Introducing: SRAM Eagle Mechanical Drivetrain

When I first got the full briefing on the SRAM AXS T-type electronic system, my mind quickly went to cables. It seemed obvious that the benefits of the Full Mount interface could be just as effective for a cable actuated system.

You are likely already aware that the whole UDH gambit wasn't about a universal derailleur hanger at all; it was about getting rid of the hanger and mounting the derailleur to the 12mm axle that is found at the rear of most recent higher level mountain bikes. This stout interface is a big part of why the system can shift so well under load, and take a punch; the hanger, which has always been the weakest link, was eliminated. At the time I knew it would be great to get those features without mortgaging your future to pay for it, but I wasn't sure that was ever going to happen. I feared we may have been doomed to a purely electronic future that would put those performance gains out of reach.

It would have been a bit of a waste if all of those UDH compatible frames could only take advantage of SRAM's new system using the very pricy Transmission electronic shifter and derailleur.

SRAM was mum about cables when T-Type was released, as you'd expect, but I remained impatiently hopeful. Considering how many frames are now built to the UDH standard, the arrival of a more reasonably-priced version without batteries or motors is great news for mountain bikers who don't want to spend a minimum of 1100 USD on a drivetrain.

While electronic shifting is nice, I don't have much problem with cables, or at least that's what I though until I got on SRAM's Eagle Mechanical 90 after over a year of riding T-type almost exclusively on my personal bike and various test bikes.

Trickling Down

After my bike was all set up with Eagle Mechanical 90 and I began using it, I noticed that I was feeling challenged. Why is the cable throw so long, I wondered (it's not), and why am I struggling to shift in certain situations that would be easy with T-Type?

It turns out I had become accustomed to the speed and convenience of buttons and servos. When you can slide your thumb over to make an instantaneous shift, and then immediately get back to handling your bike, you make changes that aren't feasible with cables. That split second longer actuation time is significant and it trains you to shift when previously you would have muscled it out or stalled, because there wasn't time. We humans get used to things very quickly but fortunately we can revert almost as fast. Before long I was getting along just fine with this modern-retro system.

Transmission Mechanical Highlights (according to SRAM)

• Full Mount/hangerless interface for robust interface
• Shifts very well under load
• fully rebuildable with replacement parts available
• Cranks available in lengths down to 155mm or 150mm for eMTB
• Shift lever is built with modern shift ergonomics and a premium textured aluminum lever touchpoint
• Full Mount Eagle 90 derailleur is the most rebuildable Eagle Transmission derailleur, with replaceable B-Knuckle, Inner/Outer Links, Bash Guards, Bushings, Cage, and Cage Assembly  

Setup

SRAM likes to say that setting up T-Type, or Eagle Mech, is easier than getting a conventional derailleur dialled, and that you'll be amazed. This may be overstating things some. The steps themselves aren't hard, but there are procedures to be followed that will be entirely foreign to anyone who has spent years reining in derailleurs dangling from a hanger.

Beyond that, everything must happen in the correct order to get the desired result. There are obviously a couple of differences here when compared to AXS T-Type: you've got to install and properly tension a cable, run the cable through (or along) your frame, and you can't shift the derailleur into the setup cog (one of two) by clicking the AXS button, as you do with T-Type (because there isn't one).

This process must happen before you install your cable, so how do you have your derailleur stay in the setup cog? SRAM has come up with an ingenious solution to that step. There is a hex shaped opening in the derailleur that accepts either a 5 or 6mm hex key. The 5 holds the derailleur in line with the 7th cog (21t) and the 6 aligns with the 8th (27t).* This is necessary because the cable will be attached after this process is complete, whereas with T-Type you can use the AXS button to shift the chain into the correct set up cog. The hex key trick is a slick solution to ease the process.

*Some bikes use one and some use the other and the SRAM AXS app should tell you which one is recommended for your bike. If your bike isn't included in the list, there is a procedure to follow to determine which cog you'll need.

Eagle 90 Shifter

Shifts are limited with Eagle Mechanical. If you are pedalling your own ass up the hill, you'll be able to bang out two cogs per shift. If you ride an eMTB, you'll only be able to get one cog per actuation.

At first it felt like the throw was quite long but that was while I was recovering from my stretch of T-type-only riding. Now that I've been reset, it actually feels like the downshifts (to a larger cog) don't require more throw than other conventional shifters. I haven't done any measurements yet but I'm waiting on a response from SRAM about how much cable is pulled or released per shift compared to other cable shifters.

