First Look! SRAM Transmission Ends the Mountain Bike “Drivetrain”

After months of spy photographs and hypothesis, the brand new direct-mount MTB rear derailleur is right here. Way over only a new mech, it’s a completely new system referred to as SRAM Transmission.

Three distinct variations — XO, XX, and XX SL — will come as full teams, and it’s referred to as a “transmission” as a result of every thing is interdependent in ways in which present “drivetrains” will not be. Which means, with a drivetrain, there are lot of various elements from completely different manufacturers with completely different tolerance stacks that may very well be used collectively. With a transmission, there’s no mixing or matching — it’s a whole group that’s optimized as a system.

SRAM says (and we’ve all probably skilled) that at a minimal, variations in frames and dropouts have necessitated issues like barrel adjusters and fine-tuning throughout setup. While you begin mixing and matching elements throughout manufacturers, small particular person tolerance outliers add as much as massive variations from bike to bike. That meant elements wanted quite a lot of built-in adjustability, notably the rear derailleur.

However all these factors of adjustment are solely there to take up the slack between frames and parts. So, SRAM designed a system that eradicated all of that slack and, thus, the changes.

Now the freehub physique, cassette, and rear derailleur match collectively completely, mechanically and at all times. So, there are not any adjustment screws wanted as a result of there are actually no extra changes wanted. Simply assemble it and it’s completely aligned.

However that’s just the start …

How SRAM Transmission Units Up Otherwise

It started years in the past with the UDH (Common Derailleur Hanger), giving each body producer a single, well-defined design parameter for rear derailleur placement in relation to the cassette/freehub physique. As bike manufacturers up to date their frames to make use of UDH, they have been successfully giving their bikes a hanger-less design, and SRAM was busy engaged on a direct-mount rear derailleur that may take full benefit of that standardized interface.

Earlier than we get too far, you’re in all probability questioning:

• Sure, all of this new stuff is designed for use as a whole system.
• No, it’s not appropriate with current Eagle 12-speed elements save for the AXS shifters.
• No, SRAM just isn’t sorry for this — its objective was to create the very best system.
• The entire drivetrain elements are marked with “T-Kind” on them to point compatibility.
• With the intention to run Transmission, you’ll want to make use of the chainrings, cassette, chain, and derailleur as a bunch.
• Nevertheless, it makes use of new Flat Prime MTB chains, that are appropriate with Street Flat Prime chains.
• So, you’ll be able to combine T-Kind cassettes and derailleurs with present SRAM highway 1x cranksets and drop bar AXS shifter levers for a mullet gravel drivetrain, so long as your highway/gravel body is UDH appropriate.

As with most SRAM launches, the brand new design brings loads of new nomenclatures. Now, the derailleur’s “Full Mount” slides over the dropout in a “Hangerless Interface,” with the mounting bolt attaching from the skin and threading into an Alignment Plate between the interior mount and the body.

The Alignment Plate acts like a washer between the derailleur and the body. Its knurled interior floor grabs onto the body, whereas a smoother again permits for derailleur rotation within the occasion of an affect. The small prongs present a spread of motion used throughout setup.

There’s no extra B-screw to set its place, however there’s a “Setup Key” with an A/B place for the Cage Lock that catches an intermediate level on the pulley cage.

That is used for preliminary set up solely, however doubles as the traditional Cage Lock pin for holding the pulley cage in an prolonged place for straightforward wheel elimination.

Your body’s design will dictate whether or not you employ A or B, and it’s merely a matter of popping the pin housing out, flipping it, and snapping it again into place.

Insert the wheel, thread within the thru-axle, after which shift the derailleur in order that the higher pulley is aligned with the “Set Up Cog” (the one with the pink plastic information behind it). Now, with the derailleur cage held within the setup place, you put in the chain, which has additionally been simplified.

Based mostly on guarantee data and its client interactions, SRAM discovered three most important issues that may finish rides:

• Unhealthy or pressured setup
• Robustness
• Shifting below load

SRAM says AXS decreased these points by about 25% over cable-actuated methods by eliminating the cables and minimizing the necessity for restrict screws. Transmission eliminates 66% of remaining tolerance points by eradicating derailleur hangers and the tolerance variations these convey.

This left chain size as one of many only a few areas left for consumer error, however now there’s an app for that. You would nonetheless arrange the bike by placing the chain on the large cog and chainring and measuring and including two hyperlinks.

Or, you can measure your chainstay size, enter your chainring dimension, and use the AXS app to find out the right variety of hyperlinks.

Or, as a result of SRAM is aware of each model that’s UDH/Hangerless appropriate, there’s a drop-down record of frames and also you merely select the bike you’ve got, your chainring dimension, and it’ll inform you what chain size you want.

