The Bike List

Groupsets: Shimano Ultegra Di2 (electronic) 6870, 22 gears

Shimano Ultegra Di2 is an electronic version of Ultegra. Despite being two distinct groupsets, they both share a number of components including the cassette, chain, chainset and brakes. The three components that make Ultegra Di2 different to standard Ultegra are the shifter/brake levers and the front and the rear derailleur which are all connected via electronic cables that typically run through the frame. Frames must be Di2-compatible, meaning that Ultegra Di2 can not be fitted to just any bike, like mechanical groupsets can.

Although Shimano first released its top-end Dura-Ace electronic groupset back in 2008, the first 10-speed Ultegra Di2 (6770) version wasn't released until June 2011. The more recent upgrade to 11-speed (6870) gearing happened in June 2013 and the electronic gearing is generally seen as an upgrade over mechanical, partly because the retail price is around 15% higher. Shimano's Ultegra Di2 groupset is common on road and triathlon bikes and is also found occasionally on cyclocross bikes between £2100 and £7000. Ultegra Di2 is twice as expensive to buy aftermarket and this is partly the reason it only begins to appear on bikes at around the £2200 mark as opposed to mechanical Ultegra which can be found on bikes just under the £1000 mark.

The dual-control integrated brake and gear levers allow you to operate both brakes and gears from the same position on the handlebars in the same way you can with Shimano's mechanical equivalent. The significant difference being that to shift down a gear (to a harder gear on the rear for example) you simply press the smooth button located behind the brake lever. To shift up a gear (to an easier gear on the rear) requires a simple press of the pimpled button also located behind the brake lever. Compared to a mechanical groupset, the effort required to change gear is significantly less and is closer to the click of a mouse button in terms of feel. Changing gear on the front derailleur works in the same way as on the rear, however, pressing the pimpled button makes the gear harder and the smooth button makes the gear easier. Like any new gearing system, electronic gearing can take a while to get accustomed to but we've found the gear changes to be snappy and exceptionally reliable. Both Shimano's top-end Dura-Ace Di2 and Ultegra Di2 groupsets offer an auto-trim function which means chain rub, typically caused when the chain is at extremes (eg. large cog on the rear and large chainring on the front) is no longer an issue as the chain guide moves automatically in response to the position of the rear derailleur. The reach is also adjustable those with smaller hands and does not require the use of plastic shims as on Tiagra and lower groupsets.

Compared with the first version of Ultegra Di2 (6770), the new Ultegra Di2 6870 derailleurs are more compact and lighter and the shifters have improved ergonomics with slimmer hoods, and improved button shapes and designs. Whilst the front derailleur remains a little bulky the rear derailleur is noticeably smaller than the first iteration and almost looks the same as the mechanical version. The newest Ultegra Di2 rear derailleur also features an automatic protection system that moves the cage out of harm's way in case of a crash. The rear derailleur is available in two versions: the SS for cassettes up to 28-tooth, and the GS for cassettes up to 32-tooth which, when combined with a compact crank, offers the same wide gearing that is available on Shimano's 11-speed 105 group below. Battery range is between 1000 and 2000 kilometres depending on conditions and how much the front derailleur is used (as this uses the most charge). The majority of the materials used throughout are a combination of aluminium and steel. Ultegra also features carbon-fibre-bodied pedals as well as carbon-fibre brake/gear levers.

Unlike their mechanical counterparts, electronic shifters offer a greater degree of flexibility and can be programmed to offer different shifting options. The rear derailleur, for example, features 'multi-shifting' where a single press and hold of the shift button will move the rear derailleur all the way up or down the cassette. Shifting can also be fine-tuned to increase or decrease the speed of shifting. The time trial shifters (ST-6871) offer arguably the best case for electronic shifting yet, as they allow riders to shifts gears whilst braking, creating a safer and more efficient riding position. Shimano claim that the Ultegra electronic time trial shifters offer the same braking power as their top-of-the-range Dura-Ace units, making them a much more affordable choice with little performance difference.

Shimano Ultegra Di2 is a performance groupset, offering race-level performance for those who need it, but it is equally at home on road bikes that will never see a race. Improvements from Shimano's top end Dura-Ace Di2 groupset have filtered down to Ultegra Di2 and as such they both share a number of technologies, with the differentiating factor usually being that Dura-Ace is lighter, although typically twice the price. For the majority of competitive and non-competitive road cyclists, Shimano Ultegra Di2 is an excellent choice. Being a performance groupset Ultegra doesn't feature a gear indicator as found on Tiagra and lower grouspets.

Strengths: Performance that rivals top-end Dura-Ace Di2 at half the price, great choice for racing but equally at home on a day-long road ride. Super-wide gear range available with 22 gears on offer, four-arm chainset design offers standard road double, semi-compact and compact chairing options, upwards-compatible with Dura-Ace Di2. Self-adjusting gears eliminating chain rub and gear cables that don't degrade with use. The relatively slim grips offer reach adjustment and click-shifting that requires no side movement and is ideal for smaller hands whilst also offering increased usability in cold conditions or when exhausted. Additional satellite shifters can be used to allow shifting from multiple positions on the handlebars. Time trial shifters allow for gear changes whilst braking improving efficiency and safety. Battery range is between 1000 and 2000 kilometres depending on conditions.

Weaknesses: Heavier than Dura-Ace, requires 11-speed rear hub so could also require a wheel upgrade. If battery runs out or fails you could be stuck with just one gear.

Price bracket of bikes that feature Ultegra: £2100 to £7000

Chainsets available: Compact (50-34), Semi-Compact (52-36) and Standard Road Double (53-39)

Colour: Gun metal grey

How many road bikes on The Bike List feature Ultegra components or groupset? 5% of all road/racing bikes.

Cost to buy Ultegra 6870 Di2 aftermarket components:

  • Road 11-speed STI brake/gear levers (ST-6870): £250 (313g)
  • Or STI Time Trial/Tri bar (ST-6871): £250 (142g)
  • Chainset: double/compact £190 (HollowTech II)
  • Road brake calipers (rim brake): £50-£60 each
  • Brake caliper (hydraulic road disc brake without rotor): £50
  • Brake caliper (mechanical cyclocross/road disc brake without rotor): £50
  • Front derailleur: £170 (braze-on type; 155g)
  • Rear derailleur: £175-£180 (SS-250g, GS-260g)
  • Hubs: front £45, rear £85
  • Cassette (CS-5800): £55-£60
  • Bottom bracket: £22 (HollowTech II)
  • Chain: £28 (CN-6800)
  • Pedals (road) SPD-SL: £110 (carbon body), 260g per pair
  • Wheelset, clincher (tubeless): front £155 /700g, rear £175/940g (tyres 19-25mm); 1640g for the pair excluding tyres, tubes and cassette.

Total cost of parts listed above, excluding disc brakes but including wheels: RRP £1560-£1590 (rim brake calliper x2); £1120-£1150 excluding wheels; available online from £950 including battery, charger and with rim brakes, but excluding pedals and wheels.

Click here to see all bikes that feature a Shimano Ultegra Di2 6870 groupset or parts.

Next groupset up: Shimano Dura-Ace mechanical (9000 series) or Dura-Ace Di2 electronic (9070 series)