"davek" wrote in message
...
Perhaps you'll know the answer to this: why do so many mountain bikes
have these ultra-narrow rims with hugely fat tyres? OK, you /can/ run a
fat tyre on a narrow rim, but surely a fatter rim would be more
appropriate?

In a nutshell: weight!
The narrowish 32 hole rims I have nearly always used for many moons (about
144 IIRC) have proved up to the job bouncing down boulders, steps,
gawd-knows-what etc whilst carrying my 80kg (more with a loaded 3litre
Camelbak), what problem would making the rim wider solve?

Rgds,
Pete