185/60R13 vs 185/55R14: Tyre Size Comparison, Diameter Difference & Speedometer Effect

If you are choosing between 185/60R13 and 185/55R14, the first question is how far apart they really are. 185/55R14 is the taller tyre: its diameter is 559.1 mm against 552.2 mm, +6.9 mm (+1.2%) larger. The sidewall goes from 111.0 mm to 101.8 mm (-9.2 mm), the circumference from 1734.8 mm to 1756.5 mm, and the revs per mile from 927.7 to 916.2. The tables below lay all of that out, then work through the speedometer effect in each direction and the clearance checks that matter before either size goes on the car.

Two things decide whether this swap makes sense: the diameter difference and the physical fit. On diameter, 185/55R14 is +1.2% larger than 185/60R13, which is inside the plus-or-minus 3% guideline. On physical fit, the width change of +0 mm and the rim change from 13 to 14 inches both need checking against the arches, suspension and steering lock. The sections below take each of those in turn, with the numbers worked out rather than asserted.

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.

185/60R13 vs 185/55R14 side by side

Measurement 185/60R13 185/55R14 Difference
Overall diameter 552.2 mm (21.7 in) 559.1 mm (22.0 in) +6.9 mm (+1.2%)
Sidewall height 111.0 mm 101.8 mm -9.2 mm
Circumference 1734.8 mm 1756.5 mm +21.7 mm
Revolutions per mile 927.7 916.2 -11.5
Section width 185 mm 185 mm +0 mm
Rim diameter 13 in 14 in +1 in

Diameter difference between 185/60R13 and 185/55R14: +6.9 mm (+1.2%)

A +1.2% 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 +21.7 mm per revolution, and the revs per mile change by -11.5, 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: 185/60R13 to 185/55R14 and back

Going from 185/60R13 to 185/55R14, the diameter grows by +1.2%, so the true speed is the indicated speed multiplied by 1.012. At 30 mph on the dial the car is really doing 30.4 mph; at 50 mph indicated it is 50.6 mph; at 70 mph indicated it is 70.9 mph. The speedometer therefore reads low after the change, which matters most at motorway speed, where even a small percentage is a real difference in miles per hour. Going the other way, from 185/55R14 back to 185/60R13, the error reverses exactly: the ratio becomes 0.988, so 70 mph indicated is really 69.1 mph.

Indicated speed Actual speed fitting 185/55R14 (from 185/60R13) Actual speed fitting 185/60R13 (from 185/55R14)
30 mph 30.4 mph 29.6 mph
50 mph 50.6 mph 49.4 mph
70 mph 70.9 mph 69.1 mph

Sidewall height and ride comfort: 185/60R13 vs 185/55R14

Sidewall height moves by -9.2 mm between these two sizes (111.0 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%. That is the point this page works through for 185/60r13 vs 185/55r14.

Width, grip and fuel use: 185/60R13 vs 185/55R14

The width gap is 0 mm (185 mm against 185 mm). Because the width is identical, grip differences here depend on the specific tyre rather than the size code. Remember that width also decides whether the tyre fits the rim: a 185 mm tyre needs a rim width within the range its maker approves, and a rim that suited 185/60R13 may not suit 185/55R14. That is a separate check from the diameter comparison, and it belongs on the list before anything is fitted.

Revolutions per mile and gearing: 185/60R13 vs 185/55R14

The revs-per-mile figures (927.7 for 185/60R13, 916.2 for 185/55R14) describe the gearing effect. 185/55R14 turns -11.5 fewer times per mile, so at any given road speed the engine turns slightly slower with 185/55R14 fitted — the gearing is effectively longer. That can make cruising a touch more relaxed and can trim fuel use slightly, but it also means slightly less acceleration from the same throttle opening, because each gear is effectively taller. The change is 1.2% either way, so the effect on everyday driving is subtle rather than transformative.

Will 185/55R14 clear after 185/60R13? What to check before fitting

Clearance is the check the numbers cannot do for you. 185/55R14 is taller and 0 mm the same width than 185/60R13, 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: 185/60R13 or 185/55R14

On this page, 185/60r13 vs 185/55r14 is the case in point: Weigh the four effects separately. Sidewall (-9.2 mm) for comfort. Width (+0 mm) for grip and rolling resistance. Diameter (+1.2%) for the speedometer, odometer and gearing. And clearance for whether the swap is physically possible at all. If the diameter is inside the plus-or-minus 3% guideline and the clearance check passes, the remaining differences are small enough to be a matter of taste; if either of those fails, the comparison is academic until it is resolved.

Related 185/60R13 vs 185/55R14 comparisons and tools

Frequently asked questions

What is the diameter difference between 185/60R13 and 185/55R14?

185/55R14 is +6.9 mm (+1.2%) larger in diameter than 185/60R13: 559.1 mm against 552.2 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 185/60R13?

The error follows the diameter ratio, +1.2%. At an indicated 30 mph the true speed would be 30.4 mph, at 50 mph indicated it would be 50.6 mph, and at 70 mph indicated it would be 70.9 mph. The full table in both directions is in the speedometer section above.

Is 185/55R14 wider than 185/60R13, and does that matter?

Neither — 185/55R14 is 185 mm wide against 185 mm for 185/60R13, a difference of +0 mm. With the same width, grip differences come from the specific tyre rather than the size. Width also affects clearance, so check the arches and suspension at full lock.

Will 185/55R14 fit my car if 185/60R13 fits?

Not necessarily. 185/55R14 is taller by 6.9 mm and 0 mm the same width, 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, 185/60R13 or 185/55R14?

Neither is better in general — it depends on what you want. 185/55R14 has a -9.2 mm sidewall difference, a +0 mm width difference and a +1.2% 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.