SRAM Eagle 90 Transmission Review: Trickle-down Mechanical

Photos and input by Logan Watts

Late last year we posted a survey asking readers, “Are you for or against wireless/electronic shifting?” 2,000 people answered, with 57% of respondents saying they were against, for a variety of reasons. The most likely culprit is reliability—people simply don’t trust wireless connections when out in the backcountry or don’t want to rely on a battery that could potentially lose its charge or be affected by environmental factors. That survey result makes a lot of sense—bikepackers and backcountry riders tend to prioritize reliability above all else. When you’re miles from the nearest town, the last thing you want is a drivetrain failure due to a dead battery or a lost connection. Mechanical shifting has been around forever and is easy to troubleshoot, while electronic systems introduce another layer of complexity. Even with SRAM’s robust wireless tech, there’s always that lingering concern about battery life, connectivity issues, or what happens if something goes wrong in a remote setting. For riders who want absolute dependability, a cable-actuated system still holds strong appeal.

SRAM’s T-Type AXS drivetrains and the new T-Type SRAM Eagle Mechanical Transmission represent two very different approaches to shifting, each with its own strengths and trade-offs. AXS brings the convenience of wireless operation, clean cable-free setups, and precise electronic shifting, while Eagle Mechanical Transmission sticks to a traditional cable-actuated design with the added benefits of a direct-mount derailleur and a theoretically more durable, lifespan-extending rebuildable system. For bikepackers and long-haul riders, the choice often comes down to reliability, serviceability, and personal preference—do you trust batteries and wireless tech in the backcountry, or do you prefer the simplicity and field-fixability of mechanical shifting?

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It has happened to all of us…

You pull off the trail, lean your fully loaded bike against a tree, and dig into your frame bag for a much-needed snack. The air is still, the only sounds are the rustling leaves and the crunch of whatever gas station snack you are stuffing into your mouth. But just as you take a sip of water, you hear that dreaded thud—your bike tipping over in slow motion, the weight of your gear pulling it down like a felled tree. Rushing over, you lift it up, only to see the derailleur twisted at an awkward angle, bent against the rocks. A deep sigh. Time to break out the multi-tool and hope it’s not a trip-ending mechanical.

When I first started wrenching on bikes professionally some 15 years ago, it seemed like 90% of shifting issues were caused by a bent derailleur hanger. Back then, bike companies were making hangers out of what felt like Swiss cheese to “save” frames and derailleurs from breaking on impact. Most of the time, a minor bend would lead to poor shifting until a rider could get to a shop for a fix. But on bigger impacts, I’ve seen hangers bend enough to push the derailleur into the spokes, causing catastrophic damage—not just to the derailleur, but also to the spokes, and in rare cases, even breaking the frame where the hanger mounted.

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Around the time 142×12 thru-axles became popular, hangers started to get a bit more robust, largely because most thru-axles threaded into the hanger to secure the rear hub to the frame. This design shift transferred crash forces directly to the derailleur itself. A seemingly harmless tip-over could cause a slight bend, throwing off shifting performance or, in some cases, making the derailleur completely unusable—leaving riders with an expensive, sometimes barely scratched, paperweight.

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Two years ago SRAM introduced the AXS Wireless Transmission with a direct-mount T-Type derailleur that eliminates one of the weakest connection points of traditional drivetrains—the fragile hanger—by bolting directly to the frame. This design isn’t just about market dominance, although that seems to be a byproduct; it provides real benefits, making the system significantly more impact-resistant and better aligned from the start. The robust design of the derailleur adds to its durability, making it more resilient to crashes and fully loaded bikepacking tip-overs.

Better yet, unlike many modern products designed to be disposable, SRAM took a different approach with T-Type, making it fully rebuildable with replaceable parts, ensuring longevity in an era of throwaway consumer goods. Setup is also surprisingly straightforward, with no finicky B-tension or limit screws—just bolt it on, set the chain length, and go. Once dialed, the system holds its tune exceptionally well, even through rough terrain, reducing the need for constant adjustments in the field. It’s a drivetrain built for riders who want reliability and long-term serviceability, whether grinding out miles deep in the backcountry or pushing limits on rugged trails.

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There were downsides. The new AXS Transmission required a UDH-compatible frame, meaning riders couldn’t just upgrade their existing setup without swapping frames. On top of that, the initial launch was limited to high-end XX and XO builds, putting it out of reach for many due to its expensive price tag. Next came the release of GX AXS T-Type bringing all the benefits of hangerless durability, precise shifting under load, and rebuildable components to a wider audience but this left many folks wondering “Where is the Mechanical version?” “What if I don’t want to rely on robots shifting my bike?” “What if the battery dies in the middle of nowhere?” “I just do not want to have to remember to charge another thing in my life!”