Overall the action feels good but I didn't notice an improvement in terms of thumb effort or smoothness compared to other high performance systems, including SRAM's, and it seems to require a little more power than higher end Shimano shifters. I appreciated the textured surface but I'd like to see a high friction rubber pad for next level grip.

Spare Parts Available for Eagle 90 derailleur

• B-Knuckle replacement kit
• Skid plate and link replacement kit
• Cage and damper assembly kit
• Cage only assembly kit
• Inner Cage replacement kit
• Pulley replacement kit
• Bushing replacement kit
• Cable & housing replacement kit

Cranks Cassette and Chain

Any T-type chain, chainring or cassette will work with an Eagle 70 or 90 derailleur, so these components are most likely to be seen as original equipment on new bikes. While SRAM doesn't recommend this, it is possible to use an aftermarket chainring or even a conventional AXS ring. This may reduce the longevity of your chain, but when I first got on T-type there wasn't a chainring available for the bike my system was mounted on, and it works perfectly to this day.

The Eagle 90 Group comes with a GX T-type chain and cassette while the 70 group introduces a step below GX. Unlike regular GX AXS, I've had a good experience riding the GX running gear on T-type and haven't noticed any premature wear. The Eagle 70 stuff can't be evaluated until there is some real world data out there from unaffiliated riders, which may take some time.

The cranks come with steel chainrings and they look fine. They are available in lengths down to 155mm for pedal bikes and 150m for eMTBs.

On The Trail

There is one Eagle Mech shift that outpaces the T-type derailleurs I've ridden, or any other system. I didn't pay it much attention until another early tester mentioned it, but upshifts, into a smaller cog/larger gear, are even smoother with the Eagle 90 system. Sometimes it doesn't even make a sound and it feels like the cog has simply magically shed some teeth. This is generally a pretty easy shift but most systems produce a clunk that is usually absent with Eagle 90.

Like T-type, this system shifts better under load than it does in the workstand or when soft pedalling. I've made some deliberately bad shifts and the 90 keeps on truckin'. It doesn't feel slower than T-type, which sometimes seems to hesitate, waiting for the right shift ramp to appear but I can't yet say if it's faster either. Speed seems a little situation-dependent so more ride time is needed.

It doesn't appear that the Eagle 90 derailleur is much smaller than T-type, but I don't seem as prone to bonking it against hard objects. That's not science, and it's early, but it seems worth noting. The shape is a little different so perhaps there is something to it. It's also possible that I'm finally getting used to giving my derailleurs a wider berth around hazards.

It's difficult to compare the way Eagle 90 shifts to, let's say Shimano XTR 9100, because that system can downshift four cogs at once, but it seems to me XTR feels a little smoother, despite not quite matching the shifting down under load performance, or the upshifting performance in any circumstances.

Final Thoughts

The only major criticisms I have had about SRAM's Transmission system are price and the fact that it's larger form-factor makes it easier to smack. Other people find the system a little slow in some circumstances but this hasn't been a detriment to my riding.

SRAM has addressed that Gucci-level pricing by bringing Eagle Mechanical down to earth (see below) and the fully rebuildable architecture helps offset the time it might take to get used to determining how much space your derailleur needs to survive over the long term.

The system shifts crisply and smoothly while easily outpacing any other cable actuated system under load. You can shift without thinking using Eagle Mech, but only one or two shifts at a time.

While Electronic T-type systems are very slick and easy to use, and I'd happily never string a cable through a frame again, I could be content using Eagle 90 for the rest of my riding life, and never have to worry about charging batteries for my derailleur and shifter again.

These systems should be available at retailers and online shortly, if they aren't already.

Prices

• Eagle 90 rear derailleur (395g) 190 USD/205 EUR/185 GBP
• Eagle 90 shifter (135g) 50 USD/55 EUR/50 GBP
• Eagle 70 rear derailleur (415g) 125 USD/ 135 EUR/120 GBP
• Eagle 70 rear shifter (145g) 30 USD/ 35.00 EUR/30 GBP
• Eagle 90 Groupset: 670 USD/730 EUR/655 GBP
• Eagle 90 eMTB Groupset: 660 USD/720 EUR/645 GBP

SRAM.com