I'm building a rigid 29er and have some tubeless ready rims with an internal width of 21mm. I was just wondering whether anyone has experience of an optimum tyre width to suit that rim width? Obviously the wider the tyre, the better for the front - to cushion hits, however I don't want the tyre to squidge up when cornering (I'm sure there's a more technical term for that).

Chain reaction have some 29 x 2.4 mountain king II protections (black chilli), which seem a good deal..or am I better getting 2.25s?

Also is there any advantage in having a narrower tyre on the rear?

Cheers...

I've run 2.4" tyres on a Stan's Crest which is about that size - didn't encounter any problems. I'm not a heavy rider and didn't experience sidewall collapse, even at less than 20psi. My preference would be to go wide if it fits / clears - improved rolling resistance, grip and comfort for minimal weight.