Marin Bikes | 2025 Alcatraz Jr.

📏Size Guide

Built for young riders who want to send jumps, learn tricks, and ride pump tracks with confidence and style.

The Marin Alcatraz JR 24 is a purpose-built dirt jump bike designed specifically for younger riders looking to progress their skills in dirt jumping, skateparks, pump tracks, and urban freestyle riding. Built around a lightweight Series 3 aluminum frame with compact 24-inch wheels, the Alcatraz JR delivers responsive handling, durability, and playful geometry for aggressive riding.

With a rigid chromoly fork, single-speed drivetrain, hydraulic disc brake, and dirt jump-specific geometry, the Alcatraz JR is built to handle jumps, manuals, pump sections, and technical tricks while remaining simple and reliable.

Key Features

• Series 3 Aluminum Dirt Jump Frame
Lightweight and durable aluminum frame with dirt jump geometry and horizontal dropouts.

• 24-Inch Wheel Platform
Compact wheels improve maneuverability and control for younger riders and smaller frames.

• Rigid Cro-Mo Fork
Strong and responsive fork design built for pump tracks, jumps, and skatepark riding.

• Single-Speed Drivetrain
Simple and reliable setup with minimal maintenance and improved chain retention.

• Hydraulic Disc Brake
Rear hydraulic disc brake provides strong and consistent stopping power.

• Dirt Jump Geometry
Short chainstays and responsive handling make the bike playful and easy to throw around.

• Wide Riser Handlebar
Improves control and stability during jumps and technical riding.

Technical Specifications

• Category
Dirt Jump Bike

• Discipline
MTB / Urban

• Frame
Series 3 6061 Aluminum, 24” Wheels, 135x10mm Horizontal Dropouts, ISCG05 Tabs

• Fork
Marin Series 2 Cro-Mo 24" Fork

• Bottom Bracket
External Sealed Cartridge Bearings

• Headset
FSA No 57E Semi-Sealed Cartridge Bearings

• Crankset
Marin Forged Alloy, 32T Direct Mount Chainring, 152mm

• Cassette
14T Single-Speed Cog

• Chain
KMC HL-1

• Brakes
Tektro HD-M280 Hydraulic Disc Brake

• Brake Rotors
160mm

• Wheelset
Marin Custom Extrusion, 27mm Inner Width

• Front Hub
Forged Alloy, Bolt-On Axle, 100mm Spacing

• Rear Hub
Forged Alloy, 135x10mm Bolt-On, Quad Sealed Bearings

• Tires
Vee Tire Rail 24x2.25"

• Handlebar
Marin Riser Alloy Bar, 700mm Width

• Stem
Marin 3D Forged Alloy, 35mm

• Seatpost
Marin Alloy, 30.9mm

• Saddle
Marin DJ Saddle

• Pedals
Alloy Platform

• Color Option
Yellow Fade (#E3C200 → #FF7A59)
Red / Pink (#D7263D / #FF6FAF)

Geometry

Suitable for dirt jumping, pump tracks, skateparks, street riding, and freestyle MTB riding.