SRAM broke its fast-paced march to wholly electronic shifting in its high-end product catalog earlier this spring with Eagle 90 Transmission, a rebuildable and fully cable-actuated drivetrain “ecosystem.” John’s been relentlessly testing it all year, both on a Kona Hei Hei and his Meriwether Storm Camo hardtail, and has some thoughts. As an increasingly woeful tech luddite, this might be the most honest (and rambly) review of the drivetrain you’ll read on the internet…

Being born in 1981, I grew up watching sci-fi films that imagined a utopian future with far-off technologies made to improve daily life. When Back to the Future Part II came out in theaters, eight-year-old me went to see it in our local movie theater. Through all the flying cars, hoverboards, Mr. Fusion, smart home tech, and quick-drying jackets, the one thing that I wanted – or felt like was believable – were Power Laces. In my eight-year-old world, nothing felt more futuristic than not having to tie your shoes.

As an adult, now 44, and having been in the bike industry since 2006, I’ve seen my share of technological flops and fads. While we haven’t gotten Power Laces, we do, at long last, have a piece of technology that we cyclists have wanted for almost just as long: a rebuildable derailleur. It may not be as dazzling as magic shoes, but nowadays I’d rather have a pair of durable, reliable 8-hole boots with waxed laces. SRAM Eagle 90 Transmission has arrived, and I can’t decide whether it’s Power Laces or leather boots.

Allow Me a Brief Soap Box

SRAM’s Transmission drivetrain utilizes a direct-mount derailleur system SRAM calls “Full Mount.” This system is very secure and well-designed, but not all frames are Full Mount compatible.

There are some things I don’t like about UDH and Full Mount, but there are plenty of things I do like about them. But I occupy a weird space in bike media. I don’t own any carbon fiber bikes. Nor do I have a single carbon fork in my menagerie of quirky bicycle phenotypes. All of my bikes are cable-actuated, and at the time of writing this, only one is UDH/Full Mount compatible.

Truthfully, I quite like the electronic shifting precision afforded by AXS on drop bar road and gravel bikes. I shift more on a gravel bike than I do on a MTB. I ride faster, push myself more. There are more moments when I’ll shift out of the saddle, too. I like the clean aesthetics of AXS on a drop bar bike, especially the smaller cassettes and derailleurs. Still, on a MTB, I never felt that an electronic derailleur added anything to my particular experience.

This isn’t me pronouncing that I’m anything but an electronic shifting Luddite. Once SRAM went all-in on electronic drivetrains for its higher-end Eagle line, I began stockpiling non-AXS mechs and cassettes from eBay and outlets like our used gear marketplace, the Rad Bazaar, fearing the brand had given up the ghost on cable-actuated drivetrains.

Late last year, I had a cryptic conversation with a SRAM product manager who’d hinted at a new drivetrain coming down the pipe for people like me. Months later, Eagle 90 Transmission was announced. While the Ecosystem, as SRAM calls it, still relies on a Full Mount derailleur, I was hopeful for the return of cable shifting from the Apple of bicycle componentry design.

But I didn’t have a Full Mount-compatible bike. Derp.

Bike Industry Conspiracy Theories

Here’s where I’ll put on my tinfoil hat. You can do so as well if you’d like. Let’s look like total kooks together. I truly believe SRAM’s UDH and, later, the Full Mount derailleurs came about because of electronic mountain bikes. All that extra torque afforded by electronic motors is why a stock Tesla will win at most drag races and also why standard derailleurs were constantly being ripped off of e-MTBs. Prior to the introduction of UDH, if you hung out at any shop for long enough, you’d be astonished at the sheer number of derailleur hanger replacements on e-MTBs.

Some of this comes from new riders getting into mountain biking during the COVID pandemic and starting with an e-MTB, not knowing how to shift properly. In short: don’t shift under load. That’s especially valuable advice when the average e-MTB motor puts out upwards of 100 Nm of torque.

