175/70R15 vs 185/60R16: Tire Size Comparison, Diameter Difference & Speedometer Effect

Comparing 175/70R15 with 185/60R16 comes down to four numbers for each size: diameter, sidewall, circumference and revs per mile. 185/60R16 is the taller tire: its diameter is 628.4 mm against 626.0 mm, +2.4 mm (+0.4%) larger. The width changes by +10 mm (175 mm to 185 mm) and the sidewall by -11.5 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.

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 +0.4% 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 175/70r15 vs 185/60r16 tire size comparison.

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.

175/70R15 vs 185/60R16 side by side

Measurement 175/70R15 185/60R16 Difference
Overall diameter 626.0 mm (24.6 in) 628.4 mm (24.7 in) +2.4 mm (+0.4%)
Sidewall height 122.5 mm 111.0 mm -11.5 mm
Circumference 1966.6 mm 1974.2 mm +7.6 mm
Revolutions per mile 818.3 815.2 -3.1
Section width 175 mm 185 mm +10 mm
Rim diameter 15 in 16 in +1 in

Diameter difference between 175/70R15 and 185/60R16: +2.4 mm (+0.4%)

The diameter gap of +2.4 mm (+0.4%) 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 +7.6 mm and the revs-per-mile difference of -3.1 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: 175/70R15 to 185/60R16 and back

Going from 175/70R15 to 185/60R16, the diameter grows by +0.4%, so the true speed is the indicated speed multiplied by 1.004. At 30 mph on the dial the car is really doing 30.1 mph; at 50 mph indicated it is 50.2 mph; at 70 mph indicated it is 70.3 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 185/60R16 back to 175/70R15, the error reverses exactly: the ratio becomes 0.996, so 70 mph indicated is really 69.7 mph.

Indicated speed Actual speed fitting 185/60R16 (from 175/70R15) Actual speed fitting 175/70R15 (from 185/60R16)
30 mph 30.1 mph 29.9 mph
50 mph 50.2 mph 49.8 mph
70 mph 70.3 mph 69.7 mph

Sidewall height and ride comfort: 175/70R15 vs 185/60R16

The sidewall is where the ride difference lives. 175/70R15 has 122.5 mm of sidewall and 185/60R16 has 111.0 mm, a change of -11.5 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 175/70R15 against 60% for 185/60R16. 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: 175/70R15 vs 185/60R16

The width gap is 10 mm (175 mm against 185 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 tire fits the rim: a 185 mm tire needs a rim width within the range its maker approves, and a rim that suited 175/70R15 may not suit 185/60R16. That is a separate check from the diameter comparison, and it belongs on the list before anything is fitted.

Revolutions per mile and gearing: 175/70R15 vs 185/60R16

The revs-per-mile figures (818.3 for 175/70R15, 815.2 for 185/60R16) describe the gearing effect. 185/60R16 turns -3.1 fewer times per mile, so at any given road speed the engine turns slightly slower with 185/60R16 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 0.4% either way, so the effect on everyday driving is subtle rather than transformative.

Will 185/60R16 clear after 175/70R15? What to check before fitting

Clearance is the check the numbers cannot do for you. 185/60R16 is taller and 10 mm wider than 175/70R15, 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 185/60R16 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 185/60R16 meet what your placard asks for, and that the 16-inch rim suits the car.

Which size suits which priority: 175/70R15 or 185/60R16

Choose on the basis of what matters to you, not on the headline alone. If ride comfort matters most, the sidewall change of -11.5 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 +0.4% 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 tire that rubs is not a viable option at any percentage.

Related 175/70R15 vs 185/60R16 comparisons and tools

Frequently asked questions

What is the diameter difference between 175/70R15 and 185/60R16?

185/60R16 is +2.4 mm (+0.4%) larger in diameter than 175/70R15: 628.4 mm against 626.0 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 185/60R16 instead of 175/70R15?

For 175/70r15 vs 185/60r16 tire size comparison, the point is this: The error follows the diameter ratio, +0.4%. At an indicated 30 mph the true speed would be 30.1 mph, at 50 mph indicated it would be 50.2 mph, and at 70 mph indicated it would be 70.3 mph. The full table in both directions is in the speedometer section above.

Is 185/60R16 wider than 175/70R15, and does that matter?

Yes — 185/60R16 is 185 mm wide against 175 mm for 175/70R15, a difference of +10 mm. A wider tire 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 185/60R16 fit my car if 175/70R15 fits?

Not necessarily. 185/60R16 is taller by 2.4 mm and 10 mm wider, and it needs a 16-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, 175/70R15 or 185/60R16?

Neither is better in general — it depends on what you want. 185/60R16 has a -11.5 mm sidewall difference, a +10 mm width difference and a +0.4% 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.