Swinley-based Bird Cycles has two full-suspension bikes: the Aeris 120 and the 145 tested here. While its 145mm of rear travel suggests a trail bike, it rides much more like a longer-travel enduro machine.
Bird Aeris 145 GX Eagle specifications
- Frame: 6066 aluminium, 145mm (5.7in) travel
- Fork: RockShox Pike RCT3 Solo Air, 150mm (5.9in) travel
- Shock: RockShox Deluxe RT3
- Drivetrain: SRAM GX Eagle (1x12)
- Wheelset: DT Swiss M 1900 SPLINE 30 wheels
- Tyres: Maxxis Minion DHF WT 3C EXO TR 27.5x2.6in and Minion DHR II WT 3C EXO TR 27.5x2.4in
- Brakes: SRAM Guide R, 180mm rotors
- Bar: Race Face Turbine 35, 760mm
- Stem: Race Face Æffect R 35, 40mm
- Seatpost: Race Face Turbine 150mm dropper
- Saddle: Fabric Scoop
- Weight: 13.88kg (30.6lb), large size without pedals
Bird Aeris 145 GX Eagle frame
The alloy frame uses a tried and tested four-bar linkage suspension design to deliver its 145mm of rear wheel travel, so nothing out of the ordinary there. It’s designed to work with a 150mm or 160mm-travel fork up front, and mine was paired with the shorter option. What is unusual is the frame geometry, which is much more extreme than the amount of travel might suggest.
With a reach of 506mm and a wheelbase of 1,255mm on the large size, this is a long bike. It is, in fact, longer than many extra-large bikes. But don’t worry, with five sizes to choose from, there should be an Aeris to fit everyone.
The effective seat angle is steep (76 degrees), while the head angle is fairly slack (65.5 degrees).
The bottom bracket sits reasonably low at 340mm, with a drop of 10mm. Cornering credentials are bolstered further by the short but not stumpy 435mm chainstays. Boost spacing is used out back. External cable routing and a threaded BB should make it that bit easier to keep the Aeris running smoothly.
Bird Aeris 145 GX Eagle kit
The DT Swiss M 1900 wheels were shod with some of my favourite tyres: ‘Wide Trail’ Maxxis Minions (2.6in DHF front, 2.4in DHR II rear). If any of these parts aren’t to your liking, you can chop and change virtually everything on Bird’s website: fork, shock, tyres, wheels, dropper, etc. This means you can pick and choose a custom build based on personal kit preferences and how deep your wallet is.
Bird Aeris 145 GX Eagle ride impressions
You could easily be fooled into thinking the Aeris has more than 145mm of travel. The long, low geometry makes it feel perfectly at home on steep, loose and fast descents, where having the front wheel punted out ahead gives more high-speed confidence and cornering stability.
This is especially true if you take the Wide Trail tyre option — lean the Minions over and the extra traction and predictability of the chunky rubber makes railing corners as easy as it comes.
The four-bar rear end and metric shock give plenty of small-bump sensitivity but still deal with the big hits with plenty of composure when they do start coming thick and fast.
There’s a touch more support in the mid stroke than on the original Aeris too, although I’d still recommend having a play with volume spacers to make the most of the travel on offer.
The frame is also a touch stiffer than before. This is a good thing, because the flipside of the Aeris 145’s impressive descending performance is that on flatter trails and climbs it feels like a much bigger bike than it is.
It’s not super-happy hustling through tight, twisty pedally sections and it’s not going to flatter your climbing prowess, so you’ll want every watt possible to go straight through to the back wheel. Thankfully the steep tube angle helps here.
Bird Aeris 145 GX Eagle early verdict
The super-stretched-out geometry of the new Aeris makes it a descent-biased shredder.