Let’s backtrack a bit. You can take off your tinfoil hat.

In 2019, SRAM touted that the UDH was designed to save bike frames from derailleur impacts. It claimed that the UDH system was designed to rotate backward upon impact, saving the frame and hopefully the derailleur in the process. I think everyone in bike media knew what was coming down the pipeline.

UDH, Full Mount, and Transmission T-Type

When Transmission was announced, it came with photos of people standing on the derailleur, showcasing the robustness of these Full Mount mechs thanks to UDH-compatible frames. The list of manufacturers grew and grew, rolling out UDH-equipped bikes. Small makers scrambled, trying to keep up with yet another new standard. Paragon Machine Works developed backward-compatible dropouts for its sliding and rocker dropout designs. Meanwhile, heaps of bike frames were deemed incompatible with these new UDH drivetrains.

That’s where this Luddite comes in. Until 2025, I didn’t own a UDH-compatible bicycle, and I own a dozen bikes. The only reason I do now is that Paragon Machine Works offers a UDH insert for its rocker dropout design (which, I might add, looks very nice).

Since the inception of Eagle 90, I’d ridden and reviewed a few bikes with UDH and electronic Full Mount SRAM Transmission and had formed opinions. But when Eagle 90 Transmission was announced, I felt like SRAM had heard our – assuming there are more of us out there – cry for mechanical groupsets. This was the technology of the past’s future I was after.

And you know what? It’s really fucking good.

Eagle 90 Transmission Design

When you endure five years of architecture design school, you’re cursed with the eye. The eye determines how you see the world. Your initial impression of an object is a trained, visceral reaction, acquired by years of critical thinking and analysis. When something is off, it is just off. Even if part of it is off, the whole system will be thrown out of balance. This is called Gestalt. Like deconstructivism – which doesn’t mean what you think it means – Gestalt was an analytical theory of psychology adopted by architectural theorists to explain why some things look balanced and others don’t.

If you’ve ever pondered door knobs – why would you? – you understand Gestalt. The most aesthetically pleasing door knobs are often the ones made from simple, easy-to-interact-with shapes, in proportions that match design and functionality. They’re not easy to find. Not even the great Mies Van Der Rohe attempted to design one. Instead, he designed door handles.

SRAM’s Eagle 90 is the door handle equivalent of the bicycle component juxtaposition of a doorknob. It is the FSB 1267 lever handle of bicycle groupsets. Not because a genius like Mies designed it, but because, let’s be honest, the bar for MTB drivetrains has been set pretty damn low since the early aughts.

Rebuildable and Right to Repair

Tinkering with vintage MTB builds is a fun hobby of mine. I like repacking hubs, rebuilding old things, and making them function as new. As Travis pointed out in his first impressions of Eagle 90 Transmission, the rebuildable derailleur is something we’ve been promised since the Huret mechs of the French 5-speed era. Of which you can still buy extra NOS parts on eBay. In a heavy dose of irony, rebuildable derailleurs were indeed the Power Laces for guys like me, and I’m assuming Travis, too.

The Right to Repair is an essential step toward a more sustainable consumer society. As I type that sentence out, I can feel Slavoj Žižek’s hand slap his forehead. But for real! Nothing about consumerism is sustainable. But bicycles are, indeed, a sustainable means of transportation and recreation. I think it’s fair to ask that we be able to rebuild our components.

Eagle 90 comes apart into eight groups of replacement parts:

• B-Knuckle replacement kit (11.7518.113.000)
• Skid plate and link replacement kit (11.7518.111.000)
• Cage and damper assembly kit (11.7518.113.002)
• Cage only assembly kit (11.7518.104.024)
• Inner Cage replacement kit (11.7518.112.000)
• Pulley replacement kit (11.7518.112.001)
• Bushing replacement kit (11.7518.114.000)
• Cable & housing replacement kit (00.7118.013.000)

That means if you flog your derailleur, it develops play, you straight up smash it on a rock, or some dummy thinks it’s actually ok to stand on your derailleur, and something bends or breaks, you can order the replacement parts, rather than scrap it as a whole. These parts are all in stock and available through every major distribution network. Some shops even have them in stock, too.

