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SHIFT 105 Di2February Offer
With Shimano, SRAM and Campagnolo now all offering you 12-speed electronic shifting, the choice of top tier groupsets for your road bike has never been larger. But which one should you choose? We’ve run through what SRAM and Shimano have to offer and picked a winner.
But it’s not just Shimano that sells 12-speed electronic shifting, with SRAM Red eTap AXS pitched at a similar level to Dura-Ace and Force eTap AXS being SRAM’s equivalent of Ultegra. SRAM pitches 12-speed electronic shifting at a lower price point too with the Rival eTap AXS groupset.
So let’s look at what each brand has to offer. We’ve not covered Campagnolo here, as its electronic offering is now limited to the very expensive Super Record EPS, which probably won’t be an option shortlisted by many riders.
The cassettes on SRAM’s 12-speed groupsets start off with a 10-tooth smallest sprocket and there are options going up as large as 36 teeth. SRAM pairs that up with smaller chainrings, so that you get similar top end range to conventional compact, semi-compact and standard chainsets with 11-tooth smallest sprockets, but the option to go down below 1:1 when paired with SRAM’s 46/33 tooth chainset. SRAM calls this its X-Range gearing and one aim is to give you a wider range on the large chainring so you don’t have to make as many front changes, with their tendency to reduce momentum.
In contrast, Shimano has stuck with an 11-tooth smallest sprocket and traditional compact and semi-compact chainring sizes, although its standard chainset is now 54/40t for even higher gearing. Its cassettes go out to 34 teeth maximum.
So SRAM gives you wider gear range options and at present it’s got more cassette options too.
SRAM X Range
There are disadvantages to SRAM’s configuration though. Drivetrain efficiency decreases as sprockets get smaller, mainly due to the larger angle through which the chain’s links need to turn. This isn’t linear, so there’s significantly more friction passing over a 10-tooth sprocket than an 11-tooth one. Measurements by component maker Silca suggest that there’s around 0.5 watts extra frictional loss with a 10-tooth sprocket. With fewer teeth engaged with the chain there’s greater wear on the components too.
SRAM says that it’s engineered its 12-speed groupsets so that frictional loss is similar to its older 11-speed ones with an 11-tooth smallest sprocket and that it’s used materials that up the longevity of its components, but it’s still something to bear in mind.
It’s also worth thinking about whether you are going to end up with little-used lower ratios on the small chainring if you’re riding on tarmac; for most reasonably fit road cyclists over most terrain the 1:1 lowest ratio offered by Shimano is likely to be adequate. SRAM pitches its 12-speed groupsets at gravel riders too, where you might need an ultra-low gear, although Shimano offers this as well with its GRX gravel groupsets.
So although SRAM is giving you more gearing options, for lower wear and friction in the highest gear ratios, it’s:
Shimano’s levers have always been miracles of miniaturisation, fitting a lot of electronics (or, for its mechanical groupsets, the cable ratchet mechanism) into a very compact lever body, alongside the hydraulic mechanisms for its disc brakes.
It’s actually made the latest 12-speed levers a little larger than its older levers, hitting the sweet spot between plenty of hood area to rest your hands on, while being small enough for those with smaller hands to grasp. The extra size also means than it’s been able to separate the up and down shifters a little more, reducing the risk of mis-shifting with its 11-speed Di2 shift levers.
In contrast, SRAM’s levers are a little larger still than Shimano’s, making them a little ungainly. On the plus side, SRAM’s single shift lever each side means that there’s no risk of a mis-shift from hitting the wrong shift button, although you can still trigger an unwanted front shift by hitting both levers together. We still reckon that Shimano’s levers are neater though.
Shimano’s 11-speed Di2 groupsets already set the mark for shift speed and that’s only increased with the introduction of the latest 12-speed Dura-Ace and Ultegra groupsets. In fact, Shimano claims that they’re 58 per cent faster at the rear and 45 per cent faster at the front than its previous models.
That significantly outclasses SRAM’s shifting, which is good but doesn’t quite give you those razor-sharp shifts of Shimano. Shimano’s front shifting in particular feels very rapid and surefooted, which is particularly welcome as front shifts tend to be the most critical to get right to avoid losing momentum. Shimano even lets you slow down shift speed via its e-Tube app if you find it’s too fast, whereas with SRAM shift speed is not configurable.
Shimano’s shift quality has always been top-notch and that carries forward to its 12-speed groupsets. In fact, the Hyperglide+ engineering transferred over from its 12-speed MTB groupsets has improved it, with Shimano saying that the ramp pattern on its 12-speed cassettes, paired with its specially designed chain and faster-acting derailleur mechanisms, contributes to its more precise shifting.
Shift quality is an area where SRAM still lags, which is particularly noticeable when you select synchronised shifting. Whereas Shimano’s front mech auto-trims as you move up the cassette towards lower gears, SRAM relies on its yaw cage, which is angled slightly on the derailleur mechanism, to alleviate chain rub on the front mech. By the time you get to the eleventh sprocket there’s significant chain rub, but this is the point at which the automatic shift from the large to the small chainring takes place and with AXS this isn’t configurable.
Rather like electric cars, whether your battery will last out is a worry for users of electronic groupsets. It’s no fun trying to ride home if your front mech has given up, although it does give you a good spin session.
