Sram GX Transmission: Without cables - is it worth switching to electric gears?

First the derailleur, then the derailleur cable, now the derailleur hanger. The US component giant Sram is retiring one component after another in its drivetrains. Together with the former predetermined breaking point between the frame and rear derailleur, the new Sram GX Transmission also retired the adjusting screws.

Sram is not only changing the way in which the rear derailleur is attached to the frame, but is also revolutionising the entire adjustment process. The motto here is mobile phone app instead of Allen key. At the same time, Sram promises unprecedented shifting performance - especially when changing gears under full load. We wanted to know: Is it worth switching from mechanical to electronic, and if so, does it have to be the expensive Transmission, or does the slightly older AXS technology change gears just as smoothly?

We got to the bottom of this question using the "ethnic group" Sram GX as an example. It offers the cheapest entry into Sram's electric universe, but at the same time has all the important technologies that also characterise the expensive drivetrains.

>> Sram GX Eagle Transmission AXS: The more affordable electric drivetrain from Sram

>> Sram GX AXS Transmission: Dust, rain, mud, snow - the 2000 kilometre test

>> Sram XX SL Eagle Transmission: Does the premium drivetrain hold up in the 3000 kilometre endurance test?

Sram GX Transmission - many advantages, but also disadvantages

Where there is light, there is also shadow: Because with the transmission drivetrains, Sram has also introduced a new standard - called T-Type. This means that the new components are not backwards-compatible, making upgrades more difficult, or at least more expensive. But more on that later.

Sram Transmission drivetrain: Foolproof assembly

Bowden cable or radio signal: The derailleur hanger has always been one of the main culprits for rattling Twelve-speed drives. The small sprocket spacing of both the mechanical and the electronic Eagle AXS required a meticulous alignment of the rear derailleur below the cassette.

The attempt to correctly adjust an Eagle derailleur with a misaligned derailleur hanger must have driven quite a few people mad. With the introduction of the UDH standard and the elimination of the derailleur hanger, Sram now uses the wheel axle as the basic constant and thus creates a fixed position for the rear derailleur.

The adjusting screws for the end stops are no longer required, and the template for the distance between the guide roller and the pinion is superfluous. This reduces assembly to a few easy-to-follow steps. The chain length is calculated using the length of the chainstays and the size of the chainring. The red marked setup sprocket serves as a reference point for the rear derailleur, the rest is regulated by the software. As long as you stick to the correct sequence, errors are virtually impossible. Only the fine-tuning of the tension was quicker in the analogue world. If, contrary to expectations, the transmission does rattle, you have to fine-tune the gears using the pod controller.

Goodbye predetermined breaking point derailleur hanger!

Previously, the derailleur hanger acted as a kind of bodyguard for the rear derailleur. In the event of a hard hit - from a stone or branch - it should break before the rear derailleur is damaged. With the new Sram GX Transmission, the rear derailleur itself has put on a protective armour: It has a much more solid construction, which is also reflected in the higher weight - the Transmission rear derailleur has a whole 193 grams more on its ribs compared to its Eagle counterpart. The real highlight, however, is the integrated shifting function, which the AXS already has. You can try it out for yourself in an impressive way: If you kick the rear derailleur with your foot, it swerves towards the spokes like a boxer - and then returns to its starting position.

In conjunction with the reinforced suspension, this gives the transmission enormous stability. However, should a part break, the Sram GX Transmission is the first derailleur that can be repaired in small parts: Whereas previously you had to replace the entire rear derailleur in the event of a defect, most components from the cage to the parallelogram to the suspension are available as spare parts - a sensible development given the street price of around 350 euros for the rear derailleur. Shortcoming: If the electronics are damaged, this is still the death knell for the rear derailleur.

Shifting under full load with the Sram GX Transmission

One of the most striking features of the Transmission drivetrains is the new flattop chain. In conjunction with the cassette, which has also been redesigned, it is intended to deliver unprecedented shifting comfort. Like the chainrings, its teeth feature the X-Sync design, with alternating narrow and wide teeth. However, both components are also mainly responsible for the fact that transmission and AXS no longer match. When shifting on the flat, you don't notice much of the revolution at first. The transmission glides smoothly and quietly over the sprockets, but the previous twelve-speed drivetrains were already able to do this - provided they were optimally adjusted. The aha moment comes when you change gears in the middle of a sprint. Even under full load uphill, the transmission lifts the chain smoothly onto the sprockets, whether up or down - a particular benefit on powerful e-drives. Where the gears used to bang like New Year's Eve firecrackers, the Sram GX Transmission is only accompanied by a quiet cracking noise.

Transmission gearshift unit more favourable than ever before

What is currently making manufacturers and dealers sweat profusely harbours an opportunity for all those willing to upgrade: Full stocks have driven prices down. According to our research, the Sram GX Transmission is available for an average of 40 per cent below the RRP just one year after its launch. Even the "old" Sram GX AXS is hardly cheaper in the shopping basket. So if you're thinking about a complete overhaul of your bike and fulfil the requirements, you should go for the Transmission. If components such as the cassette and chain are not yet past their sell-by date and you just want to get rid of the unsightly shift cables, you can immerse yourself in the electric universe for as little as €425. In this case, an upgrade kit for the GX AXS consisting of rear derailleur and controller is sufficient, as the chain, cassette and cranks are identical.

