155/70R13 vs 155/65R14: Tyre Size Comparison, Diameter Difference & Speedometer Effect

Comparing 155/70R13 with 155/65R14 comes down to four numbers for each size: diameter, sidewall, circumference and revs per mile. 155/65R14 is the taller tyre: its diameter is 557.1 mm against 547.2 mm, +9.9 mm (+1.8%) larger. The width changes by +0 mm (155 mm to 155 mm) and the sidewall by -7.7 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.

Taking 155/70r13 vs 155/65r14 tyre size comparison as 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 +1.8% 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.

155/70R13 vs 155/65R14 side by side

Measurement 155/70R13 155/65R14 Difference
Overall diameter 547.2 mm (21.5 in) 557.1 mm (21.9 in) +9.9 mm (+1.8%)
Sidewall height 108.5 mm 100.8 mm -7.7 mm
Circumference 1719.1 mm 1750.2 mm +31.1 mm
Revolutions per mile 936.2 919.5 -16.7
Section width 155 mm 155 mm +0 mm
Rim diameter 13 in 14 in +1 in

Diameter difference between 155/70R13 and 155/65R14: +9.9 mm (+1.8%)

A +1.8% 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 +31.1 mm per revolution, and the revs per mile change by -16.7, 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: 155/70R13 to 155/65R14 and back

Going from 155/70R13 to 155/65R14, the diameter grows by +1.8%, so the true speed is the indicated speed multiplied by 1.018. At 30 mph on the dial the car is really doing 30.5 mph; at 50 mph indicated it is 50.9 mph; at 70 mph indicated it is 71.3 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 155/65R14 back to 155/70R13, the error reverses exactly: the ratio becomes 0.982, so 70 mph indicated is really 68.8 mph.

Indicated speed Actual speed fitting 155/65R14 (from 155/70R13) Actual speed fitting 155/70R13 (from 155/65R14)
30 mph 30.5 mph 29.5 mph
50 mph 50.9 mph 49.1 mph
70 mph 71.3 mph 68.8 mph

Sidewall height and ride comfort: 155/70R13 vs 155/65R14

The sidewall is where the ride difference lives. 155/70R13 has 108.5 mm of sidewall and 155/65R14 has 100.8 mm, a change of -7.7 mm. Less sidewall generally means sharper steering response and less cushioning, so more of the road surface reaches the cabin. The aspect ratios tell the same story in percentage terms: 70% for 155/70R13 against 65% for 155/65R14. Sidewall height also affects vulnerability to kerb damage — a shorter sidewall leaves less rubber between the rim and the road.

Width, grip and fuel use: 155/70R13 vs 155/65R14

Width changes by +0 mm, from 155 mm to 155 mm. With the same width, the contact patch is essentially unchanged, so the grip difference between these two sizes comes from the construction and compound rather than the dimensions. 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: 155/70R13 vs 155/65R14

The revs-per-mile figures (936.2 for 155/70R13, 919.5 for 155/65R14) describe the gearing effect. 155/65R14 turns -16.7 fewer times per mile, so at any given road speed the engine turns slightly slower with 155/65R14 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 1.8% either way, so the effect on everyday driving is subtle rather than transformative.

Will 155/65R14 clear after 155/70R13? What to check before fitting

Whether 155/65R14 physically fits is a question for your car, not for this table. The numbers say it is taller by 9.9 mm and 0 mm the same width, and those are the dimensions that decide clearance — but the actual gaps depend on your arches, suspension and steering geometry. Check at full lock both ways, check with the suspension compressed, and check with the car loaded. Check the placard for the load index and speed rating, and check the rim width for a 155 mm tyre. A tyre professional can confirm all of it in one visit, and that confirmation is the step that turns a comparison into a fitment.

Which size suits which priority: 155/70R13 or 155/65R14

Weigh the four effects separately. Sidewall (-7.7 mm) for comfort. Width (+0 mm) for grip and rolling resistance. Diameter (+1.8%) 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 155/70R13 vs 155/65R14 comparisons and tools

Frequently asked questions

What is the diameter difference between 155/70R13 and 155/65R14?

155/65R14 is +9.9 mm (+1.8%) larger in diameter than 155/70R13: 557.1 mm against 547.2 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 155/65R14 instead of 155/70R13?

For 155/70r13 vs 155/65r14 tyre size comparison, the point is this: The error follows the diameter ratio, +1.8%. At an indicated 30 mph the true speed would be 30.5 mph, at 50 mph indicated it would be 50.9 mph, and at 70 mph indicated it would be 71.3 mph. The full table in both directions is in the speedometer section above.

Is 155/65R14 wider than 155/70R13, and does that matter?

Neither — 155/65R14 is 155 mm wide against 155 mm for 155/70R13, 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 155/65R14 fit my car if 155/70R13 fits?

Not necessarily. 155/65R14 is taller by 9.9 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, 155/70R13 or 155/65R14?

Neither is better in general — it depends on what you want. 155/65R14 has a -7.7 mm sidewall difference, a +0 mm width difference and a +1.8% 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.