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This question is valid for both mechanical and hydraulic brake systems.


Premises:

  • The human hand has a threshold value for what a comfortable level of squeezing force is, and one cannot comfortably reach this threshold repeatedly. (See Chris' excellent comment below.)
  • The brake system is not externally powered.
  • The usual laws of physics are being obeyed.

I am not understanding how some brakes can be unequivocally better than others. One always needs to balance power, lever force, lever freestroke, and pad clearance.

Fundamentally, brakes can be modeled as a simple lever. One causes a relatively large but weak movement at the lever, which triggers a small but forceful movement at the caliper. Hence, more brake power almost certainly is at the expense of caliper movement (which allows for some level of rotor/rim runout to avoid rubbing). A brake setup with larger pad clearances is either going to be weak, or have large lever throw. There's no free lunch.

For instance, the Shimano Saint and Zee downhill-oriented hydraulic brakes use a greater leverage ratio in the levers to create more power (which could be defined as the clamping force). The tradeoff for this reduced proportion of pad movement is their noticeably longer freestroke, i.e. how far one must pull the lever until the brake engages. Conversely, most SRAM hydraulic brakes use a "normal" freestroke and a generous pad clearance, which results in their characteristically mild power.

Of course, there are many factors involved, such as dual-pivot rim brakes, Shimano's "Servo-Wave" and SRAM's "Swinglink" variable-leverage designs, pivot bearings, two- versus four-piston hydraulic calipers, or even plain old manufacturing quality. These help overall, but on a level playing field where every brake incorporates some of these features, I don't see how any one brand's implementation clearly outshines the rest.

I suppose the root question I have is "How can $900 Trickstuff (or other premium manufacturer's) brakes be worth that price when they have to balance the exact same physical factors as $200 brakes from Shimano et al?" The high-end brakes are reportedly better than cheaper ones in every way, but I am not seeing how that is possible when considering the inverse relationships between many of these criteria.

3
  • Regarding the grip strength premise: on a long enough ride with enough braking, even a given rider's grip strength will start to fade. And not all riders have equal grip strength even in proportion to their weight. A heavy rider, on a heavy bike, with weak hands will not only need to brake harder, but will have to squeeze much harder and their hands will tire quicker
    – Chris H
    Mar 3 at 22:27
  • 1
    @ChrisH Poor wording on my part. I meant as in "regardless of brake design, you will never feel comfortable squeezing with more than X newtons of force."
    – MaplePanda
    Mar 4 at 1:08
  • that's a good way of thinking about it, but I'm thinking of a 2nd half to your sentence "... and you don't want to be using more than about 0.5X N very often." (Of course it's not just fatigue, but grip and having the ability to balance braking force between the brakes for the riding conditions)
    – Chris H
    Mar 4 at 8:46

3 Answers 3

14

There is more to it than the 3 factors you describe beyond just the conversion of one force to another. A few others:

  1. The deflection of the linkages in braking. A flimsy brake caliper will effectively increase the required lever throw and have a spongy feel, but a rock-solid caliper will either be heavier, or require more exotic materials.

  2. Adjustability or ease of setup. Some brakes are miserable to get just right, others have well placed cable stops, tensioners, and other things that let a mechanical methodically dial them in. This especially separates the winners from the losers in canti brakes for anyone that wants them to be quiet.

  3. Longevity - I think this one is pretty important too, even crappy tier brakes work pretty well when they're brand new, but can go to crap pretty rapidly, whereas better brakes last longer.

  4. Overall Weight, and overall size. Think about trying to give great tire clearance while also keeping aspect #1 under control.

  5. Trying to hit a particular price-point will change how all these factors are weighed. The cost includes not only the materials, but the manufacturing processes, and the engineering costs have to be amortized over each unit sold.

But unfortunately, engineering of anything is a balance of trade-offs, and the exact details of how those trade-offs are weighed against each other is truly the secret sauce, so, "it's a secret" is the only general answer you can get.

12
  • 2
    3b. Longevity of brake pads. The better they stop, the faster they wear.
    – Criggie
    Mar 3 at 7:32
  • 3
    1b. Flimsy levers - some force goes into bending the lever, and this also reduces travel. 1c. poor cabling (quality, routing, excessive length, bends) deflects as well
    – Chris H
    Mar 3 at 9:03
  • 3
    @Criggie's right, but it's not a simple 1-dimensional factor. More expensive (rim) pads may use 2 compounds, or just one better one, that has decent life and good stopping power. For discs, sintered pads have far better life than resin, and almost identical real-world performance (better in my case but the resin pads on my MTB are fitted to rubbish calipers)
    – Chris H
    Mar 3 at 9:07
  • 2
    I'm not sure where this fits in, but in safety-critical systems, provision has to be built in for less-than-perfect conditions. You could imagine a braking system that stops as sharply as you like, with 1-finger pressure, in the dry, but even with 4 fingers, in the wet, takes a lot further to stop. Without adjusting riding style for conditions, that's not safe. Or you could buy a old bike with chrome rims to feel it for yourself. You could call this 100% in the dry, 20% (made up) in the wet. A better all-round system might have 90% dry, 70% wet, or even 80%/79%
    – Chris H
    Mar 3 at 9:17
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    @Criggie: I’m actually surprised how long good brake pads can last. On the road bike I have over 10Mm on the original set of brake pads (using DT Swiss rims with Oxic™ ceramic coating). And it’s quite hilly here and sometimes raining.
    – Michael
    Mar 3 at 13:06
5

Talking to hydraulic disks, specifically MTB needs.

