2023-07-22 22:55:19
Direct technological comparison between third level electronic groups
Shimano 105 Di2 R7150 represents the first time the brand has introduced electronic groupset technology to their third-tier road bike groupset.
The brand’s electronic platform was previously reserved for its two best groupsets – Dura-Ace Di2 R9200 and Ultegra Di2 R8100.
The 105 Di2 launch sees Shimano following in the footsteps of SRAM, which launched Rival eTap AXS as its third tier groupset, positioned below Force and Red, in April 2021. Both brands appear to have ditched mechanical options.
Here we will directly compare the characteristics of the two groups.
Wireless vs semi-wireless
Shimano’s 105 Di2 follows its Ultegra and Dura-Ace siblings in being semi-wireless.
This allows the shifters to communicate wirelessly with the rear derailleur, which is the brains of the system. The rear derailleur is wired to the front derailleur and a central battery, usually housed inside the seat post.
We believe Shimano uses the same internal motors in 105 Di2 as Ultegra Di2 and Dura-Ace Di2, but we are awaiting confirmation from the brand.
SRAM’s eTap AXS platform, on the other hand, is completely wireless. The wireless shifters couple to the front and rear derailleurs, both equipped with removable and rechargeable batteries.
SRAM claims that the electronic performance of Rival eTap AXS is identical to that of Force and Red because it uses the same motors, chips and antennas.
Gear
Both the 105 Di2 and the Rival eTap AXS have 12 speeds.
Shimano generally goes for more conventional gear ratios, starting with a smaller 11-tooth cog, but it made some interesting decisions on 105 Di2.
SRAM, alternatively, uses a smaller 10-tooth starter sprocket to provide wider range.
Bottom bracket sizes
The Shimano 105 Di2 crankset is offered in a compact 50/34t and 52/36t format, as is also the case with Ultegra.
There is no longer a 53/39t option and if you want to use a racier 54/40t ratio you will have to look to Dura-Ace.
Rival eTap AXS is available in 48/35t and 46/33t (and 43/30t in Rival Wide). It is not available in 50/37t, which is only an option for Force and Red.
Unlike all Shimano road groupsets, Rival also comes as a single chainring option in a 46 or 40 tooth setup.
SRAM also produces an XPLR gravel version of Rival eTap AXS and its single chainring options range from 38, 40, 42, 44 and 46 teeth.
SRAM’s Rival crankset is all-alloy and uses the brand’s DUB bottom bracket standard.
Cassette sizes
The 105 Di2 and Rival eTap AXS feature 12-speed cassettes, but the brands differ in their ratio methodology.
Shimano’s 105 Di2 differs from Ultegra Di2 and Dura-Ace Di2 in that the cassette sizes offered are from a wider range – 11-34t and 11-36t.
In contrast, Ultegra R8100 and Dura-Ace R9200 are offered in 11-30t and 11-34t. The cage of the 105 R7150 is longer and is only officially compatible with a 34 tooth.
SRAM differs in their methodology by using a smaller 10-tooth cog to provide a greater overall gear range.
The brand uses its own XDR freewheel standard to fix its cassettes, as they are not compatible with an HG freewheel. Rival cassette options include 10-30t and 10-36t.
Shift
Shimano’s 105 Di2 shifter is identical to Ultegra Di2 and Dura-Ace Di2 in form, with its wrapped design. Each shifter contains two separate buttons to operate up and down shifts of the front and rear derailleur.
On its semi-wireless 12-speed groupsets, Shimano claims that forward shifting has been sped up by 45% and reverse shifting by 58%, compared to previous generation Di2 groupsets.
105 Di2 shifters are heavier than Ultegra Di2 and Dura-Ace Di2 because the lever blades are alloy rather than carbon.
SRAM Rival eTap AXS uses identical shifting logic to Force and Red – click the right shift button for a harder gear or the left button for an easier gear, or both together to shift the front derailleur.
Rival controllers have a smaller profile than Force or Red, which may signify the direction future Force and Red controllers will take.
They also forgo the two extra ports to carry extra satellite controllers and the material choice for the blades is aluminum instead of carbon.
Braking
Both the 105 Di2 and the Rival eTap AXS feature disc brake systems modeled following their more expensive counterparts, but with a few features omitted.
Like Ultegra and Dura-Ace, Shimano claims its 105 R7170 disc brakes provide 10% more clearance (compared to previous generation brakes) between the pad and rotor to alleviate any friction.
They also get a separate bleed port, accessible from the side of the caliper, to make bleeding a more intuitive process. They continue to rely on mineral oil of Shimano’s own variety, but lack Servo Wave, a feature found on Ultegra and Dura-Ace.
