symbol. Reading the full sidewall designation matters more here than relying on the size code alone.

For a 1959 Armstrong-Siddeley Sapphire, the core difference is construction rather than wheel diameter. The 185R16 choices are radial tires, while the 670-16 choices are bias-ply tires, and both fit 16-inch rims. Radials generally appeal to owners who drive their cars more regularly and want a later-style touring feel, while bias-ply tires appeal to owners prioritizing a more period-correct late-1950s presentation.

That choice should follow the role of the car. A judged restoration or authenticity-minded preservation often points toward 670-16, especially when the goal is to keep the car visually and mechanically in period spirit. A Sapphire used for longer road outings may lead you toward 185R16 instead. Once you decide on construction, compare the specific tire's rim-width guidance and sidewall markings before making the final selection.

The available 1959 Armstrong-Siddeley tires in both 185R16 and 670-16 are offered as blackwalls. That applies across the radial and bias-ply options listed for the Sapphire. A blackwall appearance is fully in keeping with the restrained, formal look expected on a British luxury saloon of this period, especially compared with more flamboyant American-market whitewall treatments.

For most Armstrong-Siddeley owners, that simplifies the decision because sidewall styling is not the variable here. The real distinction is between radial and bias-ply construction, not between different cosmetic sidewall treatments. If you are restoring the car for judged display, blackwall presentation keeps the tire visually aligned with the marque's understated character, while drivers focused on road use can choose within that same look.

Three brands cover the available 1959 Armstrong-Siddeley sizes: Michelin, Avon, and Vredestein on 185R16 radial tires, plus Firestone and Avon on 670-16 bias-ply tires. Avon appears in both size families, while Michelin and Vredestein cover the radial size only, and Firestone appears in the bias-ply size only. All of those offerings are blackwall tires for the Sapphire's 16-inch fitment.

That brand spread gives a 1959 Armstrong-Siddeley owner more than one route depending on whether the priority is traditional construction or a radial alternative. It also means brand choice alone does not answer the fitment question; the size and construction still come first. Once those are settled, compare the individual brand offerings for speed symbol, load figure, and wheel-width compatibility instead of assuming every tire in the same nominal size is identical.

Available rim-width guidance for 1959 Armstrong-Siddeley tires varies by size and by product. In 185R16, listed fitments span 4.50 to 6.00 inches on the Michelin X Radial and 5.0 to 6.5 inches on the Vredestein Sprint Classic. In 670-16, the Firestone bias-ply lists a 4.50 to 5.00 inch rim-width range. Those figures show that sharing a 16-inch rim diameter does not automatically mean every wheel width suits every tire equally well.

Wheel width is one of the most important checks to make before choosing between the radial and bias-ply options for a Sapphire. A tire can match the wheel diameter yet still be a poor choice if the rim is outside the manufacturer's approved width range. Measure the wheel you actually plan to use, especially if the car has replacement rims or a mixed set from an older restoration.

Inner-tube status on 1959 Armstrong-Siddeley tires varies by product rather than staying uniform across both sizes. The Michelin 185R16 is marked TT, which identifies it as a tube-type tire, while the other 185R16 radial listings are not marked the same way. The 670-16 bias-ply products also do not all carry identical tube wording in the sidewall designation. That makes it important to check the exact tire you are considering, not just the size family.

On a collector car, tube decisions also depend on the wheel itself and its condition. Original wheels, older rim profiles, or rims with age-related pitting can influence whether tube use is appropriate even when comparing tires of the same nominal size. If your Sapphire still uses original wheels, inspect the wheel carefully and match the tire's sidewall marking to the wheel's design before final installation.

A 1959 Armstrong-Siddeley Sapphire can use both listed tire sizes only because both 185R16 and 670-16 are built for 16-inch wheels. That confirms shared wheel diameter compatibility at the top level. It does not mean every original wheel is automatically suitable for every tire choice, because the listed product ranges show different approved rim widths within those 16-inch fitments.

That is especially important when switching from a period-style bias-ply to a radial. Many owners assume the common 16-inch diameter settles the question, but wheel width and condition still matter. If your car retains factory-type wheels, verify the width before fitting a radial, and if the car has had wheels changed at some point in its life, confirm both diameter and width before selecting either size.

A 1959 Armstrong-Siddeley should be stored in a cool, dry, dark space away from direct sunlight, electric motors, battery chargers, furnaces, and other ozone-producing equipment. Clean floors and stable temperature help, and the car should not sit for long periods on underinflated tires. Bias-ply tires such as 670-16 are more prone to taking a temporary flat spot during extended static storage, while older-style collector radials still benefit from regular movement and pressure checks.

For a Sapphire that rests through part of the year, periodic rolling or support stands can reduce stress on the tire carcass. Owners who keep the car on the ground should move it occasionally to change the contact patch and maintain proper inflation. Storage habits matter just as much as tread depth on a low-mileage collector car, because age and environment often govern tire condition before wear does.

Tires on a 1959 Armstrong-Siddeley are usually judged by age and condition rather than by mileage alone. A sensible rule is to begin careful evaluation once tires are around five to seven years old and to treat around ten years as a serious replacement threshold, even if tread remains. The DOT date code on the tire helps establish age, and collector cars often accumulate so few miles that sidewall aging becomes the main concern.

