The Fly Bikes Motosierra Frame is red with white graphics on the top tube and head tube. It features welded chainstay brake mounts, trails-specific geometry, and is set against a plain white background.
The Fly Bikes Motosierra Frame, crafted with trails-specific geometry, is displayed on a white background. It features stylized logos on the top and head tubes and has expertly welded chainstay brake mounts.
Close-up of the Fly Bikes Motosierra Frame's black fork dropouts and frame with logo, showcasing welded chainstay brake mounts that enhance its trail-specific geometry.
Close-up of a black Fly Bikes Motosierra Frame with white graphics, highlighting its trails-specific geometry and intricate welds, including welded chainstay brake mounts.
Close-up of the Fly Bikes Motosierra Frame, highlighting "MOTOSIERRA" text and a white circular saw logo on the head tube. Designed with welded chainstay brake mounts, it enhances trails-specific geometry for superior performance.
A Fly Bikes Motosierra Frame in red with white decals is shown on a black backdrop. A "Lifetime Warranty" badge appears in the top right corner, emphasizing its welded chainstay brake mounts for durability.
Close-up of the Fly Bikes Motosierra Frame's red head tube adorned with a silver and black emblem featuring trees and text, highlighting the welded chainstay brake mounts.
Close-up of the red Fly Bikes Motosierra Frame highlighting a black and white decal with design elements, featuring "Flybike" and "Moto Sierra" text, plus welded chainstay brake mounts for trails-specific geometry.
Close-up of the Fly Bikes Motosierra Frame in red, showcasing its fork ends against a black background, with precision-welded chainstay brake mounts.
Diagram of the Fly Bikes Motosierra Frame with trail-specific geometry: top tube 21"/21.4", seat tube 9.25", chainstay 14" with welded brake mounts, head tube 4.7", and bottom bracket angles of 71° and 74°.

Description

Since Sergio Layos' signature Sierra landed, Fly Bikes have wanted to do a more trails specific frame. The Motosierra is that frame: a Sierra with trails geometry, a 21" or 21.4" top tube, a 74° head tube angle and a 14" rear end slammed, sitting on an 11.5" bottom bracket height with 9.25" standover.

It is built from 4130 chromoly with Japanese Sanko triple butted tubing, a CNC machined and heat treated head tube and mid bottom bracket, and new 5mm investment cast dropouts for a 10mm axle cassette. Brake mounts are welded to the chainstays with the cable run through the seat tube. The one piece removable chain tensioner suits hubs with a cone diameter under 24mm. Claimed weight for the 21" is 2.200 kg.

Features
  • Sierra built for trails. Fly took Sergio Layos' signature Sierra and gave it trails specific geometry for die hard trails riders.
  • Slammed 14" rear end. A 14" slammed chainstay with 11.5" bottom bracket height and 9.25" standover, in a 21" or 21.4" top tube.
  • 5mm investment cast dropouts. Built for a 10mm axle cassette, with a one piece removable chain tensioner that suits hubs under 24mm cone diameter.
  • Welded chainstay brake mounts. The mounts are welded on and the cable runs through the seat tube, so the brake line stays tucked out of the way.
  • Japanese Sanko triple butted tubing. Full 4130 chromoly with a heat treated head tube and mid bottom bracket, 2.200 kg for the 21".

Specifications
  • Sizes: 21" and 21.4" top tube
  • Chainstay: 14" slammed
  • Head tube angle: 74°
  • Seat tube angle: 71°
  • Standover: 9.25"
  • Bottom bracket height: 11.5"
  • Bottom bracket: Mid, CNC machined 4130 chromoly, heat treated
  • Material: 4130 chromoly
  • Tubing: Japanese Sanko triple butted
  • Dropouts: 5mm investment cast 4130 chromoly, heat treated, 10mm axle, one piece removable chain tensioner
  • Brake mounts: Welded, chainstay
  • Cable routing: Through the seat tube
  • Head tube: 120 mm / 4.7", CNC machined 4130 chromoly, heat treated
  • Seat clamp: Investment cast 4130 chromoly, heat treated
  • Axle: 10mm cassette
  • Weight: 2.200 kg / 4.85 lb (21")
  • Note: Chain tensioner is compatible with hubs under 24mm cone diameter

Fly Bikes Motosierra Frame

Brand: Fly Bikes SKU:

$719.99 AUD

Or 4 payments of $179.99 AUD with

Colour - Gloss Dark Red

Top Tube Length - 21

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
$719.99 AUD

Price match request

Fly Bikes Motosierra Frame - Gloss Dark Red / 21

$12.99 flat-rate shipping Australia-wide

Express from $21.99

Free in-store pickup - Brisbane

Availability

2121.4
Gloss Dark Red
Gloss Black

● In stock at LUXBMX ● With supplier ● Preorder ○ Sold out

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