195/60R14 vs 185/60R15: Tyre Size Comparison, Diameter Difference & Speedometer Effect

If you are choosing between 195/60R14 and 185/60R15, the first question is how far apart they really are. 185/60R15 is the taller tyre: its diameter is 603.0 mm against 589.6 mm, +13.4 mm (+2.3%) larger. The sidewall goes from 117.0 mm to 111.0 mm (-6.0 mm), the circumference from 1852.3 mm to 1894.4 mm, and the revs per mile from 868.8 to 849.5. 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-tyre 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.

195/60R14 vs 185/60R15 side by side

Measurement 195/60R14 185/60R15 Difference
Overall diameter 589.6 mm (23.2 in) 603.0 mm (23.7 in) +13.4 mm (+2.3%)
Sidewall height 117.0 mm 111.0 mm -6.0 mm
Circumference 1852.3 mm 1894.4 mm +42.1 mm
Revolutions per mile 868.8 849.5 -19.3
Section width 195 mm 185 mm -10 mm
Rim diameter 14 in 15 in +1 in

Diameter difference between 195/60R14 and 185/60R15: +13.4 mm (+2.3%)

Put the percentage in context. The plus-or-minus 3% guideline exists because small diameter changes produce small speedometer errors, and this change is +2.3%, which is inside that band. In revs per mile the shift is -19.3 (868.8 to 849.5), and in circumference it is +42.1 mm per turn. Those are not abstract figures: every mile you drive, the car covers +42.1 mm more or less per wheel revolution than the instruments expect, and the gap accumulates exactly like interest.

Speedometer error: 195/60R14 to 185/60R15 and back

Going from 195/60R14 to 185/60R15, the diameter grows by +2.3%, so the true speed is the indicated speed multiplied by 1.023. At 30 mph on the dial the car is really doing 30.7 mph; at 50 mph indicated it is 51.1 mph; at 70 mph indicated it is 71.6 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 185/60R15 back to 195/60R14, the error reverses exactly: the ratio becomes 0.978, so 70 mph indicated is really 68.4 mph.

Indicated speed Actual speed fitting 185/60R15 (from 195/60R14) Actual speed fitting 195/60R14 (from 185/60R15)
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: 195/60R14 vs 185/60R15

Look at the sidewalls next. 117.0 mm on 195/60R14, 111.0 mm on 185/60R15: a difference of -6.0 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 (60% vs 60%) is simply the sidewall expressed as a share of the width.

Width, grip and fuel use: 195/60R14 vs 185/60R15

The width gap is 10 mm (195 mm against 185 mm). Going narrower usually trims rolling resistance and can improve behaviour in standing water, and it costs a little in dry grip. Remember that width also decides whether the tyre fits the rim: a 185 mm tyre needs a rim width within the range its maker approves, and a rim that suited 195/60R14 may not suit 185/60R15. That is a separate check from the diameter comparison, and it belongs on the list before anything is fitted.

Revolutions per mile and gearing: 195/60R14 vs 185/60R15

Gearing follows the circumference. 185/60R15 covers 1894.4 mm per revolution against 1852.3 mm for 195/60R14, so it needs -19.3 fewer revolutions per mile. At a fixed road speed the engine speed drops or rises by the same 2.3% 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 185/60R15 clear after 195/60R14? What to check before fitting

Whether 185/60R15 physically fits is a question for your car, not for this table. The numbers say it is taller by 13.4 mm and 10 mm narrower, 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 185 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: 195/60R14 or 185/60R15

Choose on the basis of what matters to you, not on the headline alone. If ride comfort matters most, the sidewall change of -6.0 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 +2.3% 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 195/60R14 vs 185/60R15 comparisons and tools

Frequently asked questions

What is the diameter difference between 195/60R14 and 185/60R15?

185/60R15 is +13.4 mm (+2.3%) larger in diameter than 195/60R14: 603.0 mm against 589.6 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 185/60R15 instead of 195/60R14?

Taking 195/60r14 vs 185/60r15 tyre size comparison as the case in point: 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 185/60R15 wider than 195/60R14, and does that matter?

No — 185/60R15 is 185 mm wide against 195 mm for 195/60R14, 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 185/60R15 fit my car if 195/60R14 fits?

Not necessarily. 185/60R15 is taller by 13.4 mm and 10 mm narrower, and it needs a 15-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, 195/60R14 or 185/60R15?

Neither is better in general — it depends on what you want. 185/60R15 has a -6.0 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.