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I have some mechanical disc brakes on a gravel bike that I find almost completely useless at stopping. I tried replacing them with better cable-actuated hydraulic brakes that were widely recommended online, but find them useless. I've tried adjusting them, but any tighter on the cable and they start rubbing on the rotor. It is already using the commonly recommended Jagwire compressionless cables/housing.

I want the most powerful brakes, but I don't care that much about the weight. What is the difference in the brakes as you upgrade from GRX 400 towards 800, Apex towards Red, Tiagra towards Dura-Ace, etc.? Is is just lighter weight, or are the higher-end brakes better at stopping too? I have another bike with Ultegra and find it completely sufficient, but I haven't used a lower-end hydraulic brake.

I know that there are also differences in the shifters and in the number of speeds, but I am only asking about the brakes. I can't find any data comparisons online for braking power, like you can find for tire rolling resistance.

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  • Cable-acutated disk brakes can be quite good. Perhaps there's something else going on here. Rather than throwing the wallet at it, have you tried cleaning the rotor?
    – Criggie
    Feb 25 at 18:28
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    Yes, the rotors are completely clean and the barrel adjusters can't be tightened anymore without it rubbing. They are fine at stopping on a flat road, but not on a very steep gravel descent, which I have done on a bike with GRX 800 before and the difference between the two is stark. To make it keep the bike in control the drop bars need to be used for more leverage whereas the GRX 800 hydraulic brakes can fully lock the wheels from the hoods.
    – senten
    Feb 25 at 18:57
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    Spending money on hydros isn't a problem, but I just don't want to end up in a situation where I buy GRX 400 or Rival and it still sucks.
    – senten
    Feb 25 at 19:01
  • From my experience (and some relatives’), the difference between basic hydraulic Shimano braces and entry level single piston mechanical brakes is huge. The difference between hydraulic with the same number of pistons much smaller (didn’t try with the same tires) - but for sustained braking, a basic hydraulic with resin pads can be limiting - but I’m speaking here about the MT200 (entry level flat bar), GRX400 can already take finned metal pads and rotors with cooling fins.
    – Rеnаud
    Feb 26 at 6:45
  • GRX400 don't have very great modulation, the higher-level ones are probably better. The best gravel brakes I've tried are Campa Ekar, but that requires a full Ekar groupset (incompatible with any other brifters). Also: Shimano Hydro brakes are the easiest to maintain/bleed (way easier than Ekar).
    – Erlkoenig
    Feb 26 at 8:52

1 Answer 1

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For Shimano road groupsets, I only spotted two differences:

  • “Ultegra-level and up” (that include GRX810/GRX820) have a feature that Shimano calls Servo Wave Action. According to the marketing material, the brakes have a different response curve and are a bit more powerful, but they do not provide quantified information about the difference.
  • In the case of the last generation of GRX (620/820) and possibly the equivalent DA/Ultegra/105: the piston travel has been increased, that limits the contact between the rotor and the pads when the rotor is hot.
  • Piston material also changes across the range (thanks Weiwen Ng), with Tiagra/Deore and down having resin pistons, while upper models have ceramic pistons.

Another point to keep in mind is the difference between "peak stopping power" (braking hard from cold brakes) and "sustained peaking power" (when you keep braking before the system can cool down - like in long downhill descents). I don't have scientific data to prove it, but it seems to me that peak stopping is quite similar across the ranges, but as increase in range, you'll have improvements in sustained stopping power, but these differences are not always directly linked to the calipers, but other components.

  • Pistons: ceramic pistons isolate better the fluid from the heat.
  • Pads: metallic pads are more heat tolerant than resin ones, and mid-range and up can take finned pads (GRX400/Tiagra)
  • Rotors: as you increase in range, heat dissipation is also improved (SLX level and up rotors are made out of a sandwich of steel for the contact pad, and aluminium for the core), XT/Ultegra and up have cooling fins.

But you can mix and match if needed in the GRX range, and fit XT rotors with finned metal pads on a GRX400 caliper.

Otherwise in the MTB segments, there’s also a difference in the number of pistons per caliper, and the kind of pads that the caliper can accept (resin vs metallic, and pads with or without cooling fins), but that kind difference doesn’t seem to exist in the road ranges (only 2 pistons, and pads can be resin or metallic, with or without cooling fins).

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    Tiagra has resin pistons. 105 and above have ceramic.
    – Weiwen Ng
    Feb 25 at 19:55
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    ServoWave means the pistons move nonlinearly with respect to brake lever position. It moves farther in the beginning and less later on. This means they can build brake calipers with larger clearance without sacrificing mechanical advantage.
    – SimonL
    Feb 26 at 12:13
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    Peak stopping power is traction limited--will be the same for all. Note that the Servo Wave brakes will require less hand force to get to this limit.
    – MaplePanda
    Feb 27 at 8:14

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