Is 295/65R18 bigger than 275/65R18?

295/65R18 is 1.02 inches taller and 20 mm wider. In overall diameter that is +3.19%, which exceeds the ±3% rule of thumb for a substitution.

How much will 295/65R18 throw off my speedometer?

Every reading scales by 1.03191. An indicated 60 mph becomes 61.9 mph, and every 100 miles on the odometer is really 103.2 miles.

How much does 295/65R18 change ground clearance over 275/65R18?

The axle centerline moves by 0.51 inches — half the diameter change, because half the extra height sits below the hub and half above it.

Will 295/65R18 fit where 275/65R18 fits?

Nothing derived from the size code can answer that. Clearance depends on wheel offset, suspension travel and body dimensions that no tire size contains. This page tells you exactly what changes dimensionally, which is the part that can be calculated.

275/65R18 vs 295/65R18

295/65R18 is +1.02″ in overall diameter and +20 mm in section width against 275/65R18 — a diameter change of +3.19%, which breaks the ±3% substitution rule. An indicated 60 mph would really be 61.9 mph.

Outside 3%

Every dimension

Difference between 275/65R18 and 295/65R18
Dimension	275/65R18 → 295/65R18	Change
Overall diameter	32.07″ → 33.10″	+1.02″ (+3.19%)
Section width	275 mm → 295 mm	+20 mm (+7.27%)
Sidewall height	178.8 mm → 191.8 mm	+13.0 mm
Rolling circumference	100.77″ → 103.98″	+3.22″
Revolutions per mile	628.8 → 609.3	−19.4
Axle height / clearance	16.04″ → 16.55″	+0.51″

275/65R18275 mm

295/65R18295 mm

275/65R18 32.07″295/65R18 33.10″

Which is taller, 275/65R18 or 295/65R18?

295/65R18 is the taller of the two, at 33.10″ against 32.07″. The gap is 1.02 inches, or 26.0 mm.

Both are metric sizes, so neither states its height directly. Both figures below are derived from the section width, aspect ratio and wheel diameter in the code. 275/65R18 is 275 mm wide with a 178.8 mm sidewall on a 18″ wheel; 295/65R18 is 295 mm wide with a 191.8 mm sidewall on a 18″ wheel.

What the speedometer will read

Indicated versus actual speed after the size change
Speedometer reads	Actual speed	Error
25 mph	25.8 mph	+0.8 mph
40 mph	41.3 mph	+1.3 mph
55 mph	56.8 mph	+1.8 mph
60 mph	61.9 mph	+1.9 mph
70 mph	72.2 mph	+2.2 mph
80 mph	82.6 mph	+2.6 mph

Fitting 295/65R18 in place of 275/65R18 multiplies every speed and distance reading by 1.03191. Over 10,000 indicated miles the odometer is out by +319 miles.

Effective gearing moves by the same proportion. A vehicle with 3.73 axles running 275/65R18 would need 3.85 to keep the same engine speed on 295/65R18. Work it out for your own axle ratio.

Full specification of each size

275/65R18

Derived dimensions for 275/65R18
Dimension	Metric	Imperial
Section width	275.0 mm	10.83″
Sidewall height	178.8 mm	7.04″
Wheel diameter	457.2 mm	18.0″
Overall diameter	814.7 mm	32.07″
Rolling circumference	2,559.5 mm	100.77″
Revolutions per mile	390.7 / km	628.8 / mile
Measuring rim (estimate)	216 mm	8.5″

295/65R18

Derived dimensions for 295/65R18
Dimension	Metric	Imperial
Section width	295.0 mm	11.61″
Sidewall height	191.8 mm	7.55″
Wheel diameter	457.2 mm	18.0″
Overall diameter	840.7 mm	33.10″
Rolling circumference	2,641.1 mm	103.98″
Revolutions per mile	378.6 / km	609.3 / mile
Measuring rim (estimate)	229 mm	9″

Rim widths differ too: 275/65R18 is designed for 8″–9.5″ and 295/65R18 for 8.5″–10″. Their measuring rims differ, so the same wheel will not be ideal for both.

Can you swap one for the other?

Outside the ±3% rule

The diameter difference of +3.19% exceeds the ±3% rule of thumb. Expect a speedometer error of about 1.9 mph at an indicated 60, and an odometer that is off by the same proportion. It is a common swap even so — it just needs the instruments recalibrated to stay honest.

Neither figure says anything about physical fitment. Whether 295/65R18 clears the strut, the fender liner and the steering stops depends on wheel offset and suspension geometry that a size code does not encode. For maintenance rather than sizing, Car Basics covers tire care.