Eagle 90 Transmission Ecosystem

SRAM calls its groupsets “ecosystems” as the individual parts to the whole operate best when used in unison. This includes brakes, droppers, suspension, and yes, even tire valves. While I’d argue the ecosystem is only necessary with electronic groupsets, there are some benefits to maintaining unity through SRAM parts. Even from an aesthetic point of view, 90 has a unique look and feel.

Previous SRAM groups looked “off” or out of place with my smaller-diameter steel or titanium tubed bikes. Instead, the angular designs matched those large-diameter carbon fiber downtubes. The drivetrain’s chassis continued similar lines found only in ways carbon fiber can be formed or designed.

When your cage has to reach a whopping 52T cassette, it’s going to get long and obtuse, but on a mountain bike with 29er wheels and 2.5″ tires, it looks more proportionate. The larger pulley wheels and derailleur size also provide an acute shifting experience.

The Eagle 90 shifter pod mounts to SRAM’s native brakes, or adapters are available from Wolf Tooth to mate to other brake systems. The same goes for the AXS dropper remote or cable-actuated remotes and droppers. All together, the ecosystem looks tidy, is minimal, and keeps the cockpit clutter down considerably.

Crankset Design

“Heavy is good, heavy is reliable. If it doesn’t work, you can always hit them with it.” Boris’ words from the Guy Ritchie classic Snatch will never not find themselves rambling around inside my head when it comes to all the discussion about how seemingly heavy bikes have gotten. I don’t believe that bike weight is as important or critical as many make it out to be. I do think that nice, lightweight cranks can offer some flex and dampen harsh trails. Meanwhile, stiff and heavy aluminum cranks like those native to the Eagle 90 ecosystem do leave me with some desires.

In terms of aesthetics, I think they look great, but they are stiff and heavy. Whether they are heavy because they’re stiff or stiff because they’re heavy is up for the armchair engineers to argue about in a comment thread on Pinkbike.

Yet, as Boris points out, heavy is reliable. And like bikes being heavier now, there is a correlation between less breakage and slightly more weight. The ’90s brought about über-weight-weenie CNC components that none of us got time for in a modern society.

An Aside: Reverb AXS

As I was meeting with Alex Rafferty from SRAM at Sea Otter, he said to me with his handsome face, perfect hair, and British accent, something along the lines of: “Now, we don’t make a cable dropper. Are you okay with a Reverb AXS?” He knew that I didn’t like batteries on my bikes. I laughed and exclaimed that I was stoked to try it out.

For me and others who run bikepacking-style saddle packs from time to time, the previous Reverb AXS droppers’ batteries interfered with those bags. They also made it impossible to run a saddle bag with a spare tube or what-have-you. And if you rode in muddy conditions, the batteries just got caked to high hell with mud. And ’round these parts, our mud hardens like cement, as evidenced by our multi-thousand-year-old houses still standing, constructed from this same mud.

This new generation Reverb AXS solves both of those problems and saves bike shop owners from the headache of having to charge a customer $400 to swap a cable dropper out on an e-MTB.

Brakes… Coming Soon!

Initially, I had penned thoughts about the Maven brakes in this post, but they need their own review. That’s coming next week.

A Luddite’s Long-Term Eagle 90 Critical Review

We don’t exist in a world where electronic shifting is a necessity. In my mind, batteries are best used for tools. Electronic cargo bikes are, in this train of thought, the same as my Milwaukee Fuel impact gun, or my electronic Vessel screwdriver. For me, a bicycle, both used as recreation or transportation, ought to be ready to roll with no fuss, no charging, no batteries. e-Cargo/Commuter bikes are car replacements, but e-MTBs are just replacements for regular MTBs. I mean that with sincerity.

