Fit Bike Co Series One Bike in red, featuring a Cro-Mo frame, black seat, black handlebars, and thick black tires, displayed side-on against a white background.

A Fit Bike Co Series One Bike with a Cro-Mo frame, black finish, tan-walled tires, black seat, and handlebars is displayed in side view on a white background.

The Fit Bike Co Series One Bike features a white Cro-Mo frame, brown seat, black handlebars and wheels, and gold branding on the frame, shown in a side view on a white background.

The Fit Bike Co Series One Bike is red with black handlebars, seat, and tires, displayed from a side view on a white background.

The Fit Bike Co Series One Bike in black features tan wall tires, a straight top tube, and a raised handlebar, displayed on a white background.

The Fit Bike Co Series One Bike is shown in black with a Cro-Mo frame, brown seat, thick tires, and a straight handlebar against a white background.

The Fit Bike Co Series One Bike, featuring a Cro-Mo frame with a white finish, black handlebars and wheels, and a brown saddle, is displayed against a plain white background.

A black Fit Bike Co Series One Bike BMX with tan tires, straight handlebars, and a Cro-Mo frame features a single gear and is shown on a white background.

Highlights

FIT's original frame, still going
Lighter frame and fork for 2026
CNC-machined integrated head tube
Fully sealed bearing front hub

Description

The Series One was FIT's first frame when they started back in 2000, and it is still their most popular bike. For 2026 it picks up a CNC-machined integrated head tube and a fully sealed bearing front hub, and both the frame and the fork have been lightened up.

It comes in three top tube sizes with matching handlebar and crank sizes, so the fit is sorted before you leave the shop. The build runs a Cro-Mo front triangle, a sealed mid bottom bracket, FIT S1W wheels with a sealed 9T cassette, 2.4" tyres and a U-brake with a two finger lever.

Features

FIT's original frame, still going. The Series One was the first frame FIT made back in 2000 and it remains their most popular bike to date.
Lighter frame and fork for 2026. FIT trimmed weight out of the S1 frame and fork, so there is less bike to lift and throw around.
CNC-machined integrated head tube. New for 2026, machined and drilled with gyro holes so a detangler can go straight in when you want one.
Fully sealed bearing front hub. Also new for 2026: sealed bearings up front roll smoothly and need far less looking after.
Three top tube sizes, parts to match. Each size comes with its own bar width and crank length, so the cockpit suits the rider from day one.

Specifications

Frame: Cro-Mo front triangle, Series One geometry
Top tube: 20.25", 20.5" or 20.75"
Fork: Cro-Mo steerer, 33mm offset, welded insert
Headset: CNC-machined integrated with gyro holes
Stem: FIT top load
Bars: 2-piece, 8.7" x 29" on 20.25" and 20.5" top tube, 9" x 29" on 20.75" top tube
Brakes: U-brake with low tension springs, linear cable
Brake lever: Two finger
Cranks: Tubular Cro-Mo, 160mm on 20.25" top tube, 165mm on 20.5", 170mm on 20.75"
Bottom bracket: Mid sealed
Sprocket: FIT Key 25T
Pedals: FIT PC
Front hub: Sealed bearing
Rear hub: Sealed 9T cassette
Rims: FIT S1W front and rear
Tyres: FIT OEM 2.4"
Seat: More padded integrated combo
Seat post: 200mm
Note: Sealed front hub and integrated head tube are new for 2026

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.

Fit Bike Co Series One Bike

Name: Fit Bike Co Series One Bike
Brand: Fit Bike Co
SKU: FTBK108-26-RED
Price: 999.99 AUD
Availability: InStock

Brand: Fit Bike Co SKU: Click to copy the SKU and show the pick location

$999.99 AUD

Or 4 payments of $249.99 AUD with

Colour - Blood Red

Top Tube Length - 20.25

A 20 inch bike is the standard adult BMX and suits riders from about 147cm up. At this wheel size the top tube is what changes the fit, so pick that by height.

Rider height	Wheel size	Top tube
60 to 91cm	12"	12 to 12.5"
81 to 106cm	14"	14 to 14.5"
96 to 122cm	16"	16 to 16.5"
122 to 147cm	18"	18 to 18.5"
147 to 157cm	20"	19.75 to 20.25"
157 to 168cm	20"	20 to 20.5"
168 to 175cm	20"	20.25 to 20.75"
175 to 183cm	20"	20.5 to 21"
183 to 190cm and up	20"	20.75 to 21.5"
160cm and up	22"	21 to 22.25"
160cm and up	24"	21.75 to 22"
160cm and up	26"	22 to 23"

Sizes overlap on purpose, so personal preference comes into it. If you land in two bands, riding style breaks the tie: longer for flow, trails and transitions, shorter for technical street and park.

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.

Top tube is measured from the centre of the seat tube to the centre of the head tube, so it is not the same as the length of the tube you can see.

A 20 inch bike is the standard adult BMX and most riders end up there, so do not size a tall child down to a smaller wheel.
22, 24 and 26 inch bikes are adult bikes with a bigger wheel, not bigger frames for taller riders.
Size up for stability through trails and transitions. Size down if you want the bike quick and twitchy for spins and grinds.
Top tube is fixed, but stem length, fork offset and bar position all shift how roomy the bike feels once you are on it.

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

Read the full buying guide