I wasn't sure if i should post this in the commuter forum, but thought the die hard Mountain Bikers might find some of this useful also,....IF, like me,.......you're tired of having to clean the slop off you and your bike from just a little rain.
I'm using my 2008 or so Specialized Stumpjumper (M5 Alloy), with a customized Surly Long Haul Trucker Fork w/disc tabs added. (It was already powder coated to match the blue on my frame) The front was pretty easy and straightforward with the braze on's and crown drilling already there. If you're running the usual suspension fork, you'll have to kit the usual suspension fork fender that helps some but leaves a lot of slop still getting through.
However, dealing with the rear of the bike the things i did should work much better, and is rock solid! As i'm using this rigid 69'er conversion as a commuter, i went with 45mm fenders from Planet Bike,....their "Cascadia" model with the stainless steel hardware and rubber mudflaps. They cover plenty for my needs using a Serfas Drifter 1.50x26 rear and a Michelin "City" 38x700c up front,......virtually the same width as the rear tire.
I found that using an altered 700c 45mm width fender worked great in this application, but see no reason a wider fender wouldn't work if you're running 2.00x26 rear. The larger diameter 700 wheel size fender looks "right", because it is positioned far outside against the rear triangle members.
Here's what i did........