No extra counting hyperlink overlap or pre-sagging your suspension to get the proper size.

Then you definately merely align the mark on the derailleur’s Full Mount with the mark on the washer plate and tighten the mounting bolt. There’s a sequence to tightening, then loosening, then retightening the mounting bolt, but it surely’s straightforward and SRAM may have a full educational video for it — and also you solely want to try this as soon as.

After it’s arrange, you’ll be able to take the wheel on and off with out affecting the derailleur’s place. However when you ever change chainring dimension or take away the derailleur, you’d must set it up once more to get the correct chain hole.

Your derailleur is now put in and completely aligned. No extra B-screw, no extra higher and decrease restrict screws, and no extra utilizing the trim buttons. Since every thing’s place in relation to every thing else is now standardized, it simply goes the place it’s purported to and shifting is ideal.

It’s additionally a a lot stronger system. By placing the rear axle right through it and supporting it with two mounts, it goes from a single-shear mount to a double-shear. And, it successfully lets the bike’s complete rear triangle act as a system fairly than a group of elements with weak hyperlinks (i.e. hangers) within the center.

How a lot stronger is it? Tons. You possibly can stand on it. Or wreck on it. Or your bike can fall over on it. Not solely is the Full Mount extremely sturdy, SRAM made it robust sufficient to resist any load it’s ever more likely to see, and to do it time and again.

And when you do smash into one thing and the derailleur rotates backward, you’ll be able to manually rotate it again till the mark on it strains up with the alignment plate. Or simply loosen the rear axle a bit and it ought to spring again into place by itself.

OK, however What if I Do Break It?

It’s fully rebuildable. Effectively, principally. The motor unit and interior parallelogram and decrease knuckle are one piece. However, the three elements which can be most weak have replaceable elements or coverings.

The principle physique has replaceable “Skid Plates,” and the outer parallelogram is now two items, and each are replaceable. The bushings are contained in these elements too, so when you do put on them out and issues get sloppy, simply substitute these and it ought to appear and feel new.

The pulley cage is now detachable with out instruments. Discover how there’s no bolt on the again of the cage’s pivot?

That’s as a result of it simply twists out, with no instruments required. This makes swaps fast and straightforward, and when you’re packing your bike for journey, simply rotate it up and out of the best way; there’s no must take away your entire derailleur from the bike.

All three fashions are fully interchangeable, so when you smash yours and wish to interchange it, you should utilize no matter your native store has readily available.

Because the clutch’s spring is now totally captured on the cage, I requested SRAM how lengthy they thought it’d be earlier than we noticed aftermarket choices with oversize pulleys and SRAM responded, “Good luck with that.”

It’s not simply the built-in clutch spring that makes it tougher to mimic. SRAM has already given it a bigger 14-tooth decrease pulley, but it surely’s no strange pulley. It’s a “Magic Wheel.” Usually, the entire pulley rotates on its bearings like regular, but when one thing obtained caught in its spokes and cage, the outer ring with the narrow-wide enamel can spin independently of the middle in order that the chain retains transferring and doesn’t jam up and break the derailleur.

Lastly, the cage itself is named “Inline Cage” and is angled barely in order that it really works with the parallelogram to maintain the decrease pulley aimed immediately on the chainring because it shifts throughout the cassette. This, amongst different refinements to the chainrings and new chains and cassette, all assist scale back noise and preserve the system operating extra easily.

SRAM Transmission: XO vs. XX vs. XX SL

At launch, there are three ranges of Transmission teams: XO, XX, and a brand new XX SL. Consider them as being for all-mountain/enduro, path, and XC, respectively. XO has progressively grow to be extra of a high-performance, do-it all group, and this new iteration totally commits to aggressive using.

The important thing variations within the derailleurs are supplies and the quantity of ending work utilized to weight-saving efforts.

XO will get the least machining, notably seen on the Full Mount cage (the half previously often called the B-knuckle). It will get extra sturdy Skid Plates and a stamped metallic pulley cage.

XX will get extra machining, slimmer Skid Plates, and a CNCd alloy pulley cage with a slimmer hub on the decrease pulley.

XX SL T-Kind derailleurs get probably the most machining, together with a bit of fabric elimination on the mounting bolt’s floor. Skid Plates are minimized, and the pulley cage will get a carbon fiber outer plate.

One final thing to notice: The clutch’s damper drive is stronger on Transmission derailleurs, so it requires extra energy to shift, making battery life barely decreased.

SRAM T-Kind Cassette

The brand new T-Kind cassettes use delicate narrow-wide tooth profiles on most cogs together with well-defined ramps and shaping. The objective is to let you shift at any time, below any load, and have it execute completely and silently.