Raw power is about by pad and disc materials and fewer losses in the pipeline. The hydraulics virtually eliminate difference in losses, so more expensive disks come with grippier pads and rotors, of which the difference is small. Even the cheapest hydraulics provide more than enough raw power, on the first stop. More expensive brakes will provide the same power on each of many subsequent stops. Cheap brake can be prone to fade sooner.

However, braking on a MTB is not about a gorilla grabbing a lever and pulling as hard as he can. Its about finesse. A good set of brakes can be accurately controlled by a single finger with instant response (feathering). The feather benefits from non-linear response - early on in the lever movement the braking is subtle brake, later in the movement it become about raw power. Friction in the system (pistons, lever piviot etc) needs to be minimized. Expansion in hoses needs to be reduced to absolute minimums, and as always, weight needs to be controlled. For the likes of Dowhill use, the heat generated in the disks needs to be dissipated without overheating the caliper (more accurately, the fluid). Better brakes do all this better.

Then there are adjustments. The Shimano range from Deore SLX to XT are essentially the same brakes with more adjustments added as you go up the range. Gorilla grabbing lever does not care about the finer adjustments, many MTBers can get quite particular about exactly where the lever is and how far it moves before pad engagement.

The improvements as you go up the price range is subtle - Most riders will notice the difference between $30 and $1000 brakes. Aside having more adjustments, I suspect few will notice meaningful difference between $100 and $200 brakes.

Then you add the marketing....

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  • 1
    Cheap hydraulics can be practically impossible to bleed (even if you can source the right adaptor or modify one to fit), thus you can never completely eliminate fade. They also seem more prone to what should be avoidable failure modes like leaking, and you can't get spares for them
    – Chris H
    Mar 3 at 22:23
  • Good point, I was thinking specifically cheap Shimano (which I am a fan of if price is a problem), they are easy to bleed, and as far as spares, pads readily available and they are so cheap and reliable replacing them is often better than the time needed to service them.
    – mattnz
    Mar 3 at 23:00
  • I'm likely to be looking into cheap Shimano hydraulics soon to replace the Promax on my hardtail. There are one or two that will allow me to use up my stock of spare pads (bought, then found the front caliper was leaking when I took the old ones out). I'm a bit tempted to go mechanical because the BB5s on my tourer are so much better than the only hydraulics I've had to work with
    – Chris H
    Mar 4 at 8:49
4

We can approach your question from another angle: What are the tangible improvements in modern braking systems over older designs?

Given the main job of a brake is to turn momentum into friction/heat and dissipate it, the concept is quite straightforward.

Modern systems eliminate more losses between the lever and caliper. Hydraulic is the most obvious example but even cable operated brakes benefit from slick, lined, low friction cables in rigid casing. Certain high performace rim brakes use ball bearing races instead of bushes at the pivot points to eliminate as much of these losses as possible. Other examples, such as cable pull ratio, partly explain why v-brakes are so powerful. Even though the lever feel is similar, the brake uses about twice as much cable travel with half the force running through it, so that even corners and pinch points have lower friction as the cable requires less tension.

Other improvements are down to manufacturing accuracy and consistency: rim brakes can operate closer to the rim on road bikes where the rim is machined flat and the rim is a stiff box section that doesn't distort under load. This is part of the reason modern road brake designs have become more powerful. Material choice can also have an effect: Mavic produce a rim called Exalith with a textured/ribbed ceramic coated surface and very hard pads that last a very long time and give more power than a standard rim due to the extra edges involved.

Disc brakes benefit from tighter tolerances and better materials at a higher price point: more advanced rotors dissipate heat better and warp less than basic cheap ones. The more heat that can be dissipated means more heat can be generated at the pad/rotor interface by using higher friction materials (eg metallic). Magura state that their 4-piston calipers provide more braking power because the two sets of edges provide more braking power. Their 4-piston calipers are not much more expensive than their equivalent 2-piston calipers so I do not think they are lying about this to get you to spend more money -- it is a result of research. But not everyone wants that extra braking effect.
Of course, using a bigger rotor also can give an improved brake effect, provided the rotor can heat up enough to give optimum braking effect for the pad compound used.
Disc brakes can use very tight tolerences between rotor and pad, maximising the leverage available to the hand. This is why good disc brakes are so much more effective than rim brakes -- the rim always needs some space for rim run out, no rim ever runs 100% true through a ride, due to the forces involved.

That's about as much as I can think of now.

2
  • This has been flagged as "not an answer." I think that there is an answer to the OP's question in here , but it's not clear what that answer is. The OP is asking about how much of an improvement is possible between designs. You list a lot of possible improvements out, but don't offer a level improvement. I'd recommend editing to make it clearer what the answer to the OP's question is.
    – jimchristie
    Mar 4 at 19:35
  • I don't think that is really quantifiable so perhaps the question is "not a question", but thankyou. @jimchristie
    – JoeK
    Mar 4 at 20:38

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