SHORT & SHORT
The Shimano 105 Di2 delivers convincing function and almost perfect ergonomics. The fact that the shifting and braking behaviour is not quite as good as the top groupsets is acceptable for the price, and the difference in weight compared to the Ultegra is also less than expected. The most affordable electric drivetrain to date, the Sram Rival eTap AXS road bike drivetrain, has a strong competitor: In comparison, the Shimano 105 Di2 is ahead in most disciplines.
The Shimano 105 Di2 in the TOUR test
With the New introduction of the Dura-Ace road bike gearstick systems and Ultegra Shimano also fuelled speculation in the summer of 2021: The market leader's two top component groupsets, which characterise the future design and function of road bikes more than almost any other product, now shift exclusively electronically using battery power. Will the mechanically actuated derailleur, which has been around for almost 100 years and is moved by a Bowden cable, become a discontinued model?
At least for road bikes, this question can be answered with the new Shimano 105 Di2 groupset, which was presented in July 2022The answer to this question is probably "yes". This is because the more affordable groupset from the Japanese component giant also relies on switches and actuators instead of levers and manual force to change gears. A mechanical version on the same basis, as was available for the previous generations of electronic Di2 groupsets, is no longer offered for the 105.
Goodbye to mechanical shifting?
Following the switch to disc brakes, Shimano has thus made a further move towards a far-reaching conversion of the road bike within a short space of time. Not everyone is happy about this. The fact that the road bike will be dependent on electrical energy in future and the function of the components will be less transparent is still the lesser evil for many.
The price development, on the other hand, is likely to give many potential customers a stomach ache, as the electronic drivetrains are significantly more expensive than the mechanical ones. Many had hoped that the 105, which has been Shimano's attractive offering for price-conscious road bike enthusiasts for 40 years, would be an uncomplicated and affordable alternative to high-tech technology.
On the other hand, Shimano's actual intention, namely to make the advanced Shimano Di2 technology affordable for less solvent target groups, may well be a successful model. The Shimano 105 Di2 offers the most important key technologies of the professional groupsets: twelve sprockets on the rear wheel, electric shifting, adjustment and other functions via smartphone app and wireless signal transmission.
Our test clarifies how well the groupset performs in comparison to the top Shimano Dura-Ace and Ultegra groupsets - but also in comparison to the main competitor from SRAM, which charges a similar price for the Rival eTap road bike drivetrain. As usual, the design of the 105 components is based on the more expensive groupsets, but unlike before, the surfaces do not look like economy versions. On the contrary: the finely brushed, graphite grey anodised surfaces of the aluminium parts even look more valuable than the matt black of the Shimano Ultegra, which is particularly noticeable on the striking crank.
Positive surprise
The first test ride reveals another positive surprise: for the first time, the levers should fit all hands. Because there is more space between the brake lever and the handlebar arch, even large hands can comfortably grip the lever body in the brake lever position; at the same time, the levers are pleasantly slim and allow even riders with short fingers to get a good grip.
The grip recesses are long and comfortable, the humps offer a fully-fledged grip position further forwards. This is a clear improvement, especially compared to the SRAM groupsets, whose grips appear somewhat clunky and angular in comparison. In addition, the shift buttons on the 105 are clearly distinguishable and provide pleasant feedback.
An innovation in the inner workings are the two button cell batteries, which are located in each grip hump and supply the radio transmitter - Dura-Ace and Ultegra only have one battery per lever. This increases the service life considerably; Shimano already promises up to two years for the Ultegra, which we found to be true after our endurance test of the groupset. (see TOUR 4/2022) seemed entirely plausible.
DisadvantageThe hidden buttons on the grip humps, which on the Dura-Ace and Ultegra can be assigned any function from shifting commands to operating the bike computer, are missing on the 105.
Shimano 105 Di2 - new weight class
The next surprise awaits when the components are weighed: the difference to the Shimano Ultegra Di2 is surprisingly small. There are less than 200 grams between our test groupsets, which is less of a difference than with previous generations. For comparison: The Dura-Ace is a good 300 grams lighter than the Ultegra. And the Rival eTap AXS from SRAM, with a good 150 grams more weight compared to the new 105, has to accept a further point deduction in the duel of low-cost electric drivetrains.
