30X4.75 Tire Size Guide

The 30X4.75 size identifies a flotation-style tire by its overall dimensions first. In this case, 30 refers to an overall tire diameter of 30 inches, and 4.75 refers to a section width of about 4.75 inches. This size is used with a 5-inch rim in the documented fitments for this code.

Unlike a modern P-metric size, the 30X4.75 does not directly show an aspect ratio, load index, or speed symbol in the size code itself. Buyers reading this older format should think of it as a dimensional description rather than a complete technical specification, then confirm the actual tire's construction, wheel match, clearance, and intended use before installation.

The 30X4.75 tire fits a 5.0-inch wheel, which is 127.0 millimeters in diameter at the bead seat. On this flotation-style size, that wheel diameter is a separate specification from the tire's outside height, so the rim must match exactly.

With older sizes like this one, wheel diameter mistakes are easy to make because the size code emphasizes the tire's outside dimensions. Rim width still matters even when the wheel diameter is correct, so buyers should compare the actual wheel profile and tire documentation carefully before mounting a replacement on an antique or specialty application.

The 30X4.75 has a section width of about 4.7 inches, which converts to roughly 119.4 millimeters. Section width measures the tire at its widest sidewall point when mounted and inflated, not across the tread face.

Clearance questions are usually driven by section width more than tread width because the sidewall is what approaches fender edges, suspension parts, and brake components first. On a narrow antique application, even a small change in sidewall bulge or wheel width can affect fit, so this number should be checked closely when comparing substitutes.

The outside diameter of the 30X4.75 tire is 30.0 inches, or 762.0 millimeters. That is the full height from the ground to the top of the tire when measured straight through the center.

Overall diameter has a direct effect on ride height, wheel-opening fill, and gearing feel on the road. For antique vehicles, it also strongly affects stance, so anyone comparing another size should treat diameter as one of the first numbers to match if the goal is to preserve original proportions and avoid unwanted clearance changes.

The 30X4.75 uses a 5.0-inch wheel diameter. On sizes written this way, the leading 30 is the tire's outside diameter, not the wheel size, and that distinction matters because a 30-inch tire does not fit a 30-inch wheel.

Collectors and first-time buyers sometimes misread flotation-style markings because the code starts with tire height instead of rim diameter. When replacing an older tire, confirm the wheel itself before focusing on overall diameter or section width, since the bead seat diameter is the non-negotiable dimension for mounting.

The 30X4.75 turns about 672.3 revolutions per mile. That figure comes from the tire's approximate circumference of 94.25 inches and shows how often it rotates over a mile of travel.

Revolutions per mile become useful when comparing this size to a substitute because a noticeable difference can change speedometer and odometer readings. On vintage vehicles, where gearing and instrumentation are already less forgiving than modern systems, keeping the replacement close in overall height usually helps preserve the original driving character.

The 30X4.75 is strongly associated here with antique vehicle use from 1926 through 1930, and its documented applications include Ajax, Essex, and Star models from that period. Its tall, narrow bias-ply layout matches the kind of profile early cars commonly used.

For a restoration, that makes the 30X4.75 a more natural period-style choice than a modern low-profile substitute. Original fitment research should still include factory literature, wheel dimensions, and body clearance, because an antique vehicle may have seen wheel changes or running-gear updates over time.

The main checks for the 30X4.75 are wheel diameter, overall tire height, section width, and physical clearance around the fender, suspension, and brakes. Because this size fits a 5-inch rim and stands 30 inches tall, buyers should confirm both the wheel and the space around it.

A tire that looks close on paper can still create problems if the mounted width changes, the wheel profile differs, or the vehicle sits lower than stock. On older vehicles especially, measure the actual wheel and inspect the car's present setup rather than assuming every surviving example still matches original factory specifications.

The 30X4.75 should not be replaced by another size on dimensions alone. Overall diameter and section width are important, but wheel diameter, construction type, load needs, and the way the tire fills the wheel opening all affect whether a substitute makes sense.

Even a close comparison size can change stance, steering response, or clearance on an antique chassis. Buyers comparing replacements should use the original size as the baseline, then verify rim fit, installed width, ride height effect, and the vehicle's intended road use before moving away from the established dimensions.

The 30X4.75 uses bias-ply construction, which typically gives an early vehicle a more period-authentic ride character than a modern radial-style replacement. With its tall, narrow proportions, it tends to preserve the upright look and slower, more deliberate response that suits antique chassis design.

Driving feel on a vehicle using the 30X4.75 will still depend on alignment, steering condition, wheel trueness, tire age, and suspension health. Owners should expect behavior consistent with an older tire design, then evaluate how the car tracks and responds at real road speeds instead of judging the size by construction type alone.

At 30.0 inches tall, the 30X4.75 has a major influence on how an antique vehicle sits and how fully the tire fills the wheel opening. Diameter also affects effective gearing because a taller tire travels farther per revolution than a shorter one.

If a substitute size ends up shorter, the vehicle may sit lower and show more gap around the tire. A taller replacement can create the opposite effect and may also change speedometer behavior. Keeping the outside diameter close is usually one of the best ways to preserve the original visual balance and road manners.

