Gravel-2X-Comparison: SRAM Red eTap AXS vs. Shimano GRX Di2

Until just a few years ago, the front derailleur was an indispensable part of road bikes, as on longer tours, steep climbs, or at higher speeds, 2x drivetrains with their greater number of gears were superior to the mostly homemade 1x drivetrains. However, the shifting processes at the front between the chainrings often caused problems; especially in cyclocross use, the chain liked to jump off or get jammed between the crank and frame.

A great alternative was then found by cyclocross and gravel bikers in the 1x drivetrains from SRAM, and later also from Shimano (GRX 1x11) and Campagnolo (Ekar 1x13), where the manufacturers omitted the front derailleur, could effectively prevent the chain from jumping off with special chainrings, and realized the necessary range of gears with larger cassettes and longer rear derailleur cages. Ultimately, SRAM perfected this approach with their 1x12 Rival/Force/Red XPLR groups, offering a wide range thanks to the matching XPLR cassette with 10-44 teeth, to climb any ascent.

Those who wanted to convert their gravel bike to slicks now and then to use it as a real road bike, were still better advised with a 2x system. Because either the 1x drivetrain - depending on the chosen chainring (36T, 38T, 40T, 42T, 44T, 46T, 48T) - lacked the relentless propulsion with a strong tailwind, in sprints on the flat or on fast descents, or forced one to work excessively uphill.

It is exactly at this point that the wheat is separated from the chaff, because to this day only Shimano with the GRX group has a 2x groupset in its range, which was explicitly designed for road bike use off the road. Whether this actually makes a difference in the terrain and how SRAM's flagship electronic road bike group RED eTap AXS with 2x12 gears performs in challenging terrain against the 2x11 challenger from Japan, will be revealed in the following report.

Due to a fortunate twist of fate, NoPain had the pleasure of test riding the same road bike with identical equipment (components, wheels, and tires) both with SRAM's electronic 1x12 top road bike groupset and with Shimano's electronic 1x11 gravel flagship for several months in familiar terrain.

Because promptly after his Scott Addict Gravel Tuned Long-Term Review (SRAM) he treated himself to a frameset and equipped it according to his personal preference - in the Scott Addict Gravel Aero Build Thread (Shimano) it was extensively reported.

On paved sections, the Scott Addict Gravel really flew. Both the seating position and body posture as well as stiffness and aerodynamics were 100% focused on propulsion, which is why a 2x drivetrain made sense for such a rocket due to its larger range of gear ratios.

Both groups offered solid performance with an unusually fine gear differentiation for gravel. Here, the SRAM with its 12 sprockets had the advantage - at least from a mathematical standpoint - and allowed for a higher top speed in the last gear (SRAM 52.8 km/h vs. Shimano 50.1 km/h). However, in the smallest gear, the gear development per crank revolution was almost identical (SRAM 2.06 m vs. Shimano 2.05 m).

Shifting through the gears at the rear was excellent with both groups, although with the SRAM Red eTap AXS there was a slight delay between the actuation of the shift lever and the actual shifting process - not necessarily disturbing and by no means as bad as with the first eTap versions, but noticeable.

Less thrilling was the somewhat finicky function of the SRAM front derailleur, which caused shifting problems or even chain drops from time to time. So I perfected the front derailleur adjustment, which actually significantly improved its function. However, it still did not match the performance of the Shimano GRX.

I felt equally enthusiastic about the Addict's rapid progress over firm gravel paths and its remarkably stable handling at high speeds on loose surfaces. The 45-millimeter-wide tires absorbed the majority of the irregularities, and the bike stabilized itself thanks to its long wheelbase, the flat 71° head angle in size M, and the resulting long trail almost by itself. Potholes, ruts, or larger stones neither disturbed the bike nor the rider, and the tubeless wheel-tire system withstood all provocations despite low pressures between 1.6 and 1.9 bar.

As far as the groupsets were concerned, a similar picture emerged as on asphalt. Both groups worked excellently - apart from the slight delay in shift commands already mentioned above and the somewhat weaker front derailleur performance of the SRAM Red eTap.

In addition, both shift/brake levers were very comfortable to hold and provided a secure grip on both the brake and the drops. Although I preferred the GRX grips in conjunction with the handlebar flare, as their ergonomics were specifically developed for outwardly bent handlebar curves, the high humps of the SRAM Red levers also allowed for secure operation in rough terrain. Once again, a tie.

Whether cobblestones, stones or roots - the Addict Gravel generally allowed for an aggressive yet safe approach to all types of terrain. However, the terrain couldn't be too bumpy over the long run, because the comfort from the aero seat post, frame, and handlebars eventually reached its limits despite the wide tires and low pressure.

A similar situation occurred during longer braking maneuvers with the SRAM Red levers. Generally, the hands rested securely on the brake levers and the levers themselves were easily accessible, but as the braking duration increased, it was not easy for me to maintain the desired braking pressure. Additionally, I had to switch to the more stable lower bar grip earlier on the SRAM Red levers than with the GRX.

I suspect it was due to the 18 mm raised pivot axis of the GRX brake lever, its curved and more massive lever shape, as well as the wider support surface on the grip body together with the grippy texture on the rubber: this provided the levers with more grip and noticeably improved safety and operability on rough terrain. Additionally, Shimano's Servo-Wave technology allowed for a great braking performance and also prevented the dreaded scraping or jingling noises of the discs. When it came to braking, the point clearly went to Shimano.

At the latest in deep mud, the SRAM fun came to an end. To be honest, the Addict Gravel Tuned struggled with more than just challenging conditions during the photo session on New Year's Eve 2021/22, as the thawing weather excessively softened the loess soil around Großrußbach in the Weinviertel; however, the performance limits of the road bike-oriented component group became apparent more clearly and quicker than expected.

While my three companions with a Shimano GRX 2x11 and a SRAM 1x12 each had maximum struggles on the same track, nothing worked at all with my RED eTap AXS after a few hundred meters. But even on rides with far less sticky dirt, the SRAM front derailleur regularly ran into trouble, and I began to dread every front shifting process.

Conclusion: The Red eTap 2x may work flawlessly on the road, but in combination with a lot of sticky dirt, a moderately self-cleaning tire tread, and little tire clearance to the bottom bracket and front derailleur battery, the groupset is only of limited use for extreme gravel riding in the long run. Moreover, the honeycomb-like, almost wasp nest-like construction of the Red 2x crankset acts like a dirt magnet.

SRAM's Red eTap AXS 2x12 is a genuine racing bike group and is primarily suitable for Granfondo use or gravel races on firm, dry, or mixed terrain on a gravel bike. At least in our experience, its front derailleur showed continuous weakness under more extreme conditions and embodied the weakest link in the chain drive from the USA.

It was only with the Shimano GRX Di2 2x11 that the Scott Addict Gravel also made an excellent impression under tough, muddy conditions and proved capable of mastering all typical gravel challenges. The one sprocket less was - at least on paper - noticeable in terms of gear jumps and the final drive ratio, but due to the better overall performance, it was absolutely bearable.

Conclusion - The faster and firmer the ground and the more typical the use for road cycling, the more the tendency towards the SRAM Red eTap AXS; the muddier the surface and the more universal the application, the more recommendable the Shimano GRX Di2 becomes.