Since its introduction, SRAM’s electronic Transmission has set the standard for modern drivetrains with its smooth performance and impressive ability to shift under load. Transmission is widely regarded as the current pinnacle for mountain bike drivetrains, but its wireless design, steep price tag, and reliance on batteries have limited its adoption amongst everyday riders. Aware of these limitations and the fact that not every rider may want to trade mechanical reliance for a slightly less-cluttered cockpit, SRAM has finally released a mechanical version of Transmission: SRAM 90. This new drivetrain builds off the existing T-Type groupset, utilizing the same cassette and chain as GX Transmission while featuring an all-new crankset, shifter, and mechanically actuated T-Type derailleur.  

SRAM has introduced SRAM 90, a mechanical version of its renowned Transmission drivetrain, offering the same cassette and chain as the electronic GX model but with a new crankset, shifter, and mechanically actuated derailleur.

I've spent the last few months aboard the SRAM 90 groupset, subjecting it to everything from early spring conditions to rim deep Pacific Northwest mud. Having extensively ridden electronic Transmission and traditional Eagle GX/X01 drivetrains, I've developed an understanding of where SRAM 90 slots into the SRAM lineup and how it performs compared to these other SRAM drivetrains. 

Eagle 90 Tech Specs

Cog Material: Aluminum/Steel

Speeds: 12

Driver: XD

Range: 10-52T (10-12-14-16-18-21-24-28-32-38-44-52)

Derailleur

The new Eagle 90 derailleur shares the same UDH full-mount interface as previous electronic Transmission derailleurs, meaning it is only compatible with UDH frames. This derailleur is SRAM's most durable and serviceable mechanical derailleur to-date. In the event of an unlucky rock strike, riders can rebuild their SRAM 90 derailleur with replaceable skid plates, parallelogram links, and cage assembly.

The profile and construction of the SRAM 90 derailleur are similar to those of their electronic counterparts. The most obvious difference is the omission of an AXS battery in favor of a derailleur cable pulley.  

The SRAM 90 derailleur maintains a similar Transmission profile but with good ol' fashion cable and housing.

Crankset

The Eagle 90 crankset consists of utilitarian black forged aluminum crank arms paired with an eye-catching silver stamped steel T-type chainring. It utilizes SRAM’s 8-bolt T-type chainring, making it compatible with X0 and XX T-type cranks and chainrings. 

SRAM 90 cranks are available in 175mm, 170mm, 165mm, 160mm, and 155mm lengths. Sizes 175mm—165mm are available options when purchasing an entire groupset, while 160mm and 155mm are available as individual components. The silver stamped steel T-Type chainring is both visually striking and extremely durable. It features the same optional composite direct-mount bash guards used on X0 T-Type chainrings. 

SRAM 90 is T-Type compatible, allowing riders to mix and match mechanical Transmission with X0 or XX Transmission cranks.

Shifter

SRAM’s mechanical Transmission shifter features a whole new profile compared to previous Eagle shifters, with updated ergonomics and a slightly textured shift lever. The shifter utilizes a new T-Type specific pull ratio and provides a fluid actuation and associated crisp "click" with each shift. Sram 90 shifters are available in standard and E-MTB specific versions. The Standard version utilizes a double-click downshift actuation, whereas the E-MTB shifter is limited to a single click action. 

The SRAM 90 shifter provides a satisfying lever actuation but lacks the adjustability of the Eagle X01 shifter.

Cassette/Chain

SRAM 90 utilizes the same XS-1275 cassette and GX T-Type chain as GX Transmission. The updated ramping of the GX Eagle Transmission cassette paired with the profile of a T-Type chain is what is responsible for Transmisison's exceptional shifting performance under load, both inboard and outboard. Its full X-SYNC design ensures that the harder you pedal, the better it shifts, offering smooth and reliable gear transitions even when putting pressure on the pedals.

This cassette boasts a 520% range, enhanced with larger 38 and 44-tooth cogs before the 52-tooth cog. This optimization results in more precise gear steps in the low end, offering better gear ratios for improved climbing and acceleration. It’s an upgrade over the traditional Eagle drivetrain’s 10-52-tooth cassette, ensuring a smoother climb through the gears.

