Widest tyre for Cararra Crossfire 2

[Kenspot]

Hi my son has a Crossfire 2, tyre size is 44-622, 700 x 42c.
He wants a wider more knobbly mountain bike like tyre rather than the slick that is fitted.
Can someone please tell me the widest tyre he can fit on the rim? I've Googled and googled and can't find a definite answer and the charts just confuse me!
There is more than 50mm between the forks at the top of the tyre.

[Pinhead]

Go into Halfords and ask them, they should know it's their bike

[Jdsk]

Welcome

You asked about the rim, but of course the tyre also has to have enough clearance on the frame, mudguards etc.

Are there any labels on the rim or wheel showing its size?

If not: "Measuring Bicycle Rims for Tire Fit":
https://sheldonbrown.com/rim-sizing.html

And when you have the rim size please let us know what it is, and which tyres you're considering.

Jonathan