Shimano unveil new 105 groupset and mechanical STI lever for hydraulic road disc brake

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Shimano unveil new 105 groupset and mechanical STI lever for hydraulic road disc brake

11-speed, four-arm chainset, high-arch brake caliper; mechanical STI for hydraulic road disc brake

Shimano has unveiled the new 11-speed evolution of its mid-range 105 groupset and a mechanical STI lever to complement its hydraulic road disc brake.

The 5800-series 105 groupset includes many features from the Japanese component giant’s flagship Dura-Ace setup, including a four-arm chainset and SILTEC-coated chain.

The new Shimano 105 5800-series groupset, also available in silver (Pic: Shimano)

And the ST-RS685 lever, intended for use with the hydraulic brake launched last year, is billed as a significant step in broadening the appeal of disc braking for road cyclists. It is compatible with existing Dura-Ace and Ultegra groups, as well as the new iteration of 105.

The most notable development of the 5800-series groupset is the move to 11 speeds, but it shares other features with its senior siblings, including a four-arm chainset and specially-treated chain. 

A new high-arch brake caliper to accommodate wider tyres (up to 28c), three 11-speed cassette options, and an STI lever intended to offer easy reach adjustment are among the developments in a groupset expected to reach shops in June.

FC-5800 chainset

The four-arm chainset that made its debut in 2012 with the launch of the top-tier Dura-Ace 9000 groupset, and which last year trickled down to Ultegra, is the most obvious development of the new 105 collection.

Shimano has introduced the four-arm chainset debuted on its top-tier Dura-Ace groupset to the new 5800-series 105 setup (Pic: Shimano)

In addition to an elegant appearance, the chainset offers one bolt circle diameter (BCD) which allows chainrings associated with ‘compact’ and ‘classic’ ratios to be used with the new crank arms. The 5800-series chainset is compatible with 34, 36, 39, 50, 52 and 53-tooth chainrings.

CS-5800 cassette

The headline development for the new 105 groupset is its capacity for 11-speed shifting and Shimano has introduced three cassettes with ratios of 12-25, 11-28, and 11-32, with the intention of delivering smaller steps between shifts to ‘optimise rhythm and cadence control’.

The headline development of the new Shimano 105 groupset is the move to an 11-speed drivetrain (Pic: Shimano)

Eleven-speed drivetrains have been the standard for the flagship Dura-Ace groupset since 2012, and last year saw the introduction of an expanded transmission of the second-tier Ultegra groupset. Shimano believes the introduction of the same technology to 105 will help fulfill its remit as a groupset for everyday riding and longer efforts at weekends.

BR-5800 brake caliper

The new Shimano 105 brake caliper represents a significant development of its predecessor. The Japanese giant has responded to a shift in the tyre market to wider profiles by equipping the 5800-series caliper with a ‘high arch’ to accommodate tyres up to 28c.

Shimano’s new, dual pivot 105 brake caliper is claimed to offer 10 per cent more stopping power than its predecessor (Pic: Shimano)

A dual pivot design is chartered territory for Shimano, even at 105 level, but the new caliper offers what Shimano describes as ‘symmetrical’ braking, applying force equally from either side to yield a claimed 10 per cent increase in stopping power.

ST-5800 shifter

Shimano’s philosophy of introducing ever-more compact shift levers continues with the ST-5800. The company claims increased comfort and control for its new shifter, and offers a further attraction to riders with small hands in the form of reach adjustment via a 10mm screw concealed beneath the lever hood.

The ST-5800 shifter offers reach adjustment via a 10mm screw concealed beneath the lever hood

As well as improved ergonomics, Shimano claims lighter and more precise shifting when the new shifter is used with the 5800-series derailleurs and polymer-coated cables.

ST-RS685 mechanical shift lever for hydraulic disc brake

Last year’s launch of the long-awaited hydraulic disc brake for road bikes saw Shimano offer it alongside an electronic shift lever. The new ST-RS685 offers mechanical shifting courtesy of a revised design in which Shimano’s engineers have managed to install a conventional shift mechanism and a mineral fluid reservoir in the lever.

The new ST-RS685 lever houses a mechanical shift mechanism and a mineral oil reservoir (Pic: Shimano)

Like the ST-5800 shifter, the lever offers 10mm of reach adjustment for riders with small hands and can be used with three of Shimano’s mechanical groupsets, each of which utilise an 11-speed drivetrain: Dura-Ace 9000, Ultegra 6800, and the new 105 5800. It’s expected to reach shops in August.

BR-RS785 hydraulic disc brake caliper and SM-RT99 rotor

The first evolution of the R785 hydraulic disc brake caliper launched last year has followed less than six months later. The BR-RS785 features a minor adjustment to the cable routing, sending it inside the caliper. The R785, which we tested on Mount Etna features a ‘banjo’ routing, with the cable routed outside the caliper. Both options will remain in the range.

Shimano has already updated the road hydraulic disc caliper and rotor (Pic: Shimano)

Further choices have been introduced by Shimano to its hydraulic disc brake range in the form of 140mm and 160mm rotors. Both use the three-layer FREEZA construction of stainless steel and aluminium that has been a feature of the company’s upscale mountain bike brakes, and which Shimano claim reduce braking temperatures by 100 degrees.

WH-RX830 disc-compatible wheelset

Shimano has added a second disc-compatible road wheel to its range after the launch last year of its aluminium RX31 hoop. The new addition – the WH-RX830 – has a carbon laminated construction like the Dura-Ace level RS81 C35 and is tubeless compatible. Spokes are laced in a two-cross pattern front and rear and on both sides of the hub.

Shimano has introduced another disc-specific road wheel to its range: the carbon laminate WH-RX830 (Pic: Shimano)

The broad, 17mm internal profile is in line with the latest thinking on the benefits of wider wheels, while the cup-and-cone hub bearing sees Shimano stick with its favoured system. Another established Shimano technology – the centre lock splined disc mount – is present and correct, and compatible with the new SM-RT99 rotors described above.

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