SRAM’s new Eagle 90 Transmission is the long hoped for cable controlled version of wireless AXS T-Type – that means it’s for battery haters or those on a tighter budget. It’s super tough and trauma resistant, while the rock solid shifting performance is exactly what hardcore or just clumsy MTB and eMTB riders need. Add that up and it just might be the best mountain bike groupset out there. It’s not all roses though, just like the SRAM AXS Eagle Transmission we reviewed, the slower shift, higher weight and need for a UDH frame means it’s not a universal win.

SRAM Eagle 90 Transmission need to know

• Full Mount UDH rear derailleur for maximum strength and stiffness
• Mapped cassette for flawless full power shifting
• Fully rebuildable rear derailleur
• Skid plates as standard on the chainset, plus steel ring options
• Stealth shifter cable alignment
• Can be converted to AXS wireless later
• Cheaper Eagle 70 Transmission version available too
• Read our news story detailing both Eagle 70 and Eagle 90 groupsets

– Short of time? Click here to skip to the verdict –

Derailleur

The Eagle 90 Transmission derailleur uses SRAM’s frame clamping Full Mount system, which only works with UDH (Universal Derailleur Hanger) frames. That rules out a lot of older bikes straight away.

If it fits it makes for a much stronger, stiffer and simpler to set up gear system though as there’s no chance of bent or otherwise misaligned frame hangers sending the indexing sideways. Because it’s a fixed position designed to work on a fixed width cassette you don’t need – or have – adjustment screws to stop the chain falling off the ends of the block.

As well as being tough enough to stand on, and designed to swing back out of harm’s way in a crash / rock strike, Eagle 90 is the most rebuildable rear mech SRAM has ever made. B-Knuckle, skid plate link, cage plates, damper, pulleys and bushings are all available as spares if they get smashed, bent or worn. A lot of the parts are also interchangeable with AXS T-Type so you can even convert from cables to wireless by adding the appropriate parts.

The chunky, rebuildable construction makes it 92g heavier and £63 more than conventional SRAM GX though and 110g heavier and £75 more than Shimano XT M8100 drivetrain. It’s 104g lighter and £300 cheaper than GX AXS T-Type wireless though. Plus if the weight really bothers you, it’s possible to swap the metal jockey wheel cage for the carbon one off the XX SL mech. This also gets you the clever stick-proof lower jockey wheel you otherwise miss out on too.

Shifter

The shifter pod gets the same bulky and boxy makeover as the rear mech. This gives SRAM the space to realign the cable exit so it matches its Stealth brakes, staying close to the bars. You even get a cable clip included to keep them tidy together.

T-Type also uses a new cable actuation ratio and “best in class friction management” – whatever that means – for a positive but not thumb-punishing feel.

There’s also a double click downshift version for pedal bikes or single downshift that’s designed for powered bikes. Either one syncs neatly with existing Matchmaker brake clamps or a standalone band.

That new cable ratio means it won’t work with older rear mechs and vice versa though. Oh and there’s a dropper lever with a ‘it works with most designs’ 14mm cable pull too if you want to be matchy matchy.

Chainset

The Eagle 90 chainset isn’t an essential part of the new Transmission kit as you can use any 12 speed compatible unit. SRAM includes it in the complete presentation box and bundle pricing though so here’s the details.

The smoothly forged crank arms get SRAM’s current signature coffin-alike inset styling, but without the full cutaway hole of X0 or the polished angles of GX AXS. Unsurprisingly it uses SRAM’s proprietary, not quite 30mm, DUB standard axle and bottom bracket too.

The arms take eight bolt or three bolt direct mount chainrings and can be bought with a bright, steel 32T chainring (which I tested) or stamped alloy ring in 30, 32 or 34 teeth. Both options come as standard with two bashguard segments (41g each), which self clamp onto the chainring to protect it from rock or log grinds.

The chainline is 55mm and the pedal bike cranks come in 175, 170, 165, 160 and 155mm cranks, while the eMTB version gets a 155mm option too. At 657g without the bash plates, weight is competitive with GX (635g), GX T-Type (661g), and XT (645g) despite the fully steel chainring.

Pricing is a definite win compared to GX T-Type (£215) and XT (£230) too.

Cassette and chain

The XS-1275 SRAM 90 relies on is the same as the T-Type AXS cassette – SRAM even calls it the GX Eagle Transmission T-Type Cassette, so bear that in mind when you’re shopping.

While you can’t obviously see it, SRAM’s dedicated cog design team (yes really) has used cassette mapping to make 44 dedicated shift zones. The teeth also use a version of the chain retaining X-Sync profiling from SRAM’s chainrings in these segments too. This minimises chain lift and maximises consistent contact.

That means you sometimes have to wait longer for a shift, but the movement is way smoother and less stressful on the chain when it happens. It doesn’t just shift well under heavy power loads either, it actually uses the tooth profiling to shift better under more strain. While it’s still a 10-52 tooth range, the biggest three sprockets (38, 44 and 52T) also make it less of a lurch than older cassettes when you’re really clawing for a climb.

The nickel plating on gears 1-8 doesn’t just look shiny, it also improves durability and reduces noise. The larger four cogs are a separate block and the SetUp cog is marked with a red ring to make targeting your initial alignment easy.

