The 1926 Ajax 6 Cyl. comes from the mid-1920s transition period, when American motorists expected more refinement and road comfort but still relied on tall, narrow bias-ply tires built for early paved and unpaved travel. That makes tire selection for this car especially dependent on confirming the exact wheel and sizing system already on the vehicle. The 1926 Ajax 6 Cyl. is associated with two bias-ply sizes, 30X4.75 and 4.75-21, and they are not interchangeable descriptions of the same fitment. Choosing between them starts with the wheel setup on the car, then moves to restoration appearance, proper dimensions, and safe road use.
Which Tire Size Is Right for The 1926 Ajax 6 Cyl.
The 1926 Ajax 6 Cyl. uses two primary tire sizes, and the first step is confirming which wheel setup the car actually has. Both sizes are bias-ply, but they differ by sizing system and rim diameter, so the key decision is not brand preference first but identifying whether the car is set up for 30X4.75 or 4.75-21 before choosing a period-style replacement.
30X4.75 is an antique diameter-by-section size, meaning the first number refers to an approximate 30-inch overall tire diameter and the second number refers to section width. On a 1926 Ajax 6 Cyl., this is a true early-style bias-ply fitment that speaks to the car's pre-war tire conventions rather than later modern sizing language. Buyers often encounter this format on vehicles that have retained very traditional wheel and tire arrangements. It is the right size to evaluate only after confirming that the car is built around this antique format and the corresponding wheel dimensions.
4.75-21 is a numeric bias-ply size in which 4.75 refers to nominal section width in inches and 21 identifies the rim diameter. For the 1926 Ajax 6 Cyl., this size reflects a later vintage numeric style that is more familiar to many pre-war tire buyers than the oldest diameter-by-section format. Its practical role is straightforward once the wheel diameter is confirmed, because the tire choice then becomes a matter of selecting the proper period-style bias-ply fitment for the car's existing setup. This size should be matched to the vehicle's actual wheels rather than assumed from appearance alone.
The covered sub-model fitment is simple in one sense and still requires verification in another: the Base model is associated with both primary tire sizes. That means the important check is the wheel and tire setup on the car itself, since the sub-model name alone does not narrow the fitment to one size.
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1926 Ajax 6 Cyl. Base
The 1926 Ajax 6 Cyl. Base is associated with both 30X4.75 and 4.75-21 bias-ply tires rather than one single size. Tire selection therefore starts with confirming which wheel diameter and sizing convention the car currently uses, then choosing a period-style bias-ply tire that matches that 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.
Frequently Asked Questions
Owners of a 1926 Ajax 6 Cyl. usually need to sort out two key issues first: which of the two vintage bias-ply sizes belongs on the car, and what should be inspected on the wheels and vehicle before putting it back on the road.
Tire Size & Fitment
What tire size fits a 1926 Ajax 6 Cyl.?
The 1926 Ajax 6 Cyl. is associated with two primary bias-ply tire sizes: 30X4.75 and 4.75-21. Those are two distinct fitments, not two ways of writing the same tire size, so the correct choice depends on the wheel and tire setup that is already on the car.
A buyer should confirm the actual rim diameter before choosing either size, because 30X4.75 and 4.75-21 belong to different sizing conventions. On an early collector car like this, wheels may have been changed long ago, so measuring the wheel and checking the existing tire markings is more reliable than assuming one size applies to every surviving example.
What size rim does a 1926 Ajax 6 Cyl. use?
The 1926 Ajax 6 Cyl. appears with two different rim diameters depending on which primary tire size is on the car. The 30X4.75 fitment is associated with a 5.0-inch rim diameter, while the 4.75-21 fitment uses a 21-inch rim diameter.
That difference makes wheel confirmation the most important fitment step on this vehicle. A vintage tire size can look familiar on paper but still be completely wrong for the wheel in front of you, so it is worth checking the wheel itself, the old tire markings, and the overall setup before selecting a replacement for road use or restoration work.
Does the 1926 Ajax 6 Cyl. Base use the same tire size?
The 1926 Ajax 6 Cyl. Base is associated with both 30X4.75 and 4.75-21 rather than a single dedicated tire size. In practical terms, the Base designation does not settle the tire question by itself, because either vintage bias-ply size may be relevant depending on the car's wheel arrangement.
That means the decision moves from sub-model identification to physical verification of the car. Looking at the wheel diameter, checking any remaining sidewall markings, and comparing the current setup to the tire size you plan to use will help avoid ordering a tire that matches the model name but not the actual wheel on the vehicle.
Choosing the Right Tire
What should I consider when choosing a tire for a 1926 Ajax 6 Cyl.?
Start with the size and wheel setup, because the 1926 Ajax 6 Cyl. is associated with both 30X4.75 and 4.75-21 bias-ply tires. Once the correct fitment is confirmed, the next priorities are maintaining the proper vintage look, staying with the correct construction type, and selecting a tire that suits the car's intended use.