That matters on a Sapphire because a car that looks lightly used can still be running on tires that have aged out. Radial or bias-ply, the decision should be driven by calendar age, cracking, hardening, and service history rather than tread appearance alone. If the car's history is unclear, checking the date codes and inspecting all five tires, including the spare, is a smart first step before regular road use.

Tires on a 1959 Armstrong-Siddeley should be inspected before every drive, and they deserve a more thorough inspection before any longer outing. Look for sidewall cracking, cuts, bulges, irregular tread wear, and pressure loss. On cars using tube-type fitments or tube-compatible setups, valve stems and slow leaks deserve extra attention because a car that sits between drives can lose pressure without obvious visual warning.

That inspection routine is especially important on a collector car that may spend weeks or months parked between uses. A brief walk-around can catch aging issues that would not be obvious from tread depth alone. Before a tour or highway run, also inspect the spare and confirm the tire pressures are correct for the specific tire on the car, since old assumptions from a previous set may not apply to the current fitment.

A 1959 Armstrong-Siddeley Sapphire would have been associated with bias-ply tire practice as standard period fitment, making a 670-16 bias-ply size the most historically in-character choice among the available options. The radial 185R16 choices represent a later-style alternative rather than the default late-1950s construction expectation. Original-equipment branding could vary by market and delivery, so the key historical point is the construction type and size family more than a single universal brand name.

For a restoration, that means starting with the car's intended judging standard. If the goal is authenticity, a blackwall bias-ply in 670-16 aligns most closely with the era. If the car has export-market history, replacement wheels, or a long-standing radial conversion, it is still wise to compare the current setup to period references. Marque clubs and factory literature remain the best places to confirm market-specific tire details beyond the broad period-correct construction.

Correct tire fitment absolutely matters when showing a 1959 Armstrong-Siddeley, especially in classes that emphasize factory appearance and period fidelity. Judges and knowledgeable enthusiasts often notice whether the car wears the appropriate size family, construction type, and sidewall treatment for its era. On a formal British saloon like the Sapphire, a blackwall bias-ply presentation is generally more in keeping with period expectations than a modernized-looking radial conversion.

That does not mean every event will judge tire choices the same way, but it does mean tires are part of the car's visual and historical story. A radial can be entirely reasonable for touring, yet still be a deduction point in originality-focused judging. If the car is being prepared for concours display, consult event rules and marque specialists first so the tire choice supports the exact standard you are trying to meet.

Within the 670-16 size for a 1959 Armstrong-Siddeley, the Firestone and Avon offerings differ in the details shown with the tire. The Firestone Classic Bias Ply lists a maximum load of 1130 at 30 psi and a rim-width range of 4.50 to 5.00 inches, while the Avon Turbospeed Mk4 is shown as 670H16 89H with a listed load capacity of 1,279 pounds. Both are blackwall bias-ply tires for 16-inch wheels.

For an Armstrong-Siddeley owner, that comparison matters because two tires in the same nominal size can still differ in how they are labeled and what supporting specifications they publish. One may fit your wheel-width situation more clearly, while the other may appeal if you are comparing speed-symbol information. The smart move is to compare the actual wheel on the car, the intended driving use, and the specific sidewall designation before deciding between them.

1959 Armstrong-Siddeley tires can be suitable for highway use when they are the correct size, properly inflated, in sound condition, and matched to the intended driving style. Among the listed options, the 185R16 radial products include S-rated and V-rated examples, which correspond to 112 mph and 149 mph ceilings, while the Avon 670H16 bias-ply carries an H rating of 130 mph. Those speed symbols exceed normal U.S. highway speeds, but their value depends on the tire's age, inflation, load, and condition.

On a car like the Sapphire, the broader mechanical condition of the vehicle often matters more than the tire's headline speed symbol during real-world touring. Brakes, steering, suspension, and wheel condition all deserve equal attention on a late-1950s luxury car. A highway-capable tire does not make an unrestored chassis ready for sustained speed, so evaluate the car as a whole rather than treating the tire rating as the only safety measure.

Inflation pressure for 1959 Armstrong-Siddeley tires should follow the vehicle's original guidance for the size and use case, while also respecting the tire manufacturer's rated information for the specific product. Among the listed choices, the Firestone 670-16 shows 1130 at 30 psi, and the Vredestein 185VR16 shows 1,433 pounds at 51 psi. Those figures are load-and-pressure ratings for those tires, not blanket inflation instructions to apply across every 16-inch option.

That distinction is important because a radial and a bias-ply of similar overall fitment may call for different operating pressures on the car. Start with the factory recommendation for the relevant size family, then compare it with the tire maker's guidance for the exact tire installed. Never transfer a pressure number from one size to another just because both fit a 16-inch wheel, and recheck pressures when the car returns to service after storage.

Before taking a 1959 Armstrong-Siddeley on a longer drive, inspect each tire for sidewall cracking, cuts, bulges, uneven wear, and correct cold inflation pressure. Check valve stems carefully, and if the car uses a tube-type fitment, pay particular attention to slow leaks and the condition of the spare. Also confirm that wheel nuts are secure and that the tire age is still appropriate for road use, not just visually acceptable.

A longer outing in a vintage Armstrong-Siddeley also calls for a broader mechanical check beyond the tires. Steering response, brake feel, suspension behavior, fluid levels, and cooling-system condition all matter on a late-1950s touring car. Tire readiness is only one part of the equation, but it is the part that meets the road first, so making a careful pre-drive inspection routine part of ownership is well worth the time.