09/12/2009
When it comes to equipping a mountain bike, the choice of braking system is paramount. Among the favoured components by many riders and manufacturers alike, Shimano's XT disc brakes, specifically the M8000 series, have garnered significant attention. This particular model often stands out in the mid-price category for its impressive array of performance-oriented features, drawing from Shimano's extensive research and development in higher-end groupsets. As Shimano consistently refines its offerings, the XT line benefits from this trickle-down technology, bringing advanced features to a more accessible price point.
One of the key advantages of the XT M8000 over its Deore counterparts lies in its inclusion of Shimano's premium Ice-Tech features. These are not merely marketing buzzwords; they translate into tangible benefits for the rider, especially during demanding descents. The Ice-Tech system comprises finned, steel-backed sintered brake pads and aluminium-cored rotors. The primary purpose of this design is to manage heat effectively. During prolonged or steep descents, brakes can generate substantial heat, leading to a phenomenon known as 'brake fade,' where performance degrades. The Ice-Tech components are engineered to dissipate this heat more efficiently, thereby preventing inconsistencies and maintaining reliable stopping power even under sustained stress. Our testing confirmed that these features indeed provided confidence on long, challenging descents, with no significant concerns about overheating.
However, no component is without its potential quirks. During our evaluation of the XT M8000 brakes, a recurring issue emerged: a need for bleeding after only a couple of test rides. This was attributed to some peculiar bite point issues. The lever feel was not consistently predictable; at times, the lever would pull uncomfortably close to the handlebar, while on other occasions, it would feel firmer and engage earlier. Despite our best efforts to rectify this through adjustments, the inconsistency persisted. Furthermore, the 'free stroke' adjustment screw on the lever, intended to fine-tune the point at which the pads engage, appeared to make little to no discernible difference in its function. This variability in the bite point meant that riders had to constantly adapt their braking technique during descents, which can be disconcerting when precision is crucial.
The subject of bleeding brings us to another important aspect of Shimano's hydraulic disc brakes: the use of mineral oil. Unlike many other brands that opt for DOT fluids, Shimano's commitment to mineral oil offers a significant advantage in terms of safety and ease of use for home mechanics. Mineral oil is less corrosive and generally considered safer to handle. While you will need Shimano's specifically designed bleed kit, which includes a bleed 'bucket,' some clear tubing, and the mineral oil itself, this can be acquired for a relatively modest sum, often around £10. As we discovered, the bleeding process itself is straightforward once you have the correct tools and a basic understanding of the procedure. This user-friendliness is a definite plus for those who prefer to perform their own maintenance.
In terms of raw power, the XT M8000 brakes proved to be the most potent within their category during our testing. They offered a substantial amount of stopping force, which is undoubtedly a desirable trait for mountain biking. Initially, modulating this power could be somewhat challenging. The sheer force available meant that a delicate touch was required to avoid abrupt stops or locking up the wheels. However, with a bit of practice and adaptation, riders could learn to harness this power effectively, making the most of the braking capabilities. Nevertheless, as mentioned earlier, the variable bite point remained a concern, necessitating constant micro-adjustments during descents to maintain optimal control.
Let's delve deeper into the components and their implications:
Brake Levers (BL-M8000): These levers are designed for ergonomic comfort and precise control. They feature Shimano's Servo Wave action, which provides a quicker bite point and increased leverage throughout the lever stroke. This is intended to offer more power with less effort. The levers are typically made from a combination of aluminium and composite materials for a balance of strength and weight.
Brake Calipers (BR-M8000): The M8000 calipers are generally 2-piston designs, common for cross-country and trail riding. They are engineered to work seamlessly with Shimano's Ice-Tech brake pads and rotors. The caliper design promotes efficient heat dissipation and ensures a secure mounting to the frame and fork.
Brake Pads: As highlighted, the finned Ice-Tech pads (often J04C or similar designations) are a key feature. The fins help to increase the surface area for heat radiation, working in conjunction with the aluminium core of the rotor. The sintered compound offers durability and consistent performance in a wide range of conditions, including wet and muddy environments, though they can sometimes be a bit noisier than organic pads.
Rotors (SM-RT81/SM-RT86): The Ice-Tech rotors, often featuring an aluminium core sandwiched between two steel layers, are crucial for heat management. The aluminium core acts as a heat sink, drawing heat away from the braking surface. This design significantly reduces the risk of brake fade on long descents. Riders can choose between different rotor sizes (e.g., 160mm, 180mm, 203mm) depending on their riding style and the demands of their terrain.
Comparison with Competitors:
When considering the best XT disc brake, it's useful to place it in context with other offerings in the market. While the XT M8000 offers excellent power and the benefits of Ice-Tech at a competitive price, other brands might offer different strengths. For example, SRAM's Guide or G2 series brakes are often praised for their superior modulation and tool-free reach adjustment. However, they might come at a higher price point or use DOT fluid, which some riders prefer to avoid. Brands like Magura offer unique technologies, such as their Carbotecture levers, which can provide a very light yet stiff feel. Ultimately, the 'best' brake often comes down to rider preference, budget, and the specific demands of their riding discipline.
Frequently Asked Questions:
Q1: Are Shimano XT M8000 brakes good for downhill riding?
A1: While the XT M8000 brakes offer significant power and Ice-Tech benefits, they are generally considered more suited for cross-country and trail riding. For aggressive downhill or enduro riding, Shimano's Saint or Zee groupsets, or offerings from other brands specifically designed for gravity riding, might provide more consistent power and heat management under extreme conditions.
Q2: How do I bleed Shimano XT M8000 brakes?
A2: You will need the Shimano bleed kit, clear tubing, and Shimano mineral oil. Attach the tubing to the caliper bleed port and the bleed bucket. Open the bleed port screw, and slowly pump the lever while ensuring the reservoir cap is open. Allow fluid to flow through until bubbles are no longer visible. Close the bleed port screw, then release the lever. Remove the tubing and replace the reservoir cap. Ensure you follow the specific instructions provided with your bleed kit.
Q3: What is the main advantage of Ice-Tech?
A3: The primary advantage of Ice-Tech is significantly improved heat management. This leads to more consistent braking performance, reduced brake fade on long descents, and increased component lifespan.
Q4: Can I use XT M8000 brakes with other brands' rotors or pads?
A4: While you can physically fit rotors and pads from other brands, it is highly recommended to use genuine Shimano Ice-Tech rotors and pads with the XT M8000 system to achieve optimal performance and benefit from the intended heat dissipation technology. Mixing components can lead to unpredictable results and may void warranties.
In conclusion, the Shimano XT M8000 disc brake represents a strong contender in the mid-range market. Its powerful performance, coupled with the crucial Ice-Tech features for heat management, makes it a reliable choice for many mountain bikers. However, potential buyers should be aware of the reported bite point inconsistencies and the need for regular bleeding. For riders who prioritise raw stopping power and are comfortable with occasional maintenance, the XT M8000 offers excellent value and performance. For those who demand absolute consistency and modulation above all else, exploring other options might be worthwhile, but often at a higher cost.
If you want to read more articles similar to Shimano XT Disc Brakes: A Closer Look, you can visit the Brakes category.