There’s just one cog with an odd tooth rely quantity, and that’s the “setup” gear indicated by that pink plastic insert, which is just there to point out you which ones cog to make use of throughout the system’s set up. It’s not a noise damper, help, or anything.

All the opposite cogs have even tooth counts and a narrow-wide X-Sync profile. The “huge” enamel aren’t as huge as on the chainrings, and relying on the place they sit on the cog, they may have completely different or no huge shaping. That is to enhance chain retention and shifting below load.

The opposite massive think about shifting enchancment is the shift ramp shaping. They’re designed to help the chain and keep fixed contact and engagement even throughout shifts. They’re additionally there to make sure correct switch of the outer plates onto the huge enamel, and vice versa.

Should you occur to place the chain on within the flawed “timing” throughout setup, SRAM says it’ll simply skip forward in your first couple of pedal strokes to get the narrow-wide timing. However as soon as it’s on and rolling, it can shift such that the outer chain plates land on the huge enamel, and vice versa. Mixed with the tremendous stiff Full Mount derailleur, you’ve got a system that works collectively to supply seamless, sturdy shifting.

This results in an essential level: Transmission shifts slower than Eagle AXS.

Every shift may be very intentional. Should you faucet the shift button a number of occasions actually rapidly, the derailleur will carry out one shift at a time, pause for half a second, then execute the subsequent shift. It’s bizarre, but it surely works. I’ll have a full journey report quickly and canopy this in additional element however suffice it to say you’ll be able to shift at any time and it received’t hesitate, however you’ll be able to’t simply smash via 5 gears directly both.

Gone is the X-Dome one-piece machined metal cassette physique, which was mild but additionally ridiculously costly.

The brand new designs combine machined multi-cog elements with separate cogs pinned into place. The XO and XX cassettes have completely different finishes however are in any other case the identical. They each use a machined metal one-piece decrease cluster for the primary 9 cogs. The tenth and eleventh cogs are metal and are pinned to an alloy twelfth cog, which is then pinned onto the decrease cluster to create a one-piece unit.

The XX SL cassette replaces the tenth and eleventh cog with alloy to save lots of weight however makes use of the identical machined-plus-pinned building.

Can I Use the Transmission Cassette With out the Direct Mount Derailleur?

Transmission runs on a 55mm chainline (customary is 52 mm).

Since there’s no derailleur hanger anymore, the XD driver physique’s finish cap sits immediately towards the derailleur physique, not a dropout, therefore the “Full Mount” title.

This lets SRAM transfer the cassette outboard 2.5 mm to make up for that, so the connection between the chain and cassette is (mainly) the identical as earlier than.

This truly offers bike manufacturers extra chainring and tire clearance on the chainstay, but it surely means you’ll in all probability want so as to add extra spacers on the drive aspect between the BB and crankset. It nonetheless makes use of DUB spindles and there’s nothing new in regards to the backside brackets, so any DUB BB will work.

Due to all this, the brand new cassette is incompatible with older drivetrains, primarily as a result of it strikes outboard and will (probably would) rub towards the hanger, UDH, or dropout.

What About Tremendous Increase Bikes?

At launch, there’s no 56.5mm SuperBoost crankset spindle. However you can add a T-Kind chainring to appropriate SRAM cranks on a Tremendous Increase bike as a result of it’s not the cranks themselves which can be T-Kind, it’s the chainring.

SRAM T-Kind Flat Prime MTB Chains

The brand new Flattop mountain chains are SRAM’s strongest chains ever. XO has customary pins and plates, XX will get hole pins, and XX SL will get hole pins and cut-outs on the outer plates. XX and XX SL get their Exhausting Chrome end for improved sturdiness.

Sure, they appear like Street Flattop chains, however no, you shouldn’t use a Street Flattop chain on this MTB group. For mullet gravel builds, use the MTB Flattop chain.

They arrive with 126 hyperlinks and use a brand new T-Kind Flattop Fast Hyperlink that, SRAM says, is unquestionably not meant to be reused.

SRAM advised us that, technically, you’re not purported to reuse any fast hyperlinks, however let’s be actual, most of us do. However SRAM likes to remind you once more that you just shouldn’t do this. The precise press-fit design side hasn’t modified, but it surely says it weakens somewhat if you launch it, and it’s best to simply substitute it with a brand new one. Additionally, the unique Eagle 12-speed chain quicklinks shouldn’t be used on the Flattop chains.

SRAM Transmission Cranksets, Energy Meters, and Chainrings

Every group will get its personal crankset. Carbon cranks are successfully the identical as earlier than. XX is mainly the prior XO with a foam core. XX SL is mainly the prior XX with a hole carbon arm.

