1978 Opel Tire Fitment Guide

1978 Opel vehicles use two tire sizes: 155R13 and 175/70R13. Both sizes apply to the Opel model, and both mount on 13-inch wheels. The 155R13 has products built around a 4.00 to 5.50 inch rim-width range, while the 175/70R13 uses products built around a 4.5 to 6.0 inch rim-width range.

That means the decision is not about choosing between different Opel model families in 1978, but about confirming which of the two sizes belongs on your particular car. A quick check of the existing tires, the wheel width, and any factory or restoration records will usually settle the question before you move on to brand or tread selection.

On a 1978 Opel, 155R13 is a euro-metric radial size. The 155 refers to the tire's section width in millimeters, the R identifies radial construction, and the 13 is the wheel diameter in inches. Because no aspect ratio is written into the size itself, this format conventionally points to an 80-series radial profile.

For an Opel of this era, that code signals a relatively narrow, tall-sidewall radial that looks at home on a late-1970s European compact. If your car currently wears 155R13 tires, staying with that size preserves the original diameter relationship more closely than switching sizes without first checking clearance, wheel width, and overall stance.

On a 1978 Opel, 175/70R13 is a metric radial size with more information built into the code. The 175 is the section width in millimeters, 70 is the aspect ratio, the R indicates radial construction, and 13 is the wheel diameter in inches. Compared with 155R13, it is wider and uses a shorter sidewall profile.

That shorter profile changes the tire's proportions even though it still fits a 13-inch wheel. Owners often encounter this size on Opels set up for a slightly broader contact patch and a more modern late-1970s profile, so it is wise to confirm what is already on the car and whether the wheel width falls comfortably within the tire's range before making a change.

Choose the size that matches your 1978 Opel's actual setup, because both 155R13 and 175/70R13 were used and both are radial tires rather than a bias-ply-versus-radial decision. The 155R13 is the narrower euro-metric option with a taller implied profile, while the 175/70R13 is a wider metric radial with a defined 70-series sidewall. Both fit 13-inch wheels, but they are not interchangeable by assumption.

The practical difference is in overall proportion, wheel-width compatibility, and the look of the car as much as basic fitment. If your goal is to preserve a distinctly period European appearance, the 155R13 may be the better match; if your Opel is already configured around the wider size, the 175/70R13 keeps that setup intact. Check the existing tire size and wheel width before deciding.

1978 Opel tires in both 155R13 and 175/70R13 are available in blackwall form. Michelin and Dunlop cover the 155R13 size with blackwall radials, and Avon covers the 175/70R13 size with a blackwall radial. No alternate whitewall or specialty sidewall treatment appears within these Opel sizes.

That blackwall presentation is entirely appropriate for a late-1970s European compact, where a clean, understated sidewall generally suits the car's original market character. If your goal is visual authenticity, sidewall style is a straightforward decision here; the more important choice is making sure the tire size and proportions match the way your Opel was equipped or restored.

Three brands cover 1978 Opel fitments. Michelin and Dunlop produce 155R13 options, while Avon produces the 175/70R13 option. All three are radial tires and all appear in blackwall form, which keeps the choices aligned with the sort of understated styling most buyers expect on a German compact from the late 1970s.

Brand choice matters most after the size question is settled. If your Opel uses 155R13, you have two distinct brand paths to consider; if it uses 175/70R13, the Avon option becomes the size-specific route. That makes your first job identifying the correct size, then comparing how each brand's casing, profile, and intended character fit your plans for the car.

Rim-width guidance for 1978 Opel tires depends on the size. The 155R13 products are built for wheels from 4.00 to 5.50 inches wide, while the 175/70R13 product is built for wheels from 4.5 to 6.0 inches wide. Both sizes share a 13-inch rim diameter, but the acceptable wheel-width range changes with the tire's section width and profile.

That is why wheel diameter alone is not enough when selecting tires for a 1978 Opel. A narrow wheel that suits a 155R13 may sit outside the ideal range for a 175/70R13, and a wider wheel may favor the 175-series tire. Measuring the wheel before purchase is the cleanest way to avoid sidewall distortion, clearance issues, or an awkward stance.

Inner-tube requirements on 1978 Opel tires depend on the exact product you choose. The Michelin 155HR13 carries a TL marking, which identifies it as tubeless, while the Dunlop 155R13 uses a different sidewall size marking that should be confirmed directly on the tire before final installation decisions are made. The 175/70R13 Avon product also should be matched to the wheel and the tire's own sidewall markings.

The wheel itself matters as much as the tire marking, especially on older cars that may have original, restored, or replacement rims. A sound tubeless-design tire still needs a wheel in proper condition to run that way. Before mounting anything on a 1978 Opel, confirm the tire marking, inspect the wheel's bead area, and decide on tubes only after those two pieces agree.

Original 1978 Opel wheels can potentially be used with both sizes because 155R13 and 175/70R13 both mount on 13-inch rims. That shared wheel diameter is the basic point of compatibility. The remaining question is whether the wheel width falls within the approved range for the exact tire size you want to run.

A wheel that works well with 155R13 may not automatically be the right match for 175/70R13, even though both are 13-inch tires. Before changing sizes, measure the wheel width and compare it to the tire's intended range. That extra step helps preserve proper sidewall shape and keeps your Opel's steering feel and appearance closer to what you expect.

A 1978 Opel should be stored away from direct sunlight, ozone sources such as electric motors or battery chargers, and damp surfaces that can age the rubber and wheels. Keep the tires at proper pressure and move the car periodically so it does not sit in one position for months at a time. Radial tires generally tolerate storage better than old bias-ply designs, but they still age from heat, light, and long inactivity.