Earlier this year, we saw my new Meriwether Storm Camo hardtail. I love my Meriwether and have an ideal build kit in my mind for the following months. Yes, that includes Eagle 90 — or at least part of it. For me, the cranks are the only thing that feels out of place on the bike, both physically in terms of heft – they weigh 827 grams with a 30t chainring – and emotionally, in terms of aesthetics, on the bike.  I wish the cranks were silver to balance this particular build. They do, however, match the visual lines of the bike with its beefy-ass oversized downtube. I also miss the 28-tooth chainring produced by aftermarket manufacturers like Wolf Tooth for the older 3-bolt design.

The Reverb AXS’s new battery location makes it compatible with bikepacking-style saddle packs and spare tire tube saddle bags, which is nice. Even with a dry bag atop its custom rack, there’s no battery interference now. This new battery location looks less obtuse when a full-length dropper is utilized, too. I’ve yet to have a single issue with it in the 6 months of heavy use and have no notes. I’ve only charged the battery once, when I first got the bike. Honestly, I see why these droppers are so popular on eMTBs and carbon bikes with internal routing, particularly with batteries/motors.

The AXS Reverb is very useful for those use cases.

User Experience

When it comes to switching back to mechanical shifting, SRAM didn’t half-ass the user experience. Eagle 90 feels as concise and crisp as the pre-AXS mechs I’ve come to love, provided you follow the installation instructions and torque it to spec, ensuring to align the tick marks on the Full Mount derailleur. You know, basic stuff!

Every cable-actuated system will require some adjustment after the cable stretches. SRAM’s Eagle 90 shifter makes it easy for on-the-fly adjustment. If your chain is having a hard time nesting on the cassette, turn the barrel adjuster a quarter turn. Done. The shift feels like typing on a typewriter, not clicking away on an iPhone like AXS feels to me. On an MTB, where shifting almost exclusively happens on climbs for me, I was impressed at its ability to do so under slight load or as you begin to charge down the descent. The actuation is crisp and solid.

Eagle 90 feels like driving a manual transmission in a 1980s Toyota –  like the 1985 SR5 Xtra Cab 4×4 pickup truck Marty McFly desired in Back to the Future.

Eagle 90 Critiques

Every design project will have its flaws, as perceived by the user, which is why reviews are so fun. They’re entirely subjective. Some things that might bother one person could go unnoticed by others. Read on for some notes I’ve made while riding Eagle 90 since March.

The revelation that the chainring bash guard is proprietary to the various chainring tooth count caused my local bike shop owner and me to exclaim, “WHYYYYYYYYYYY!??!?!”  However, knowing that the stamped steel ring and replacement bash guard still cost under $30 offered some respite to the cynicism of proprietary design and development.

While on this topic, may I ask why switch from the now prolific 3-bolt pattern to a new 8-bolt design? Again, this discourages users from buying the new crankset, and causes third-party manufacturers to have to have so many SKUs to address both crank bolt designs. For instance, Wolf Tooth now has to make both 3-bolt and 8-bolt chainrings with the same tooth profile. If you want to read more about why things like this feel icky, read this Dust-Up article.

Since the system is Full Mount proprietary, you’ve got to have a bike with a UDH dropout design. If you don’t, you’re SOL.

I’ve found the shifter pod rattles/vibrates when pedaling across the pavement, on both Eagle 90 kits I’ve ridden. I’ve tried everything to reduce this vibration, but it is an elusive one. Have you had this issue?

Clearances, Tolerances, and Compatibilities

Unlike the pre-AXS mechanical derailleurs, these new Eagle 90 mechs stick out further from the wheel when in the smallest, 10-tooth cog. As I’ve rarely, if ever, smashed a pre-AXS mech on my normal lunch loop, I’ve hit this mech numerous times.

The plastic bushing used on the UDH dropout appears to wear faster than I’d like, but I suppose it’s better to wear out a $5 part than the frame itself.

