The Aether range of bikes grew from the Bird’s need to replace the short travel Aeris 120 bike. Bird wanted a bike that was more aggressive with a shorter back-end, slacker head angle and steeper seat angle. At the same time, Bird also wanted to build a 29er with less travel than its 150mm AM9 – another bike that’s received strong reviews here at BikeRadar.
As such, this 130mm travel 29er has arrived, and Bird has seen it as an opportunity to use carbon for the first time too.
Bird will be offering the bike in a Raw Carbon finish.Bird Cycleworks
Aether 9 C carbon creation
Designing a bike with carbon provides more freedom, says Bird designer Dan Hodge. Compared to aluminium, using carbon means the frame isn’t just a collection of tubes welded together. The more fluid shapes available mean that pivot points can be blended together into the shapes and locations desired.
This freedom also means Bird is able to design to certain requirements. For example, the down tube is kinked, which leaves the lower section at the same angle as the shock (determined partially by the desired suspension kinematic). This not only works aesthetically, but also allows more space for larger water bottles.
Plenty of room in the front triangle for a large bottle.Bird Cycleworks
However, there are challenges too. Fitting a 29in wheel with clearance for 2.6in tyres into a short back-end – the Aether 9 C has 430mm chainstays – while also wanting to run a 34t chainring means space is tight.
Bird says that this has been resolved by using deep chainstays that can handle the clearances required.
Deep chainstays ensure the back-end is stiff enough, while still allowing plenty of room for chunky tyres and a 34t chainring.Bird Cycleworks
A game of numbers
While the mountain bike industry has been building longer, lower and slacker bikes for a number of years now, Bird was an early adopter of this style of geometry – reaches have always been long, head angles slack, and seat angles steep.
This continues on the Aether 9 C, with seat angles that change with frame sizes – getting steeper on the larger frames. This, says Bird, is in a bid to keep taller riders centred between the wheels and helps keep effective seat angles nice and steep when longer dropper posts are used.
Bird says the short back-end is there to keep handling playful, while the roomy front-end and slack head angle give stability and confidence, as well as comfort.
Finally, a low bottom bracket (BB) helps carve corners. Bird wants the bike to have a capable, yet playful feeling that’ll work on everything from uplift days to long hauls in the hills.
A four-bar suspension system delivers 130mm of travel.Bird Cycleworks
The bike uses a four-bar suspension system that is apparently tuned for efficient pedalling and a lively feel, thanks to plenty of mid-stroke support, as well as plenty of ramp-up towards the end of the travel for big-hit capability, reflecting what we found with the Aether 7 during our testing.
Aether 9 C fine details
While previous bikes from Bird have had external cable routing, for ease of maintenance, this bike comes with the cables routed internally.
This is the second Aether bike, but Bird’s first carbon frame.Bird Cycleworks
One issue that can arise from bikes designed for a range of territories is that the rear brake hose can be a pain to route if the frame’s internal cable entry points aren’t set up for either a left- or right-hand rear brake lever.
But Bird says that it’s designed a dual entry system with a ‘Y Connector’ in the frame, which enables the rear brake hose to be fed in from either side of the head tube, with it exiting the frame in the right place regardless.
The bike is designed for 140mm travel forks.Bird Cycleworks
The bike is designed with 140mm travel forks and offsets between 42 and 46mm (though fork offsets between 37 to 51mm should work too). Fork axle to crown lengths should be between 541mm to 561mm.
Claimed weights for the frames range from 2,780g in a medium to 2,870g in an XL
Bird Aether 9 C geometry
Bird has been building long, low and slack bikes since it started.Bird Cycleworks
Bird will offer the Aether 9 C in four sizes – Medium, Medium-Long, Large and Extra Large.
Key geometry figures for a Large are:
Seat tube: 455mm
Head angle (sagged): 65 degrees (64.8 degrees)
Effective seat angle: 77.5 degrees
BB height (sagged): 330mm (289mm)
Bird Aether 9 C models
The bike is designed to be suitable for pretty much anything, from park days to big rides in the hills.Bird Cycleworks
One of Bird’s biggest selling points is the option to alter the spec on a bike at the point of purchase – whether it be due to kit preference or budget.
Bird will offer three options and spec can be adjusted on each model: a frame only build; Shimano 12-speed build; and SRAM Eagle build.
The basic specs of these are listed below.
Bird Aether 9 C frame only
The frameset comes with a rear axle, mech hanger and frame protection. A RockShox Deluxe Select+ shock is an extra £160, but information on shock dimensions and damping tunes is available.
There’s the option to add items such as a headset, seat clamp and seatpost if you wish.
Colour options are Flat Cap Green or Gloss Raw Carbon.
Bird Aether 9 C Shimano 12-speed
A Shimano 12-speed build is listed with a RockShox Deluxe Select+ shock and Pike Ultimate RC2 fork.
It comes with a Shimano Deore groupset, DT Swiss XMC 1501 carbon wheels and SRAM G2 R brakes.
The price of the bike can be raised or lowered with a number of alternative component selections, including alloy wheels, different suspension forks or alternative drivetrains.
Bird Aether 9 C SRAM Eagle build
It’s a similar story with the SRAM Eagle builds. In this case, just shy of £3,500 gets you the same suspension, RockShox Deluxe Select+ shock and Pike Ultimate RC2 fork, a GX Eagle groupset and alloy DT Swiss XM1700 wheels.
As before, specs are adjustable to suit your preferences.
Riding since the age of 13, Technical Editor Tom has ridden hundreds of bikes over the past few years, from aero race bikes to EWS-ready enduro rigs, with a fair few others in between. Most likely found in the woods practicing his scandi-flicks.