175/60R14 vs 185/55R14: Tyre Size Comparison, Diameter Difference & Speedometer Effect

175/60R14 and 185/55R14 look like near neighbours on paper, but the numbers tell a more precise story. 185/55R14 is the shorter tyre: its diameter is 559.1 mm against 565.6 mm, -6.5 mm (-1.1%) smaller. Width moves +10 mm, sidewall height moves -3.2 mm, and the circumference changes by -20.4 mm, which is what the speedometer feels. This comparison works through the side-by-side measurements, the speedometer error at 30, 50 and 70 mph in both directions, and the practical effects on ride comfort, grip and wheel-arch clearance.

On this page, 175/60r14 vs 185/55r14 tyre size comparison is the case in point: Before the tables, keep the context straight. These are nominal new-tyre dimensions, computed from the size codes: real tyres vary slightly by brand, model, wear and inflation pressure. A -1.1% difference is within the plus-or-minus 3% guideline that is commonly used for speedometer accuracy, and the speedometer tables below show exactly what that percentage means at real road speeds. The rest of the page covers sidewall, grip, gearing and the clearance checks that decide whether the larger size can physically fit.

This is a calculation, not a safety approval. Always check your vehicle's door-jamb placard, load index and speed rating, and confirm fitment with a tyre professional before fitting a different tyre size.

175/60R14 vs 185/55R14 side by side

Measurement 175/60R14 185/55R14 Difference
Overall diameter 565.6 mm (22.3 in) 559.1 mm (22.0 in) -6.5 mm (-1.1%)
Sidewall height 105.0 mm 101.8 mm -3.2 mm
Circumference 1776.9 mm 1756.5 mm -20.4 mm
Revolutions per mile 905.7 916.2 +10.5
Section width 175 mm 185 mm +10 mm
Rim diameter 14 in 14 in +0 in

Diameter difference between 175/60R14 and 185/55R14: -6.5 mm (-1.1%)

A -1.1% diameter change is small enough to sit inside the commonly used plus-or-minus 3% guideline, so the speedometer error it introduces stays modest. The circumference changes by -20.4 mm per revolution, and the revs per mile change by +10.5, which is the same story told from the car's point of view: the instruments count revolutions, so fewer revs per mile means the car travels further per revolution than the instruments assume. That drift also affects the odometer, so recorded mileage moves by the same percentage over time.

Speedometer error: 175/60R14 to 185/55R14 and back

The maths is a single ratio. 185/55R14 over 175/60R14 is 0.989, so every indicated speed after the swap is multiplied by that number to get the true speed: 30 becomes 29.7, 50 becomes 49.4 and 70 becomes 69.2 mph. In the reverse direction the ratio is 1.012, so 70 mph indicated is 70.8 mph in reality. The table below shows both directions at all three speeds, so you can check whichever direction applies to your car without doing the arithmetic yourself.

Indicated speed Actual speed fitting 185/55R14 (from 175/60R14) Actual speed fitting 175/60R14 (from 185/55R14)
30 mph 29.7 mph 30.3 mph
50 mph 49.4 mph 50.6 mph
70 mph 69.2 mph 70.8 mph

Sidewall height and ride comfort: 175/60R14 vs 185/55R14

Sidewall height moves by -3.2 mm between these two sizes (105.0 mm to 101.8 mm), and that is enough to feel. A taller sidewall flexes more, which softens sharp impacts and gives the tyre more give over potholes; a shorter sidewall flexes less, which sharpens the steering response and leaves the rim closer to the road surface on a hard hit. Which of those you get depends on the direction of the change — here the sidewall shrinks — and on the aspect ratio shift from 60% to 55%.

Width, grip and fuel use: 175/60R14 vs 185/55R14

Taking 175/60r14 vs 185/55r14 tyre size comparison as the case in point: On width, the two sizes are 10 mm apart. The wider tyre (185/55R14) offers more rubber on the road, which tends to mean more grip in the dry and slightly more resistance to roll. Do not expect a dramatic change in fuel use from a width change of this size; the bigger influences on fuel use are the tyre compound, the pressure and the way the car is driven.

Revolutions per mile and gearing: 175/60R14 vs 185/55R14

Gearing follows the circumference. 185/55R14 covers 1756.5 mm per revolution against 1776.9 mm for 175/60R14, so it needs +10.5 fewer revolutions per mile. At a fixed road speed the engine speed drops or rises by the same 1.1% as the diameter change. With the shorter size the engine sits slightly higher in the rev range at cruising speed, which sharpens response a little at the cost of a small amount of fuel. Either way the effect is proportional to the diameter difference, not larger than it.

Will 185/55R14 clear after 175/60R14? What to check before fitting

Clearance is the check the numbers cannot do for you. 185/55R14 is shorter and 10 mm wider than 175/60R14, so check the wheel arches, the suspension components and the steering lock: turn the wheel fully in both directions and check for contact, and check again with the suspension compressed and the car loaded as it will actually be used. A size that clears when the car is stationary and unloaded can still rub over a bump or at full lock. This page does not claim that 185/55R14 clears your car, and no diameter table can — only a physical check on your vehicle can confirm it. Also confirm the load index and speed rating of 185/55R14 meet what your placard asks for, and that the 14-inch rim suits the car.

Which size suits which priority: 175/60R14 or 185/55R14

The decision comes down to priorities. Comfort follows the sidewall (-3.2 mm here). Grip follows the width (+10 mm here). Instrument accuracy follows the diameter (-1.1% here). Gearing and cruising engine speed follow the revs-per-mile change (+10.5). None of those is large in this comparison, which is why the practical checks — clearance, load index, speed rating, rim width — deserve as much attention as the numbers. Get those right and the size choice becomes a matter of preference rather than a risk.

Related 175/60R14 vs 185/55R14 comparisons and tools

Frequently asked questions

What is the diameter difference between 175/60R14 and 185/55R14?

185/55R14 is -6.5 mm (-1.1%) smaller in diameter than 175/60R14: 559.1 mm against 565.6 mm. That is inside the commonly used plus-or-minus 3% guideline for keeping speedometer error small.

How much will my speedometer be out if I fit 185/55R14 instead of 175/60R14?

The error follows the diameter ratio, -1.1%. At an indicated 30 mph the true speed would be 29.7 mph, at 50 mph indicated it would be 49.4 mph, and at 70 mph indicated it would be 69.2 mph. The full table in both directions is in the speedometer section above.

Is 185/55R14 wider than 175/60R14, and does that matter?

Yes — 185/55R14 is 185 mm wide against 175 mm for 175/60R14, a difference of +10 mm. A wider tyre generally gives more dry grip and can increase rolling resistance and road noise slightly. Width also affects clearance, so check the arches and suspension at full lock.

Will 185/55R14 fit my car if 175/60R14 fits?

Not necessarily. 185/55R14 is shorter by 6.5 mm and 10 mm wider, and it needs a 14-inch rim. Check the wheel arches, suspension and steering lock at full lock in both directions, with the car loaded, and confirm the load index and speed rating against your door-jamb placard. A tyre professional can confirm fitment on your vehicle.

Which size is better, 175/60R14 or 185/55R14?

Neither is better in general — it depends on what you want. 185/55R14 has a -3.2 mm sidewall difference, a +10 mm width difference and a -1.1% diameter difference, so the trade-offs are comfort, grip and instrument accuracy respectively. If the diameter is within the plus-or-minus 3% guideline and the clearance check passes, the choice is a matter of preference; if not, resolve those two points first.