Gas Wheels & Tyres Fitment Tools

Tyre Size Calculator

Compare your current tyre size against a new setup and instantly see the difference in overall diameter, sidewall height, vehicle clearance and speedometer reading.

Existing Setup

Current Tyre

265/65R17
mm
%
in

Example tyre marking: 265 / 65 R17

Proposed Setup

New Tyre

285/70R17
mm
%
in

Example tyre marking: 285 / 70 R17

Current 265/65R17
→
New 285/70R17

Your Comparison

Measurements are calculated from nominal tyre dimensions.

0.00% diameter change

Current Setup

Overall Diameter
Diameter in Inches
Sidewall Height
Circumference

New Setup

Overall Diameter
Diameter in Inches
Sidewall Height
Circumference

Difference Summary

Diameter Change
Ride Height / Clearance Approximate change at the axle
Circumference Difference per wheel revolution
Speedometer Approximate speedometer variation

What happens at an indicated 100 km/h?

Your actual road speed will change slightly with the new tyre diameter.

100.0 km/h actual
Fitment Note: This calculator is a guide only. Actual tyre dimensions and vehicle fitment can vary depending on tyre manufacturer, wheel width, wheel offset, suspension setup, guard clearance, alignment and vehicle modifications. Always confirm fitment before purchasing.

Understanding Tyre Sizes

What Does 285/70R17 Mean?

Metric tyre sizing contains three important measurements. Understanding them makes it much easier to compare tyre sizes and choose the right combination for your vehicle.

285 Tyre section width measured in millimetres.
70 Sidewall height expressed as a percentage of tyre width.
R17 Radial tyre designed to fit a 17-inch wheel.

Before Changing Tyre Size

Bigger Isn't Always Better

Increasing tyre diameter can provide additional ground clearance and change the overall stance of your vehicle, but larger tyres can also affect gearing, braking, steering clearance and speedometer accuracy. Wheel offset and width are equally important when determining whether the complete package will fit correctly.

Offset Determines how far inward or outward the wheel sits.
Width Can affect tyre shape, guard clearance and suspension clearance.
Diameter Influences ground clearance and effective gearing.

Need Help With Fitment?

Let Gas Wheels & Tyres Help You Choose

Not sure what tyre size, wheel width or offset will work best? Send us your vehicle details and the Gas Wheels & Tyres team can help recommend the right combination.

Get A Wheel & Tyre Recommendation