The Fly Bikes Sierra Frame features a minimalist design with a geometric structure, made from durable black 4130 CrMo.
Close-up of the Fly Bikes Sierra Frame with forest-themed graphics, featuring a 4130 CrMo black bicycle frame and visible joints.
Close-up of a black Fly Bikes Sierra Frame highlighting branding and graphics. Crafted with 4130 CrMo for strength, the tubing connections feature a matte finish.
Close-up of three black Investment Cast bicycle fork dropouts with a sleek, matte finish set against a white background, designed to perfectly complement the rugged durability of the Fly Bikes Sierra Frame made of 4130 CrMo.
Close-up of the Fly Bikes Sierra Frame made from 4130 CrMo, featuring "Sierra" in white on its sleek black surface. Near the joint is an emblem with a mountain and gear design that adds rugged elegance.
The Fly Bikes Sierra Frame offers durability with its black 4130 CrMo construction, highlighted by sleek white graphics and "SIERRA" text. A "Lifetime Warranty" badge in the top right corner guarantees a trustworthy investment for riders.
The Fly Bikes Sierra Frame diagram shows dimensions: top tube 20.6"/21"/21.4", head tube 4.45", seat tube angle 71°, frame angle 75°, bottom bracket 11.5", chainstay 13.6", and seat tube length 8.75". Made from durable 4130 CrMo with investment cast components for enhanced performance.
Fly Bikes Sierra Frame in red features a 4130 CrMo build with white graphics, a "Lifetime Warranty" badge on the top right, and Investment Cast components for enhanced durability against the stark black background.
Close-up of a Fly Bikes Sierra Frame in red, made from durable 4130 CrMo steel, featuring the word "Sierra" and an emblem with trees on a stylish black background.
Close-up of a red Fly Bikes Sierra frame crafted from durable 4130 CrMo with a matte finish, featuring tree decals and "USA" on the vertical tube, against a black background.
Close-up of a Fly Bikes Sierra Frame dropout on a black background, highlighting the 4130 CrMo steel rear fork ends with bolt holes.

Description

Sergio Layos has been one of the most stylish riders on the planet for donkeys, and the Sierra is his signature frame. A couple of the boys here at LUXBMX have run one and were absolutely hyped on it: a low 11.5" bottom bracket height, 8.75" standover and a 13.6" rear end, in 20.6", 21" and 21.4" top tube lengths.

It is built from 4130 chromoly with Japanese Sanko triple butted tubing, multi-butted and tapered, plus internal and external gussets and a CNC machined heat treated head tube and mid bottom bracket. The seat post clamp, seatstay bridge and dropouts are investment cast and heat treated, the clamp using the Horizontal Cut System and the dropouts running integrated chain tensioners. Brake mounts are removable EBS style on the chainstays, head tube angle is 75° and seat tube 71°, with a claimed 2.200 kg for the 21".

Features
  • Sergio Layos' signature frame. Serg is easily one of the most stylish riders going, and this is the frame he runs.
  • Low bottom bracket, low standover. An 11.5" bottom bracket height and 8.75" standover with a 13.6" rear end: a couple of the crew here have run one and rated it.
  • Three top tube lengths. 20.6", 21" and 21.4", all with a 75° head tube angle and a 71° seat tube angle.
  • Removable EBS brake mounts. The chainstay mounts come off when you ride brakeless and bolt back on when you want a rear brake. EBS brake kit not included.
  • Investment cast where it counts. Cast dropouts with integrated chain tensioners, a cast seat clamp with the Horizontal Cut System and a cast seatstay bridge, 2.200 kg in the 21".

Specifications
  • Sizes: 20.6", 21" and 21.4" top tube
  • Chainstay: 13.6"
  • Head tube angle: 75°
  • Seat tube angle: 71°
  • Standover: 8.75"
  • Bottom bracket height: 11.5"
  • Bottom bracket: Mid, CNC machined 4130 chromoly, heat treated
  • Material: 4130 chromoly
  • Tubing: Japanese Sanko triple butted, multi-butted and tapered, internal and external gussets
  • Dropouts: Investment cast 4130 chromoly, heat treated, integrated chain tensioners
  • Brake mounts: Removable EBS style, chainstay. Brake kit not included
  • Head tube: 113 mm / 4.45", CNC machined 4130 chromoly, heat treated
  • Seat clamp: Investment cast 4130 chromoly, heat treated, Horizontal Cut System
  • Weight: 2.200 kg / 4.85 lb (21")
  • Note: Lifetime warranty. Replacement stickers included

Fly Bikes Sierra Frame

Brand: Fly Bikes SKU:

$749.99 AUD

Or 4 payments of $187.49 AUD with

Colour - Flat Black

Top Tube Length - 21.4

20 inch BMX frame sizing

Frames are sized by top tube length. Start with your height, then let riding style decide where in the range you land.

Rider heightTop tube
147 to 157cm19.75 to 20.25"
157 to 168cm20 to 20.5"
168 to 175cm20.25 to 20.75"
175 to 183cm20.5 to 21"
183 to 190cm and up20.75 to 21.5"

The height bands overlap on purpose. If you land in two of them, riding style breaks the tie: longer for flow, trails and transitions, shorter for technical street and park. Plenty of riders, pros included, deliberately ride longer than a chart suggests.

How to measure

Top tube is measured from the centre of the seat tube to the centre of the head tube, so it is not the length of the tube you can see. Measure your current frame that way and compare.

  • 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 once you buy, but chainstay length, stem length, fork offset and bar position all change how the built bike feels.

Not sure? Tell us your height and how you ride, and we will tell you what we would put you on.

Read the full buying guide

20 inch BMX frame sizing

Frames are sized by top tube length. Start with your height, then let riding style decide where in the range you land.

Rider heightTop tube
147 to 157cm19.75 to 20.25"
157 to 168cm20 to 20.5"
168 to 175cm20.25 to 20.75"
175 to 183cm20.5 to 21"
183 to 190cm and up20.75 to 21.5"

The height bands overlap on purpose. If you land in two of them, riding style breaks the tie: longer for flow, trails and transitions, shorter for technical street and park. Plenty of riders, pros included, deliberately ride longer than a chart suggests.

How to measure

Top tube is measured from the centre of the seat tube to the centre of the head tube, so it is not the length of the tube you can see. Measure your current frame that way and compare.

  • 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 once you buy, but chainstay length, stem length, fork offset and bar position all change how the built bike feels.

Not sure? Tell us your height and how you ride, and we will tell you what we would put you on.

Read the full buying guide
$749.99 AUD

Price match request

Fly Bikes Sierra Frame - Flat Black / 21.4

$12.99 flat-rate shipping Australia-wide

Express from $21.99

Free in-store pickup - Brisbane

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