It's been just over two years since SRAM released its wireless, hanger-less, and adjustment-free Transmission drivetrain. In an era of marginal gains, Transmission represented a fundamental change in shifting, ushering in new expectations for drivetrain simplicity, consistency, and performance under load. It seemed that SRAM had committed to electronic shifting and wasn't looking back. But where did that leave all the cable-actuated connoisseurs? The battery balkers? The core mountain bikers who won't let electronics soil the purity of their ride? Or all of us who can't cough up $1,000+ for a drivetrain?
Introducing Eagle 90 and 70 Transmission, the next generation of SRAM mechanical mountain bike drivetrains.
Mechanical Transmission Overview
It might come as a shocker, but the main difference between Eagle 90 and 70 and AXS Transmission, besides weight and price, is the simple fact that the derailleur is moved by a shifter cable instead of a little motor.
Eagle 90 and 70 can be thought of as the entry-point to ride and experience Transmission, with Eagle 70 being the cheaper, heavier option of the two. Impressively, SRAM has packed many of the same design elements into the groupsets as its fancier wireless options, including a Full Mount (hangerless) derailleur, a Flattop chain, and X-Sync shifting technology. This means there are no limits or b-tension adjustments on the derailleur, and riders can expect the same shift-under-load abilities and feel as AXS Transmission.
X-Sync shifting technology is what enables Transmission's wild ability to change gears smoothly while you're hammering on the pedals. It combines SRAM's narrower Flattop chain with precise cassette shift ramps that gently hand the chain between gears. It's also what causes the AXS derailleurs to pause ever so slightly between gears as it waits for the next shift ramp—a phenomenon that's been a point of contention for many riders. For those who can't stand this lag, rejoice. Mechanical Transmission is lag-free when shifting in either direction on the cassette. The chain begins moving the moment you engage a gear change at the shifter.
AXS Transmission derailleurs are pretty darn tough, and SRAM wanted to offer the same robustness with Eagle 90 and 70. Both derailleurs pass SRAM's 'can support the weight of a human' test thanks to the strength that's baked into the Full Mount design. They also use the same in-line geometry as AXS derailleurs, and feature many replaceable parts.
The Eagle 70 derailleur features a steel cage and a new drag spring damper with a higher output torque than previous generations. It has a replaceable full mount, skid plate, outer parallelogram link, and cage assembly.
The Eagle 90 derailleur features an aluminum cage and the same Type 4 damper used in AXS Transmission derailleurs. It has more replaceable parts than any other SRAM derailleur, including a replaceable full mount, inner and outer parallelogram links, skid plate, b-knuckle, and cage assembly.
The shifters have a new stealth design that routes the cable parallel to the handlebar to match SRAM's stealth brake routing. The shifters also use a new T-Type cable actuation ratio and revised paddle positioning. SRAM claims these changes stack up to offer 'a higher quality of shift than any previous mechanical system.' We'll let this claim prove its legitimacy in time. From our initial setup, the ergonomics of the shifter are natural and familiar. However, moving the downshift paddle to achieve an easier gear does take a decent amount of force.
There are single- and double-click shifter options. Single-click shifters are for e-bikes and only allow for one gear shift at a time, while double-click shifters are for human-powered riding, and can downshift two gears at a time. The only significant difference between Eagle 90 and 70 shifters is the 70 model is available with an integrated clamp or MatchMakerX, while the 90 model is only offered with MatchMaker X.
Both groupsets include new aluminum cranks. The Eagle 90 cranks share more design elements with AXS Transmission models, while the Eagle 70 cranks are fairly basic. You can only get the cranks with a DUB wide spindle and a 55mm chain line, and there are more lengths to pick from than ever before. Eagle 90 is offered in 155, 160, 165, 170, and 175mm lengths, as well as a 150mm option for e-bikes. Eagle 70 is offered in 155, 160, 165, 170, and 175mm lengths, along with a 160mm option for e-bikes. The e-bike cranks are available for SRAM/Brose, Bosch, and motors that use an international spline interface (ISIS).
The cranks come stock with steel chainrings and the same bash guards found on GX and X01 T-type cranks. Eagle 70 cranks use a 3-bolt interface, while Eagle 90 uses an 8-bolt interface like the other Transmission groupsets. This means you can swap to a lighter aluminum chainring to save a few grams with Eagle 90.
