Shimano Di2 vs SRAM AXS

If you’ve ever used a mechanical Shimano STI shifter, the switch to Di2 is easy; however, instead of using levers to shift gears, all you need to do is press one of the two buttons on the lever. By default, the buttons on the right lever control the rear derailleur and the left lever controls the front – just like with mechanical. Some riders claim that, because of the close placement of the buttons, it is easy to mis-shift; however, this only seems to be an issue for riders with large hands or winter gloves on.

Compared with AXS, the shape of the Di2 hoods is leaner while remaining ergonomic. The hood shapes of 105, Ultegra, and Dura-Ace are identical.

SRAM AXS levers simplify gear changing with just a single button on each shifter. In the default setting, the right shifter moves into a higher/faster gear and the left shifter moves into a lower/slower gear. To activate the front derailleur, you simply press both shifters at the same time.

AXS hoods are a little “chunkier” feeling than Di2 – a quality which may be preferable for riders with larger hands.

One of the biggest differences between Di2 and AXS is the batteries. Di2 uses a single lithium-ion battery that is stored in the seatpost. To charge it, you use a special USB cable that attaches to the rear derailleur. In our experience, a single charge can last for months – so it’s not much of a hassle.

SRAM batteries, on the other hand, are specific to each derailleur and can be removed from the bike to charge them. This is great because you can easily have a spare battery or two just in case one dies (or it could be a bad thing if you are prone to forgetting things). While it’s hard to exactly gauge which brand has better battery life overall, it does seem like Shimano Di2 lasts slightly longer than SRAM AXS on a single charge.

Both Shimano and SRAM shifters use small coin batteries which are not rechargeable. Shimano Di2 shifters use CR1632 batteries and SRAM AXS shifters use CR2032 batteries. Both manufacturers claim that their shifter batteries last for approximately 2 years of riders; however, it seems that the real-life results can be quite unpredictable.

Both Di2 and AXS derailleurs use a small motor to actuate the shifting mechanism. It seems to be generally accepted that Di2 shifters are a little faster than AXS (especially for the front derailleur), but other than that, the derailleur performance is negligible.

The biggest difference between the two is in appearance. Shimano Di2 derailleurs look much more like mechanical derailleurs with only a small wire to hint at their electronic nature. SRAM AXS derailleurs, on the other hand, sport a large external battery pack which makes them stand out a little more; however, the fully wireless nature of AXS means that there are no cables to be found.

Both Shimano and SRAM offer many gearing options for their electronic shifting groupsets. While the trend among professional cyclists has been to use bigger chainrings, amateur cyclists have embraced having easier gears to fall back on. Both SRAM Red and Shimano Dura-Ace offer large chainrings to meet the needs of racers; however, the lower tiers such as Rival and 105 focus more on gear ratios that are suitable for casual riding.

Shimano’s 12-speed cassettes still use the classic Hyperglide (HG) freehub body design that has been the industry standard for over 30 years – though the freehub has been elongated slightly for use with 11 and 12-speed cassettes. SRAM AXS cassettes, on the other hand, use SRAM’s proprietary XDR freehub. The XDR freehub is a threaded system which allows for the use of a 10-tooth cog on the cassette.

Learn more about freehub bodies.

While both Di2 and AXS use hydraulic disc brakes, there are some subtle differences between the two. While both options seem to provide similar amounts of braking power, many reviewers seem to feel that the Shimano brakes provide better modulation – especially on the higher-tier Dura-Ace Ultegra options which use Servo Wave technology and offer an extra 10mm of pad clearance. If you do your own maintenance, the Shimano disc brakes also offer a much easier bleeding process.

Rim Brakes – if you are looking to upgrade your older rim brake bike to electronic shifting, your options will be much more limited. The only choices for cable-actuated brakes are Shimano Dura-Ace and Ultegra. The latest generation of SRAM AXS is not available for rim brakes.

While SRAM AXS is fully wireless, Shimano Di2 is only semi-wireless – with small cables connecting both derailleurs and the battery. If you’re buying a complete bike with Di2, you won’t need to worry about the cables; however, if you are looking to upgrade your current bike, routing the cables adds an extra step in the process. SRAM AXS, on the other hand, is simply “plug and play” – all you have to do is mount the components on the bike, adjust them properly, pair them, and ride.

In the era of interconnectivity, it’s worth considering what devices pair well together. One of the big advantages of AXS over Di2 is its simple integration with other AXS components such as wireless blip shifters, AXS dropper seatposts, and Rockshox Flight Attendant (for those on MTB). At the moment, AXS also offers more configurations for gravel and mountain bikes – so riders can easily create a “mullet” drivetrain with road shifters on the bars and MTB gearing in the rear.

Both AXS and Di2 offer a companion app that allows you to customize the buttons and controls along with update the device firmware to make sure your shifting is performing at its best. The Shimano Di2 app (E-Tube Project), also allows you to adjust the speed of your shifts.  

In most cases, Shimano groupsets tend to be a little lighter than their SRAM “equivalents;” however, Di2 also tends to be a little more expensive than AXS. Though it’s not always the case, in the current road bike lineup from Specialized, Dura-Ace and Red bikes and Ultegra and Force bikes are priced the same. So, the choice there is no longer about price and really just about whether you prefer Di2 or AXS.  

If you read closely, you may have noticed that I am a bit of a Shimano fan. I absolutely love the crisp shifts and the smooth Servo Wave braking. That said, I’ve owned bikes with both Di2 and AXS and enjoyed riding both. If money was not an issue, I would always choose Shimano, however, the integration potential with AXS makes it an attractive option for both gravel and mountain bikes. At the end of the day, the differences are negligible and the ride is really all that matters.