If the car will be parked for an extended season, a clean, dry floor and occasional rolling are usually enough for a lightly driven collector Opel. Some owners also use stands to reduce static loading during long storage, especially if the suspension and tires will not be exercised for months. Good storage habits protect both appearance and road behavior when the car returns to use.

Tires on a 1978 Opel should be judged more by age and condition than by mileage alone, because collector cars often cover very few miles each year. A sensible rule is to begin evaluating tires closely around five to seven years of age and to treat about ten years as the point where replacement deserves serious consideration even if tread remains. The DOT date code on the sidewall is the key age reference.

A low-mile Opel can still be riding on old rubber that looks decent at first glance but has hardened internally or developed sidewall age cracking. That is especially important on a small European car where tire compliance is a noticeable part of ride and handling. When in doubt, let age and condition guide the decision more than tread depth alone.

Tires on a 1978 Opel deserve a quick inspection before every drive and a more deliberate inspection before any longer outing. Look for sidewall cracking, cuts, bulges, uneven wear, and pressure loss, and make sure the tread is free from weathering or separation. Valve stems and the spare should be part of the same check, especially on a car that spends long stretches parked.

Regular inspection matters because collector-car tire problems often appear from age, storage conditions, or underuse rather than from heavy mileage. A brief walkaround catches most issues before they become roadside problems. On an older Opel with small-diameter tires, even modest pressure loss can change the way the car tracks and steers, so pressure checks should be routine rather than occasional.

A 1978 Opel Opel would have been equipped in the radial era, and the two sizes associated with the car are 155R13 and 175/70R13. Both are radial constructions, which aligns with what buyers expect from a late-1970s European compact rather than an earlier bias-ply car. No original-equipment brand should be assumed without checking factory literature or marque-specific references for the exact market version of the car.

For restoration work, the safest approach is to confirm the size on the car's original tire placard, owner's literature, or a respected Opel club source, then choose a tire whose proportions and sidewall appearance suit that research. Getting the construction type right is straightforward here because both available fitments are radial; the finer point is selecting the correct size and visual profile.

Correct tire fitment does matter when showing a 1978 Opel, especially if the event places weight on authenticity. Judges and knowledgeable enthusiasts will notice whether the car wears the proper size family, whether the construction matches the period, and whether the sidewall style looks appropriate for a late-1970s European road car. On this Opel, blackwall radial presentation is consistent with that era's character.

The biggest authenticity mistakes usually come from using a noticeably different overall profile or a size that changes the stance of the car. A 155R13 and a 175/70R13 can each be correct in the right context, but they are not visually identical. Before a judged event, compare your car against factory photos, period brochures, and event-specific standards from Opel specialists.

Michelin XAS-FF and Dunlop SP Sport Aquajet both cover the 155R13 size for a 1978 Opel, and both are blackwall radial tires weighing 20 pounds. The Michelin carries a 155HR13 78H TL sidewall marking and is built around a 4.00 to 5.50 inch rim-width range, while the Dunlop appears as a 155R13 78H radial and carries a stated maximum load capacity of 937 pounds. Both use the same 13-inch rim diameter.

For a buyer, that means the choice is less about broad fitment and more about the exact tire character and sidewall specification that best suits the car. If wheel width is a deciding factor, the Michelin's range is clearly defined. If you are comparing two 155R13 options for an originality-minded European compact, checking the sidewall marking and the intended wheel match is the smart next step.

1978 Opel tires can be appropriate for highway driving when they are in good condition, correctly inflated, and matched to the car's wheels. The current 155R13 and 175/70R13 offerings carry H speed ratings, which correspond to a 130 mph ceiling. That far exceeds normal U.S. highway speeds, so on a healthy collector Opel the car's own age, brakes, suspension, and overall mechanical condition often become the more important real-world limit.

Highway confidence depends less on the catalog speed symbol by itself and more on the total condition of the vehicle and tires together. A freshly inspected radial on a sound wheel is one thing; an old tire with age cracking or a long-stored spare is another. Before regular highway use, make sure the tires are age-appropriate, pressure-stable, and free from visible deterioration.

Inflation pressure on a 1978 Opel should follow the factory vehicle recommendation first, with the tire manufacturer's maximum pressure and load marking used as a construction limit rather than a blanket running pressure. The Dunlop 155R13 carries a stated maximum load capacity of 937 pounds, while pressure and load details vary by exact product and should not be transferred from one size to another. The 155R13 and 175/70R13 should be treated as separate fitments when setting pressure.

That means the best practice is to start with the owner's manual or tire placard if it survives, then compare that recommendation to the modern reproduction or replacement tire's sidewall information. Do not inflate by appearance alone, and do not assume that a pressure suitable for a 155R13 is automatically correct for a 175/70R13. Correct pressure is one of the simplest ways to protect handling, wear, and ride quality.

Before a longer drive in a 1978 Opel, inspect each tire for cracking, cuts, bulges, uneven wear, embedded debris, and stable air pressure. Check the valve stems, confirm the spare is usable, and make sure the wheel hardware is secure and the tread is free from signs of separation or severe aging. A small older car like an Opel is sensitive to tire condition, so small issues can quickly affect tracking and confidence on the road.

That tire inspection should be part of a broader pre-drive routine that also covers brakes, fluids, belts, lights, and cooling-system health. If the car has been sitting, pay special attention to flat-spotting, pressure loss, and any vibration during the first miles. Catching those problems in the garage is far preferable to discovering them once the trip is underway.