This is the information for the Air 9

- all measurements are based off of an 80mm travel fork
- 31.6mm seat post size, 400mm length recommended
- 35mm seat clamp size (not included)
- 34.9 front derailleur size, low mount (top swing) top pull recommended
- 68mm BB shell

The Air 9 is Niner's all new race ready, super light cross country machine. It combines Niner's proven philosophy of geometry with Easton's amazing Scandium tubeset to create the best riding, most agile 29er frame in Niner's already proven arsenal.

The 29" wheel causes many changes to the bike that needed to be addressed. It doesn't work to just apply the standard 26" wheel cross country approved geometry to the 29" wheel platform. The Air 9 has a short head tube to compensate for the taller front end, which will keep handlebar positions from getting too high. In addition, the short seat tube (16.5" for the medium) offers a better stand over height while keeping the front triangle stiffer for those out of the saddle efforts. This frame was designed for use with a 410mm seat post. S-Bend seat and chain stays allow for some vertical compliance of the wheel as well as increasing the mud clearance, lowering the Q factor, and creating more heel clearance. New to the Air 9 are more radically shaped chainstays to offer even more tire clearance than previous Niner models. Short chain stays (for a 29" wheel) keep the back end tucked in and the wheelbase manageable while the longer effective top tube lengths offer good stability and clearance from toe overlap.

Translating our acclaimed geometry of the ONE 9 into a geared frame wasn't that easy. Keeping the chainstays short and still leaving room for the front derailleur was a challenge, but Niner met that challenge head on. The chainstays on the geard bike are only 5mm longer than the chainstays on the single speed, and the Air 9 can accept all low mount front derailleurs, even the newest generation of Shimano front derailleurs that have eluded our competition.

If you took a glance at the geometry chart, the 72 degree head tube angle might stand out as extremely steep and alarm bells might be ringing. Remember, the larger wheels alter the way the bike handles as well. By increasing the diameter of the wheel, the "trail" is also increased. The trail is determined by drawing a vertical line from the drop out of the fork to the ground, and another line that follows the head tube angle all the way to the ground. The distance between where these two points meet the ground is called the trail (see trail chart). You can see the difference in trail between the 26" wheel (the smaller circle) and the 29" wheel (the larger circle) in the chart. For a 71 degree head tube angle, the 26" wheel has a trail of 76mm while the trail for the 29" wheel with the same head tube angle grows to 87mm (all other tings being equal like the fork height, etc.). As the trail becomes larger, the steering starts to have a flip-flop washed out feeling. One way to compensate for this is to increase the rake of the fork. Since we do not currently have enough power to ask the fork manufactures to do this, we took care of it the other way, to increase the head angle, thus decreasing the trail. Once again, you can see on the trail chart that the trail for the 29" wheel with a 72 degree head tube angle is 80mm, much closer to the trail of the 26" wheel with a 71 degree head tube angle. The 72 degree head tube angle on Niner bikes gives the perfect balance of control and liveliness to the front end. In addition, the Niner geometry works brilliantly with either an 80mm or 100mm fork.

You'll notice that the SMALL Niner has a slacker head tube angle and a steeper seat tube angle. This was to allow for better toe clearance with the front wheel. With the larger tires of the 29" wheel, toe overlap is an important factor. We had to make sure that there was ample room for a normal size foot to clear the front wheel. If you're 5'6" and wear a size twelve shoe, you might have some problems here, but then again, you should probably be in the circus.

One more important note on Geometry: Our SMALL frames do not have a water bottle mount on the seat tube. This is to allow full adjustment of the seat post, so when you lower it, it doesn't stop where the screw goes into the frame for the water bottle. We felt it was more important to be able to get the seat out of the way for those hairy descents.