It’s the front mech that stops shifting first if your Shimano battery is low on charge. If your SRAM rear mech battery is drained you can stop and swap it for the front derailleur battery, so again you’ll only have a working rear mech.
An advantage of Shimano’s wired configuration over SRAM’s separate batteries in its derailleurs is that Shimano’s internal battery has a higher capacity and longer battery life; whereas SRAM’s batteries will last for around 60 hours of riding each, Shimano says that its battery will power your shifters for around 1000km.
On the other hand, it’s easier to recharge SRAM’s batteries as you just unclip them from the mechs and put them in the USB charging cradle. With Shimano you’ll need to park your bike near a power outlet and hook up the rear mech to charge it up. Shimano does give you an extra-long charging cable though.
Shimano has made some big leaps forward in configurability with its latest 12-speed groupsets. It used to be that you needed to wire the bike up to a computer and use the rather clunky PC-based eTube app to make any configuration changes. The alternative was to buy a separate D-Fly wireless unit and wire it into your Di2 system - most bikes didn’t come with this included and the shift of many high spec bikes to internal wiring made it awkward to find somewhere to place it.
Shimano now matches SRAM AXS though, with a Bluetooth antenna built into the rear mech that gives you a wireless connection to its smartphone app.
There’s a bit more you can do with the Shimano eTube app than with the SRAM AXS app. That includes changing shift points with synchronised shifting and altering the speed of shifting as well as reprogramming the third shifter button on each lever to operate other electronics.
Both Shimano and SRAM offer brake lever reach and bite point adjustment, so you can get a disc brake set-up that suits you. Shimano now includes its Servo Wave tech in its road brakes, which gives a non-linear response to the lever pull. This makes it easier to feather the brakes, while still offering the brake’s full power further into the lever stroke.
Shimano’s brake pads now retract 10 per cent further than with its older models too. Coupled with low thermal distortion brake rotors shared with its MTB groupsets, this helps reduce the potential for irritating brake rub when the brakes get hot.
Note too that both brands give you a cable-operated rim brake option.
Despite the larger chainsets used by Shimano, its groupsets remain slightly lighter than SRAM’s at each level. Precise weights are tricky due to there being so many different configuration options, but a Shimano Dura-Ace groupset has a quoted weight of 2438g as against SRAM Red eTap AXS at 2518g.
Ultegra R8100 comes in at 2716g versus 2979g for Force eTap AXS while an equivalent Rival 12-speed groupset will weigh around 3,205g, according to Cycling Weekly.
At the top of the groupset tree, Shimano Dura-Ace is slightly cheaper than SRAM Red eTap AXS and that price differential carries on down to Ultegra, which undercuts SRAM Force eTap AXS. That’s true whether you go for a power meter chainset or the unmetered options.
SRAM’s third tier Rival eTap AXS undercuts Ultegra though. The electronics are the same as in Red and Force, although you sacrifice a little functionality, like the option to add satellite shifters, and there’s more steel in evidence which ups Rival’s weight. If you want a power meter, Rival’s is single sided only. But Rival eTap AXS does give riders the most affordable entry point into electronic shifting.
Both SRAM and Shimano 12-speed groupsets provide versatile, high quality shifting. SRAM gives you more gearing options than Shimano including wider range and single ring compatibility. That’s particularly useful if you’re looking to take on gravel (for which Shimano has its 11-speed and 10-speed GRX groupsets) or want a pared down rig for flat time trials.But for the general road rider, we reckon that Shimano wins out over SRAM with its slicker shifting, longer range between charges and greater configurability. There are options with adequate gear range for the majority of road riders too. That’s why we spec Shimano groupsets on our road bike range and Shimano GRX on our adventure bikes.
You compare the battery life of the two systems in different scales: time for Sram and distance for Shimano. The conclusion is drawn that Shimano has the advantage here, but Sram’s 60 hours riding at a conservative 25km/h would yield 1500km.
Couple this with the fact that with one flat Sram battery the rider can choose which derailleur to keep functioning, and it’s easy to have a spare on hand.
I’m a Shimano aficionado, but in this case it seems to be advantage Sram.
Thank you for breaking down the differences in and unbiased manner. I’m looking at buying a new road bike for 2023 in a mid-upper trim level which come with either Ultegra Di2 12 speed or the SRAM Force eTap AXS 12 speed group set. I appreciate you taking the time to break down the advantages and disadvantages of each set. My current bike has Ultegra Di2 11 speed which I am very happy with so I had a pre-disposition to the 12 speed Ultegra. Your evaluation has helped with my decision to opt for the Shimano Ultegra Di2 even if it simply re-enforced my preference. Thanks again.
A friend has the SRAM Force Groupset and she does a lot of miles on Zwift. She has already worn out one SRAM Cassette and aside from being expensive to replace they are almost impossible to get hold of in the UK, or were at the point she needed one. She was lucky as a friend had a spare he gave her. A load of us had a discussion about the various wear rates of Shimano and SRAM Cassettes and the view was based on evidence from riders who used both Brands that SRAM wears out quicker. Would have been useful to have this in the article because the price and longevity of the item needs to be considered. I was looking to buy a SRAM Groupset equipped bike but have changed my mind having discovered the wear rate of SRAM Cassettes