165/70R13 vs 175/65R13: Tyre Size Comparison, Diameter Difference & Speedometer Effect

165/70R13 and 175/65R13 look like near neighbours on paper, but the numbers tell a more precise story. 175/65R13 is the shorter tyre: its diameter is 557.7 mm against 561.2 mm, -3.5 mm (-0.6%) smaller. Width moves +10 mm, sidewall height moves -1.7 mm, and the circumference changes by -11.0 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.

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 -0.6% 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. That is the point this page works through for 165/70r13 vs 175/65r13.

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 175/65R13 side by side

Measurement 165/70R13 175/65R13 Difference
Overall diameter 561.2 mm (22.1 in) 557.7 mm (22.0 in) -3.5 mm (-0.6%)
Sidewall height 115.5 mm 113.8 mm -1.7 mm
Circumference 1763.1 mm 1752.1 mm -11.0 mm
Revolutions per mile 912.8 918.5 +5.7
Section width 165 mm 175 mm +10 mm
Rim diameter 13 in 13 in +0 in

Diameter difference between 165/70R13 and 175/65R13: -3.5 mm (-0.6%)

The diameter gap of -3.5 mm (-0.6%) 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 -11.0 mm and the revs-per-mile difference of +5.7 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 175/65R13 and back

The maths is a single ratio. 175/65R13 over 165/70R13 is 0.994, so every indicated speed after the swap is multiplied by that number to get the true speed: 30 becomes 29.8, 50 becomes 49.7 and 70 becomes 69.6 mph. In the reverse direction the ratio is 1.006, so 70 mph indicated is 70.4 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 175/65R13 (from 165/70R13) Actual speed fitting 165/70R13 (from 175/65R13)
30 mph 29.8 mph 30.2 mph
50 mph 49.7 mph 50.3 mph
70 mph 69.6 mph 70.4 mph

Sidewall height and ride comfort: 165/70R13 vs 175/65R13

Look at the sidewalls next. 115.5 mm on 165/70R13, 113.8 mm on 175/65R13: a difference of -1.7 mm. That is the flexible part of the tyre, 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 (70% vs 65%) is simply the sidewall expressed as a share of the width.

Width, grip and fuel use: 165/70R13 vs 175/65R13

The width gap is 10 mm (165 mm against 175 mm). Going wider usually buys dry grip and a more planted feel, and it costs a little in rolling resistance and road noise. Remember that width also decides whether the tyre fits the rim: a 175 mm tyre needs a rim width within the range its maker approves, and a rim that suited 165/70R13 may not suit 175/65R13. That is a separate check from the diameter comparison, and it belongs on the list before anything is fitted.

Revolutions per mile and gearing: 165/70R13 vs 175/65R13

The revs-per-mile figures (912.8 for 165/70R13, 918.5 for 175/65R13) describe the gearing effect. 175/65R13 turns +5.7 fewer times per mile, so at any given road speed the engine turns slightly slower with 175/65R13 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 0.6% either way, so the effect on everyday driving is subtle rather than transformative.

Will 175/65R13 clear after 165/70R13? What to check before fitting

Do not skip the physical check. The diameter difference is -0.6% and the width difference is +10 mm, and both of those affect whether 175/65R13 fits where 165/70R13 did. Check the gap between the tyre and the arch, the gap to the suspension arms and struts, and the clearance at full steering lock in both directions. Repeat the check with weight in the car, because suspension travel changes the geometry. If the tyre touches anything at any point in that check, it does not fit, whatever the diameter percentage says. The load index and speed rating need confirming against the placard too, and the rim width must suit a 175 mm tyre.

Which size suits which priority: 165/70R13 or 175/65R13

Choose on the basis of what matters to you, not on the headline alone. If ride comfort matters most, the sidewall change of -1.7 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 -0.6% 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. That is the point this page works through for 165/70r13 vs 175/65r13.

Related 165/70R13 vs 175/65R13 comparisons and tools

Frequently asked questions

What is the diameter difference between 165/70R13 and 175/65R13?

175/65R13 is -3.5 mm (-0.6%) smaller in diameter than 165/70R13: 557.7 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 175/65R13 instead of 165/70R13?

For 165/70r13 vs 175/65r13, the point is this: The error follows the diameter ratio, -0.6%. At an indicated 30 mph the true speed would be 29.8 mph, at 50 mph indicated it would be 49.7 mph, and at 70 mph indicated it would be 69.6 mph. The full table in both directions is in the speedometer section above.

Is 175/65R13 wider than 165/70R13, and does that matter?

Yes — 175/65R13 is 175 mm wide against 165 mm for 165/70R13, 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 175/65R13 fit my car if 165/70R13 fits?

Not necessarily. 175/65R13 is shorter by 3.5 mm and 10 mm wider, and it needs a 13-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 175/65R13?

Neither is better in general — it depends on what you want. 175/65R13 has a -1.7 mm sidewall difference, a +10 mm width difference and a -0.6% 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.