Servo Wave introduces a non-linear relationship between lever and pad travel, which is believed to improve braking modulation.
The 105 R7170 brakes also feature Shimano’s free-stroke adjustment, which was omitted from the outgoing R7000 series.
SRAM Rival eTap AXS disc brakes use the same two-piece caliper body found on Force and Red and rely on DOT fluid. It differs from its more expensive siblings because it lacks the brand’s Bleeding Edge technology, a specific bleed port that allows for faster and easier bleeding.
There is also no contact point adjustment like on Force or Red, although reach adjustment is retained.
Neither 105 Di2 nor Rival eTap AXS are available in a rim brake setup, unlike their more expensive counterparts.
Connectivity
Shimano continues to use its eTube iOS/Android/Windows app to pair shifters and derailleurs together, as well as customize the shifting arrangement or add third-party devices, such as a Garmin.
SRAM continues to use its AIREA technology which allows shifters and derailleurs to communicate, as well as BLE for smartphone app communication and ANT+ for connectivity to head units.
On Shimano’s eTube and SRAM’s AXS iOS/Android app, you can customize the shift controls to your preference.
Conception
Although appearances are subjective, the 105 Di2 and Rival eTap AXS feature broadly similar design features to their more expensive siblings.
105 Di2 incorporates the same shifter design as Ultegra and Dura-Ace, but loses the auxiliary button on top of the cowls, as well as the ability to install satellite shifters.
The 105 Di2 lever also lacks the ability to accept a Di2 wire, a feature found on Ultegra Di2 and Dura-Ace Di2 if you want to increase your battery life.
Rival, on the other hand, also largely incorporates the design aesthetic of Force and Red, albeit with major revisions to its shifter.
The shifter is less bulbous than Force or Red, as they forgo the two extra ports that would be used for satellite shifters, as well as brake contact point adjustment.
The cowls themselves also differ from Force and Red, with a liner grip pattern that mirrors the texture on the shifter.
Compatibility
Shimano 105 Di2 is compatible with most frames and wheels, as the 12-speed cassette is backwards compatible with existing HG freehub bodies.
Your frame will need to have internal routing between the derailleurs and the seat post or seat tube to house the battery.
SRAM Rival eTap AXS is compatible with more frames than 105 Di2 because it is completely wireless, so it can be run on externally routed frames.
However, you will need to make sure you get wheels with an XDR freehub body, which is less common than Shimano’s HG standard.
Availablity
SRAM’s Rival eTap AXS is available now.
We are awaiting news from Shimano on specific 105 Di2 availability. We expect it to follow Shimano’s usual availability trajectory, where it is initially found on complete bikes, and then it will be available for purchase separately.
Gravel
SRAM’s Rival eTap AXS is also available as a gravel groupset as it comes in an XPLR and Wide option.
XPLR is a gravel-specific groupset with a 10-44t cassette and matching rear derailleur.
Wide is a higher gearing for road and off-road use that uses a smaller ratio on the bottom bracket with a revised front derailleur.
Rival can also be paired with SRAM’s Eagle mountain bike ecosystem, which might be useful for bikepacking or “extreme” gravel riding.
Shimano’s 105 Di2 is not designed specifically for use on gravel and Shimano has its GRX ecosystem for this purpose, which is 11-speed.
Power meters
SRAM Rival eTap AXS has a power meter upgrade option, which is available on the complete crankset as original equipment or it can be upgraded. The Quarq DUB PWR unit offers single-sided power measurement and the battery life is one year.
Shimano hasn’t released a 105-series power meter, but the groupset will likely be supported by third-party power meter manufacturers in due course.
Reading
A complete 105 Di2 groupset would weigh 2995g with a 50/34t crankset, 172.5mm cranks and 11-34t cassette including cables.
In a broadly similar spec (46/33 crankset with unspecified crank length and 10-33 cassette), SRAM’s Rival eTap AXS groupset comes in at 3,109g.
Considering that 105 Di2 relies on a larger internal battery and two Di2 wires, the fact that it is 100g lighter is nothing to sniff at. That said, 100g isn’t a huge difference and unlikely to noticeably affect real-world performance.
Prix
SRAM Rival eTap AXS sells for £1,268 in its 2x road configuration, or £1,470 with a power meter. In its 1x format, it sells for £1,056, or £1,258 with a power meter.
Shimano’s 105 Di2 has an RRP of £1,730/$1,890. European and Australian prices are to be confirmed.
In the past, we’ve found that RRPs don’t always reflect actual prices, which was especially true with Shimano products. However, with the coronavirus pandemic and component shortages, it’s unlikely there will be such a price disparity in the future.
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