The flat top chain is also shared with GX Eagle Transmission T-Type and again doesn’t only look really neat, it also improves strength and durability as there’s no unnecessary sculpting of the non contact face of each link. The pins are solid for full maximum strength eMTB work or just hench hamstring compatibility too.

Setting up Eagle 90

Presuming you’ve got a UDH frame, Eagle 90 is the easiest cable operated gearset I’ve ever fitted. Whip the UDH insert out then go through SRAM’s ‘Hang and Tighten’ process (watch the SRAM instruction video rather than trusting me) to get it on in the right position. No B tension screw or top or bottom limiters to worry about, just get the chain length right off the SRAM app.

OK there is one thing, that little roller on the back that you have to thread the cable through is still a tense situation, especially when reusing a cable that might fray. But with a little pre-bend and some wheel waggling I got there in the end.

Apart from that though it’s way ahead of the faff of installing most cable systems. There’s no outward angle on the cable exit either like Shimano, so while there’ll still be a loop dangling out there it’s less likely to catch on trailside sticks or other bikes on uplift trailers etc.

Performance

Given that the actual derailleur dimensions, shift movement, mapped cassette and chain are the same as AXS T-Type the shifts are exactly the same, just without the little electric whirr. On the plus side that means however hard I’m going I can always get a clean, solid shift rather than straining your thumb or audibly crucifying the chain to get it across the cogs.

Interestingly it did take me a while to fully adapt and accept that Eagle 90 could grab a gear fine even under full power and fully embrace the advantage. That was just a case or de-learning years of nursing chains across cassettes: instinctively balancing feel through the lever and tension in the chain through my feet to get a clean shift on previous cable systems though.

The shift feel itself is clean, clear and slightly lighter in feel than previous GX. That makes it less clunky than Shimano XT and a lot easier on the thumbs than TRP 12 speed rear mech and shifter.  There’s enough resistance to stop you changing gear accidentally if your thumb is hovering near it on rough terrain though so I reckon they’ve judged it really well. 90 also gets an alloy downshift lever compared to the plastic one on 70 but there’s no angle off sweep change like fancier, older SRAM trigger shifters.

After two months of full-on hammer that’s been enough to rub some bald spots on the crank arms and put some decent scars on the chainring skid plates and bottom of the jockey wheel cage. Eagle 90 is still shifting perfectly though.

I’ve had to take up a tiny bit of cable stretch and it’ll occasionally dither a bit in the work stand when it’s not under load but on the trail where it matters it hasn’t skipped or slurred a single shift. Those scars and scuffs have come from some serious knocks, drops and slides down the trail too. That means you’re going to have to hit it very hard to need to rebuild it, but it’s great to have that facility for reduced stress on tight, rocky trails or just general dumb moments.

While I wasn’t mad keen on the extra weight of the bash segments at first they’ve definitely saved the chain and chainring from some pain, so I’ll be keeping one of them on (I always lead with my right foot). The cranks feel as solid and flex free as their ancient ancestors and while I’ve been riding 170mm arms the fact you can get proper short options is great.

Previous experience with the chain and cassette when running AXS T-Type suggests they’ll last a lot longer than most other options in terms of wear. The better-managed, restricted-rate shifting also reduces stress on the chain and snap issues compared with Shimano and TRP systems.

Wait, what? Restricted-rate shifting? Yes, as I said at the start, the trigger will only let you change two gears at a time. Shimano and older SRAM drivetrains will have a good go at trying to gulp down five or six downshifts if you give the lever a full sweep.

In reality though that sort of excess nearly always ends up sounding really ugly and potentially snapping or unshipping your chain, even if you’re totally backed off on torque. However, even going three shifts a time is going to get you a lot faster up and down the block than with T-Type on rapidly changing terrain or speeds.

That said, if you’ve heard about – or experienced – single shifts feeling awkwardly laggy on T-type compared with older SRAM or Shimano, that’s not the full story.

Sure, in the smallest four sprockets the extra shift ramps on older GX or Shimano XT cassettes generally translates into three shifts in just over a crank turn, while more carefully choreographed T-Type will only manage two. While it doesn’t sound a massive deal that is a noticeable lag on the trail.

However get into the middle four Shimano and old SRAM slow down to two and then 1.5 shifts per turn. Or less if they miss a gate and fumble the shift, which damn near never happens with T-Type.

By the time you’re heaving up into the biggest four all three systems are shifting once a crank turn, but T-Type is using far less effort as it’s not physically lifting the chain as much. While I’ve got no actual drag figures to prove it scientifically my two month old SRAM 90 also felt less draggy in terms of chain angle in the largest cogs compared to brand new Shimano too.

That’s a thing on the trail too, not just in the work stand, especially on long, dirty rides where whatever lube you started with is a distant memory.

Something to upset weight watchers though is that the big modular mech and a few extra grams in chainset can’t offset the slightly lighter cassette. That puts Eagle 90 at 1627g, compared to wired GX at 1510g and XT at 1535g for gears and chainset without chain. Interestingly the much lighter wireless controller means GX AXS is only 26g heavier too.

Eagle 90 is also £106 spendier than wired GX and £45 more than Shimano XT for the same package. Actuating the same shift performance with wires rather than wireless saves you £525.