How much bigger are these than the 2.1s in real terms (i know 0.15).
I want to put them on a trek EX9 and have just got some Bonty 2.25 xr4 and their massive causing a bit of frame rub . Where as the previous bontys jones xr 2.2 were small in comparision.
i've gone off on a tangent ! i know the 2.1s will fit but fancy a bit more volume.
Any opinions

On the whole, a lot bigger – in all directions.

Try a Larsen 2.35, not quite as wide but deeper.

Yes they are a lot bigger, 2.1 is the best of the 3 sizes, the 1.8 is great on the rear but they let go rather unpredictably in the corners if used on the front,

i have the 2.1 on my rigid and they are great as a do anything tyre.

Would people not recommend a 2.4 NN as a large volume tyre for trail centres,alps etc?

As above, a lot bigger, but I'd go Maxxis Ardent 2.25