Keep in mind the AutoDesk story? Seems that’s precisely the way it designed the brand new alloy XO crankset. After inputting the standards, AI spit out a number of design choices. SRAM sorted via these to seek out the design it favored after which optimized that for precise using circumstances.

The raised portion will get polished precisely the place somebody’s heel would rub it, holding it wanting recent. Extra importantly, it’s very robust and really stiff, holding with the trail-to-enduro vibe the XO group is aimed toward.

All three are available in 165/170/175mm arm lengths.

The brand new T-Kind chainring tooth profiles are optimized for the brand new Flattop chain, so they’re barely completely different than non-T-Kind chainrings. And so they now use the 8-bolt direct-mount interface, not the 3-bolt. Chainring dimension choices are:

• XO: 30/32/34
• XX: 30/32/34/36
• XX SL: 32/34/36/38

Additionally they have T-Kind chainrings for Bosch, Brose, and Shimano Steps e-bike methods, in addition to their very own T-Kind e-bike cranksets.

Each XO and XX cranksets include built-in bash guards on the chainrings. They’re detachable and positioned solely the place you want them. They’re model-specific and chainring size-specific.

The XO bashguards have backing plates, however the XX ones save a little bit of weight by bolting immediately collectively. Happily, the heavier stamped XO chainring and the extra closely machined XX model (and XX SL) are all interchangeable between any of the cranksets.

SRAM may have two energy meter choices for Transmission. Not proven, the XO/XX cranksets each have left-side spindle-based energy meters obtainable, both as a whole crankset or as a left-only improve for an current group.

The XX SL group will get an built-in Quarq energy meter spider with new thread-on chainrings. It’s a intelligent design that permits for fast chainring swaps (a particular instrument really useful and obtainable, however … you’ll be able to in all probability do it with a series whip).

As soon as twisted on, a set screw prevents unintended loosening. It makes use of a replaceable CR2032 battery good for 200 hours of run time and connects through ANT+ and Low Power Bluetooth. Commonplace direct-mount 1x chainrings will even be obtainable, both offered individually or as a part of the crankset.

All three of the ability meters will join with its Flight Attendant suspension too, so there’s no want so as to add a further cadence sensor to make use of its auto-adjusting suspension.

SRAM AXS Pod Controllers

The one a part of the brand new teams that’s cross-compatible are the brand new pod shifters — that means, you’ll be able to run these with Eagle AXS and you’ll run AXS paddle shifters (Street, MTB, Blips) with the brand new Transmission derailleurs. Something that may very well be managed with AXS remotes (Reverb, and so forth.) will work with these too. They arrive in two variations — customary and deluxe — and with two completely different mounts.

The direct-mount clamps on to your bar, with a slim band that ought to match into any cockpit setup. The Matchmaker mount attaches to SRAM’s brake lever clamps and gives a wider vary of lateral adjustment than the two-position system of the originals.

The usual Pod has fastened concave button pads. The Deluxe model has detachable buttons with each concave and convex pads; combine or match to create the precise tactile expertise you need. You can too flip them left to proper, rotate them independently of the mount’s rotation, and assign the buttons to do no matter you need through the AXS app.

The Pods’ pairing button does nonetheless work as a trim button, which is nice for establishing AXS teams, however SRAM says it’s unlikely you’ll ever want to make use of it for Transmission teams.

SRAM Transmission Precise Weights

Keep in mind the three causes SRAM gave for making this group? Weight wasn’t one in all them. That stated, it’s all respectably light-weight.

All cranks measured are 175mm lengths. The XO crankset is available in at 667 g plus 81 g for bash guards for 748 g full.

The XX crankset is 542 g with 53 g bash guards, 595 g full.

The XX SL crankset with energy meter and 34-tooth chainring is 550 g.

I didn’t have a normal chainring to weigh, however at simply an 8g weight achieve so as to add an influence meter, there’s mainly no penalty past value.

Cassettes vary from 449 g for XO to 419 g for XX SL. Batteries add 25 g.

XX and XO cassettes are practically an identical at 382 g and 381 g. In some way, I didn’t weigh the SL cassette however shall be including this later as soon as I do. Claimed weight is 345 g for XX SL cassette and claimed weight for XO/XX is 380 g.

Chain weights are 282 g (XO), 274 g (XX) and 264 g (XX SL).

Shifter Pods are 35 g every. MMX mount with brake lever clamp is 35 g, and the standalone mount is 1 2g (47 g – 35 g).

SRAM Transmission Pricing & Availability

Costs above are for particular person customary parts, and under are for full teams and chainrings.

All SRAM Transmission elements begin transport at launch in March 2023. Anticipate rapid availability on full bikes and separate aftermarket availability very quickly. Mainly, if in case you have a motorcycle with a UDH hanger on it, it’s appropriate.

SRAM.com