Tyre Size Calculator & Comparison
TyreDispatch.co.nz v3.0
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Compare up to 4 tyre sizes side-by-side. See how width, sidewall height, and diameter changes affect your speedometer, WOF compliance, ride comfort, and grip — with live NZ pricing and shop links.
Enter Tyre Sizes
Selected Sizes
Specifications
How to Read Tyre Sizes
Metric
205 / 55 / R16
205mm width · Sidewall = 55% of 205mm (112.75mm) · 16" rim
Imperial
31 / 10.5 / R15
31" overall diameter · 10.5" width · 15" rim
Visual Comparison
Front View
Enter sizes and click Calculate
Side View
Speedometer Impact
| Your speedo reads | Actual speed (T2) | Actual speed (T3) | Actual speed (T4) |
|---|
Assumes your speedometer was calibrated for Tyre 1 (your original size). Actual vehicle speedometers also have manufacturer tolerances of up to 4%.
NZ WOF Compliance Check
Being within 5% is just the first check. To pass a NZ WOF with a different tyre size, all three of these must be true:
1. Diameter within ±5% — The replacement tyre's overall diameter must be within 5% of the vehicle manufacturer's original specification. Exceeding this requires LVV certification (~$400–800).
2. Fits your rims — The tyre width must be compatible with your rim width. A 275mm tyre on a 7" rim designed for 205–225mm tyres won't seat properly and is unsafe. Check the "Rec. Rim Width" row in the results table above.
3. No fouling (rubbing) — The VIRM states a tyre will fail WOF if "there are signs that a tyre is fouling on another part of the vehicle". This means any evidence of the tyre contacting guards, suspension, or steering components — including at full steering lock or under compression — is technically grounds for rejection. Going wider or taller increases the risk, especially on vehicles with tight wheel wells. Even the same width on a taller profile can rub the inner guard at full lock on some cars.
Practical tip: If changing sizes, fit the tyres, then turn the steering wheel to full lock in both directions while someone watches for clearance. Also check with the suspension compressed (e.g. pushing down on the guard). If there's contact, you'll need spacers, guard trimming, or a different size.
Use our WOF Axle Checker → | Full WOF Tyre Guide →
1. Diameter within ±5% — The replacement tyre's overall diameter must be within 5% of the vehicle manufacturer's original specification. Exceeding this requires LVV certification (~$400–800).
2. Fits your rims — The tyre width must be compatible with your rim width. A 275mm tyre on a 7" rim designed for 205–225mm tyres won't seat properly and is unsafe. Check the "Rec. Rim Width" row in the results table above.
3. No fouling (rubbing) — The VIRM states a tyre will fail WOF if "there are signs that a tyre is fouling on another part of the vehicle". This means any evidence of the tyre contacting guards, suspension, or steering components — including at full steering lock or under compression — is technically grounds for rejection. Going wider or taller increases the risk, especially on vehicles with tight wheel wells. Even the same width on a taller profile can rub the inner guard at full lock on some cars.
Practical tip: If changing sizes, fit the tyres, then turn the steering wheel to full lock in both directions while someone watches for clearance. Also check with the suspension compressed (e.g. pushing down on the guard). If there's contact, you'll need spacers, guard trimming, or a different size.
Use our WOF Axle Checker → | Full WOF Tyre Guide →
Shop Similar Sizes
Alternative tyre sizes with a similar overall diameter to Tyre 1. All WOF-compliant options.
| Size | Diameter | Sidewall | Width |
|---|
Sizes shown are common NZ fitments within ±5% diameter of Tyre 1.
Need a specific size? Get a quote →
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