SRAM’s Eagle range has become a little confusing. We now have Eagle S-Series, Eagle Transmission, T-Type, AXS and several generations of older Eagle parts still fitted to bikes.
The good news is that the new S-Series is fairly straightforward. If your bike has a conventional derailleur hanger and an older 12-speed SX, NX, GX, X01 or XX1 Eagle drivetrain, S-Series provides new components that can keep it running.
There are three levels: S100, S200 and S500 AXS. You can replace a worn or damaged component without buying an entire groupset, and in many cases your existing cassette, chainring and crankset can remain on the bike.
First, Work Out Which Eagle System You Have
Before ordering anything, look at how the rear derailleur attaches to the bike.
Conventional Eagle Drivetrain systems use a normal derailleur hanger. This includes SX, NX, GX, X01 and XX1 Eagle, along with the new S100, S200 and S500 components.
Eagle Transmission uses a derailleur that mounts directly around the frame’s UDH interface. Eagle 70, Eagle 90, GX Transmission, X0 Transmission, XX Transmission and XX SL Transmission are all part of this T-Type system.
Both systems carry the Eagle name, but they are not the same drivetrain. Their chains, cassettes and rear derailleurs should not be mixed unless SRAM specifically confirms compatibility.
If the derailleur mounts directly to the frame, or the bike has a flat-top T-Type chain, check exactly which system you have before ordering parts.
The Short Version
| S-Series level | Shifting | Best used for | Cassette compatibility | Our view |
|---|---|---|---|---|
| Eagle S100 | Mechanical | Replacing SX and NX Eagle | 10–50T and 11–50T | The sensible repair option |
| Eagle S200 | Mechanical | Replacing or upgrading mechanical Eagle | 10–50T, 11–50T and 10–52T | The best mechanical choice for most riders |
| Eagle S500 AXS | Wireless | Replacing older Eagle AXS or converting mechanical Eagle to AXS | 10–50T, 11–50T and 10–52T | The way to add AXS without changing to Transmission |
You do not have to match every component name. For example, an S200 derailleur can work with an older compatible Eagle shifter and cassette, provided the cassette size is supported and the remaining drivetrain components are in good condition.
Eagle S100 – A Good Fix Without Overspending
The SRAM Eagle S100 Rear Derailleur replaces the old SX and NX level. It is aimed at riders who need something strong, dependable and sensibly priced.
S100 is limited to a 50-tooth largest sprocket. That means it works with an 11–50T Eagle cassette on an HG freehub or a 10–50T Eagle cassette on an XD driver. It does not work with a 10–52T cassette.
If you have damaged an SX or NX derailleur and the rest of the drivetrain is still good, S100 is probably all you need. There is no real benefit in replacing the cassette, crankset and shifter simply so every component has the same name printed on it.
The SRAM Eagle S100 Shifter has a longer lever than older entry-level Eagle controls, giving it a lighter action. Its cable routing also sits neatly alongside modern brake hoses.
You can keep your existing Eagle shifter if it is working properly. However, if the old shifter feels heavy or inconsistent, we would fit the S100 shifter with a fresh inner cable and housing. Dirty or damaged cable housing causes plenty of shifting problems and is often overlooked when riders start replacing more expensive components.
S100 makes sense for recreational mountain bikes, everyday trail bikes and e-bikes running a 50-tooth cassette. It is also a good choice when the aim is to get a reliable bike back on the trail without turning the repair into a complete drivetrain rebuild.
Eagle S200 – The Mechanical Option We Would Usually Recommend
The SRAM Eagle S200 Rear Derailleur is the higher-level mechanical option in the new S-Series range.
It works with conventional Eagle 10–50T, 11–50T and 10–52T cassettes, so you are not restricted to one cassette size. It also uses SRAM’s Type 3 clutch to help control the chain over rough ground.
For most riders wanting a mechanical Eagle upgrade, S200 is the option we would choose. It supports the full conventional Eagle cassette range and provides proven cable shifting without adding batteries or electronic components.
The SRAM Eagle S200 Shifter has a textured paddle and a modern lever position. It feels good at the bar, but replacing your existing shifter is not compulsory. An older compatible Eagle mechanical shifter can be retained if it is in good condition.
