165/70R13 vs 155/70R14: Tyre Size Comparison, Diameter Difference & Speedometer Effect

Comparing 165/70R13 with 155/70R14 comes down to four numbers for each size: diameter, sidewall, circumference and revs per mile. 155/70R14 is the taller tyre: its diameter is 572.6 mm against 561.2 mm, +11.4 mm (+2.0%) larger. The width changes by -10 mm (165 mm to 155 mm) and the sidewall by -7.0 mm. This page puts both sizes side by side, works out the diameter difference in millimetres and percent, shows the speedometer error in both directions at 30, 50 and 70 mph, and explains what the change means for ride, grip and clearance — so you can judge the swap with the actual figures in front of you.

On this page, 165/70r13 vs 155/70r14 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 +2.0% 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.

165/70R13 vs 155/70R14 side by side

Measurement 165/70R13 155/70R14 Difference
Overall diameter 561.2 mm (22.1 in) 572.6 mm (22.5 in) +11.4 mm (+2.0%)
Sidewall height 115.5 mm 108.5 mm -7.0 mm
Circumference 1763.1 mm 1798.9 mm +35.8 mm
Revolutions per mile 912.8 894.6 -18.2
Section width 165 mm 155 mm -10 mm
Rim diameter 13 in 14 in +1 in

Diameter difference between 165/70R13 and 155/70R14: +11.4 mm (+2.0%)

The diameter gap of +11.4 mm (+2.0%) 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 +35.8 mm and the revs-per-mile difference of -18.2 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: 165/70R13 to 155/70R14 and back

The maths is a single ratio. 155/70R14 over 165/70R13 is 1.020, so every indicated speed after the swap is multiplied by that number to get the true speed: 30 becomes 30.6, 50 becomes 51.0 and 70 becomes 71.4 mph. In the reverse direction the ratio is 0.980, so 70 mph indicated is 68.6 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 155/70R14 (from 165/70R13) Actual speed fitting 165/70R13 (from 155/70R14)
30 mph 30.6 mph 29.4 mph
50 mph 51.0 mph 49.0 mph
70 mph 71.4 mph 68.6 mph

Sidewall height and ride comfort: 165/70R13 vs 155/70R14

Sidewall height moves by -7.0 mm between these two sizes (115.5 mm to 108.5 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 70% to 70%.

Width, grip and fuel use: 165/70R13 vs 155/70R14

Width changes by -10 mm, from 165 mm to 155 mm. A narrower tyre 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 tyre 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 tyre models involved.

Revolutions per mile and gearing: 165/70R13 vs 155/70R14

Gearing follows the circumference. 155/70R14 covers 1798.9 mm per revolution against 1763.1 mm for 165/70R13, so it needs -18.2 fewer revolutions per mile. At a fixed road speed the engine speed drops or rises by the same 2.0% as the diameter change. With the taller size the engine sits slightly lower in the rev range at cruising speed, which some drivers like and which can help fuel use a little. Either way the effect is proportional to the diameter difference, not larger than it.

Will 155/70R14 clear after 165/70R13? What to check before fitting

Clearance is the check the numbers cannot do for you. 155/70R14 is taller and 10 mm narrower than 165/70R13, 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 155/70R14 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 155/70R14 meet what your placard asks for, and that the 14-inch rim suits the car.

Which size suits which priority: 165/70R13 or 155/70R14

For 165/70r13 vs 155/70r14, the point is this: Choose on the basis of what matters to you, not on the headline alone. If ride comfort matters most, the sidewall change of -7.0 mm is the figure to weigh. If grip matters most, the width change of -10 mm is the one to weigh. If keeping the instruments accurate matters most, the diameter change of +2.0% is the one to weigh — and if it is outside the plus-or-minus 3% guideline, ask about recalibration. And if the answer to the clearance check is uncertain, that outranks all three: a tyre that rubs is not a viable option at any percentage.

Related 165/70R13 vs 155/70R14 comparisons and tools

Frequently asked questions

What is the diameter difference between 165/70R13 and 155/70R14?

155/70R14 is +11.4 mm (+2.0%) larger in diameter than 165/70R13: 572.6 mm against 561.2 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 155/70R14 instead of 165/70R13?

The error follows the diameter ratio, +2.0%. At an indicated 30 mph the true speed would be 30.6 mph, at 50 mph indicated it would be 51.0 mph, and at 70 mph indicated it would be 71.4 mph. The full table in both directions is in the speedometer section above. That is the point this page works through for 165/70r13 vs 155/70r14.

Is 155/70R14 wider than 165/70R13, and does that matter?

No — 155/70R14 is 155 mm wide against 165 mm for 165/70R13, a difference of -10 mm. A narrower tyre 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 155/70R14 fit my car if 165/70R13 fits?

Not necessarily. 155/70R14 is taller by 11.4 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 tyre professional can confirm fitment on your vehicle.

Which size is better, 165/70R13 or 155/70R14?

Neither is better in general — it depends on what you want. 155/70R14 has a -7.0 mm sidewall difference, a -10 mm width difference and a +2.0% 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.