SRAM 90 combines the XS-1275 cassette and GX T-Type chain for smooth, precise shifting, and a 520% range.

The GX Eagle Transmission cassette is designed with a 55mm chainline, ensuring less extreme chain angles across the full range for less wear and increased precision. It features a Pindome design for gears 1-8 and a single-piece mini-cluster for gears 9-12, making installation simple with the clearly marked Setup Cog. Additionally, the cassette is nickel-plated, enhancing durability and giving it a silver finish. 

The GX Eagle Transmission Flattop chain utilizes a unique flat top profile and provides the smooth shifting feel and ability to shift under load that Transmission is known for. It is fully approved for E-MTB use, with solid pins that offer reliability and strength suitable for demanding riders and the added torque of e-bike motors.

Riding Impressions

Over the past few weeks, I have been cramming as much riding in as possible with a SRAM 90 groupset setup on my Stumpjumper EVO. Weather has fluctuated wildly in the early months of the year, allowing me to subject this group set to a range of conditions. Through that time, this groupset was subjected to a healthy amount of being put away in the garage wet and covered in mud, just to do it all over again the next day. 

The SRAM 90 shifter actuates smoothly, providing a satisfying mechanical "click" accompanying each change. While the updated ergonomics of the new shifter are subtle improvements, I personally still favor the Eagle X01 shifter for its robust feel and ability to adjust the angle of the shift lever. While the SRAM 90 shifter levers have fixed positions, I was still able to tailor them to my preferred position via the two MMX mounting points.

Throughout the testing period, SRAM 90 delivered smooth shifting and reliable performance, proving to be a more accessible alternative to AXS Transmission drivetrains.

Similar to AXS Transmission, the willingness of SRAM 90 to shift gears no matter the riding scenario is impressive. The overall shifting quality and smooth nature of SRAM 90 outperforms the Eagle GX and X01 drivetrains I've previously used. Unlike traditional Eagle drivetrains, SRAM 90 doesn't get bound up under load or when frantically dumping gears to get up a steep section of trail. While those issues can be avoided aboard Eagle drivetrains with some rider finesse and more selective shifting, the ability to just rattle through the gears wherever and whenever you please is a notable performance benefit. 

The SRAM 90 groupset even outperforms X0 and XX Transmission with the speed at which it shifts. While AXS Transmission still stands at the top of the Transmission lineup, I've experienced it has a limited response time to how fast it can respond to rider inputs. With SRAM 90, I found I could repeatedly shift up and down the cassette as fast as my hand could provide the inputs without the ever-so-slight delay I experienced with the AXS POD.

The shift quality of T-type Transmission drivetrains outperforms any alternative I've ridden. I've previously stayed away from committing to AXS Transmission due to its higher price tag and reliance on batteries, but with the introduction of SRAM 90, I don't have much of an excuse. SRAM 90 allows riders to experience the refined quality of SRAM Transmission without any of the previous barriers to entry. 

Durability

Over the few weeks I’ve had aboard SRAM 90, its performance has been flawless, with only a few turns of the barrel adjuster to accommodate for some cable stretch. While I haven’t smacked the derailleur on anything notable, its increased serviceability provides peace of mind compared to the traditional Eagle derailleur, which would have to be fully replaced. The GX T-Type cassette and chain have already proven extremely durable when paired with GX Transmission, outperforming traditional GX Eagle components. I anticipate the same increased long-term durability when paired with SRAM 90. 

Verdict

Over the past few weeks, I've extensively tested the SRAM 90 groupset on my Stumpjumper EVO, experiencing its performance in a variety of weather conditions and riding scenarios. The smooth, responsive shifting of T-Type stands out, with SRAM 90 delivering faster and more reliable performance than previous Eagle drivetrains. While the updated ergonomics of the shifter are an improvement, some riders may still prefer the Eagle X01 for its customizable lever or the more refined AXS Pod shifter. Overall, SRAM 90 offers a high-quality, accessible alternative to more expensive AXS Transmission drivetrains, making it an impressive option for riders seeking the benefits of Transmission in a traditional mechanical package.