Shimano 105 goes Di2

It was only a matter of time.

40 years after its introduction, Shimano 105, the component giant’s venerable third-tier road group, is getting arguably its biggest overhaul ever, making the leap from mechanical to electronic, and getting a 12th cog in the cassette for good measure.

105 has always represented excellent shifting performance at an affordable cost, offering trickle down tech from Dura-Ace and Ultegra. As Di2, Shimano’s biggest technology of the 21st century enters its teenage years, electronic shifting tech has finally come down in price enough to be available in Shimano’s key value-performance blend of a groupset.

Related

• SRAM Rival eTap AXS review: A solid electronic group
• Review: Shimano Dura-Ace R9200 refines an already excellent Di2 group

Trickle down tech

This latest electronic evolution of the group has long been expected, especially since SRAM made the leap to electronic only for its Rival 12-speed group a little over a year ago. As was the case with mechanical 11-speed shifting, 105 looks and functions very similarly to its cousins Ultegra and Dura-Ace, enjoying a healthy dose of trickle down tech, just with lower-cost materials and a resulting weight penalty.

As with those two more expensive groups, which were overhauled last year, 105 Di2 — known officially as 105 R7100 — features semi-wireless shifting, where the shifters communicate wirelessly with a single central battery, which is wired into the derailleurs. It’s a system that only requires charging one battery, usually housed in the seatpost, via a cable that plugs into the rear derailleur, instead of individually charging each derailleur battery like on SRAM eTap.

The same Di2 battery has also been borrowed from Ultegra and Dura-Ace for 105, meaning battery life, which has long been a strong selling point of Di2, should be comparable.

One thing that isn’t a direct analog to 12-speed Dura-Ace and Ultegra is shift speed. It’s a bit slower on 105 Di2, but still comparable with the very fast 11-speed Dura-Ace Di2 group, says Shimano. Part of the reason is the use of a Hyperglide chain rather than the latest Hyperglide+ (not all the latest tech trickles down).

Gearing options

Because 105 is geared toward a more entry level or enthusiast-level consumer, the gear ratios available on the group feature a wider range with better climbing gears. Cassette options include both 11-34T and 11-36T, while the crankset will be a 50/34T at launch, with a 52/36T option to follow. That means a sub 1:1 climbing gear is possible. For comparison, Ultegra has a 11-30T casssette available in addition to an 11-34T, while Dura-Ace has both of those in addition to a 11-28T cassette.

Ultegra and Dura-Ace both offer the same two crankset options as 105, with a 54/40T also available for Dura-Ace. The cranks are available in 160mm, 165mm, 170mm, 172.5mm, and 175mm.

And as with 12-speed Dura-Ace and Ultegra, Shimano has stuck with 11 teeth for the lowest cog.  For comparison, SRAM has moved to a 10-tooth cog, and Campagnolo even a nine-tooth cog for its Ekar group, providing both groups a bigger sprint gear, which means the chainrings can shrink proportionately and still provide a wide gear ratio for sprints and descents. Shrinking the cog is not without its drawbacks, however.

Part of the decision behind not shrinking the sprint gear has to do with the higher efficiencies of a bigger cog — the same reason why aftermarket derailleur pulley wheels get so big. But the decision to stick with 11 teeth also provides the added benefit of backwards compatibility with previous freehubs, which means your current wheels will work just fine with the new group. 

Speaking of inter-compatibility, 105 Di2 can be used with 12-speed Ultegra and Dura-Ace parts, within certain restraints around derailleur compatibility. The 105 11-36T cassette can’t be used with the shorter rear deraillaur cage of Ultegra and Dura-Ace, and the 105 Di2 front derailleur also has a max chainring size of 52, so 54-40T Dura-Ace chainrings won’t work on 105.

Improved Brakes

While people will choose 105 based largely, or even solely, on its shifting performance, the Di2 version has also gotten some improvement to its brakes. One of the driving forces behind the switch to disc brakes over the past several years has been better braking, and Shimano says it has managed to make its already excellent hydraulic braking even better, once again borrowing tech from the latest Dura-Ace and Ultegra groups.

The brake pads now have a faster initial contact with the rotor, and then continue to engage over a wider time period, increasing control. Shimano achieves that even while adding a 10% wider pad-to-rotor clearance, meaning it’s quieter too. Anyone who bleeds their own brakes will also appreciate that this process is now easier because the new calipers don’t need to be removed from the frame during the process.

The brake hoods have also been updated to the same shape as 12-speed Dura-Ace and Ultegra, with a raised hood, more ergonomic shape, and a different brake lever shape for more control over stopping. However, the 105 hoods do not have extra ports to attach satellite shifters.

The 105 version also features a second coin cell battery to power the brake hoods, providing about three-years of battery life. Shimano added a second battery for ease of maintenance — more battery life means less frequent battery changes at a very modest weight penalty.

Another important brake detail: while this will no doubt disappoint some people, 105 Di2 is disc-brake only.

Pricing

Shimano 105’s reason to exist is to provide value — great shifting at a reasonable cost. The shift to electronic definitely brings the price up with it. 

A full build at retail pricing is $1,887, compared to $1,140 for 11-speed mechanical 105. The caveat is that many people who will ride 105 will do so as part of a pre-built bike, and manufacturers negotiate cheaper OEM pricing, so many riders won’t see quite that high of a price reflected in the overall build. Regardless, it does reflect climbing costs of what has traditionally been a group available on bikes in the mid-$1,000 to low-$2,000 range. For example, an alloy road bike like the latest Specialized Allez with SRAM Rival AXS has climbed to $3,000. It’s a trend that could easily price entry level riders and those on a budget out of the sport.

For comparison, SRAM Rival AXS costs about $1,400 for a 2x version without a power meter.

Full pricing spec:

Weight

As seen on the previous chart, the claimed weight for a full build is about 3,068 grams, a slight penalty over 11-speed mechanical at 2,978g, but pretty close especially when you consider the extra cog and battery on the Di2 version. That has SRAM Rival (3,202g for 2x) beat, and comes impressively close to the second tier Force AXS group (2,979 grams for 2x).

Compared to 12-speed Ultegra and Dura-Ace, the weight differences are a little bigger, with the former coming in at 2,691g and the latter at 2,438g.

E-TUBE PROJECT app

The E-TUBE PROJECT app Shimano created alongside its 12-speed Di2 groups to program them also works with 105 Di2. The app allows riders to change shift speed, the number of shifts per shifter button press, and more, without the cumbersome desktop software required on 11-speed Di2 groups. 

New wheels

The 105 level of components is more than a groupset. In addition to the new groupset, Shimano has unveiled two new road wheelsets that represent its lowest cost carbon wheels ever, the C32 climbing set and C46 all-around set. The C32 has a 32mm rim profile, 21mm internal rim width, and claimed weight of 1,502g. The C46 has a 46mm rim depth, 21mm internal rim width, and a claimed weight of 1,610g. 

Each set is tubeless ready, compatible with both 11-speed and 12-speed cassettes, and costs $1,050.