Today SRAM answered with the Eagle 90 Mechanical Transmission, the world’s first mechanical groupset to use a Full Mount interface (UDH) instead of a derailleur hanger. In this review, we’ll round up the components, then talk about installation, serviceability, and how it performed over a 200-mile testing period.

Weights and Pricing

Before we dig into the details about each component and how they performed, let’s take a look at pricing and weights, as I imagine that’s what a lot of people will want to see off the bat. The two tables below show the Eagle 90 groupset alongside every other 12-speed SRAM group we tested, plus the new Eagle 70 drivetrain, which in our eyes equates to the current Eagle SX line. The key for the others is as follows: GX=Eagle GX (mechanical); X01=Eagle X01 (mechanical); GX AXS=GX AXS (wireless); GX T2=GX Transmission (wireless); X0 T2=X0 Transmission (wireless).

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Based on the weights and prices, it’s pretty clear that the Eagle 90 Mechanical Transmission is slated to be in the same tier as Eagle GX. It basically costs about $45 more and weighs about the same, save the very heavy crankset.

Eagle 90 Transmission Derailleur (RD-90-A1)

The new Eagle 90 Transmission derailleur was built with the same Full Mount design as its electronic counterparts, and SRAM claims it’s the strongest mechanical derailleur the brand has ever produced. However, unlike the wireless Transmission derailleurs, it doesn’t have a built-in “Overload Clutch”—the internal mechanism that allows it to move inboard when it experiences an impact; then seamlessly reset into place. It seems to be built like a tank, though, and it’s designed for the longterm, featuring a spare parts list complete with replaceable inner and outer parallelogram links, skid plates, and a tool-free threaded cage assembly, making it completely rebuildable, which is very refreshing to hear.

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The bad news is that the Eagle 90 Derailleur introduces an entirely new T-Type cable actuation ratio, which was unfortunate to hear since that implies that it won’t work with old 12-speed Eagle shifters. However, that seems like business as usual when a completely new mechanical drivetrain hits the streets.

Eagle XS-1275 Cassette (CS-XS-1275)

The Eagle 90 Transmission uses the same 10-52 tooth cassette used in the GX Eagle Transmission, so there’s not much new to see here other than a slight update to the color. It retains its 520% range with Eagle Transmission cassette mapping, designed to enable smoother shifting under load and improved shift timing. It utilizes SRAM’s “Pindome” design for cogs 1-8 and a Mini Cluster for gears 9-12. It weighed 442 grams on our scale—which is approximately 61 grams heavier than the XO Transmission cassette and 97 grams more than the ultra-light XX SL cassette.

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The XS-1275 Cassette is designed for a 55mm chainline and is optimized with larger 38 and 44-teeth cogs prior to the 52-tooth cog (10,12,14,16,18,21,24,28,32,38,44,52) for improved gear steps in the low end (compared to the Eagle drivetrain 10-52-tooth cassette). It also has a clearly marked Setup Cog for the install procedure (more on that later).

Eagle 90 Transmission Shifter (SL-90-A1)

The Eagle 90 Shifter has a revised lever position, a new T-Type cable actuation ratio, and a double-click downshift optimized to shift under load on non-e-bikes (there’s a single-click e-bike version available, too). One thing that really stood out to me was the ergonomics of the shift paddles, particularly the concave profile of the upshift paddle, which fits my thumb perfectly. SRAM nailed the design here, making shifting feel intuitive and comfortable.

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Performance-wise, it’s on par with past GX Eagle shifters—solid and reliable—though not quite as refined as the X01-level shifting feel. That said, at $50 USD, I don’t expect top-tier precision, just nitpicking a bit. SRAM also limited the system to shifting only two gears at a time, which feels like a smart move, likely helping maintain smooth transitions between gears under load. It’s a small but thoughtful detail that adds to the overall performance of the system.

Eagle 90 Transmission Crankset (FC-90-A1)

The new Eagle 90 crankset is on the chunky side, clearly made to be a sturdy solution for the heavy duty use. However, that’s not necessarily a bad thing as it probably translates to a long-lasting component. It also includes a silver stamped steel T-Type chainring, which is a plus.

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Other details include 8-bolt chainring compatibility and two optional chainring size-specific bashguards. The Eagle 90 crankset has a DUB Wide spindle for a 55mm chainline and comes in 175mm, 170mm, 165mm, 160mm, and 155mm crank arm lengths.

