Quick Answer
- ND Miata (2016 to 2026): 195/50R16 or 205/45R17. NC (2006 to 2014): 205/50R16 or 205/45R17. NB (2000 to 2005): 185/60R14, 195/50R15, 205/45R16 or 205/40R17, as listed in Mazda's owner's manuals.
- The 205/45R17 is 24.26 in tall (calculated). Against the ND 195/50R16 (23.68 in) that is +2.5%, so an indicated 60 mph is 61.5 mph.
- Mazda warns that a size other than the one specified could seriously affect ride, handling, ground clearance and speedometer calibration. No NA (1989 to 1997) manual is available yet.
Miata common sizes, quick load:
NB MX-5
2000–2005Lug nut torque: 88–118 N·m (65–87 ft·lbf) (2002 to 2005 manuals)
NC MX-5
2006–2014Lug nut torque: 88–118 N·m (65–87 ft·lbf)
ND MX-5
2016–2026Lug nut torque: 108–147 N·m (80–108 ft·lbf)
Mazda Factory Tire Sizes: Miata NB, NC and ND
Sizes, load and speed ratings and pressures are from Mazda U.S. owner's manuals. Diameter, sidewall and revolutions per mile are calculated from the size.
| Gen | Years | Tire Size | Diam (in, calc.) | Diam (mm, calc.) | Sidewall (in, calc.) | Revs/Mile (calc.) | Cold Pressure (manual) |
|---|---|---|---|---|---|---|---|
| NB | 2000 | 185/60R14 82H | 22.74 | 577.6 | 4.37 | 887 | 180 kPa (26 psi) |
| NB | 2000 to 2005 | 195/50R15 82V | 22.68 | 576.0 | 3.84 | 889 | 180 kPa (26 psi) |
| NB | 2001 to 2005 | 205/45R16 83W | 23.26 | 590.9 | 3.63 | 867 | 180 kPa (26 psi) |
| NB | 2005 | 205/40R17 80W | 23.46 | 595.8 | 3.23 | 860 | 200 / 220 kPa front / rear (29 / 32 psi) |
| NC | 2006 to 2014 | 205/50R16 87V | 24.07 | 611.4 | 4.04 | 838 | 200 kPa (29 psi) |
| NC | 2006 to 2014 | 205/45R17 84W | 24.26 | 616.3 | 3.63 | 831 | 200 kPa (29 psi) |
| ND | 2016 to 2026 | 195/50R16 84V | 23.68 | 601.4 | 3.84 | 852 | 200 kPa (29 psi) |
| ND | 2016 to 2026 | 205/45R17 84W | 24.26 | 616.3 | 3.63 | 831 | 200 kPa (29 psi) |
NA (1989 to 1997) and 1999 manuals are not covered; the 2000 and 2001 NB pages come from scanned manuals. Bolt pattern, centre bore and offset are not published in the manuals, so they are not shown.
Mazda Factory Size Comparisons
Each row compares two sizes that Mazda lists for the same generation. Differences are calculated. The MX-5 Miata tire guide by generation covers NA to ND in more detail, the diameter and speedometer comparison for any two sizes handles sizes not listed here, and the wheel offset and backspacing converter helps with new wheels.
| Gen | Size A | Size B | Diameter Change (calc.) | Change % |
|---|---|---|---|---|
| NB | 185/60R14 | 195/50R15 | -0.06″ | -0.28% |
| NB | 195/50R15 | 205/45R16 | +0.59″ | +2.59% |
| NB | 205/45R16 | 205/40R17 | +0.19″ | +0.83% |
| NC | 205/50R16 | 205/45R17 | +0.19″ | +0.80% |
| ND | 195/50R16 | 205/45R17 | +0.59″ | +2.48% |
Formulas Used
Metric Tire (e.g. 205/45R17): Sidewall (mm) = Width × Aspect ÷ 100 = 205 × 0.45 = 92.25 mm Overall Diameter = Rim × 25.4 + 2 × Sidewall = 431.8 + 184.5 = 616.3 mm = 24.26″ Circumference (in) = π × 24.26 = 76.2″ Revs / Mile = 63,360 ÷ 76.2 = 831 Speedometer Error (%): Error = (New Diameter ÷ Stock Diameter − 1) × 100 Larger tire → speedometer reads LOW (you are going faster than shown). Smaller tire → speedometer reads HIGH (you are going slower than shown). Ground Clearance Change: Clearance Change = Diameter Delta ÷ 2 All values on this page marked "calculated" come from these formulas. Factory sizes, tire pressures and lug nut torque come from Mazda's owner's manuals.
How to Use the Miata Tire Size Calculator
Decode Size
- Click a Mazda factory size preset or type a size in the input field (format: 205/45R17).
- Click "Calculate" to see overall diameter, sidewall height, circumference and revolutions per mile.
- Use the Inches / Metric toggle at the top to switch result units.
- Click a factory size in the grid at the bottom to load it into the decoder.
Compare Sizes
- Use the "Load stock size" buttons to fill Stock (A) with a Mazda factory size, or type any metric size.
- Enter the new size you are considering in the New (B) field.
- Click "Compare Sizes" to see the diameter change, speedometer error and the true-speed table.
- Continental guidance is to keep the rolling circumference within 3%; this is not a Mazda specification. Confirm other sizes with a Mazda dealer.
Gen Size Check
- Select your Miata generation (NB, NC or ND).
- The panel shows the factory sizes, cold tire pressure and lug nut torque from the owner's manuals.
- Enter a width, aspect ratio and rim size, then click "Compare Size" to see the change against the factory size.
By Diameter
- Click a Mazda factory diameter button or type a target diameter and rim size.
- Click "Find Sizes" to list standard metric sizes within ±2% of that diameter, closest first.