In this article:

• Learn how SHIMANO’s new XTR and DEORE XT Di2 platform offers two wireless derailleur options to match different riding styles and terrain.
• Discover the key benefits of the new 9-45T cassette and short cage derailleur setup, including more ground clearance, tighter gear steps, lighter weight, and improved chain management.
• Read about how the 9-45T cassette allows riders to maintain a full gear range when paired with the right front chainring.

When every second counts, every shift matters. SHIMANO’s XTR and DEORE XT groups have long set the standard for mountain bike performance, from World Cup racing to backcountry epics to everyday trail riding. Now, SHIMANO MTB enters a new era with lightning fast wireless Di2 shifting and a drivetrain platform that features smart choices so more riders can experience this hallmark high-performance shifting.

The new wireless drivetrains include a compact 9-45T cassette and a matching short cage rear derailleur, adding extra ground clearance and tighter gear steps with minimal sacrifice to overall gear range, including no sacrifice to top or bottom gear ratios. For riders seeking wireless simplicity and performance without compromise, the new Di2 system delivers reliably fast shifting and modern customization options via the E-TUBE PROJECT app.

Not every trail, race, or rider is the same, and that’s exactly why SHIMANO developed two distinct rear derailleur options for the new Di2 platform. Both derailleurs feature wireless shifting, durable race-proven construction, but where they differ is in their application.

• SGS Long Cage – Designed to work with wide-range 10-51T cassettes.
• GS Short Cage – Tuned for a tighter 9-45T cassette.

This gives riders the flexibility to choose the drivetrain that best fits their terrain, fitness, and style. Whether you need the all-day versatility of a 10-51T setup or the tight responsiveness of a 9-45T cassette, SHIMANO has you covered.

What’s the appeal of a tighter cassette when bigger steps seem to be the trend? The new 9-45T cassette is all about refined performance. It’s aimed at riders who prefer tighter gear steps for smoother cadence control, faster acceleration, and fewer dramatic jumps between cogs without giving up critical top-end or climbing gears. When paired with the right front chainring, you get a more compact drivetrain with no loss of low-end climbing gears or top end driving gears.

Key Benefits of the 9-45T Setup:

• Increased Ground Clearance – Shorter derailleur cage and smaller cassette reduce hang-up risk in technical terrain.
• Better Chain Management – Higher chain tension and less drivetrain slap for a quieter, more secure ride.
• No Lost High or Low Speeds – Maintain a full gear range when paired with the right front chainring for your terrain and fitness.
• Tighter Gear Steps – Helps maintain smoother cadence, ideal for high-output racing and rolling terrain.
• Reduced Weight – Smaller cogs, fewer chain links and shorter derailleur mean fewer grams on your race rig.

Who It’s For:

• Fast Trail Riders – Riders who prioritize speed, efficiency, and cadence control.
• Powerful Riders – Those who can comfortably push a higher gear and don’t need a 51T cog.
• Weight-Conscious Builders – Anyone trying to trim grams and build a lighter, snappier bike.

Whether you're racing Enduros or looking to optimize your trail bike for speed and flow, the 9-45T system delivers crisp, race-tuned performance in a compact, race-ready package.

Not sure what is right for you and your needs? Check out this handy infographic that weighs the features of each the 9-45t and 10-51t options available in Shimano’s MTB Drivetrains:

At the heart of this new drivetrain is SHIMANO’s wireless Di2 shifting, delivering incredibly fast, accurate shifts every time. Both rear derailleurs are packed with smart functionality:

• Automatic Impact Recovery – Intelligent motor design allows the Di2 Rear Derailleur to return to it’s original position after impact with objects on trail.
• Wireless Di2 Shift Protocol – Lightning-fast wireless shift protocol now offered in full range, Hyperglide+ MTB drivetrains.
• E-TUBE PROJECT App – Personalize shift behavior, firmware, and gear mapping on the fly.

Of course, these new drivetrains maintain SHIMANO’s hallmark durability, tested under the harshest race conditions by the fastest riders in the world.

The latest evolution of SHIMANO MTB isn’t just a refresh; it’s a rethinking of what high-performance mountain bike drivetrains can be. With the introduction of the 9-45T cassette and short cage derailleur, SHIMANO enables riders to fine-tune their bikes for their specific goals and terrain. Whether you’re charging down the mountain mid-race or carving fast, flowing lines on your local trails, the new short cage setup delivers the crisp, responsive feel and modern wireless control today’s riders’ demand. SHIMANO is still the top of the podium, but now, it’s also part of your personal best.