I’ve found that the 35 Nm of torque required for proper UDH installation isn’t enough for some carbon bikes. After talking to the brand managers from the bike companies, they have blamed it on their own dropout tolerances. Meanwhile, my aluminum Paragon Machine Works dropouts never developed any such play, and 35 Nm was enough to securely fasten the 90 mech to my frame.

Dub not being a 30 mm spindle drives me nuts. Nuts! Now, SRAM didn’t do a good job communicating this, but the reason Dub isn’t exactly 30 mm is that they had to make room for the little plastic spacers inside the bearings. That plastic compensates for the often unavoidable tolerance issues in frames. It’s why the original BB30 (naked press-fit bearings) was such a disaster. There was no wiggle room, and bearings wouldn’t last. It was easier for SRAM to make the spindle slightly smaller than to make the bearings slightly bigger. But having 29 mm Dub and 30 mm bottom bracket standards is somewhat frustrating from a consumer standpoint.

Overview and Final Build Iteration

I’m sold on Eagle 90 as a UDH-requisite drivetrain. While I’ll get into the Maven brakes next week, I’m wholly impressed with the entire ecosystem as presented. And if I weren’t such a Luddite, I’d even keep the Reverb AXS on this build. While the dropper never gave me an issue, I can’t help but think a silver PNW Components dropper would complement this build better. Along those lines and because I like my bling, I will be swapping out the crankset for my eeWings Ti cranks and a 3-bolt Wolf Tooth 0 mm offset 28 t chainring.

Doing this is a little murky because SRAM has two spindle lengths. There’s standard and MTB Wide. A little confusing, but much better than the square-taper days. A 0 mm-offset 3-bolt Drop Stop B Wolf Tooth ring will make any standard SRAM 3-bolt crank work with Eagle 90 or Transmission. Or, if you have an MTB-Wide SRAM crank, they make a $20 steel 3-bolt 3mm offset ring. I wish they made a steel 0 mm ring, but no luck yet, as far as I know.

While the ecology of the Eagle 90 will be violated, the heart of the system has proven to be a reliable one, and I’m sold on it. Thanks to Paragon Machine Works, if I ever want to go backwards with this bike’s compatibility, I can buy a non-UDH rocker insert and run a normal derailleur on it. In doing so, I’d also regain the ability to adjust the effective chainstay length, too.

TL;DR from a Luddite

My childhood was spent fascinated by glimpses into our technologically advanced future, courtesy of movies like Back to the Future. I dreamed of a Mr. Fusion compost mini nuclear fission reactor that could power vintage cars, and Nikes featuring Power Laces filled my youthful head. In the present day, adult John spends his time looking for the perfect waxed laces for his leather work boots – which, I might add, have been resoled three times in my 15 years of ownership.

Thinking I’d have to abandon high-end SRAM drivetrains when they switched to all electronic shifting, I was really stoked to ride Eagle 90. For us Luddites, it says SRAM is still listening to us. Which, in today’s world of relentless pursuits of futuristic technologies, feels like a pause and acknowledgement that bicycles ought to remain relatively simple machines.

By the way, in 2016, Nike released Marty McFly’s Air MAG shoes, complete with Power Laces. Sometimes when science fiction becomes fact, the allure is lost. Especially since you have to plug in the Air MAG to charge them each night…

Pros

• Crisp, precise shifting
• Shift is in-line and on-par with XO1 Eagle (pre AXS)
• Rebuildable (yay, finally)
• Stamped steel chainring is $20
• Full Mount install on aluminum dropouts is super consistent and solid

Cons

• Requires UDH-equipped frames
• Bash guard is different for every single chainring size (can’t run a 32t BG on the 30t ring, etc)
• Crankset is heavy
• The shifter vibrates while riding on pavement
• Full Mount torque spec of 35 Nm sometimes isn’t enough to remove play/chasing carbon frame tolerances

See more at SRAM.