Cassettes are the only components in both groupsets that are not new. Any T-Type cassette will work, but SRAM pairs the XS-1270 cassette with Eagle 70 and the XS-1275 cassette with Eagle 90. The XS-1270 is the only T-Type cassette that fits on a spline freehub instead of an XD driver, and the XS-1275 is what comes with GX AXS Transmission. Eagle 70 does get its own new chain, while the Eagle 90 groupset comes with a GX Transmission chain.
Compatibility
Eagle 90 and 70 are not backward compatible with SRAM's previous Eagle mechanical groupsets because they use Flattop chains and have different shifter cable actuation ratios. Your frame must also be UDH compatible to accommodate the Full Mount derailleurs. So if you're currently riding a mechanical Eagle drivetrain and were hoping to get just a new derailleur or shifter, you'll have to commit to the whole groupset.
Eagle 90 and 70 are cross-compatible within the 'Eagle Transmission Ecosystem.' This includes any component marked as T-Type, including higher-end cassettes, chains, chainrings, and cranks, as well as replacement derailleur pulleys, cages and cage assemblies, mount bushings, and knurled rings. The mount bolts of Eagle 70 and 90 derailleurs are also the same as GX and S-1000 derailleurs.
Weight and Price Comparison
If price is an easy metric to compare groupsets, then Eagle 70 is a notch above SRAM's mechanical NX Eagle, and Eagle 90 is a notch above mechanical GX Eagle. If you're looking at weight, both new drivetrains are heavier than the mechanical groupsets they replace, as well as GX Eagle Transmission.
Most of the weight lies in the cranksets. The derailleurs are also heavier than the NX, GX, and X01 mechanical derailleurs, but are lighter than AXS Transmission derailleurs. With the compatibility of T-Type components opening up the ability to mix and match a groupset, we'd consider going with nicer cranks or a cassette (especially on the Eagle 70 groupset) to shave some weight.
Least to Most Expensive
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Installation & Setup Process
Setting up mechanical Transmission is nearly identical to setting up an AXS system. The main difference is the addition of a final cable tensioning step that mimics how you would tension any cable drivetrain.
Using SRAM's Full Mount Chain Length Guide, you enter the make, model and size of your bike, and the size of your chainring, and they provide the setup key position, chain length, and setup cog. From there, you follow the steps to hang the derailleur and rear wheel and install the chain. Then, with the derailleur in the setup position and gear, you pull tension by hand while spinning the cranks before tightening the derailleur onto the frame.
If you've set up Transmission before, you're probably wondering how you hold the derailleur in the setup cog without cable tension. Luckily, SRAM made a nifty cutout in the bottom of the parallelogram that fits a 4 or 5mm hex wrench (depending on your setup cog) to hold the derailleur extended just the right amount.
The final step is to tension the cable. There is a barrel adjuster on the shifter to add tension once you've pulled the cable tight. During setup, we found that you can pull the cable fairly snug, and then you will need to back the barrel adjuster out 2-4 turns to get the derailleur to move up the cassette.
Compared to a traditional mechanical system, setup is easier, faster, and requires less fine-tuning. Compared to AXS Transmission, the prepare, hang, and tighten steps are mostly the same. However, the time it takes to route housing through the frame, plus the time to dial in tension at the end, does make for a less streamlined process.
For help performing the prepare, hang, tighten, and route installation process, make sure to check out SRAM's step-by-step installation guide.
Eagle 70 Transmission
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Eagle 90 Transmission
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We have an Eagle 90 groupset currently mounted to a test bike and ready to hit the trails. Look for our impressions in the coming months, and let us know if you have any specific questions below.
View key specs of Transmission groupsets and compare them to other drivetrains in the Vital MTB Product Guide.
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Free shipping on orders over $50 (continental U.S. only).
International shipping available. Some exclusions apply. |
Free shipping on orders over $50 (continental U.S. only).
International shipping available. Some exclusions apply. $650.00
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Free shipping on orders over $50 (contiguous U.S. only).
International shipping available. Some exclusions apply. |
Free shipping on orders over $50 (contiguous U.S. only).
International shipping available. Some exclusions apply. $735.00
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Free shipping on orders over $69 (continental U.S. only).
International shipping available. Some exclusions apply. |
Free shipping on orders over $69 (continental U.S. only).
International shipping available. Some exclusions apply. $605.00
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Free shipping on orders over $49 (continental U.S. only).
International shipping available. Some exclusions apply. |
Free shipping on orders over $49 (continental U.S. only).
International shipping available. Some exclusions apply. $735.00
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SRAM Eagle 70 T-Type Derailleur
$140.00
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3/27/2025 7:00am
View replies to: SRAM Mechanical Transmission Overview: Eagle 90 and Eagle 70
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