Fortnite Chapter 3 Season 1: How to upgrade a vehicle with Chonkers

You must first locate a set of Chonkers (also known as the Off-Road Tires vehicle mod) before upgrading your car. Chonkers are available at gas stations as well as the Chonkers Speedway. They occasionally drop as ground treasure, but you'll typically have to demolish something to get them to drop.  

A Chonker pick-up should drop a pile of tyres, and vehicles frequently do as well. The pick-up will appear to be a single tyre, but it will actually be a full set.

A Chonkers vehicle mod takes up one slot in your inventory and functions similarly to a grenade. To use Chonkers to enhance a vehicle, simply choose them from your inventory and toss them at it. A set of massive new off-road tyres and a higher axel will appear out of nowhere on the car. Off-road, that car will now handle a lot better and drive far faster.

If you don't strike a vehicle with the Chonkers, a mound of tyres will appear wherever the "grenade" lands. If you interact with the pile of tyres by accident, you can retrieve the Chonkers pick-up. Although they may be utilised as emergency cover in a need, there aren't many situations when you'd want to produce a pile of tyres on purpose.