A restoration-focused owner may place appearance and period-style proportions first, while a touring-oriented owner may focus more heavily on condition, wheel integrity, and careful fitment verification. On a 1920s vehicle, old changes made by previous owners are common, so the most useful approach is to match the new tire to the actual wheels and overall vehicle setup rather than relying on assumptions.
How do I choose between 30X4.75 and 4.75-21 tires for a 1926 Ajax 6 Cyl.?
Choose between 30X4.75 and 4.75-21 by identifying which wheel and sizing system your 1926 Ajax 6 Cyl. actually uses. The first is an antique diameter-by-section size, while the second is a numeric bias-ply size tied to a 21-inch rim, so they serve different wheel configurations.
The best next step is to inspect the current tires, measure the wheel, and confirm that the size language on the replacement matches the hardware on the car. Early vehicles are often restored or updated over long periods of time, and that makes physical verification far more important than assuming one vintage tire size belongs on every car with the same year and model.
Why does the 1926 Ajax 6 Cyl. have more than one tire size?
More than one tire size appears for the 1926 Ajax 6 Cyl. because vintage vehicles can be associated with different wheel and tire conventions within the same model range. Here, both 30X4.75 and 4.75-21 are bias-ply fitments, but they represent different sizing systems and different rim diameters.
For the buyer, that means tire selection is really a wheel-identification exercise first. Once the vehicle's current setup is confirmed, the choice becomes much simpler, because the correct replacement should match that established size format and wheel diameter rather than trying to bridge between two different vintage fitment standards.
Restoration & Appearance
Which tire should I choose for a period-style 1926 Ajax 6 Cyl.?
For a period-style 1926 Ajax 6 Cyl., the right starting point is the tire size and bias-ply construction that matches the wheel setup already on the car. Both 30X4.75 and 4.75-21 are vintage-style bias-ply fitments, so the goal is to choose the one that suits the vehicle's existing wheels rather than forcing a modern interpretation.
Appearance matters on a 1920s automobile because tire shape and proportions strongly influence the car's stance. Buyers pursuing a historically faithful presentation should also compare their car against period photos, marque references, or restoration records, especially if the vehicle has changed hands many times and its wheels may not be exactly as originally configured.
Does correct tire fitment matter for a 1926 Ajax 6 Cyl. restoration?
Correct tire fitment matters a great deal on a 1926 Ajax 6 Cyl. because early cars wear their tires visually and mechanically in a very prominent way. The wrong size or the wrong wheel match can alter the car's stance, affect fender and steering clearance, and undermine an otherwise careful restoration.
Even when the goal is mainly appearance, fitment should still be verified as a working mechanical choice. A tire that looks traditional but does not match the wheel correctly can create problems once the car is driven, so restoration-minded owners should balance period-style presentation with careful confirmation of wheel diameter, construction type, and overall compatibility.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 1926 Ajax 6 Cyl.?
Yes, modifications can affect tire fitment on a 1926 Ajax 6 Cyl., especially because early collector cars often pass through decades of repairs, restorations, and wheel changes. Replacement wheels, brake work, suspension alterations, or body adjustments can all change which tire size actually belongs on the car today.
That is why the safest approach is to inspect the vehicle as it currently sits instead of assuming the fitment has remained unchanged since new. Wheel diameter, wheel condition, clearance at full steering lock, and the relationship between the tire and surrounding bodywork should all be checked before settling on either 30X4.75 or 4.75-21.
What should I inspect before driving a 1926 Ajax 6 Cyl. on new tires?
Before driving a 1926 Ajax 6 Cyl. on new tires, inspect the wheels for damage or corrosion, confirm that the tire size matches the wheel, and make sure the tires seat properly and hold air consistently. It is also wise to look over the steering and suspension for looseness that could affect how the car tracks.
A short local test drive is usually a better first step than heading straight onto a longer route. Tire pressure, sidewall condition, lug hardware, and any signs of rubbing should be reviewed again after initial driving, especially on a low-use collector car that may reveal dormant mechanical issues once it returns to road service.
How should tires on a collector 1926 Ajax 6 Cyl. be maintained?
Tires on a collector 1926 Ajax 6 Cyl. should be maintained with regular pressure checks, routine visual inspection, and careful storage habits. Because cars from this era are often driven infrequently, aging and storage-related deterioration can become just as important as tread wear when evaluating whether the tires remain roadworthy.
Keeping the car away from prolonged sunlight, moisture, and ozone sources helps preserve the rubber between drives. Owners should also watch for cracking, bulges, cuts, flat-spotting, or gradual air loss, and they should inspect the tires before each outing rather than relying on mileage alone to judge condition on a seldom-driven vintage automobile.
