
A workmate gave me his kids unused Giant MTX with these 2.0 tyres:

The Giant’s Kenda tyres have much bigger grip knobs, but although they're labelled as 2.0, the body of the tyre is about narrower. But the knob width equals 2.0 inches.
Is it worth changing them over? The Kendas just look kinda cheap but that doesn't mean they won't be a grip improvement on soft gravel.
Otherwise, can you get half decent 20" knobblies that aren't the price of an adult tyre? He's probably got another 18 months on this bike.