Read the quad tyre size
The quad tyre size consists in three numbers.
On the sidewall, you'll find another marking on the "number of plies" It measures sidewall resistance related to thickness and rigidity. A tyre with a great number of plies has more resistance to shocks and punctures at the expense of flexibility and comfort.
If you use your quad on the road, you must keep the original tyre size in compliance with the Highway Code.
If you use you quad off-road, feel free to customize you rim and tyre sizes for those you are more comfortable with.