The prototype SRAM Eagle AXS direct-mount rear derailleur and new T-Type SL Eagle Cassette have been spotted at the World Cup races under several riders.
I spied it sitting still and grabbed a lot of closeup photos that reveal new details and features. Here’s the TL;DR info:
- New derailleur uses the SRAM UDH frame standard to mount around the dropout, eliminating the hanger altogether.
- Called T-Type, it’s unclear whether you’ll be able to mix and match with current 12-speed Eagle Cassettes and chains
- New Eagle SL cassette uses a mixed pinned-plus-machined construction
- There appears to be a damper inside the cassette, likely to reduce noise and/or vibration.
- A new one-piece Quarq MTB power meter chainring joins the group.
I spotted these on the Canyon Lux Ultimate raced by Loana Lecomte to four UCI XCO podium finishes in 2022, including two first places.
Or, at least this particular bike was raced at Val di Sole for certain. But the group has seen some mileage based on the scratches and worn finish on the derailleur in particular…which suggests it’s quite durable.
SRAM Direct-Mount Eagle AXS derailleur
The Background:
A few years ago, SRAM introduced the UDH (Universal Derailleur Standard), offering a single part to replace the hundreds of unique hangers being used across brands. It offered a clear benefit to riders, shops, and manufacturers.
It also got the brands to design their frames around a single standard that, conveniently, will now work with this direct-mount rear derailleur.
The Benefits:
The main benefit should be a stronger, stiffer derailleur with better alignment, resulting in better shifting.
It’s stronger and stiffer because it’s now mounted directly to the bicycle’s frame, sandwiching the dropout. This removes the hanger from the equation and instead attaches via the rear axle…sort of.
You wouldn’t want the derailleur to fall off when you pull your wheel out, so it appears to have a bolt that will secure it to the dropout, then it’s likely that the rear hub’s axle will thread into it from the other side.
The upper mounting section looks robust, with all the critical bits sitting well inboard of the frame. Having a likely (very) expensive part in a high impact area means it’s also likely that SRAM is making it very strong.
Their current AXS derailleurs allow the parallelograms to decouple from the movement gears during an impact, then automatically reposition themselves to the correct gear. I suspect this will do the same, protecting it from damage. The scratches on this one suggest it’s seen a lot of impacts.
By aligning the derailleur with the rear axle, it keeps it perfectly perpendicular to the cogs. This removes any imperfections with hanger alignment that could dilute shifting precision.
On the inside of the dropout, a silver metal piece sits between the dropout and derailleur, likely acting as a washer. But it also has a small nub that is aligned with a mark on the derailleur, suggesting this serves to help get the rotational position correct.
There’s no B-screw visible, however there’s a small, nearly hidden bolt on the inside face of the mount that could be a functionally similar adjustment screw.
It appears as though the pulley cage angles outward slightly (image on left), which could be to maximize tire clearance and keep it away from the spokes.
Looks like it’ll have ANT+ and Bluetooth communication, which should let it communicate gear selection to compatible GPS cycling computers.
The one part I can’t figure out is the two-position Cage Lock. This one has “A” and “B” positions, with what appears to be a flip-chip style insert to swap positions.
Cage Lock is what holds the cage down to release chain tension for easier wheel removal, so I’m not sure what the benefit of two different positions is here unless it’s to accommodate different frame designs. The pulley cage itself also has A/B markings on it.
The pulleys are bigger, with 14 teeth on the upper and 16 on the lower (2 more teeth per wheel than the current Eagle MTB derailleurs’ 12/14 counts). Larger pulley wheels supposedly reduce drag.
The cage is marked with “T-Type”, and the cassette has a similar marking. Hopefully this does not mean the parts won’t be cross-compatible with existing Eagle parts.
The new design appears to position the top pulley slightly more forward, which would improve chain wrap (the amount of chain in contact with each cog) and reduce the likelihood of chain skips.
Eagle SL cassette
The Background:
Current Eagle XX1 and XO1 cassettes use a lighter (and more expensive to manufacture) one-piece machined steel body with the largest cog being alloy and pressed into place. GX and lower use a multi-piece pinned construction that’s heavier, but cheaper.
And now?
A new Eagle SL 12-speed cassette appears to use a pinned construction for the top three cogs, then pins a one-piece 9-cog cluster to the bottom of that.
But there’s a big difference between this and the pinned GX cassette. On this SL cassette, the cogs and cluster are all pinned directly to the largest cog. The GX cassette’s cogs are all pinned to each other in succession, meaning each individual cog must also support the force of the ones around it.
The lower 9-cog cluster is likely steel and machined as a single piece just like the current X-Dome cassettes.
This could save weight if the top three cogs are now alloy, instead of just the largest one. Presumably there are other tricks up its sleeve.
For reference, 10-52 XX1/XO1 cassettes weigh in at ~375g. The 10-52 GX cassette is ~455g.
The Eagle SL cassette here is still 12 speeds, and it’s a 10-52 (520% range) model.
But the ratios between the upper cogs are different. I count them as:
- Current Eagle 12sp: 10,12,14,16,18,21,24,28,32,36,42,52
- New Eagle SL 12sp: 10,12,14,16,18,21,24,28,32,38,44,52
This would give a bigger jump between 9 and 10, but evens them out between 10, 11 & 12, so that there’s a less dramatic jump when shifting into the largest “bail out” gear. The smaller cogs appear to be the same.
The other big difference is this flexible rubber-looking insert. I’m guessing it’s there to reduce vibration and damp noise.
SRAM uses rubber damping rings on their Red road cassette, so there’s precedence for such things.
New SRAM Flat Top Hollow Chain
In what may bode well for road bikes, too, this Flat Top chain is the first I’ve seen with hollowed outer plates. Those plus what appear to be hollow pins mean a lighter chain, and the first Flat Top chain for mountain bikes.
Prototype one-piece power meter MTB chainrings
The bike also had this Blackbox (SRAM’s MTB nomenclature for prototype development parts) one-piece Quarq powermeter chainring.
The current mountain bike power meter is just a spider that uses a typical 4-bolt chainring attachment. This one looks much sleeker, and is likely much stiffer.
The chainring teeth have rounder edges, and the wider teeth are slightly taller, just like their road and gravel chainrings…which use a Flat Top chain. By contrast, SRAM’s current X-Sync MTB chains have equal-length teeth and sharper, square-edged points.
This suggests that it’s the chainring, not the cassette, that could be the part you need to change to run this new chain.
They appear to have an interesting assembly method. Note the “Tighten —>” imprint and the small, ramped notches on the edges of the power meter’s body. This suggests that the chainring threads onto the power meter, then locks into place with a bolt (or several).
I hope this allows the chainrings to be swapped without having to change the power meter, but SRAM has set a precedent of recyclable (disposable) power meters for road bikes, so we’ll see. Considering the increased wear MTB chainrings see, it makes sense that they’re replaceable…and also because with 1x setups, swapping tooth counts based on the course happens more often.
When does the SRAM Direct Mount rear derailleur launch?
All of the information here is speculation based on what is visible. I spoke with several bike brand product managers on the condition of anonymity, and the general consensus is that these products are not officially launching until Spring 2023 at the earliest, and even they don’t have all the tech details yet. SRAM does not comment on unreleased products.
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