SRAM Transmission – first build and ride

SRAM’s new ‘Transmission’ system broke cover late in 2022, and a year later we’re starting to see it arrive in GX form as both upgrade kits and OEM on high-end bikes.

SRAM claims that every part of the Transmission system is new and incompatible with previous generations of 12-speed products. We think there’s a fair bit of marketing hyperbole in there – especially when it comes to chains and chainrings – but the visual and technical differences with the other system components is striking.

The kit is impressively packed in a large multi-layered box. The version for DUB cranksets has a pair of chainring protectors fixed firmly to the chainring, but the Bosch eMTB version has a clip-on chain guide that looks certain to clip off during a ride. We didn’t use it on our bike.

The Transmission system (AKA ‘T-type’) only works with frames that use the UDH rear dropout system, invented by SRAM a few years ago and released to the world for free. When UDH was announced, SRAM told us that it was to eliminate the myriad of design for derailleur hangers, and every bike shop would have them in stock. One hanger to rule them all, right? Now we know why they gave away the design of UDH for free to every bike manufacturer – it was necessary to allow Transmission!

The biggest innovation with T-type is the mounting system of the rear derailleur. The UDH hanger is removed and the T-type RD mounts directly to the frame on both sides of the dropout.

This mounting system is super strong and there’s plenty of tiktoks where people are standing on the derailleur without it bending. We didn’t try that 🙂

The setup of the new RD is totally new, and all the old systems of limit screws and B-tension adjustment are gone. There’s a specific chain length and other setup parameters required for your bike model and size, calculated by the AXS App or on SRAMS’s website. The original UDH hanger is removed and the RD is mounted with the wheel off the bike then the chain is tensioned with the wheel in place.

The new RD comes with a unique quick-release cage that includes both cage plates, jockey wheels and the clutch. Hopefully the replacement price is low enough to keep a spare in the van for carpark repairs.

If there’s a downside to the T-type universe, it’s the requirement to run an XD rear hub – there’s only one cassette option currently! This won’t be an issue for most people who are ready to spend 2K on a groupset, but it does add $500ish if your favourite wheels have Microspline or HG hubs.

SRAM have halved the size of the shifter unit and we’re impressed. The new shifter has two simple buttons and is barely bigger than the coin battery inside it. We like that SRAM could halve the size of it in five years, this the speed of change driving MTB tech and we love it.

Our Bosch bike took about two hours to convert from Shimano XT to SRAM T-type. With the eBike there’s some mucking around with removing the outer shift cable and ensuring that other electrical cabling isn’t affected. On an acoustic it’s normally as simple as gently drawing the cable from the head tube, normally done in 30 seconds.
Fortunately our favourite carbon wheelset features a Hope Pro4 hub with XD driver!

We fitted all of the components to our demo bike without any modifications or changes from SRAM’s design. Normally we’d strip a new chain and wax it but with this new setup we wanted to know how it worked out of the box. Pairing the components in the SRAM app was a snap as always and configuring the buttons was a 30 second job.

Our first ride impression was that SRAM has delivered on their promise of seamless shifting under full load. This has never been possible before – from any drivetrain manufacturer – and for this alone the system gets a 10/10 from the judges.

Over the next few weeks we’ll be testing the shift-under-load capability on some of our tougher local climbs, with a mix of riders aboard. We expect it to have issues with the ultra-tough short climb out of a creekbed, stay tuned!

Things we love about the T-type system:
> Shifting under load
> New smaller shifter with sensible buttons
> Easily replaceable derailleur cage and clutch
> Bashguard mounted directly to the chainring for acoustics

Things we don’t love about the T-type system:
> The cost of entry is crazy high
> Clip-on chain guard for eMTB bikes
> No cassette options other than XD