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Bird Aeris 9 is a 160-180mm travel affordable alloy enduro bike

bird aeris 9 160mm 180mm travel super enduro mtb jet black
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Bird is replacing its long-standing 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 all-mountain bracket and into the world of Enduro, or even Super Enduro. The Aeris 9 is an aluminum frame only, for now. It retains the familiar four-bar suspension platform and the reasonable pricing 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 preference.

Bird Aeris 9 

bird aeris 9 160mm travel enduro bike
The Bird Aeris 9 in the Blurple Colorway

The Bird Aeris 9 is a 160mm travel full suspension mountain bike, but with the purchase of an aftermarket link and a longer stroke shock, it has the capacity to run 180mm rear wheel travel. The headtube is approved for use with a 180mm fork, too, so you can upgrade from Enduro to Super Enduro as and when you taste demands it, and your bank balance permits it.

bird aeris 9 with coil shock raw color
The flip-chip on the chainstay permits 6mm adjustment. Increasing it concomitantly slackens the head angle by 0.5° and lowers the BB 7mm
  • Intention: Enduro Riding
  • 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 seen from Bird yet. In addition to the two travel configurations, there is also scope to increase chainstay length from 440mm to 446mm by virtue of a flip-chip at the chainstay pivot location; it also lowers the BB height  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 axle in a bid to improve bearing longevity; Bird say the frame’s boost rear end has sufficient tire clearance for a 29″ x 2.6″ tire.

The bike comes in sizes M, ML, L and XL. Bird don’t specify a range of rider heights for each frame, indicating just one middle-ground rider height suitable for each frame. At the smaller end, a rider height of around 5’6″ is indicated for the Medium frame, while a rider height of around 6’4″ for the XL. It should be noted that the Aeris 9 reach figures are very generous; 457mm in Medium, 486mm in ML, 515mm in Large and 544mm in XL. Wheelbase on the latter is 1330mm. 

bird aeris 9 geometry
The geometry chart provided by Bird pertains to the 440mm chainstay length.

In the 160mm mode with 440mm stays, the Aeris 9 has a 64° head angle. Seat tube angles get steeper as you look up through the frame sizing, starting at an effective 77° in Medium, topping out at 78.5° on the XL. That will help to keep weight more central, particularly for taller riders who can sometimes end up with their weight biased too far to the rear in the seated pedaling position, making steep, technical climbing trickier. The bottom bracket sits at 340mm, sinking to 290mm at the recommended 30% sag.

bird aeris 9 mtb internal or external cable routing

For the first time, Bird have added cable ports to an aluminum frame to allow riders the option to run cables internally. It’s not the preference of the folk at Bird – they like the easy maintenance that external cable routing allows for – but appreciate that everyone is different.

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

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

Pricing & Availability

Bird have expanded the number of suspension brands they are working with, adding Formula and Fast into the mix alongside Cane Creek, RockShox and Fox. You can pick up the Bird Aeris 9 as a frameset only for £1,430, with complete bike builds starting from £2870.

The Bird website allows you to pretty much configure the bike as you want it, and there are far, far too many possible combinations to list here. Bird’s recommended build for a “really nice” spec comes in at £3875 – that 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 at both ends and a finishing kit from the Bird range complemented with parts from Race Face.

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

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


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