On our extensive test rides, the strange derailleur noise is noticeable on the first climb, which sounds much louder and shriller than the more expensive groupsets, which have recently become much quieter than their predecessors. Is Shimano using the motor from the last Di2 generation for cost reasons? Shimano did not want to confirm this assumption. However, because the motor housing is also visibly larger than that of the Dura-Ace and Ultegra, the suspicion is obvious.
Shimano 105 Di2: The weight comparison
This is not a functional disadvantage; the shifting behaviour is typical for Di2, even under load. Chain jamming, grinding or rattling cannot be provoked even with the wildest manoeuvres. The chain also runs smoothly over the sprockets on the rear wheel. However, the chain known from the Deore MTB groupset, which Shimano includes with the 105, does not have the so-called "Hyperglide+" technology, which is intended to make the shifting processes on the Dura-Ace and Ultegra even faster and more efficient.
The fact that the shifting processes are a little louder and slower as a result can be noticed in direct comparison if you pay attention to it; however, this is not annoying. Compared to the Rival eTap AXS from SRAM, Shimano also scores points here: Because the signals are processed faster in the Di2 environment, the rear derailleur responds to the push of a button with no perceived delay. SRAM's transmission protocol requires a fraction of a second's thinking time.
The brakes on the 105 are also missing an innovation that we were looking for in the Test of the Shimano Dura-Ace and the Ultegra: the Servo Wave technology, in which the braking force increases disproportionately with increasing hand force. This becomes noticeable on steep descents and at high speeds when a lot of braking power is required. The expensive groupsets are then more playful, while the 105 levers require a little more force. Apart from that, the stoppers impress with a pleasant pressure point and flawless modulation, provided that high-quality brake discs are fitted to the bike.
The distance between the pads and discs on the 105 brakes has also been increased, which virtually eliminates the constant grinding that occurs briefly with Shimano discs after heavy braking. Brake mechanics will be pleased that the brakes are now much easier to bleed. With the newly positioned bleed screw, the brake calliper can remain screwed to the frame or fork during servicing.
Shimano 105 Di2 - Gear ratios
The configuration options for the new 105 have been radically streamlined: there is now only one rear derailleur that serves all gear ratios. This makes things much clearer. There are still two crank options, 50/34 and 52/36, as well as two cassettes with 11-34 and 11-36 gradations.
While hardly anyone will miss the professional 53/39 crankset, the mountain-compatible cassettes may be too coarse for cyclists who prefer close-ratio gearing, especially on flat terrain. If you want a finer gear, you will have to choose a more expensive Ultegra cassette. Mixing components within the Di2 environment is fortunately not a problem, with a few rather insignificant exceptions. For example, the Ultegra and Dura-Ace rear derailleurs, which are limited to 34 teeth, cannot accommodate the large 105 cassette; at the front, the 105 front derailleur is limited to a maximum chainring size of 52 teeth.
Older wheels with an eleven-speed freehub can still be used with the new 105. The 105 Di2 is an attractive offer for anyone thinking of switching from a mechanical to an electric drivetrain. Depending on the configuration, the groupset will cost around 1500 euros, around 600 euros less than the Ultegra. The cheapest complete bikes with the 105 are just over 3000 euros.
Competitor SRAM is currently slightly cheaper with the Rival eTap AXS, but the convincing function of the Shimano 105 Di2 seems worth the extra cost. Like the Ultegra, the previous eleven-speed 105 is available as a mechanical version for the time being, and spare parts are also still available. So if you don't (yet) want to shift electrically, you can still delay the change.
New wheels
With the 105 Di2, Shimano is also offering carbon wheels with 105-level aero rims for the first time. They are a modern 21 millimetre wide and suitable for tubeless tyres, and can also be combined with older single-speed drivetrains. Two rim heights are available, the flatter 32 millimetre version should weigh around 1500 grams per set, the 46 millimetre high all-rounders a good 100 grams more. The price for each is 1249 euros.
Jens Klötzer
Editor
