Test 2015: Road bikes with disc brakes - 12 mid-range road bikes with disc brakes on test

That was quick: The selection of road bikes with hydraulic disc brakes has increased rapidly within a year - there are not only significantly more bikes, but also more different and cheaper ones. As a reminder: In our first test (see TOUR 6/2014), technology on road bikes was still a novelty. There were only a good handful of bikes and actually only one functioning brake - the BR-RS 785 from Shimano, which in turn could only be combined with the Di2 electronic shifting system. This made the new technology expensive. The models tested at the time cost between 4,000 and 8,000 euros. But it was foreseeable that this would change quickly. Competitor SRAM intensively revised the recently recalled disc brakes of the top Red groupset and now offers a whole range of hydraulic disc brakes, which are available at significantly lower prices in the Rival and Force groupsets. Shimano is now also combining hydraulic discs with mechanical shifting: The hydro levers with the designation ST-R 685 are at Ultegra level and are predominantly combined with this shifting system by bike manufacturers.

We tested these mid-range racers (you can find the entire article as a PDF download below):

- Bulls Alpine Hawk
- Cannondale Synapse Carbon Ultimate Disc
- Felt Z4 Disc
- Focus Cayo 4.0
- Giant Defy Advanced
- Haibike Challenge XR Pro
- Merida Ride Disc 7000
- Rose Xeon CDX 4400
- Simplon Inissio Granfondo
- Specialized Tarmac Pro Disc Race
- Stevens Arcalis Disc Ultegra
- Trek Domane 6.2 Disc

Our current test brings together twelve bikes that are likely to interest significantly more cyclists than the expensive pioneers. The actual range is much larger, as many of the bikes are available in several equipment variants, and some large manufacturers such as Specialized or Cannondale have even more disc models in their range. The variety is good in two ways: on the one hand, it increases the likelihood of finding the ideal bike. On the other hand, the larger range puts pressure on prices.

New findings

Our specification for the test invitation was: mid-range bikes with hydraulic disc brakes and mechanical gears. Technically, all bikes fulfil this specification, but it is astonishing how far some manufacturers stretch the term "mid-range": The bikes in the test cost between €2,400 and €5,300. Insight one: The entry into disc brake pleasure is now available at - relatively - low prices. Felt and Focus put fairly priced racers on their bikes for € 2,400 and € 2,500 respectively. The Rival component group from SRAM makes it possible - the third series from the American manufacturer offers everything a modern road bike drivetrain needs with 22 gears and many gear ratio variants; there is no noticeable difference in braking behaviour compared to the top groupsets. The Rival is roughly on a par with Shimano's 105, but you won't find these parts on bikes with hydraulic discs. Bikes with Shimano's Ultegra, on the other hand, are several hundred euros more expensive, with the cheapest test bike from Stevens costing € 2,700. Insight two: So-called premium brands are considerably more expensive. Without question, Trek and Specialized offer fine bikes that are above average in many respects; Trek, for example, a pioneering comfort frame, Specialized very good wheels, saddle and handlebars as well as low weight. However, in view of comparable shifting and braking components, the prices of € 4,800 (Trek) and € 5,300 (Specialized) are still difficult to negotiate.

The conceptual diversity of the bikes is pleasing: the spectrum ranges from distinctive comfort geometries from Trek and Merida to racy sports bikes such as Specialized or Focus, with many all-rounders in between. Many manufacturers design their disc racers to be particularly suitable for touring and enable a wide range of uses; mudguards and wide tyres can be fitted to models with a more upright, comfortable riding position. Simplon's Inissio is an all-rounder that can also be fitted with off-road tyres, while Stevens offers a bike with an aerodynamically optimised frame. The development is therefore not limited to one type of bike.

With the disc brake, the thru-axle is also on the rise, only half of the framesets in the test still have classic quick-releases. This can cause the discs to rub against the pads after hard braking if the lever is not closed tightly enough. The thru-axle eliminates such problems; handling is just as simple, but takes a few seconds longer. Focus offers a smart quick-release system that secures the axle with a single twist. Shimano introduces a new mounting standard for the brake bodies, which can be seen on the Rose and Simplon. In the direct mount version, the threads are located in the fork and chainstay, which makes it easier to manufacture the framesets, but requires a separate adapter. As much development work goes into the frames, sometimes it's the little things that get in the way: Since hydraulic brake lines are not under tension like a normal brake, they sometimes rattle annoyingly in the tube on bumps - we particularly noticed this with Rose, Trek and Giant.

Something rattles

There is no general answer as to which brake is better. The Shimano brakes can be operated more sensitively with less manual force, are slightly easier to modulate and the pressure point is clearer. But there is no advantage without a disadvantage: the levers tend to rattle as the preload is low. This does not happen with SRAM levers, but they require a little more hand force and the pressure point is not quite as defined. However, once the brake is applied, there is plenty of braking power. With Shimano, the braking behaviour depends heavily on the disc used. While SRAM only allows discs with a diameter of 160 millimetres for road bikes (140 millimetres are only available for crossers), Shimano leaves the configuration entirely up to the bike manufacturer: there are three qualities of brake discs in two sizes each and four types of pads to choose from; each combination responds differently, develops different braking power and withstands different loads.

Our endurance test last year showed that Shimano discs on road bikes tend to be undersized, which can be dangerous: 140 mm discs with an aluminium core are too small in the mountains in our opinion, but this is the usual configuration recommended by Shimano. Even the 160-millimetre disc failed in our practical test on a steep descent with a system weight of 100 kilos because the aluminium core of the brake disc melted under the heat of an emergency stop (see TOUR 6/2014 and Video). There are no corresponding instructions from the manufacturer.

There are hardly any arguments in favour of the small discs. The weight advantage per disc is an irrelevant 20 grams. Aerodynamic disadvantages are also not an issue with the less race-orientated alignment of most wheels. That leaves the appearance. But a disc road bike deviates greatly from classic visual habits anyway, so why keep the diameter small at the expense of safety? Two examples from our test show how different the braking behaviour can be: The 140-millimetre steel disc fitted to the Giant barely reaches the level of modern rim brakes, and the annoying squealing is only a side issue. With IceTech discs, whose braking surface is subsequently machined, the response behaviour is already better. With 160 millimetre discs, braking performance also improves significantly - a configuration that we can recommend in good conscience for riders up to 85 kilograms for all purposes. Bulls even gives the same brake a 180 millimetre disc from the mountain bike, which results in a completely different, much more direct response and much higher braking forces - even for full braking, the index finger is sufficient here. Although this combination is not intended by Shimano, it is also not prohibited - after all, the BR-R 785 is "only" a modified XT mountain bike brake. We would recommend this combination for heavy riders and touring cyclists, as the large disc is more stable under high demands - and weighs less than 40 grams more. The problem, however, is that a 180 mm disc fits through the fork on very few bikes.

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