Tyre Load Rating Upgrade Calculator
Calculate required load index after adding modifications like bull bars, canopies, and roof racks. Get instant before/after comparison.
Why Vehicle Modifications Require Tyre Upgrades
When you add accessories to your vehicle, you're increasing its weight - and your tyres need to handle that extra load. Common modifications that affect load ratings include:
- Bull bars – Add 80-150kg to front axle load
- Canopies and tonneau covers – Add 80-120kg to rear axle
- Roof racks (when loaded) – Add 50-100kg to overall weight
- Winches – Add 50-70kg to front load
- Tray backs and toolboxes – Add 150-250kg to rear axle
This calculator helps you determine if your current tyres are still adequate after modifications, or what load rating you need to upgrade to. It includes quick-select buttons for common NZ vehicle accessories.
🔧 Tyre Upgrade Calculator
Calculate required load index after modifications
How to Use This Calculator
Enter Current Details
Input your current tyre load index and vehicle GVM from your compliance plate.
Select Modifications
Choose from common accessories like bull bars and canopies, or enter custom weight manually.
See Before/After Comparison
View side-by-side comparison of current vs required specifications with safety margins.
Get Upgrade Recommendations
See exactly which load index you need to upgrade to for safe operation with your modifications.
📚 Want to Learn More?
Understand how modifications affect load ratings, WOF requirements, and everything about upgrading your tyres in New Zealand.
Read Complete NZ Load Rating Guide →
