Mountain bike style mudguards

[webmal]

I just bought a new Trek DS for my teenage son and I want to purchase a few accessories. I'm interested in the mountain bike style mudguards (rear mudguard that clips onto the seat post) so his school backpack doesn't get wet in winter. My question is, is the *front* mudguard (attached to the downtube) also important? i.e. besides his shoes, will his clothes get wet?

I understand that mudguards aren't cool

[Cheesewheel]

The back mudguard will prevent flinging dirty water up the back. Even a little bit of surface moisture on the road is efficiently picked up by the back wheel and artistically deposited up the middle of the back. A front one helps prevent the shoes getting soaked, but this is only really an issue when going through puddles. As far as getting wet from the rain goes, its the forward facing parts of the body that cop it the most (torso, arms thighs) ... but at least the mudguards play a role in keeping the mud off your son

Mtb mudguards can also easily be snapped on and off if the coolness is a factor

[RobertL]

I've never tried them, but I have grave doubts about the usefulness of front mudguards that fit to the downtube. The front wheel does throw up water, and that does make your shoes wet, but I don't see how a mudguard fitted to the frame can stop much water when your front wheel swings from side to side. A mudguard fitted to the fork will - because it moves with the wheel - but not one fitted to the frame.