If we were fitting S200 to an older bike, we would also inspect the derailleur hanger, cable housing, chain and cassette. A new derailleur will not shift properly if the hanger is slightly bent or the cable is dragging through contaminated housing.
That basic workshop inspection often makes more difference than jumping from one component level to another.
Eagle S500 AXS – Wireless Shifting for a Hanger-Mounted Eagle Bike
SRAM Eagle S500 AXS is the wireless option in the S-Series range. It is designed for conventional hanger-mounted Eagle drivetrains rather than Full Mount T-Type Transmission systems.
The SRAM Eagle S500 AXS Rear Derailleur can replace older X1, GX, X01 and XX1 Eagle AXS derailleurs. It can also convert a compatible mechanical Eagle drivetrain to wireless shifting.
This is particularly useful if you have a good mountain bike that cannot accept a Full Mount Eagle Transmission derailleur. You can gain wireless AXS shifting without replacing a serviceable conventional Eagle cassette, crankset or chainring.
The Easiest Way to Convert to Wireless Eagle AXS
The SRAM S500 Eagle AXS Upgrade Kit is the simplest way to complete the conversion. It packages the essential AXS components and setup equipment together.
- Eagle S500 AXS rear derailleur with protector
- AXS Pod Controller with discrete clamp
- AXS derailleur battery
- USB-C battery charger
- Eagle PowerLock
- Chain-gap setup tool
Wireless shifting delivers a consistent controller feel because there is no gear cable or housing to develop friction as it wears or becomes contaminated. You can also customise the controller functions through the SRAM AXS app.
We like AXS, but it is not automatically the correct choice for every rider. A properly installed S200 mechanical drivetrain still shifts extremely well and never needs charging. Choose S500 AXS when you genuinely want wireless shifting, cleaner cable routing and customisable controls—not simply because it sits at the top of the S-Series range.
Compatibility note: S500 AXS is for conventional Eagle Drivetrain components. It is not designed to run with an Eagle Transmission T-Type cassette or T-Type Flattop chain.
Shop the SRAM S500 Eagle AXS Upgrade Kit
Can You Keep Your Current Cassette?
In most cases, yes.
If it is a compatible conventional Eagle cassette and it is not worn out, it can normally remain on the bike. Make sure the new derailleur supports its largest sprocket.
| Existing Eagle cassette | S100 | S200 | S500 AXS |
|---|---|---|---|
| 11–50T HG | Yes | Yes | Yes |
| 10–50T XD | Yes | Yes | Yes |
| 10–52T XD | No | Yes | Yes |
| Transmission T-Type cassette | No | No | No |
The 11–50T option fits a traditional Shimano-style HG freehub body. SRAM’s PG-1210 is the newer replacement for the familiar NX PG-1230 cassette.
The lighter 10–50T and 10–52T conventional Eagle cassettes use an SRAM XD driver. If your wheel currently has an HG freehub, check whether a suitable XD driver is available for the hub before planning a cassette upgrade.
Moving from an 11-tooth smallest sprocket to a 10-tooth sprocket may sound like a simple cassette change, but the freehub standard is the detail that frequently catches riders out.
Do You Need to Replace the Chain?
Only if it is worn, damaged or no longer matches the condition of the cassette.
We would measure the chain before deciding. If a worn chain has been running on the cassette for too long, fitting a new chain on its own can result in skipping when you apply pressure to the pedals.
S100, S200 and S500 chains sit within the conventional Eagle Drivetrain family. You can choose the chain that suits your budget without having to match the name printed on the derailleur.
The SRAM Eagle S200 12-Speed Chain is the practical choice for most bikes. The SRAM Eagle S500 12-Speed Chain is available in Gold and Rainbow for riders wanting a premium finish.
Do not use a T-Type Flattop chain on an S-Series Eagle Drivetrain. It may look similar to SRAM’s other 12-speed chains, but it is designed for Eagle Transmission.
The S500 chain is a premium option for conventional 12-speed Eagle Drivetrain systems.
Is a New Crankset Worth It?
Not always.
A crankset can be a worthwhile upgrade if you want shorter crank arms, lower weight or need to replace a worn chainring. It is not normally where we would start when trying to improve shifting performance.
