‘Twenty-six ain’t dead’ in the dirt jump/4X/slopestyle world, and we love getting out on the ‘little’ bikes as often as we can — although the Calibre Astronut is a bit bigger than most, with a 680mm front centre and 390mm chainstays (386mm slammed).
The team at Calibre is based a stone’s throw from the Bolehills BMX track and Monkey Bumps dirt jumps in Sheffield, and it shows. This bike loves to go fast and big!
Drivetrain: Two-piece alloy cranks with half-link chain (1×1)
Wheelset: Calibre rims on Formula hubs
Tyres: Schwalbe Table Top 26×2.25in
Brakes: Tektro, 160mm rotors
Bar: Calibre, 750mm
Stem: Calibre, 50mm
Seatpost/saddle: Pivotal integrated
Weight: 12kg (26.46lb)
Calibre Astronut frame and kit
The hydroformed 6061 aluminium frame has a tapered head tube, making any future fork upgrades straightforward, and a threaded bottom bracket. Boxy seat- and chainstays keep things stiff where it matters.
My pre-production frame had a built-in rear mech hanger, but the final bikes will come with a replaceable one, along with a nifty brake slider to keep the caliper in place as you move the back wheel around in the horizontal dropouts.
At this price I was expecting the components to be fairly basic and thought some might need upgrading as soon as you could afford it, but everything specced on the Astronut is solid.
While the head tube is tapered, the fork steerer isn’t, but it makes future upgrading easierJonny Ashelford / Immediate Media
The Manitou Circus Sport fork is pretty hefty and has a straight steerer tube, but it offered all the support I needed and I’d only upgrade it to save weight. It’s great to see Calibre speccing a half-link chain because it allows you to get the chain tension just right without sacrificing any effective chainstay length.
Tektro provides the brakes, on 160mm rotors, and, again, I had no issues with them. I took the front one off because it’s not needed for dirt jumping, but it’s worth having if you want to race 4X or slalom, and must be fitted if you want to use the bike around town.
The Calibre-branded rims laced to Formula hubs stayed true, but the gappy freehub engagement made it a bit tricky to get going on tight start ramps, such as that in the 417 Bike Park’s Dirt Barn in Gloucestershire, where we shot our pictures.
While the Schwalbe Table Top tyres are fine for dirt jumping, their hard compound and low-profile tread can make them a little slippery on tarmac and paved surfaces.
Calibre Astronut ride impressions
xxxxxJonny Ashelford / Immediate Media
As soon as you swing a leg over the Astronut you can tell that this is a bike designed by mountain bikers. It is long, but that helps keep things stable at speed.
If you’re just starting out in the dirt jump world, this is going to be a great bike to learn on. You’ll have to work a bit harder to get the front up for manuals, but once you find the balance point, you’ll be less likely to loop out over the back wheel.
The weight at the front, due to the fork, is noticeable at first but you soon get used to it. It takes more effort to get the Astronut through tight jumps than some shorter, more compact DJ bikes, but open it up on a BMX or 4X track and you’ll be throwing whips and scrubbing every jump in sight!
Calibre rider Simon Pages took his Astronut to sixth place in the slopestyle comp at this year’s Crankworx Rotorua, so under the right person, there’s no stopping this frame. We’d even be keen to stick some gears and the front brake back on and see if we can find a 4X race to enter.
Calibre Astronut early verdict
Impressive dirt jumper that’s worth upgrading once you’ve worn out the capable stock kit specced.
Calibre Astronut availability
The Calibre Astronut jump bike will be on sale from the 8th of October.