Mechanical vs hydraulic disc brakes – understanding the differences
The two braking systems look broadly familiar and work quite differently but which is best for you?
Off-road braking systems have been a contentious issue in component design for decades. The influence of road cycling has loomed over off-road and adventure riding since the first mountain bikes were ridden in Marin County back in the mid-1970s. And the road bike braking systems that were first employed were woefully inadequate for the demands of steep and loose descents.
In terms of the best brakes for MTB, gravel and adventure riding there's an ongoing debate: mechanical vs hydraulic disc brakes. Let's take a closer look and unpack the differences to help you decide which type is best for you.
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Despite the cantilever brake being a standard for decades, mountain bikers quickly realised that disc brakes offered powerful stopping performance for off-road riding. During mountain biking’s exceptional developmental phase in the 1990s, the first disc brake systems were fitted and regarded with great scepticism.
Most doubters believed mountain bikes weren’t heavy enough or trails extreme enough to warrant disc brakes - but they were wrong. The disc brake now dominates both road and off-road disciplines and with good reason. Disc brakes have superior stopping power, better fade resistance and superior modulation. And they work in wet conditions, where a rim or cantilever brake can become lethally feeble.
As disc-brake actuation has become the standard, two types are currently employed across the spectrum: mechanical and hydraulic. While both systems look broadly familiar, they work quite differently and the cost difference is notable, too.
Vitus Mythique 29 VRS Brakes-22.jpg, by Rachael Gurney
What are mechanical disc brakes?
The first mountain bike disc brake systems were all cable actuated. That meant they used a simple cable tension system to activate the calipers and push those brake pads onto the rotors, creating deceleration. Cable-actuated mechanical disc brakes are simple and hugely reliable. There is very little to go wrong – in theory, but a mechanical system’s cabling is exposed and can fray or stretch with aggressive use.
The most pronounced issue with any mechanical brake system is, that without hydraulic boosting, cable-actuated disc brakes can fade dramatically on long and steep descents. To keep the cable tension and caliper compression operating requires a lot of finger and hand endurance. Most riders lack the hand strength to accomplish that. If you are using all your hand strength and dexterity to pull brakes, there’s less capacity left for tactile feedback through the levers and handlebars. That could mean reduced steering and bike placement confidence.
As frame geometry, suspension technology and tyre design improved over time, mountain bikers ventured down steeper and more technical trails. Riders started discovering the limits of cable-operated disc brakes, which triggered the demand for those first hydraulic systems in the 1990s.
SRAM G2 Guide brakes, by SRAM G2 Guide brakes
What are hydraulic disc brakes?
Hydraulic disc brakes make your finger inputs immensely powerful and the modulation and feedback is far superior to that of the cable-actuated equivalent. The pressurised fluid in the system significantly amplifies your finger pressure and leverage on the brake lever. In fact, for some novice riders, the safest method of discovering how potent a hydraulic disc brake system can be is on a lawn at low speeds.
The tremendous stopping power and fade resistance of hydraulic disc brakes come at a price and we don’t only mean retail. On average, hydraulic disc brakes are two or three times the cost of a mechanical system. And beyond the dearer initial purchase price, compared to mechanical disc brakes, a hydraulic system requires seasonal maintenance, too, adding to the cost of ownership.
Even the best hydraulic brake systems will eventually develop air bubbles or ingest contaminants. That creates a wandering bite point on the brake lever and regressive braking potency over time, especially on those long singletrack descents or steep rocky sections where disc brakes earn their keep.
Pipedream Alice Detail Brakes-10.jpg, by Rachael Gurney
Hydraulic vs mechanical disc brakes - Which is best for you?
Unlike many things in off-road cycling, this is an easy question to answer. To retain the desired performance from your hydraulic disc brake system, it requires seasonal bleeding. And that’s a servicing cost that doesn’t apply to mechanical brakes.
You need hydraulic brakes if you are riding a mountain bike on trails. No question. The margin of safety that hydraulic disc brakes provide, when having to control deceleration rolling into and over technical trail features, are inarguable. There are fewer worse feelings in mountain biking than seeing a technical trail feature or switchback corner approach and suffering finger fatigue while desperately pulling on a mechanical brake system’s levers.
The cost of hydraulic brake system maintenance is unquestionably worth the performance. Suppose you are going to venture for a weekend away in any bike park. Or plan on visiting the Alps for a mountain biking adventure. Hydraulic brakes deliver the fade-free stopping power you need on intimidatingly steep descents.
Another benefit of hydraulic disc braking systems is the lever feedback and bite-point precision. When venturing down unfamiliar and technical trails, a hydraulic disc brake set-up has unmatched lever feel and braking accuracy. That allows you to match deceleration requirements with the terrain surface and available grip.
Merida Silex 9000 Detail Brakes.JPG, by Andy Lloyd
Hydraulic vs mechanical disc brakes - Pros and cons
What is the case for a simpler mechanical system if hydraulic disc brakes are so good? Simplicity and cost. Off-road riders on a budget, or those keen on using their bikes for exploration riding and gravel travel can find great purpose in a cable-operated disc brake system. Gravel bikes, adventure bikes and mild fire road riding are three off-road cycling applications where a cable-operated disc brake system is entirely adequate.
For adventure off-road cyclists, the reliability and simplicity of a mechanical system can be deeply valuable. Trying to source brake bleed kits, hoses, attachments or spares for a hydraulic brake system after a crash or cable snag, can be hugely challenging in rural areas. Suppose you are exploring the specification for that new gravel or off-road adventure bike build. Mechanical disc brakes offer an ideal midpoint between braking power, durability and low future ownership cost, for a robust build that rolls out of the workshop within budget.
There is much to be said for the benefits of hydraulic disc brake modulation, especially when rolling down a treacherously loose gravel road surface, on narrowish tyres. That’s when the sensitivity and adjustability of a hydraulic brake system can be the difference between a confident riding experience and dreaded brake lock-up, triggering potential waywardness and loss of control.
Calibre Dark Peak-6 Brakes.jpg, by Rachael Gurney
Hydraulic vs mechanical disc brakes - How to choose
For riders on a budget or those who want the all-weather deceleration performance of disc brakes, a cable-actuated mechanical system is fine. A mechanical system unquestionably has its place if you are intuitive with your braking modulation and are given to exploring the most isolated of gravel routes and trails. Where spares and servicing back-up, is negligible.
For adventure bike riders, who add many frame bags for multi-day routes, the additional rolling momentum usually justifies hydraulic braking power. In mountain biking, there is no question: hydraulic brakes are a must. The maintenance burden is only once a season, and a hydraulic braking system’s confidence is massive.
A last word on the superiority of hydraulic brakes for challenging trails and hardcore mountain biking. Trail and enduro riders are rolling huge tyres, often sized 29x2.5in and beyond 1,000g in weight. That’s a lot of rotational mass. On steep trails, an abundance of braking power is never a disadvantage and hydraulic brake systems prove their worth with a greater caliper piston count.
Mechanical brakes are single-piston, while most hydraulic brakes are two-piston. Trail and enduro calipers, having four-piston. The benefit of more pistons is better brake-lever-to-pad pressure distribution. This delivers more power and less brake fade by using additional pad material (where those extra pistons are pressuring) for brake actuation.
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