The SRAM Eagle S100 Crankset is the tough, cost-effective option. The SRAM Eagle S200 Crankset uses aluminium arms and is available in several lengths, including shorter 155mm and 160mm options. The SRAM Eagle S500 Crankset uses carbon arms to reduce weight.
Shorter cranks can improve pedal clearance and suit some riders better, but we would not select crank length from rider height alone. Bike geometry, leg proportions, riding style and saddle position all affect the correct choice.
Before ordering a crankset, check the bottom bracket, spindle standard, chainline, chainring size and frame clearance. If the current crank and chainring are working properly, there is nothing wrong with retaining them.
What Is the S100 UDH Half Mount?
S100 can use SRAM’s optional UDH Half Mount when fitted to a UDH-compatible frame.
The Half Mount supports the derailleur hanger and provides additional protection from knocks. It is a useful addition, but it is not the same as Eagle Transmission’s Full Mount system.
The derailleur still requires conventional limit-screw, chain-gap and cable adjustment. Installing the Half Mount does not turn an S100 drivetrain into Eagle Transmission.
The Half Mount hardware is specific to S100. It cannot simply be fitted to an S200, S500 or older Eagle derailleur.
What Should You Use on an E-Bike?
For a mechanical drivetrain, use the dedicated single-click version of the shifter.
Single-click means one push of the lever produces one shift. This reduces the chance of several gears being forced through the drivetrain while the motor is applying high torque.
It is still worth easing your pressure on the pedals slightly during a shift. You do not need to stop pedalling, but backing off momentarily is much easier on the chain, cassette and chainring.
No derailleur can completely protect a drivetrain from repeated shifts made under full motor load.
Common SRAM Eagle Upgrade Scenarios
You Have Damaged an SX or NX Derailleur
If the bike has a conventional 10–50T or 11–50T Eagle cassette, fit an S100 derailleur. Check the hanger alignment and replace the gear cable and housing if they are old. Keep the remaining drivetrain components if they are still serviceable.
You Want Better Mechanical Shifting
Go with S200. It supports the full conventional Eagle Drivetrain cassette range and leaves you the option of using a 52-tooth cassette later.
You Want to Convert Your Existing Eagle Bike to Wireless
Use the SRAM S500 Eagle AXS Upgrade Kit. You can normally retain your conventional Eagle cassette, chain, crankset and chainring if they are compatible, unworn and in good working condition.
Before fitting the kit, check the derailleur hanger alignment and measure the chain for wear. Correct chain-gap adjustment is also essential for clean shifting across the cassette.
Your Wheel Has an HG Freehub
Stay with an 11–50T Eagle cassette unless you are prepared to change the driver body. Pair it with S100 or S200 depending on your budget, cassette size and how hard the bike is ridden.
You Want to Change from Eagle Drivetrain to Eagle Transmission
Treat this as a complete drivetrain conversion. Confirm that the frame has a suitable UDH interface, then use matching T-Type components, including the derailleur, cassette, chain, chainring and controller.
Trying to retain a selection of conventional S-Series components during a Transmission conversion usually creates more compatibility problems than it solves.
Our Thoughts
SRAM has made the naming simpler, but choosing the correct upgrade still comes down to what is already fitted to the bike.
S100 is a good, honest repair option. If an SX or NX derailleur has been damaged and the bike has a 50-tooth cassette, there is no need to spend more unless you want to.
S200 is our pick for most mechanical upgrades. It supports both 50 and 52-tooth conventional Eagle cassettes, shifts well and keeps the drivetrain relatively simple.
S500 AXS is the interesting option for riders with a good hanger-mounted Eagle bike who want wireless shifting. The complete S500 Eagle AXS Upgrade Kit provides a straightforward electronic upgrade without forcing a move to Eagle Transmission.
Before buying anything, check the chain wear, cassette condition, hanger alignment and gear cable. There is little point fitting an expensive derailleur to a worn drivetrain and expecting it to shift like a new bike.
Sometimes the best upgrade is a higher-level component. Other times, it is a new cable, a correctly aligned hanger and a proper workshop setup.
Need Help Working Out What Fits?
Bring your bike into Chain Reaction Christchurch or contact us before ordering. We can identify the drivetrain, check the cassette and freehub, measure chain wear and work out which components can sensibly remain on the bike.
