Hydraulic mountain bike brakes are amazing, to the point where good brakes are often the most impressive component to new riders when they start riding.
It is nearly impossible to imagine hydraulic mountain bike brakes getting replaced by something even better - but that’s what riders in the early 1990s said when everyone was on cable-actuated brakes. Hydraulic systems were regarded with suspicion as a needless complexity and cost escalation, but now they form the basic underpinnings of the best mountain bike brakes. And that trend might be repeating with ABS.
2023 canyon grand canyonON 9 abs bo.jpg, by Liam Mercer
The natural progression for hydraulic mountain bike brakes is to enhance them with a pulse braking function, enabled by an anti-lock braking system(ABS). The technology is well-established and standardised in the automotive industry and works on the principle of avoiding brake lock-up and skidding, which would increase braking distance. Now, the system is increasingly seen on mountain bikes, as well.
ABS pulses and regulates the brake system’s pressure to optimise the available surface friction (grip) and brake force. The theory is that a rotating wheel, under decelerating force, will stop safer than a locked wheel that is skidding due to lack of traction. ABS can be a lifesaver in wet conditions on a high-friction braking surface, like asphalt. That is why most cycling ABS systems have been targeting commuter and cargo bikes.
Bosch-eBike_Partnership_with_Tektro_eBike_ABS_Press Photo_2.jpg, by Matt Lamy
Are skids useful?
ABS brakes don’t come without issues, especially off-road. There is very little friction when a braking surface is dynamic – wet rock and roots, or loose over hardpack. And that can be problematic.
On a gravel road or muddy trail, some riders might feel it is better to lock up brakes and dig their tyres into the terrain, having them act as land anchors, instead of an ABS allowing wheel rotation. Why? Because an ABS could keep the wheels rotating longer than you’d prefer. It is a peculiar statement, but those braking bumps on the run-in to steep switchback corners might exist for a good reason… Or not.
For years, cycling has been experimenting with the theory of ABS. Shimano and Bosch have ABS installed on their bikes. Over the last decade, batteries have become smaller and more potent, with processors and sensors following a similar trend of nearly exponential improvement. The result is that a mountain bike ABS has more potential in 2023 than it would have had in 2013. Control sensors and the batteries required to activate, actuate and power a mountain bike ABS are now more readily available.
‘Lever feel’ or lock-up addiction?
The question is whether mountain bikers have become too familiar with and tolerant of brake lock-ups. Or at least, brake ‘feel’.
All experienced mountain bikers have experienced coming in too hot and locking the brakes to scrub off speed before a jump, drop, rock garden or switchback. Riders can anticipate brake lock-up by lever feel, across various terrain types, in all weather conditions. Familiarity with the bite point, linearity, and eventual lock-up point of your brakes are all part of the riding experience.
On slippery trail surfaces, ABS could dilute lever feel. With ABS, there is a loss of lever feel when the system is triggered and starts regulating the pressure. This could be an issue for mountain bikers who value a ‘purity’ of trail feedback from their handlebar controls, especially the brake levers.
But why would trail feedback through your brake levers be important? There are two ways of determining the available grip levels when descending a trail: turning and braking. Expert riders establish how much grip is available when leaning the bike aggressively when cornering, but that requires a lot of skill. That’s why the brake lever gives most riders a good reference for trail surface grip levels, as you brake for that first rock garden or switchback.
You’ll hear riders talk about ‘feeling’ their way down a steep and technical trail. And that’s because they are on the brakes, ‘feeling’ for prevailing trail surface grip levels, by interpreting braking feedback. But if riders successfully evolved from the ‘feel’ of cable-actuated brakes to hydraulic, surely the same will happen, with ABS, over time?
E-bikes and ABS
What about e-bikes and advanced braking? E-bikes are heavy and roll down steep terrain at greater speed, potentially requiring enhanced brakes. E-bikes should be the ideal platform for ABS, because the integrated electronics and batteries to power an ABS system are already onboard. But then, wouldn’t e-bikes simply benefit from bigger brake rotors?
The debate about rotor size and ABS is real. Isn’t the solution for better braking to upsize brake rotors? Not quite. Larger brake rotors have better heat dissipation properties and will resist fading, but they don’t make a huge difference regarding the actual brake lock-up point.
Riding the largest possible brake rotors on an e-bike is always advisable to ensure consistent braking performance on a long, steep descent. But upsizing your brake rotors will not dramatically alter the lock-up point or ABS intervention threshold, which is more a function of trail surface friction and tyre grip.
2023 Wilier Urta Max SLR riding, by Wilier
Should you be riding an ABS-equipped mountain bike?
ABS or not, then? There is no question that a locked-up front wheel isn’t great for turning. But some riders occasionally use rear-wheel lock-up to reposition their bike in steep and tight terrain. Trail builders hate hearing a skidding rear wheel, but it’s a feature of braking zones are a universal feature the world over when angling into an off-camber switchback.
An ABS system could be useful for mountain bikes, and specifically, e-bikes. The braking burden is almost entirely on a front wheel in steep terrain. Imagine having the confidence of knowing that a severe front brake lever pull will never result in a front wheel skid?
ABS can serve a confidence purpose for newbie riders, and those who wish to ride a heavy e-bike in steep and technical terrain. But conventional hydraulic brakes might still be superior for advanced mountain bikers, especially those who value trail feedback through their brake levers.
If we reference historical brake technology development in mountain biking, more sophisticated systems have become standardised as costs and complexity reduce with increased volumes. It's still relatively rare to encounter a mountain bike with ABS. But in the late 1990s, it was equally rare to encounter a mountain bike with hydraulic brakes…
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