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by Ed Brazier June 16, 2022 4 min read

Special races call for special bikes if you ask me. Or maybe this year's Steel City DH was an excuse to try an idea that's been on my mind for a while...

We don't think like other bike brands, and we don't act like other bike brands either. That spirit of independence is hard-baked into the ethos. We're always asking Wouldn't it be sick if? So every now and then when we get an idea for a bike that makes no commercial sense, there's nothing stopping us from doing it. And sometimes, the results can be beautiful.

When the Filter was originally conceived, we sketched out an idea for a rad-as-possible short travel bike. Before we'd done any detailed work on layout, packaging or kinematics, we had this idea of what the Filter could be. That's how they all start; with an idea that really inspires us. And at that point we straight away saw the possibility to do a 4x variant. Call it a 4x bike, a Dual bike, a Slopeduro bike, a jib bike... whatever you want; but you get what I mean.

As the project progressed it became clear that we couldn't really have the trail bike that we wanted and a genuine 4x bike in the same package; at least not without making compromises. Turns out sometimes there is something stopping us. So we reluctantly had to shelve it. But good ideas never die and this one in particular kept itching away. So when we signed up for Steel City DH we finally had the excuse we'd been looking for...

Airdrop Filter 4x

Filter 4x Build

The frame itself is a prototype Filter. We made a few changes after this so the size is somewhere between a Small and a Medium. Andy was racing Steel City and he's 6' tall so this was a good size for him. I think reach might be 450mm but don't quote me on it. 

Airdrop Filter 4x

We stuck with the stock Rockshox Pike Ultimate at 150mm to preserve the head-angle and front-end height, but banged a load of tokens in there to get a bit more progression.

Airdrop Filter 4xThe high-front end theme carried through to the cockpit. Andy's fairly tall and used to riding a high front end on his Edit and the Slacker. So we went with 20mm Burgtec spacers below the 35mm mk3 Enduro stem, with a 50mm rise Josh Bryceland bar. Andy runs ODI Longeck grips on all his bikes.

Airdrop Filter 4x

In it's stock configuration, the Filter offers 135mm travel out back. That's with a 185x55mm shock. You can get 50mm stroke shocks in the same size which would deliver 122mm travel, and given that the track JP had built for Steel City was super smooth, we talked about going down that route. We also looked at running a MegNeg air can with higher pressure. In the end we decided we were too tight to buy a non-stock shock just for an experimental bike and opted for the 185x55 with a couple of tokens in it. And it worked great. While we're on the picture note the E*thirteen TRS chain guide with a top guide and lower bash guard. It's a good combo with no unwanted noise and zero drag.

Burgtec Boost Saddle

Let's face it, this bike isn't designed for pedalling. Or at least not sitting-down-and-pedalling. So we ditched the dropper post which also ditches quite a bit of weight and cleans up the controls, and fitted a Burgtec Boost DJ saddle. It's comfy and well made but more importantly, it looks sick.

Singlespeed Drivetrain

We stole the drivetrain off one of the Slacker prototypes. It's a SRAM GX DH 7-speed 11-25t cassette and a GX DH short-case rear mech. The chain's a random gold KMC number we had kicking about. For a bike like this there's no need for a wide range of gears so we did away with a long, slappy chain and a long mech that can get in the way. Best to keep things tight. 

You might be wondering if we looked at singlespeed and the answer is obviously! As there's a bit of chain-growth in the Filter's kinematics, we'd have to run a tensioner but that's OK - we've got SB One's GC3 tensioners in the workshop (they're for Slacker singlespeed builds). So yeah you definitely could set this up singlespeed but we didn't know what sort of ratio would work best so we opted for the 7-speed group.

Fortus 35 Wheels & Michelin Wild Enduro Tyres

The wheels are 27.5" Hope Fortus 35W rims of Pro 4 hubs. They're actually the wheels of my old Edit v4 prototype, and perhaps not the ultimate choice for a bike of this sort. Ideally we'd go for something with faster pickup in the rear hub and a slightly narrower, tougher and lighter rim. So Industry 9 hydra's laced onto DT FR560 or similar. We're not made of money you know!

Anyway these wheels are round and true so they went on the bike. And they look good. In terms of tyres we weren't sure of the surface. With the benefit of hindsight, we might have gone with something faster rolling but Andy's main thing was that he wanted a tyre with good sidewall support; he didn't want to be rolling tyres off rims through all those slashy turns, so we went with Michelin Wild Enduros. No inserts required, but we did run tubes. 

Burgtec Mk5 Penthouse Flats

Burgtec Mk5 Penthouse Flats. You had to ask?

I didn't get a shot of the brakes but they're an old set of Avid X0 Trail brakes. I know, Avid brakes had a bad name but the X0 Trails were sick. And they still are. They've been languishing in a box for a couple of years but they still feel mint and there's plenty of power. 

Airdrop Filter 4x

Airdrop Filter 4x

So... Can I buy One?

Yes. And no. Sometimes when we do these experimental bikes, they're great for the very specific thing we built them for, but wouldn't actually be much good for other things. This, on the other hand, would be a great bike for all sort of things. For a start we preserved the front and rear travel and also the wheel size, so we haven't messed with the geometry at all. The kinematics are fine since we only payed with the damper tunes and pressures. We're not offering these as a full build but it wouldn't be too hard to put something like this together yourself.

So yeah, get yourself a Filter Frame and crack on.



Ed Brazier
Ed Brazier

Ed is the owner of Airdrop Bikes. A former web and graphic designer, he sacked off his job one day and decided to start up a bike brand.

1 Response


September 26, 2022

I wish i could buy this.

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