SunRace MZ903 Cassette - 12 Speed - 11-51T
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Product Information
Full details
The SunRace MZ903 12-speed mountain bike cassette is designed for riders who want to upgrade or replace their drivetrain components while maintaining compatibility with standard Shimano HG freehubs. It offers a broad 11-51T gear range, making it ideal for conquering steep climbs and maintaining speed on flat terrain, though its 510g weight makes it heavier than some high-end titanium or aluminum alternatives.
All features
| Model Part Number | CSMZ903 |
|---|---|
| Brand | SunRace |
Extended Product Information
FAQs
Does this cassette fit a Micro Spline hub?
No, this cassette is designed specifically for Shimano HG (HyperGlide) splined freehub bodies.
Can I use this with an 11-speed derailleur?
No, this is a 12-speed cassette and requires a 12-speed derailleur and shifter for correct indexing and cable pull.
What is the gear ratio progression?
The sprocket progression is 11-13-15-17-19-21-24-28-33-39-45-51 teeth.
Is it compatible with SRAM 12-speed chains?
While it is designed for Shimano 12-speed systems, it generally works with most 12-speed chains, but using a Shimano-compatible 12-speed chain is recommended for the best shifting performance.
How much does the MZ903 weigh?
The cassette has a total weight of approximately 510 grams.
Troubleshooting
Difficulty shifting into the 51T cog
Check the B-tension screw on your rear derailleur. It may need to be adjusted to provide enough clearance between the pulley wheel and the large cog.
Excessive chain noise or skipping
Verify that your derailleur hanger is straight and ensure the cable tension is properly indexed according to the manufacturer's 12-speed setup guide.
Cassette wobbles on the freehub
Ensure the lockring is tightened to the correct torque specification and check that all spacers were installed correctly during the initial setup.
Pros and Cons
Pros
- High compatibility with standard HG freehubs
- Excellent wide-range gearing for climbing
- Reliable and durable steel construction
- More affordable than original equipment manufacturer equivalents
Cons
- Heavier than high-end 12-speed cassettes at 510g
- Requires a 12-speed specific derailleur and shifter
- Not compatible with Micro Spline or SRAM XD freehub bodies
Setup, Compatibility & Care
To install the MZ903, you will need a standard cassette lockring tool and a chain whip. Ensure your freehub body is cleaned and lightly greased before sliding the cassette onto the splines, taking note of the widest spline alignment. Tighten the lockring to the manufacturer-recommended torque, usually 40Nm. Compatibility is strictly limited to Shimano HG freehubs and 12-speed drivetrains; it will not function with SRAM XD or Shimano Micro Spline systems. For maintenance, keep the cassette clean of trail grit and debris using a stiff brush and degreaser to prolong the lifespan of the teeth and maintain shifting performance. Regularly check for chain wear, as a stretched chain will accelerate the wear of the steel cogs significantly.