Our verdict on the Sram GX Eagle Transmission

The GX AXS is a very inexpensive upgrade for those who want to get a taste of electric power for little money - and is also compatible with the higher-quality Sram drivetrains. However, if you need to replace the chain and cassette anyway, we recommend switching to the GX Transmission - provided the bike is designed for it. For almost the same price, you get a better electric drivetrain. - Stefan Frey, BIKE editor

Three circuits - two duels

With the new Transmission, Sram offers three options in the twelve-speed range. Which raises two questions: Is it worth switching from the classic GX to wireless? And if electric, why not the brand new Transmission?

1 - Sram GX Eagle: mechanical vs. electronic

On average, the mechanical GX costs just half as much as a Sram GX AXS - an enormous price difference considering that the analogue GX already shifts excellently. There are hardly any differences on the flat. The gears are crisp and precise, even with the shifter cable. The GX trigger is intuitive to operate. If you push the large lever all the way down, the rear derailleur raises the chain a full five levels. The number of gears to be shifted can be finely adjusted thanks to the resistance on the lever. You can literally feel the chain moving over the sprockets. The AXS controller, on the other hand, does not provide any feedback, and even with the somewhat more defined pod controller of the Transmission, you have to rely on the servomotor on the rear derailleur to do its job. In factory mode, you have to shift each gear individually. However, the stepless mode can be easily activated via the app and is more convenient. With the mechanical GX, you only have to go down one click at a time, but with a quick thumb, you can change gears much faster than with a classic gearstick - even if it can get a little louder under load.

Mechanically unbeatable in terms of price

Although the new Transmission rear derailleur can be extensively repaired, the mechanical counterpart is still unbeatably cheap at a price of just over 100 euros and can be replaced without any stomach ache in the event of a defect. The weight is almost the same, with only the GX Transmission weighing slightly more at 2000 grams. If you don't mind the cables and are not afraid of the somewhat more complex assembly, the mechanical GX is still a reliable partner.

2 - Sram GX Eagle AXS vs. Sram GX Eagle Transmission

There is one aspect of the Sram GX Transmission that still surprises even after numerous tours: the almost silent shifting under full load - even when changing to heavier gears, you can pedal at full power. The transmission does the job flawlessly, but often takes its time. The slight delay is intended to improve the accuracy of the shifting aids, optimise the shifting process and prevent damage. In general, the new drivetrain is significantly quieter than the GX AXS. Even over root carpets, the stronger clutch prevents chain slap very effectively.

The new pod controllers are also impressive. Thanks to the division into two independent push buttons, operation is more intuitive and the buttons provide clearer feedback, especially in hectic situations, while the gear changes with both the "tub" and the rocker paddle of the AXS controller always remained somewhat undefined. A small drawback: riders with large hands find it difficult to find a suitable position with the Matchmaker clamp and have to switch to the separate Infinity clamp.

Sram GX Transmission shifts significantly slower

However, the speed at which the transmission changes several gears at once is unusual - controlled and extremely precise, but somewhat slow. This is particularly noticeable in Multishift mode. The GX AXS is significantly faster when downshifting in sprints or when quickly switching between downhill and uphill.

The GX AXS is just ahead in terms of weight. However, the Transmission scores points with its simpler assembly and the possibility of extensive repairs to the rear derailleur. The price is also almost identical. Apart from the slightly slower gear changes, there is hardly anything in favour of the older Eagle AXS.

We have already been able to subject the GX Transmission to an extensive endurance test. 2000 kilometres through dust, mud and snow - read our conclusion here.

What the BIKE editors say

Conclusion Max Fuchs, Editor BIKE

In the past, I often had to adjust the derailleur hanger after hard enduro rides or crashes. This is no longer necessary with the Transmission. The gears are absolutely robust. Nevertheless, the battery management annoys me. If there was a mechanical version of the transmission, I would swap it immediately.

Conclusion Jan Timmermann, Editor BIKE

With the classic AXS, shifting gears is more like a computer game. Its electronics are lightning fast and audible. The Transmission is my first choice for racing. It needs more time and vigour, but also tolerates more power input.

What you need to know to make the switch

With the transmission shifters, Sram has created a new system that is not compatible with old parts. You need to pay attention to these points when changing:

Can the Sram GX Transmission drivetrain be fitted to any frame?

No. The prerequisite for this is that the frame has a UDH derailleur hanger is available. This is the only way to connect the transmission rear derailleur directly to the frame.

Can I continue to use my old crank?

There has also been a change to the cranks with the transmission: the chain line has been adjusted from 52 to 55 millimetres to reduce wear with less skewing. The so-called DUB MTB Wide cranks only fit on frames designed for this purpose. Manufacturers who equip their frames with a UDH derailleur hanger usually also use the DUB MTB Wide standard for the crank.

What components do I need to convert to a radio control system?

This depends on the system: When switching from a mechanical GX to a GX AXS, the rear derailleur and controller are basically sufficient, as the cassette, chain and crank are identical. If you want to switch to a transmission drivetrain, you need to invest in a complete set including cassette and chain. Due to the so-called X-Sync technology, the Transmission components are not backwards compatible.

Are AXS and Transmission components compatible with each other?

No. Transmission only works as a separate system consisting of rear derailleur, cassette, chain and chainring. Sram calls the standard T-Type. The components are not backwards compatible. The chain and cassette cannot be interchanged due to the special X-Sync profile.

Can the new pod controllers be combined with older AXS groups?

In contrast to the pure drivetrain components, the different controllers are compatible with all Sram wireless shifters. The choice is yours: would you prefer to change gears with the old AXS controllers or the new pods? This applies equally to transmission and AXS drivetrains.

Do transmission cassettes require a special freewheel?

No. Although the cassettes were developed from scratch, they are screwed onto the familiar XD freehub. Nevertheless, they cannot be combined with the classic Eagle components.