Installation

SRAM claims Eagle 90 offers an “Unbelievably simple setup procedure that will blow your mind the first time you do it.” Their tag line of “Prepare. Hang. Tighten.” mostly rings true, but if you’re coming from history of wrenching on traditional derailleurs, setup will take some time to get the hang of—you kind of have to let go of the past, so to speak. That being said, after installing one the process will go a lot smoother with the second or third. The Prepare part involves heading to this page on the SRAM website to look up your bikes brand, model, frame size as well which size chainring you are running. In my case this was the Esker Hayduke LVS, which is in the system. You can also use the SRAM AXS app on your phone to do this. Once all of those data fields are entered, the app generates your T-Type chain length (the number of links in the chain needed for your specific application), Set up Key position A or B (a small flippable key located on the cage lock mechanism), supported chainring sizes for the chain length, and the Setup Cog Position (which cog on the cassette is used to set the derailleur).

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After these key setup points are determined, you can move on to the installation process. SRAM offers a great selection of installation/service videos on their website to help aid the home mechanic in installation of this kit. There are a couple little nuances that they explain in the videos that will help the folks come as close to perfect performance as possible.

Overall the installation process was pretty easy. I think the average home mechanic will have no problem installing and maintaining this new system. That being said, there are a few caveats. Factors such as switching chainring size or moving adjustable dropouts can affect the shifting performance. I usually run my dropouts all the way back on my Esker Hayduke LVS. However, SRAM’s database has the LVS chainstays listed at 600mm, measured with the dropouts all the way forward, which is the number they use to calculate chain length. The chainstay length in the rear position measures out to 620mm. That 20mm difference does have an effect on the shift performance. The shifting is not terrible, but it’s worth noting if you have adjustable dropouts. One additional note is that SRAM warns that all T-type drivetrains are very sensitive to proper torque spec values. A properly calibrated torque wrench should be used installing both the cassette and derailleur.

Serviceability

The right to repair has been a hot topic lately not just in the cycling world but in other facets of our daily lives. Cell phones, computers, cars and even farm equipment have seen a lot of pushback from the public about the ability of consumers or independent shops to access specialty tools, parts or service guides to repair their products. SRAM’s T-Type transmission derailleurs strike a balance between cutting-edge tech and real-world serviceability, making them a solid choice for riders who value both performance and longevity. Unlike older systems that often force a full derailleur replacement after a hard hit, the T-Type design allows for key components—like the outer parallelogram link, skid plates, and derailleur cages—to be swapped out without tossing the whole unit.

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SRAM also provides service manuals and replacement parts, ensuring that independent mechanics and home wrenches alike can keep their drivetrains running smoothly. The ability to replace high-wear parts such as the pins and bushings in the derailleur, instead of scrapping the whole thing makes a strong case for repairability in modern drivetrains. Here’s a list of the replacement parts and kits SRAM is offering:

• B-Knuckle replacement kit P-Knuckle replacement kit
• Skid plate, outer and inner link replacement kit
• Cage and damper assembly kit
• Cage without damper replacement kit
• Inner Cage replacement kit Pulley replacement kit Bushing replacement kit
• Cable & housing replacement kit

On the Trail

Since installing it on my Hayduke LVS, I’ve put around 200 miles on the Eagle 90 Transmission, about half of which was fully loaded bikepacking. While that’s not nearly enough use to provide a proper review on its longevity and durability, it’s been plenty to get a feel for how it performs and what it’s made of. My first impressions have all been positive. It shifts beautifully. In fact, just after we installed it, Logan took it for a spin around the neighborhood and said something to the effect of, “the derailleur is so quiet when downshifting that it’s hard to even know that it shifted.”

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My first ride with the new Eagle 90 system took me up the Bracken Mountain trail, just on the outskirts of downtown Brevard. Right out of the gate, the first half-mile consists of a steep series of switchbacks, littered with roots, ruts, and the occasional rock. This climb always sends my heart rate through the roof, making gear selection crucial for each section. In the past, I’ve had plenty of moments where I tried to shift last-minute—while also breathing out of my eyes—only to be met with some awful noises from the rear mech. I have been lucky to not suffer from the dreaded sheared chain/knee to the handlebar combo. For me, Transmission has helped alleviate the worry, however. I am still breathing through my eyes, but the ability to shift under full power while negotiating steep, technical sections is a game-changer, letting me focus on my line and where I need to put down power to clear obstacles.

On the descents, the Transmission’s clutch kept things impressively silent—well, as quiet as it could with the extra-long chain my Hayduke LVS requires, making it more prone to chain slap when in higher gears. I did bottom out on the bash guard a couple of times on rocks I tried to roll over, but it shrugged it off like no big deal. Some riders looking to shave weight from the bottom line might be tempted to remove the guard, but I appreciate the added protection it provides for the chainring. There’s nothing worse than bending a chainring in the middle of nowhere.

• Model/Size Tested: SRAM Eagle 90 Mechanical Transmission
• Actual Weight: 2,064 grams
• Place of Manufacture: Taiwan
• Price: $695
• Manufacturer’s Details: SRAM

Further Reading

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