185/80R15 vs 195/70R16: Tyre Size Comparison, Diameter Difference & Speedometer Effect

Comparing 185/80R15 with 195/70R16 comes down to four numbers for each size: diameter, sidewall, circumference and revs per mile. 195/70R16 is the taller tyre: its diameter is 679.4 mm against 677.0 mm, +2.4 mm (+0.4%) larger. The width changes by +10 mm (185 mm to 195 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-tyre 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.

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.

185/80R15 vs 195/70R16 side by side

Measurement 185/80R15 195/70R16 Difference
Overall diameter 677.0 mm (26.7 in) 679.4 mm (26.7 in) +2.4 mm (+0.4%)
Sidewall height 148.0 mm 136.5 mm -11.5 mm
Circumference 2126.9 mm 2134.4 mm +7.5 mm
Revolutions per mile 756.7 754.0 -2.7
Section width 185 mm 195 mm +10 mm
Rim diameter 15 in 16 in +1 in

Diameter difference between 185/80R15 and 195/70R16: +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 +7.5 mm and the revs-per-mile difference of -2.7 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: 185/80R15 to 195/70R16 and back

Here is what the speedometer does in practice. Fit 195/70R16 where 185/80R15 was, and the dial understates or overstates speed by 0.4%: indicated 30 mph is really 30.1 mph, indicated 50 mph is really 50.2 mph, and indicated 70 mph is really 70.2 mph. Swap back from 195/70R16 to 185/80R15 and the error flips sign — 70 mph indicated becomes 69.8 mph. The odometer drifts by the same percentage in each direction, so recorded mileage and any service intervals based on it shift too.

Indicated speed Actual speed fitting 195/70R16 (from 185/80R15) Actual speed fitting 185/80R15 (from 195/70R16)
30 mph 30.1 mph 29.9 mph
50 mph 50.2 mph 49.8 mph
70 mph 70.2 mph 69.8 mph

Sidewall height and ride comfort: 185/80R15 vs 195/70R16

The sidewall is where the ride difference lives. 185/80R15 has 148.0 mm of sidewall and 195/70R16 has 136.5 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: 80% for 185/80R15 against 70% for 195/70R16. 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: 185/80R15 vs 195/70R16

On width, the two sizes are 10 mm apart. The wider tyre (195/70R16) offers more rubber on the road, which tends to mean more grip in the dry and slightly more resistance to roll. Do not expect a dramatic change in fuel use from a width change of this size; the bigger influences on fuel use are the tyre compound, the pressure and the way the car is driven.

Revolutions per mile and gearing: 185/80R15 vs 195/70R16

Gearing follows the circumference. 195/70R16 covers 2134.4 mm per revolution against 2126.9 mm for 185/80R15, so it needs -2.7 fewer revolutions per mile. At a fixed road speed the engine speed drops or rises by the same 0.4% 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 195/70R16 clear after 185/80R15? What to check before fitting

Whether 195/70R16 physically fits is a question for your car, not for this table. The numbers say it is taller by 2.4 mm and 10 mm wider, 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 195 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: 185/80R15 or 195/70R16

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 tyre that rubs is not a viable option at any percentage.

Related 185/80R15 vs 195/70R16 comparisons and tools

Frequently asked questions

What is the diameter difference between 185/80R15 and 195/70R16?

195/70R16 is +2.4 mm (+0.4%) larger in diameter than 185/80R15: 679.4 mm against 677.0 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 195/70R16 instead of 185/80R15?

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 70.2 mph. The full table in both directions is in the speedometer section above.

Is 195/70R16 wider than 185/80R15, and does that matter?

Yes — 195/70R16 is 195 mm wide against 185 mm for 185/80R15, 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 195/70R16 fit my car if 185/80R15 fits?

Not necessarily. 195/70R16 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 tyre professional can confirm fitment on your vehicle.

Which size is better, 185/80R15 or 195/70R16?

Neither is better in general — it depends on what you want. 195/70R16 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.