Exact Tire Model Dimension Comparator
Compare the real size of two tire models. Use the calculator below. Results update as you type.
How the Exact Tire Model Dimension Comparator Works
This comparator works by comparing the published dimensions of 2 specific tire models in the same nominal size. It reports diameter, width and revs per mile gaps.
- Enter Model A's published diameter, width and revs per mile.
- Enter Model B's published values.
- Read the diameter gap in inches, millimeters and percent.
- Read the revs per mile gap, which is the figure AWD makers check.
The Formula
The formula is Gap (%) = (Model B − Model A) ÷ Model A × 100, applied to each published dimension.
Diameter Gap (%) = (D_B − D_A) ÷ D_A × 100 Revs Gap (%) = (Revs_B − Revs_A) ÷ Revs_A × 100 Width Gap (mm) = W_B − W_AWorked example: Model A is 31.9 in and Model B is 31.5 in. The gap is −0.4 in (−10.2 mm), or −1.25%.
Conversion Table
The conversion table converts published height gaps of 0.1 in to 0.8 in into percent for 6 tire diameters. A 0.5 in gap is 1.92% on a 26 in tire and 1.43% on a 35 in tire.
Use the table to judge whether a published gap matters. Gaps under 1% rarely change speedometer readings by more than 0.6 mph (1 km/h) at highway speed.
| Model A Diameter (in) | 0.1 in gap | 0.2 in gap | 0.3 in gap | 0.5 in gap | 0.8 in gap |
|---|---|---|---|---|---|
| 26.0 | 0.38% | 0.77% | 1.15% | 1.92% | 3.08% |
| 28.0 | 0.36% | 0.71% | 1.07% | 1.79% | 2.86% |
| 30.0 | 0.33% | 0.67% | 1.00% | 1.67% | 2.67% |
| 32.0 | 0.31% | 0.62% | 0.94% | 1.56% | 2.50% |
| 34.0 | 0.29% | 0.59% | 0.88% | 1.47% | 2.35% |
| 35.0 | 0.29% | 0.57% | 0.86% | 1.43% | 2.29% |
What Is the Exact Tire Model Dimension Comparator?
The Exact Tire Model Dimension Comparator is a tool that compares 2 tire models of the same size using each maker's published data. Two tires labeled 265/70R17 can differ by 0.5 in (13 mm) in height and 0.4 in (10 mm) in width.
The comparator works with the numbers on spec sheets: overall diameter, section width, tread depth and revs per mile. Those measured values are more accurate than nominal math for tight-fit decisions.
Common Uses
This comparator has 4 uses: replacing one tire on AWD, mixing brands, tight-fitment checks and brand selection.
- Replace one AWD tire: Find a model close to the remaining 3.
- Mix brands: Check front and rear axle sets from different makers.
- Check tight fitments: Use real heights near fender limits.
- Pick a brand: Choose the model with the height you want.