Rock Shox Dart 3 vs Recon XC Air

This is a question probably better asked over at MTBR.com - much more knowledge over details like this over there.

The Dart fork is a coil-only shock system.  Simple little metal springs skrunching up then rebounding.  The RECON for is an air coiled fork; much more tunability.  Also 32 mm fork stanchions v. 30 for the Dart.   Go to mtbr.com and review the 2.  Especially for Xterra-type racing, the Recon wins hands down.

The dart would be fine for commuting, but put it off road and it is woefully inadequate.

The biggest factors are going to be size of the stanchions and the type of spring. The Dart uses 28mm stanchions. On the Recon, 32mm. This is going to make the Recon have better steering precision and it will hold a line better. In other words it won't deflect as much when you hit an obstacle.

The dart is a coil spring fork. The only adjustment is how much preload is on the fork. If you are average in weight for your height it is fine. If you are outside average, lighter or heavier you will most likely need different springs. The Recon is a coil/air spring. I forget the specifics of the recon, but this generally means that one leg has a coil spring, the other side uses air and is adjustable via schrader valve although you will need a special shock pump to make adjustments. Coil springs are good for small bump compliance, but as noted on the dart, lack much adjustability in relation to the weight of the rider or riding conditions. They also tend to be a very linear spring meaning it will take nearly the same amount of force to compress the fork the first half of the travel as the second half. This is nice for a really long travel fork because it will allow you to use all of the travel but on shorter forks it means you are more likely to bottom out on big hits. With a completely air sprung fork you get a highly progressive spring rate. It's a fine line to get it set where you can use all the travel while not bottoming out on all the but the hardest hits. A mixed fork the like Recon is a nice mix with the coil spring giving small bump compliance and sensitivity and the air spring giving a moderately progressive spring rate and easy adjustability. Generally mixed forks run at much lower pressures then a totally air sprung fork.

That was probably way more info then what you need. What you really need to know is that the Recon is almost a pound lighter then the Dart. The recon really is a much nicer fork if the cost is minimal is would be a very good upgrade. Unless you go from a good fork to a cheap fork, you really don't notice a difference, but a nice fork can inspire confidence and a crappy fork can rob it from you.

The reason you need a special pump to adjust forks shocks is that it needs to do higher pressure and lower volume then a tire pump.

Is adjustability one word or two?

I just have to add that a coil only system does not mean it's a bad thing. One of the nicest forks in my stable is coil only. Although it cost twice what the dart costs and has an open oil bath. Coil alone is bad when there is no other adjustment or dampening. On a nice fork you can adjust rebound and compression as well as having the ability to tune progressiveness by changing oil height. Based on past experiences (on a ton of forks) I'd much rather have a coil sprung fork with an open oil bath then a full air fork. I think the mixed forks give a nice balance to the plush compliant feel of a coil and the adjustability of an air fork. Supposedly the new crop of long travel air sprung forks have really bridged the gap to get close on feel to a coil fork, but I'd like to spend some time on the long travel air forks before I give a valid opinion on them. Though it's not going to happen till I move somewhere with hills and build another DH bike.

Until 2008 I was a mountain biker 90% of my cycling time, and suspension tuning was my specialty when I was a mechanic.

Fantastic. 

Thanks for all your help. Dart is out, Recon is definitely in. 

There are 2 bikes I'm looking at, they are the same frames and same general components on ther rest of the bike, just different forks, the 2 I mentioned.