195/80R15 vs 205/75R15: Tyre Size Comparison, Diameter Difference & Speedometer Effect

Comparing 195/80R15 with 205/75R15 comes down to four numbers for each size: diameter, sidewall, circumference and revs per mile. 205/75R15 is the shorter tyre: its diameter is 688.5 mm against 693.0 mm, -4.5 mm (-0.6%) smaller. The width changes by +10 mm (195 mm to 205 mm) and the sidewall by -2.2 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.

Taking 195/80r15 vs 205/75r15 tyre size comparison as the case in point: The short version: a -0.6% diameter difference is inside the commonly used plus-or-minus 3% guideline, which is the usual yardstick for keeping speedometer error small. But diameter is only the first check. The two sizes also differ in width by 10 mm and in rim size (15 inches against 15 inches), so a swap means different wheels as well unless the rims already match. Read the whole comparison before deciding — the clearance and load-index sections matter as much as the headline percentage.

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.

195/80R15 vs 205/75R15 side by side

Measurement 195/80R15 205/75R15 Difference
Overall diameter 693.0 mm (27.3 in) 688.5 mm (27.1 in) -4.5 mm (-0.6%)
Sidewall height 156.0 mm 153.8 mm -2.2 mm
Circumference 2177.1 mm 2163.0 mm -14.1 mm
Revolutions per mile 739.2 744.0 +4.8
Section width 195 mm 205 mm +10 mm
Rim diameter 15 in 15 in +0 in

Diameter difference between 195/80R15 and 205/75R15: -4.5 mm (-0.6%)

Put the percentage in context. The plus-or-minus 3% guideline exists because small diameter changes produce small speedometer errors, and this change is -0.6%, which is inside that band. In revs per mile the shift is +4.8 (739.2 to 744.0), and in circumference it is -14.1 mm per turn. Those are not abstract figures: every mile you drive, the car covers -14.1 mm more or less per wheel revolution than the instruments expect, and the gap accumulates exactly like interest.

Speedometer error: 195/80R15 to 205/75R15 and back

Going from 195/80R15 to 205/75R15, the diameter grows by -0.6%, so the true speed is the indicated speed multiplied by 0.994. At 30 mph on the dial the car is really doing 29.8 mph; at 50 mph indicated it is 49.7 mph; at 70 mph indicated it is 69.5 mph. The speedometer therefore reads high 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 205/75R15 back to 195/80R15, the error reverses exactly: the ratio becomes 1.007, so 70 mph indicated is really 70.5 mph.

Indicated speed Actual speed fitting 205/75R15 (from 195/80R15) Actual speed fitting 195/80R15 (from 205/75R15)
30 mph 29.8 mph 30.2 mph
50 mph 49.7 mph 50.3 mph
70 mph 69.5 mph 70.5 mph

Sidewall height and ride comfort: 195/80R15 vs 205/75R15

Sidewall height moves by -2.2 mm between these two sizes (156.0 mm to 153.8 mm), and that is enough to feel. A taller sidewall flexes more, which softens sharp impacts and gives the tyre more give over potholes; a shorter sidewall flexes less, which sharpens the steering response and leaves the rim closer to the road surface on a hard hit. Which of those you get depends on the direction of the change — here the sidewall shrinks — and on the aspect ratio shift from 80% to 75%.

Width, grip and fuel use: 195/80R15 vs 205/75R15

The width gap is 10 mm (195 mm against 205 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 205 mm tyre needs a rim width within the range its maker approves, and a rim that suited 195/80R15 may not suit 205/75R15. That is a separate check from the diameter comparison, and it belongs on the list before anything is fitted.

Revolutions per mile and gearing: 195/80R15 vs 205/75R15

Gearing follows the circumference. 205/75R15 covers 2163.0 mm per revolution against 2177.1 mm for 195/80R15, so it needs +4.8 fewer revolutions per mile. At a fixed road speed the engine speed drops or rises by the same 0.6% as the diameter change. With the shorter size the engine sits slightly higher in the rev range at cruising speed, which sharpens response a little at the cost of a small amount of fuel. Either way the effect is proportional to the diameter difference, not larger than it.

Will 205/75R15 clear after 195/80R15? 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 205/75R15 fits where 195/80R15 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 205 mm tyre.

Which size suits which priority: 195/80R15 or 205/75R15

Choose on the basis of what matters to you, not on the headline alone. If ride comfort matters most, the sidewall change of -2.2 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.

Related 195/80R15 vs 205/75R15 comparisons and tools

Frequently asked questions

What is the diameter difference between 195/80R15 and 205/75R15?

205/75R15 is -4.5 mm (-0.6%) smaller in diameter than 195/80R15: 688.5 mm against 693.0 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 205/75R15 instead of 195/80R15?

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

Is 205/75R15 wider than 195/80R15, and does that matter?

Yes — 205/75R15 is 205 mm wide against 195 mm for 195/80R15, 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 205/75R15 fit my car if 195/80R15 fits?

Not necessarily. 205/75R15 is shorter by 4.5 mm and 10 mm wider, 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, 195/80R15 or 205/75R15?

Neither is better in general — it depends on what you want. 205/75R15 has a -2.2 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.