165/65R13 vs 155/65R14: Tire Size Comparison, Diameter Difference & Speedometer Effect

If you are choosing between 165/65R13 and 155/65R14, the first question is how far apart they really are. 155/65R14 is the taller tire: its diameter is 557.1 mm against 544.7 mm, +12.4 mm (+2.3%) larger. The sidewall goes from 107.2 mm to 100.8 mm (-6.4 mm), the circumference from 1711.2 mm to 1750.2 mm, and the revs per mile from 940.5 to 919.5. 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.

Before the tables, keep the context straight. These are nominal new-tire dimensions, computed from the size codes: real tyres vary slightly by brand, model, wear and inflation pressure. A +2.3% 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.

165/65R13 vs 155/65R14 side by side

Measurement 165/65R13 155/65R14 Difference
Overall diameter 544.7 mm (21.4 in) 557.1 mm (21.9 in) +12.4 mm (+2.3%)
Sidewall height 107.2 mm 100.8 mm -6.4 mm
Circumference 1711.2 mm 1750.2 mm +39.0 mm
Revolutions per mile 940.5 919.5 -21.0
Section width 165 mm 155 mm -10 mm
Rim diameter 13 in 14 in +1 in

Diameter difference between 165/65R13 and 155/65R14: +12.4 mm (+2.3%)

The diameter gap of +12.4 mm (+2.3%) is the number to carry away from this section. It is inside the plus-or-minus 3% guideline, and it shows up directly in the speedometer tables below. The circumference difference of +39.0 mm and the revs-per-mile difference of -21.0 are the same change expressed differently — the first is what the road sees, the second is what the car's sensors count. Neither is a safety judgement on its own; both are inputs to the fitment checks further down the page.

Speedometer error: 165/65R13 to 155/65R14 and back

Here is what the speedometer does in practice. Fit 155/65R14 where 165/65R13 was, and the dial understates or overstates speed by 2.3%: indicated 30 mph is really 30.7 mph, indicated 50 mph is really 51.1 mph, and indicated 70 mph is really 71.6 mph. Swap back from 155/65R14 to 165/65R13 and the error flips sign — 70 mph indicated becomes 68.4 mph. The odometer drifts by the same percentage in each direction, so recorded mileage and any service intervals based on it shift too.

Indicated speed Actual speed fitting 155/65R14 (from 165/65R13) Actual speed fitting 165/65R13 (from 155/65R14)
30 mph 30.7 mph 29.3 mph
50 mph 51.1 mph 48.9 mph
70 mph 71.6 mph 68.4 mph

Sidewall height and ride comfort: 165/65R13 vs 155/65R14

Look at the sidewalls next. 107.2 mm on 165/65R13, 100.8 mm on 155/65R14: a difference of -6.4 mm. That is the flexible part of the tire, and it is the first thing that absorbs a bump. A shorter sidewall transmits more of the road to the driver, which feels more direct but less forgiving on rough surfaces. Aspect ratio (65% vs 65%) is simply the sidewall expressed as a share of the width.

Width, grip and fuel use: 165/65R13 vs 155/65R14

Width changes by -10 mm, from 165 mm to 155 mm. A narrower tire puts a smaller contact patch on the road, which generally reduces rolling resistance and can help in standing water, but it gives up some dry grip compared with the wider size. Fuel use moves with rolling resistance, so a wider tire can cost a small amount of fuel over time — the effect is real but modest for a change of this size, and it is not something this page can put a precise number on without knowing the exact tire models involved.

Revolutions per mile and gearing: 165/65R13 vs 155/65R14

Think of the gearing change as the diameter change in disguise. The revs-per-mile gap is -21.0, which is 2.3% of the original figure — the same percentage as the diameter gap. That is because revs per mile is just a mile divided by the circumference, and the circumference is pi times the diameter. So everything the gearing does — engine speed at a given road speed, acceleration in each gear, cruising refinement — shifts by 2.3% and no more. Small percentages mean small effects, which is another reason the plus-or-minus 3% guideline is a useful yardstick.

Will 155/65R14 clear after 165/65R13? What to check before fitting

Clearance is the check the numbers cannot do for you. 155/65R14 is taller and 10 mm narrower than 165/65R13, 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 155/65R14 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 155/65R14 meet what your placard asks for, and that the 14-inch rim suits the car.

Which size suits which priority: 165/65R13 or 155/65R14

The decision comes down to priorities. Comfort follows the sidewall (-6.4 mm here). Grip follows the width (-10 mm here). Instrument accuracy follows the diameter (+2.3% here). Gearing and cruising engine speed follow the revs-per-mile change (-21.0). 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 165/65R13 vs 155/65R14 comparisons and tools

Frequently asked questions

What is the diameter difference between 165/65R13 and 155/65R14?

155/65R14 is +12.4 mm (+2.3%) larger in diameter than 165/65R13: 557.1 mm against 544.7 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 155/65R14 instead of 165/65R13?

For 165/65r13 vs 155/65r14 tire size comparison, the point is this: The error follows the diameter ratio, +2.3%. At an indicated 30 mph the true speed would be 30.7 mph, at 50 mph indicated it would be 51.1 mph, and at 70 mph indicated it would be 71.6 mph. The full table in both directions is in the speedometer section above.

Is 155/65R14 wider than 165/65R13, and does that matter?

No — 155/65R14 is 155 mm wide against 165 mm for 165/65R13, a difference of -10 mm. A narrower tire generally gives less rolling resistance and can behave better in standing water, with slightly less dry grip. Width also affects clearance, so check the arches and suspension at full lock.

Will 155/65R14 fit my car if 165/65R13 fits?

Not necessarily. 155/65R14 is taller by 12.4 mm and 10 mm narrower, 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 tire professional can confirm fitment on your vehicle.

Which size is better, 165/65R13 or 155/65R14?

Neither is better in general — it depends on what you want. 155/65R14 has a -6.4 mm sidewall difference, a -10 mm width difference and a +2.3% 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.