Shimano are introducing a new XTR mountain bike electronic groupset with a Synchro Shift function that allows one lever to control both mechs.

We usually confine ourselves to road cycling here on road.cc (the clue’s in the name), with a bit of cyclocross thrown in to add to the flavour, and don’t often touch mountain biking. We’re telling you about this new technology, though, because we wonder whether Shimano will transfer it over to their road groupsets soon.

The big news if you’re a mountain biker is that Shimano have announced the launch of their first electronic groupset for MTB, XTR Di2 (M9050). XTR is Shimano’s top-level mountain bike groupset, the MTB equivalent of Dura-Ace.

We won’t go into any detail on the electronicness of XTR because Di2 has been around in the road world since the 2009 product year, and the XTR version works on the same E-tube platform as the current road Di2 groupsets.

You’re probably already familiar with the concept, Shimano claiming, “The Di2 platform offers a number of advantages over a regular mechanical system including faster, more accurate and more powerful shifting which remains consistent in all riding conditions.”

The bit that we’re most interested in is Synchro Shift.

“With Synchro Shift enabled, it is possible to control both derailleurs with just one shifter,” say Shimano. “The front derailleur reads the position of the rear derailleur and automatically operates the front shift to position the gears in the most efficient gear and best chain line so the rider never has to worry about front shifting and correction shifts again. Synchro Shift… improves efficiency of shifting and riding.”

Essentially, you just decide whether you want to change up or down, and the Di2 system does the rest automatically. You don’t need to worry about the chainring/sprocket combination, that is all decided for you. If you want to go one gear harder and the most efficient way of achieving that is for you to be in a bigger chainring, the Di2 will move you there.

“Shimano have used all the data from test riding to produce two pre-set [Synchro Shift] shifting maps,” the brand says. “E-tube allows the rider to change these pre-sets and create their own preferred shifting map. While riding it is possible to change between the programmed shifting maps or change back to manual mode.”

Di2 is massively programmable and you don’t have to use Synchro Shift if you don’t want to. The XTR Di2 system has a digital display that indicates the battery level, gear position, shift mode (manual or Synchro) and suspension mode. You can change the shift mode using a button on the display.

Could Shimano transfer the Synchro Shift feature over to the road world? We don’t see why they wouldn’t, especially as it would be so easy to switch off if you didn’t want it.

Most road bikes use a double chainset (with two chainrings) rather than the triple you find on most mountain bikes (XTR Di2 will be in double and triple options), so you might argue that the Synchro Shift wouldn’t be as useful, but it could stop you from using the big sprocket while you’re in the big chainring – cross-chaining.

Imagine your bike is fitted with a 50/34-tooth chainset, for example, and an 11-25 cassette. Synchro Shift would never let you use the big (50-tooth) chainring and the biggest sprocket (the 25-tooth), for example, it would stop you from cross-chaining by putting you into the small chainring (34-tooth) and the 17-tooth sprocket. This would give you exactly the same gear as 50-25, but in a more efficient manner.

Are you wondering what happens if the Synchro Shift system moves the chain to another chainring when you’re not expecting it? You’re riding out of the saddle and want to change up a gear, and the Di2 brain decides the best way to do that involves moving you to a different chainring; how does that feel?

Well, we just don’t know because we’ve not used Synchro Shift yet – no one has outside of Shimano and their test riders. Shimano reckon that XTR Di2 has undergone over 20,000 test kilometres so presumably they’ve thought it all through and are happy with the results, but we have no experience to report.

Way back in 2000, by the way, Shimano bought the patents of former French component manufacturer EGS. One of those patents was for EGS’s Synchro Shift system for mountain bikes. This original Synchro Shift was a twist grip system with a righthand shifter that operated two cables, controlling both the front and the rear mechs.

“The front and rear derailleurs are highly synchronized,” said EGS. “Riders can concentrate on steering without worrying about the best gear to choose, as this is done ‘instinctively’ by the single shifter which selects the most suitable gear and at the same time ensures the best chain line.

“The sequential mode, like a gearbox of the same type, lets you run up and down through the gears, by clicking the shifter forward or backwards depending on the lay of the land. This gear shift technique makes it impossible to make a mistake by getting into the wrong gear.”

Obviously, Shimano’s electronic system bears little resemblance to the original Synchro Shift, but it’s a similar concept and it’s interesting that they’ve chosen to keep the same name.

The new Shimano XTR Di2 will be available from this autumn onwards (assuming it arrives on time). We don’t have prices yet.