The 30X4.75 can be used on modern roads only after the tire's actual condition, age, wheel match, and intended use are reviewed carefully. Bias-ply behavior is different from modern radial behavior, and an antique vehicle's suspension, braking system, and steering design also shape how it feels in present-day traffic.

Drivers planning regular road use should inspect for cracking, air loss, uneven wear, and wheel issues before depending on any antique-size tire. Long trips call for an especially careful check of tread condition, mounted balance, and load demands so the tire and vehicle setup remain appropriate for the speeds and distances involved.

A good 30X4.75 should match the intended wheel diameter, maintain the proper tall narrow profile, and be built with consistent dimensions from tire to tire. On an antique application, sizing accuracy matters as much as tread because small dimensional changes can alter stance, steering response, and body clearance.

Construction quality should be judged alongside the vehicle's purpose. A car being restored for period appearance may place more value on authentic bias-ply character, while a regularly driven antique may demand closer attention to current condition, balancing quality, and how evenly a matched set performs once mounted.

Matched-set consistency matters with the 30X4.75 because older narrow-profile tires have a visible effect on both appearance and driving character. Differences in overall height, section width, or carcass shape from one tire to another can make an antique vehicle sit unevenly or steer inconsistently.

When replacing only one or two tires, compare dimensions and construction carefully against the tires already on the vehicle. Restorers and drivers alike usually benefit from a uniform set because even small variation in profile or age can stand out on early cars with exposed wheels and simple suspension geometry.

Bias-ply construction is often the right choice when the goal for the 30X4.75 is to maintain authentic appearance and driving character on an antique vehicle. It matches the type of construction commonly associated with early applications in the late 1920s and keeps the tire's visual proportions in line with period expectations.

Quality still depends on selecting the correct size, confirming wheel condition, and using tires that suit the vehicle's real use. A well-chosen bias-ply tire can look right and perform appropriately for an early car, but buyers should still inspect manufacturing details, set uniformity, and condition before deciding.

The 30X4.75 should be inspected regularly for sidewall cracking, tread separation, bulges, cuts, uneven wear, and recurring air loss. Antique-size tires can age out even when tread depth still looks usable, especially if the vehicle spends long periods parked or stored in changing temperatures.

Time, heat, sunlight, moisture, and ozone exposure all matter as much as mileage on a collector vehicle. Owners should check the tire before every driving season and again before longer trips, because a tire with very little road use can still become unsuitable once the rubber and internal structure begin to deteriorate.

The 30X4.75 lasts best when stored away from direct sunlight, electric motors, ozone sources, standing moisture, and large temperature swings. On a collector vehicle that sits for long periods, clean dry storage and periodic movement help reduce flat spotting and limit stress on the same contact patch.

Seasonal storage is especially important with a bias-ply tire because long stationary periods can affect shape and ride quality once the car goes back on the road. If the vehicle is stored for months at a time, inspect the tires carefully before driving again and confirm that the wheel and tire system remains in sound condition.

The 30X4.75 should be checked before routine drives and more carefully before extended outings. Look for pressure loss, irregular wear, visible cracking, and any change in how the car tracks or steers, since those signs can point to tire condition issues or wheel and suspension problems.

Regular inspection matters on antique fitments because the vehicle itself may have older wheels, older steering parts, and lower operating margins than a modern car. A quick walk-around catches many problems early, while periodic close inspection helps owners decide whether the tire is still serviceable for the way the vehicle is being used.

The 30X4.75 should be replaced when age-related cracking, bulges, repeated air loss, impact damage, or structural concerns appear, even if the tread still looks decent. Tread depth alone does not tell the full story on an antique-size tire, especially one that may have spent years in storage or low-mileage use.

Collectors sometimes see good-looking tread and assume the tire is still roadworthy, but rubber hardening and internal deterioration can develop long before the tread is worn out. Before driving at road speeds, inspect the full tire and wheel assembly carefully and consult a qualified tire professional if condition or serviceability is in doubt.

The key safety checks for the 30X4.75 are correct 5-inch wheel diameter, sound wheel condition, visible tire condition, and adequate clearance once mounted. Buyers and owners should also confirm that the tire's actual construction and service characteristics match the vehicle's intended use rather than relying on size alone.

Before a longer drive, inspect for cuts, weathering, shifted wear patterns, and any wobble or vibration that could indicate mounting or wheel issues. Antique vehicles place extra importance on these checks because steering, brakes, and suspension design are less forgiving than those of newer vehicles.

The 30X4.75 should be reviewed like any specialty or antique-size tire before road use, with attention to current sidewall markings, vehicle requirements, and local inspection expectations. Buyers should not assume that a correct-looking size automatically answers every road-use question for every jurisdiction or every vehicle setup.

Local rules, intended speed, wheel condition, and the overall state of the vehicle all influence whether an antique-size tire is appropriate for use. Reviewing the tire's current markings and having the complete wheel-and-tire system checked by a qualified professional is the safest way to avoid surprises before regular driving.