Towing Load Calculator
Calculate the required tyre load index for your vehicle when towing. Includes towball weight calculator with NZ trailer presets.
Why Towing Loads Matter
When you tow a trailer, the towball weight (downward force) is added to your vehicle's rear axle load. This is critical because:
- Towball weight is 8-15% of trailer weight – A 2,000kg caravan puts 160-300kg on your rear tyres
- Rear tyres carry all the extra weight – Front tyres work harder too due to steering and braking forces
- Inadequate tyres can fail catastrophically – Heat buildup from overloading causes blowouts at speed
- WOF compliance is essential – Your tyres must have capacity for vehicle + towball weight
This calculator helps you determine if your current tyres are adequate for towing, or what load rating you need to upgrade to. Select from common NZ trailers like caravans, boats, and horse floats.
🚙 Towing Load Calculator
Calculate required load index for towing
💡 What is Towball Weight?
Towball weight is the downward force that your trailer exerts on your vehicle's towbar. It's typically 8-15% of the trailer's total weight and is carried entirely by your vehicle's rear tyres.
Too high (>15%): Overloads rear, lifts front, reduces steering control
Too low (<8%): Trailer can sway dangerously, risk of jacknifing
How to Use This Calculator
Select Trailer Type
Choose from common NZ trailers like caravans, boats, or horse floats. The calculator auto-fills typical weights and towball percentages.
Enter Vehicle Details
Input your vehicle's rear axle weight (typically 40-50% of GVM). Check your compliance plate if unsure.
Review Towball Weight
See the calculated towball weight in both percentage and kilograms. This is what your rear tyres must carry.
Get Load Index Requirements
See both minimum and recommended load index ratings for safe towing with proper safety margins.
📚 Want to Learn More?
Understand load ratings, WOF requirements, safety margins, and everything about tyre load capacity for towing in New Zealand.
Read Complete NZ Load Rating Guide →
