195/75R14 vs 195/70R15: Tyre Size Comparison, Diameter Difference & Speedometer Effect

Comparing 195/75R14 with 195/70R15 comes down to four numbers for each size: diameter, sidewall, circumference and revs per mile. 195/70R15 is the taller tyre: its diameter is 654.0 mm against 648.1 mm, +5.9 mm (+0.9%) larger. The width changes by +0 mm (195 mm to 195 mm) and the sidewall by -9.7 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.

Two things decide whether this swap makes sense: the diameter difference and the physical fit. On diameter, 195/70R15 is +0.9% larger than 195/75R14, which is inside the plus-or-minus 3% guideline. On physical fit, the width change of +0 mm and the rim change from 14 to 15 inches both need checking against the arches, suspension and steering lock. The sections below take each of those in turn, with the numbers worked out rather than asserted.

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.

195/75R14 vs 195/70R15 side by side

Measurement 195/75R14 195/70R15 Difference
Overall diameter 648.1 mm (25.5 in) 654.0 mm (25.7 in) +5.9 mm (+0.9%)
Sidewall height 146.2 mm 136.5 mm -9.7 mm
Circumference 2036.1 mm 2054.6 mm +18.5 mm
Revolutions per mile 790.4 783.3 -7.1
Section width 195 mm 195 mm +0 mm
Rim diameter 14 in 15 in +1 in

Diameter difference between 195/75R14 and 195/70R15: +5.9 mm (+0.9%)

Put the percentage in context. The plus-or-minus 3% guideline exists because small diameter changes produce small speedometer errors, and this change is +0.9%, which is inside that band. In revs per mile the shift is -7.1 (790.4 to 783.3), and in circumference it is +18.5 mm per turn. Those are not abstract figures: every mile you drive, the car covers +18.5 mm more or less per wheel revolution than the instruments expect, and the gap accumulates exactly like interest.

Speedometer error: 195/75R14 to 195/70R15 and back

Here is what the speedometer does in practice. Fit 195/70R15 where 195/75R14 was, and the dial understates or overstates speed by 0.9%: indicated 30 mph is really 30.3 mph, indicated 50 mph is really 50.5 mph, and indicated 70 mph is really 70.6 mph. Swap back from 195/70R15 to 195/75R14 and the error flips sign — 70 mph indicated becomes 69.4 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 195/70R15 (from 195/75R14) Actual speed fitting 195/75R14 (from 195/70R15)
30 mph 30.3 mph 29.7 mph
50 mph 50.5 mph 49.5 mph
70 mph 70.6 mph 69.4 mph

Sidewall height and ride comfort: 195/75R14 vs 195/70R15

Look at the sidewalls next. 146.2 mm on 195/75R14, 136.5 mm on 195/70R15: a difference of -9.7 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 (75% vs 70%) is simply the sidewall expressed as a share of the width.

Width, grip and fuel use: 195/75R14 vs 195/70R15

On width, the two sizes are 0 mm apart. The width is the same, so neither size has a contact-patch advantage over the other. Both are 195 mm wide, so the difference here is the aspect ratio (75% vs 70%) and the rim (14 in vs 15 in). 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: 195/75R14 vs 195/70R15

Think of the gearing change as the diameter change in disguise. The revs-per-mile gap is -7.1, which is 0.9% of the original figure — the same percentage as the diameter gap. That is because revs per mile is just a mile divided by the circumference, and the circumference is pi times the diameter. So everything the gearing does — engine speed at a given road speed, acceleration in each gear, cruising refinement — shifts by 0.9% and no more. Small percentages mean small effects, which is another reason the plus-or-minus 3% guideline is a useful yardstick.

Will 195/70R15 clear after 195/75R14? What to check before fitting

Whether 195/70R15 physically fits is a question for your car, not for this table. The numbers say it is taller by 5.9 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 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: 195/75R14 or 195/70R15

For 195/75r14 vs 195/70r15 tyre size comparison, the point is this: Choose on the basis of what matters to you, not on the headline alone. If ride comfort matters most, the sidewall change of -9.7 mm is the figure to weigh. If grip matters most, the width change of +0 mm is the one to weigh. If keeping the instruments accurate matters most, the diameter change of +0.9% 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 195/75R14 vs 195/70R15 comparisons and tools

Frequently asked questions

What is the diameter difference between 195/75R14 and 195/70R15?

195/70R15 is +5.9 mm (+0.9%) larger in diameter than 195/75R14: 654.0 mm against 648.1 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 195/70R15 instead of 195/75R14?

Taking 195/75r14 vs 195/70r15 tyre size comparison as the case in point: The error follows the diameter ratio, +0.9%. At an indicated 30 mph the true speed would be 30.3 mph, at 50 mph indicated it would be 50.5 mph, and at 70 mph indicated it would be 70.6 mph. The full table in both directions is in the speedometer section above.

Is 195/70R15 wider than 195/75R14, and does that matter?

Neither — 195/70R15 is 195 mm wide against 195 mm for 195/75R14, 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 195/70R15 fit my car if 195/75R14 fits?

Not necessarily. 195/70R15 is taller by 5.9 mm and 0 mm the same width, 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, 195/75R14 or 195/70R15?

Neither is better in general — it depends on what you want. 195/70R15 has a -9.7 mm sidewall difference, a +0 mm width difference and a +0.9% 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.