Radio Cobalt Junior Bike (2021) / Black / 18.5TT

Radio Cobalt Junior Bike (2021) / Cyan / 18.5TT

A red BMX race bike with a black seat, black handlebars, and thin tires. The frame and rims flaunt red accents. This Radio Cobalt Junior Bike has a single gear and a rear brake.

A red Radio Cobalt Junior Bike with black handlebars and tires, featuring a lightweight frame and a single gear system, perfect for those who love the thrill of racing.

Close-up view of the front section of a red BMX race bike, showing the fork, tire, and part of the frame. The tire is branded "ARISUN XLR8" and the frame has a "Radio Cobalt Junior Bike" label from Cobalt bikes.

Red bicycle with a close-up view of its black saddle, pedal, and drivetrain components. The bike, a Radio Cobalt Junior Bike, has a sleek frame design and detailed features reflecting top-notch craftsmanship.

Close-up of a red bicycle seat with "Radio Cobalt Junior Bike" branding on a black saddle, attached to a metallic red BMX race bike frame and rear wheel.

Close-up of a Radio Cobalt Junior Bike's crankset and rear tire, showing the chainring, pedals, and part of the frame.

Close-up of the rear wheel and gear mechanism of a Radio Cobalt Junior Bike, showing the spokes, chain, and derailleur against a white background.

Close-up of a Radio Cobalt Junior Bike's rear wheel and gears with black spokes, a red metal frame, and a tire on a ruler for calibration.

The Radio Cobalt Junior Bike features a red frame, black tires, and a straight handlebar, set against a white background—an ideal entry-level BMX race bike.

Description

The Radio Raceline has continued its upwards trajectory in the "ready to race" category of complete off-the-shelf race bikes. Every one of their bikes in the Cobalt range can go from the shop to the podium with ease, and is the perfect entry level race bike for your young rider.

This beast is stacked full of loads of epic Radio parts to ensure a ride like no other! Radio Raceline Cobalt Grips provide loads of grip for your hands, The Radio Raceline Cobalt Hubs laced up to double walled Radio Raceline A-M5 Rims, which means they can take a beating you shredder starts to send the jumpks. After all, every BMX kids just wants to jump stuff, and this bike will take that punishment as they learn the ropes of BMX racing.

Fresh out of the box for with incredible paint and graphics, you’ll be able to spot a Cobalt on the track very easily. All Cobalt bikes now feature full sealed front hubs and integrated headsets, making them simply unbeatable when comparing price to spec. the cobalt is one seriously unstoppable machine.

We sell loads of these complete race bikes, and for good reason, awesome build quality at this price point makes them extremely great value and will last a season or two before your racer grows into the next size.

Features

Ready to race out of the box. Every bike in the Cobalt range can go from the shop to the podium, which makes it a solid entry level race bike.
Light 6061-T6 alloy frame. 8.07 kg all up, with forged dropouts and an internal chain tensioner to hold the rear wheel where you set it.
Fully sealed Cobalt hubs. Sealed cnc alloy hubs laced to double wall A-M5 rims take the punishment when your young racer starts sending the jumps.
40 x 16 gearing, 155mm cranks. A 49.75" ratio on forged alloy 3-piece cranks that are cut short to suit smaller legs turning laps.
Sized for a growing racer. An 18.5" top tube and 24" bars fit a young rider, and the build will last a season or two before the next size up.

Specifications

Size: 18.5" top tube
Frame: 6061-T6 alloy, forged dropouts with internal chain tensioner
Top tube: 18.5"
Chainstay: 12.85"
Head tube angle: 73°
Seat tube angle: 71°
Bottom bracket height: 10.4"
Fork: CrMo, 1" butted steerer, hi-ten legs, 23 mm offset
Headset: Radio Raceline integrated, sealed, 1"
Stem: Radio Raceline Cobalt top loader, 40 mm reach, alloy
Bars: 4130 CrMo, seamless, 4.25" rise, 24" wide, 8° backsweep, 2° upsweep
Grips: Radio Raceline Cobalt, diamond knurling, closed end, flangeless, 130 mm
Brakes: Radio Raceline Mini V-Brake, rear
Brake lever: Radio Raceline Junior, rear
Cranks: Radio Raceline Cobalt 3pc, forged alloy, 155 mm
Bottom bracket: Radio Raceline, BSA square taper, sealed
Sprocket: Radio Raceline, 40T, alloy
Chain: KMC Z6, 1/2" x 3/32"
Pedals: Radio Raceline Cobalt Junior, nylon
Front hub: Radio Raceline Cobalt, cnc alloy, fully sealed, 28h, 3/8" crmo axle
Rear hub: Radio Raceline Cobalt, cnc alloy, fully sealed, 28h, flip flop, 3/8" crmo axle
Rear cog: ATA freewheel, 16T, 1/2" x 3/32", crmo
Rims: Radio Raceline A-M5, double wall, 28h, alloy, front and rear
Tyres: Arisun XLR8, 20" x 1-1/8"
Seat: Radio Raceline Mini combo
Seat post: Radio Raceline, 22.2 mm, alloy
Seat clamp: Radio Raceline, forged alloy
Gearing: 40 x 16, 49.75" ratio
Weight: 8.07 kg

Assembly information

Your bike ships mostly assembled in the box. Finishing it takes most people 10 to 20 minutes with basic tools, and the video above walks through every step.

Fit the handlebars and line them up with the front wheel
Fit the front wheel, pedals and seat post
Check the brakes and tyre pressure before the first ride

Tools: Allen key set and a 15mm, 17mm or 19mm spanner for the pedals and axle nuts (bikes can vary between these three sizes). A socket is needed if installing pegs.

Rather have it done? Ask us about extra assembly before you order, or any local bike shop can finish the build for a small fee.

Radio Cobalt Junior Bike

Name: Radio Cobalt Junior Bike
Brand: Radio
SKU: RABK169-21-RED
Price: 899.99 AUD
Availability: OutOfStock

Brand: Radio SKU: Click to copy the SKU and show the pick location

$799.99 AUD

Or 4 payments of $199.99 AUD with

Recommended Rider Height:

120-150cm

Colour - Metallic Red

Top Tube Length - 18.5

Race frames are sized by class, and the class you ride is set by rider height rather than age.

Size	Rider height	Top tube
Micro (18" wheels)	Under 120cm	16.25"
Mini (20" wheels)	110 to 140cm	17 to 18"
Junior	120 to 150cm	18.25 to 18.75"
Expert	130 to 170cm	19.5 to 19.75"
Expert XL	145 to 170cm	20 to 20.75"
Pro	150 to 175cm	20.25 to 20.75"
Pro XL	165 to 180cm	21 to 21.25"
Pro XXL	170 to 185cm and up	21.5 to 21.85"
Pro XXXL	175cm and up	22"
Pro XXXXL	180cm and up	22.5"
Cruiser (24" wheels)	175cm and up	21.5" and up

Heights overlap between classes on purpose. Where you land in two, a growing rider is usually better on the larger, and a rider who wants the bike to turn faster on the smaller. Some brands label the Pro size Pro L, with the same fit.

How to measure

Stand your rider against a wall in the shoes they ride in, heels flat, and mark the top of their head. Measure from the floor to the mark.

Between two sizes and still growing? Take the larger size.
Racing gates and wanting the bike to turn faster? Take the smaller size.
Top tube is the number that actually changes the fit, so compare it against the bike they ride now.

Not sure? Send us their height and we will tell you what we would put them on.

Read the full buying guide