One rear brake is enough. Dirt bikers agree on this point. Anything else damages the flow and only leads to knots in the brake line during tricks. Special areas of use require special material and setups. If the area of use is less narrowly defined, you have to think more globally. Since a mountain bike, unlike a dirt bike, can do pretty much anything and, as an all-terrain bike, should be able to cope with any situation, all-round qualities are required. This is especially true for disc brakes. After all, these are safety-relevant components. Everything is conceivable, from a moderate home ride with only a few metres of elevation gain to steep Canary Island trails and mountain pass descents in the Alps.
In order to do justice to this broad spectrum of challenges and also cover extremes, we once again took nine new disc brake models to our demanding test track near Bolzano and to BIKE's own drum test bench. Formula, FSA, Hope, Magura, Shimano and Sram are all represented in this test, some with two new models. Prices range from €151 for the Formula CR3 to €325 for the K-Force from component company FSA, which is breaking new ground in terms of brakes with its debut model. We were particularly excited about the new MT line from Magura. With the MT7, the Swabians sent a powerful four-piston anchor and, on top of that, the renovated MT8 into the test. Also exciting: the two new XTR brakes with Freeza technology from Shimano and the new Sram Guide presented in 2014, which replaces the previous Trail models. The test field is divided into two groups. Five lightweight brakes, each of which we tested with 160 and 180 mm discs. As well as four models for all-mountain to enduro use with 180 mm and 203 mm discs.
Ergonomics is an often underestimated factor that determines whether a brake feels good or not even before the first metre is ridden. The so-called shop test provides information about the brake feel, which ideally underpins confidence in the brake. Is the lever comfortable on the finger? Is the pressure point clearly defined? Does the brake engage early or is the free travel too long? Can the brake levers be adjusted to the size of your hand? As an additional decision-making aid, we therefore specify the lever width adjustment and the free travel of the lever (pressure point position adjustment) in every test report.
Magura has redesigned the lever of the new MT8, which is now much flatter and no longer tapered at the end where the finger rests. A clear improvement. However, the Swabians have lost the ergonomic advantage they gained with the lever width adjustment, which was already criticised last year. The minimum distance between the lever and the handlebars on the MT7 and MT8 is the same as the maximum distance of most competitors. This means that Magura excludes riders with small hands or those who prefer a close lever setting. The lightweight race brake from Hope with its short lever also occupies a special position. The testers liked the clear, firm pressure point. The shape of the brake lever with the only minimally pronounced bend at the end of the lever was less well received. The outer stop is too small, creating the feeling that the finger could easily slip outwards. There is also criticism of the shape of the two Formula brake levers. Due to their round, narrow profile, they offer the finger very little surface area. This is particularly noticeable at high hand force. Overall, we liked the lever ergonomics of the FSA K-Force and the Sram Guide the best.
Braking force and stability are crucial
In addition to ergonomics, controllable braking force and stability contribute to the decisive quality of a brake. In terms of braking power, the new MT generation from Magura really comes up trumps. The four-piston caliper of the MT7 produces the greatest deceleration we have ever measured on our test bench. In practice, this means low manual force and ample reserves with very good modulation. The MT8 is also hardly recognisable compared to last year. As a lightweight brake with a 180 mm disc, it even ranks between the heavier trail brakes in terms of braking force. The Formula CR3 also impresses with its powerful braking force. Its stability is also beyond reproach.
How stable a brake is depends heavily on the rider's weight. To find out the exact limits of a brake, we therefore tested it with three different rider weights (75, 85 and 95 kg). What works fine for a 75-kilo rider can be a total failure with ten kilos more. Brakes react extremely sensitively to weight, which is why we tend to recommend the larger brake disc for more reserves. The weight disadvantage of the larger disc including adapter is on average only 49 grams per brake.
With an average gradient of 20 per cent over 700 metres in altitude, our traditional test track poses tough challenges that pushed many a brake to the limit and revealed weak points in extreme situations. There were defects again this time. Both in the practical and laboratory tests. Once again, the IceTech discs of the two Shimano XTR brakes (from the 85-kilo rider upwards) melted during the stability test, which was accompanied by a subsequent defect in the brake pads. The new IceTech Freeza brake discs with cooling fins on the aluminium core do manage to reduce the pad and disc temperature. However, they cannot prevent the somewhat later onset of failure under extreme loads. The Sram Centreline discs were also still susceptible to heat distortion. They warped under high loads, but ran almost straight again after a cooling phase. Only when unscrewed from the hub did a shielding of the disc become apparent; uncritical, but still worse than the rest of the field, where there were no defects.
We are aware that the average rider will never reach this load in normal low mountain use and therefore most likely will not have to expect any failures. This is one reason why we only devalue the stability of the otherwise functionally flawless brakes. Nevertheless, it is our duty to also test the worst-case scenario, which no manufacturer can or should rule out, as confirmed by a number of cases of damage in practice. After all, a bike is a wide-ranging all-rounder whose territory should be restricted by the brakes as a last resort.
You can find these MTB disc brakes in the BIKE test:
Disc brakes for racing:
- Formula R1 Racing
- FSA K-Force
- Hope Stealth Race X2 Evo
- Magura MT8
- Shimano XTR Race M-9000
Disc brakes for All Mountain/Enduro:
- Formula CR3
- Magura MT7
- Shimano XTR Trail M-9020
- SRAM Guide RSC
You can read this article or the entire issue of BIKE 2/2015 in the BIKE app (iTunes and Google Play) or buy the issue in the DK shop reorder:
