Avid mechanical Disc brake BB7 -$49.95 -Cambriabike.com SRAM Juicy 5 – $94.98 ( they also sell juicy 7 )- blueskycycling.com Check the EMD9 (Niner),Ventana El Rey and Moots XZ 29er at Bikebling.com too!

Most people that try 29′ers prefer them to 26′ers. The main advantage of easily rolling over obstacles seems to more than offset the disadvantages of slower handling and more weight. Your best bet would be to find a shop (or a friend) to let you try one on the type of terrain you ride on.

Try for some very respectable 29′ers at reasonable prices.

One caveat: if you are shorter than about 5’6″ you may have a tough time finding one in a small enough frame.

not really that much,i have a trek 3900 too and recently got a 2007 cannondale rush 5 for $1500.it was well worth ir,i dont know what ur price range is but i would highly reccomend canondale maybe a 2008 rush 5 or 2009 rush 6,those are both in the $1600 price range. if you can find one with a lefty for that price i would definatly get it unless it has mechanical brakes,then get one with a fox fork because it will have hydraulic brakes.if you can find a prophet with a lefty even better

if you want to upgrade your bike instead(which is what i was going to do,but i wanted a full suspention)
i would reccomed geting a fox TALAS fork,shimano XTR dual control shifters,shimano LX brake calipers, Shimano XT rear derailer, shimano LX front derailer, an FSA crank, shimano XT cassete and chain, michlin mountain X-Trem tires( the red ones), i would reccomend using 8 inch rotors for the brakes, and now that im thinking about it i dont think you could put disk brakes in the rear(thats how it was on older top of the line bikes, v-brakes in the rear and disks up front) but thats not a big deal because thay makes XTR dual control levers for v-brakes also

Good luck with whatever you do

I was confused when I first heard about 29′er tyres and wheels.

However I soon found out that they seem to be 700 wheels with
off-road tyres. Just like my cyclocross bike.

There are several points on the 26″ vs 29″ tires.
29″ due to it’s larger dia. rolls over objects better.
29″ also due to it’s larger dia. turns slightly slower.
26″ is able to be accelerated faster because it has less mass.
26″ tires and tubes are easy to find, greater selection.
29″ riders find it is easier to carry more momentum when riding.
If going with a solid fork then the 29″ tire/rim is the way to go as it will not ride as harsh as a 26″ would.

I would steer away from anything besides either a 700 mm or a 26 inch wheel. You will have a hard time finding tubes and tires. My mountain bike just sits in the garage, I ride my hybrid road bike (mountain bike geometry, road wheels/tires.)

The wheels are 3″ larger. It tends to roll over more terrain with less interruption. I’m not sure if these bikes are going to be a fad or not though. It’s not like you can go just anywhere and get a tube or tire either.
If you want disc brakes, stay away from mechanical units and go for the hydraulic ones.
What you really need is a good suspension fork. The unit you have on that bike is pretty basic, more for taking on bike paths than the trail. I would definitely go for a mid level Marzocchi, Rock Shox, Manitou, or any Fox fork. That would make a huge difference.