Bird Aeris 9 is an affordable alloy enduro bike with 160-180mm of travel


Posted on Aug 3, 2022 by Jessie-May Morgan

Bird is replacing its long-running Aeris AM9 with an all-new long-travel 29er, more simply named the Aeris 9. Its ability to run 160-180mm of balanced front and rear wheel travel pushes it out of the off-road bracket and into the world of Enduro, even Super Enduro. The Aeris 9 is an aluminum frame only, for now. It retains the familiar four-bar suspension platform and reasonable price we’ve come to expect from Bird, adding a flip-chip at the chainstay to allow riders to run a longer or shorter rear center length. according to their preferences.

Aeris Bird 9

The Bird Aeris 9 in the Blurple colorway

The Bird Aeris 9 is a full suspension mountain bike with 160mm of travel, but with the purchase of an aftermarket link and longer stroke shock, it has the ability to run a rear wheel travel of 180mm. The head tube is also approved for use with a 180mm fork, so you can switch from Enduro to Super Enduro as and when you want, and your bank balance allows.

bird aeris 9 with coil shock raw color

The flip-chip on the base allows an adjustment of 6 mm. Raising it concomitantly loosens the head angle by 0.5° and lowers the BB by 7mm

  • Intent: Enduro driving
  • Fork travel: 160mm/180mm
  • Rear wheel travel: 160mm/180mm
  • Wheel size: 29″
  • Head angle: 64°
  • Frame material: Aluminum
  • Starting price: £2870

The Aeris 9 is the most adjustable mountain bike we’ve ever seen from Bird. In addition to the two travel configurations, it is also possible to increase the length of the chainstay from 440mm to 446mm thanks to a flip-chip at the location of the chainstay pivot; it also lowers the height of the BB by 7mm and slackens the head angle by half a degree.

bird aeris 9 flip-chip chainstay length adjustment

The new Aeris 9 sees full double-lip oil seals on a larger main pivot shaft in an effort to improve bearing longevity; Bird says the boost rear of the frame has enough tire clearance for a 29″ x 2.6″ tire.

The bike is available in sizes M, ML, L and XL. Bird does not specify a range of jumper heights for each frame, stating only one intermediate jumper height suitable for each frame. At the smaller end, a rider height of around 5’6″ is listed for the medium frame, while a rider height of around 6’4″ for the XL. Note that the range figures of Aeris 9 are very generous; 457 mm in Medium, 486 mm in ML, 515 mm in Large and 544 mm in XL. The wheelbase of the latter is 1330 mm.

bird aeris 9 geometry

The geometry chart provided by Bird is for the chainstay length of 440mm.

In 160mm mode with 440mm stays, the Aeris 9 has a 64° head angle. Seat tube angles get steeper as you look across the frame size, starting at an effective 77° in Medium, reaching 78.5° on the XL. This will help keep the weight more central, especially for taller riders who can sometimes find themselves with their weight pushed too far back in the seated pedaling position, making technical and steep climbing more difficult. The bottom bracket sits at 340mm, dropping to 290mm at the recommended 30% sag.

bird aeris 9 mtb internal or external cable routing

For the first time, Bird has added cable ports to an aluminum frame to allow riders to route cables internally. It’s not the Bird folks’ preference – they like the ease of maintenance that the external cable routing allows – but appreciate that everyone is different.

bird aeris 9 formula mod coil shock piggyback

The Aeris 9 is said to work well with both air and coil shocks; Bird is now able to supply complete builds with suspension components from Formula, such as the Coil Shock MOD seen here.

The Aeris 9 has a 73mm threaded bottom bracket, ZS 44/ZS 56 tapered headset, SRAM UDH and ISCG05 mounts for a chain guide and bash guard. The seatpost diameter is 31.6mm.

Price and availability

Bird has expanded the number of suspension brands it works with, adding Formula and Fast to the mix alongside Cane Creek, RockShox and Fox. You can get the Bird Aeris 9 as a frameset only for £1,430, with complete bike builds starting at £2870.

The Bird website lets you configure the bike pretty much however you want, and there are far, far too many possible combinations to list here. Bird’s recommended build for a ‘really nice’ spec costs £3875 – this gets you a SRAM GX Eagle 12-speed drivetrain, SRAM G2R brakes, RockShox Ultimate forks and Super Deluxe Ultimate Coil shock, Bird Factory wheels, Maxxis Assegai tires on both ends and a finishing kit from the Bird line complete with Race Face parts.

For our UK readers, it’s worth mentioning that the Bird Aeris 9 will be available for demo on the following dates:

  • September 3 – 4 – Scottish Enduro Series at Pitfichie, Aberdeenshire, Scotland
  • September 9 to 11 – Laggan Wolftrax, Scotland
  • September 16 to 18 – Tweedlove Festival, Peebles, Scotland


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