The new Bird Aether shows 27.5in wheels still very much have their place

29ers might steal the limelight, but Bird is firmly backing the 27.5 wheelsize with its latest trail bike

Bird Aether

It certainly seems most new bikes that arrive on the market these days sport the larger 29in wheels, proving popular on both the trails and in racing. However, Bird has set out to show us that there’s still plenty of life left in the smaller 27.5in wheelsize with its latest trail bike, the Aether.


The Aether is an aluminium, 130mm travel trail bike, built for 140mm forks. As we’ve come to expect from the UK based brand, the Aether has forward-thinking geometry and offers excellent value for money.

Bird Aether
The Aether is the latest in Bird’s growing catalogue.
Tom Marvin / Immediate Media

Bird wanted the Aether to be a hard-hitting, super-fun riding trail bike to replace the Aeris 120 and Aeris 120LT.

The Aeris 120 had almost class-leading progressive geometry, and the team from Swinley felt it was time for the bike to get an update. With prototypes designed and ridden, the bike showed enough of a difference from the Aeris 120 that Bird felt it warranted a new name: Aether.

Bird Aether frame highlights

The Aether shares its 6066-T6 tubeset with the older Aeris 120, but the kinematics and geometry have been updated to reflect what Bird wanted from the new bike.

Bird Aether
Bird designs its bikes in the UK.
Tom Marvin / Immediate Media

The geometry is very contemporary, with a long, stretched out front-end for stability and a very short rear, which Bird says is to make it as fun a ride as possible.

The seat angle is steep to centre weight between the wheels on technical climbs. At the front, the slack head angle, coupled with short 37mm offset forks, means stability at speed, but it’s handling is still quick enough to aid agility and responsiveness.

Bird Aether geometry
The Aether’s size-specific geometry.
Tom Marvin / Immediate Media
Bird Aether geometry
Bird Aether’s non-size specific geometry.
Tom Marvin / Immediate Media

Bird’s frames are nice and no-nonsense. External cable and hose routing not only makes a frame easier to maintain but presumably helps keep costs reasonable.

Likewise, a threaded bottom bracket shell tends to prove popular. The frames have room for 2.6in tyres at the back, while it’s based around a metric length shock.

Bird Aether cable routing
We like external cable routing – much more maintenance friendly!
Tom Marvin / Immediate Media

The pivots and linkages all come assembled with a self-locking collet system, while the technical datasheet comes with all the torque settings and Loctite codes for each and every pivot. We really appreciate this attention to detail.

Final details include a bolt-on ISCG05 chainguide mount, a rear SRAM Maxle axle and 31.6mm diameter seat tube.

Bird Aether chainguide
The Aether will take a chainguide, should you wish.
Tom Marvin / Immediate Media

Updated suspension kinematics

Bird uses a four-bar linkage to control the 130mm of rear-wheel travel, with all pivots running on bearings.

The swinglink drops from the top tube and the shock mounts into a brace, also dropping down from the top tube. The rear chainstays are asymmetrical to boost stiffness.

Bird Aether linkage
A four-bar linkage is used on the Aether.
Tom Marvin / Immediate Media

Bird’s engineer Dan Hodge says that Bird’s main suspension design has been tweaked over the years to get where it is now for a bike that’s fun to ride, as well as being capable up and downhills.

Therefore, the Aether has quite a lot of progression in its linkage, meaning there should be ample pop to aid jumps and bunny hops over obstacles, and it should also be able to deal smoothly with bigger impacts.

The anti-squat has been refined for the bike, too, in order to ensure it pedals well with the shock fully open, while still avoiding giving harsh pedal kickback over more lumpy terrain.

RockShox Metric shock
A Metric length shock is used on the new Aether.
Tom Marvin / Immediate Media

Bird has produced some great bikes based around its suspension and geometry, such as the Aeris AM9.

Bird Aether build and spec options

Bird offers a range of off-the-shelf builds, as well as frame only packages. However, within the individual builds there’s a wide range of optional upgrades and swaps. This means there’s ample opportunity to get particular spec options fitted to the bike to suit your preferences and budget.

RockShox 2020 Deluxe Ultimate
The 2020 Deluxe Ultimate lets you adjust the compression setting in its open mode.
Tom Marvin / Immediate Media

Framesets will start at around £1,290 (with a RockShox Deluxe Select+ RT shock, Bird rear axle and Bird QR seat clamp), with prices roughly following those set by Bird’s 29er Aeris AM9.

Bikes will start at approximately £2,035, with a 12-speed SRAM SX Eagle drivetrain, RockShox 35 fork and a DT Swiss M1900 wheelset shod in Maxxis tyres.

A full top-spec build, with XTR gears, Hope brakes, Ultimate level Pike fork, Super Deluxe suspension and DT Swiss XMC1200 carbon wheels will set you back around £5,100.

Hope MicroSpline hub
This is the first bike we’ve had with Hope’s MicroSpline freehub for Shimano’s 12-speed groupsets.
Tom Marvin / Immediate Media

The build shown here costs £3,500, and has been built for our 2020 Trail Bike of the Year test.

It comes with Pike and Deluxe Ultimate suspension, XT running gear, DT Swiss wheels and RaceFace/Fabric/Bird branded finishing kit.

Bird Aether
Bird lets you customise the spec depending on preference and budget.
Tom Marvin / Immediate Media

Look out for a full review of the Aether as part of our Trail Bike of the Year test, coming to BikeRadar and MBUK magazine soon.