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Hayes Prime Mountain Bike Disc Brakes Unveiled

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hayes prime lightweight hydraulic disc brakes for cross country and freeride mountain bikes

After a week of buildup, Hayes Disc Brakes has finally unveiled their all-new Prime hydraulic disc brakes.

Featuring a slew of new technology, they represent the future of Hayes’ disc brake offerings.  Chief among the new features are:

  • 10º Tilt Bore – Keeps the Master Cylinder closer to the bar and optimizes lever reach.
  • Top Loading Pads – Switch brake pads without removing the wheel
  • Two-Piece Rotor – Lighter, stiffer and stronger than their old one-piece designs
  • New Pad Material – Less noise, better heat dissipation
  • Top Tube – rubber sleeve on hose keeps it from rubbing your frame the wrong way

There’s also a big new feature that they’re not quite revealing called Poppet Cam Stroke Adjustment, and it’s said to be the “secret sauce” behind the new Prime brakes.

OK, lots more to cover.  Go ahead and make the jump and we’ll get started…

That fuzzed out part is the Poppet Cam Stroke Adjustment, and Hayes’ ain’t talking.  In fact, I called Joel (HBG’s PM for the brakes) and all I can say is that we’re working on a nice technical article to explain it all, but here’s some inkling of what to look for: It’s an entirely new way of managing fluid expansion and brake pad wear compensation. Avid has their TaperBore, and Formula has their system.  Now Hayes has something they think is better. And, I think, that’s only part of the story.

In the meantime, here’s some other details.

The lever uses a two-piece clamp, which allows for quick, easy removal without moving other bits of the cockpit.  The mounting angle is set 10º inward to bring it slightly closer to the bar, taking it ever so slightly out of harm’s way and putting the lever just a bit closer.

For fine tuning lever reach, they’ve kept their Top Hat adjustment dial that moves the lever in or out without affecting pad contact.  Having used this on the Hayes Gram brakes we reviewed, it’s a very nifty feature and makes for quick, easy tool-free adjustments on the trail.

To further improve their brakes, the Prime gets an all-new two-piece rotor.  It keeps their “sweeping fin” design, but drops down to 110g (6″) while increasing stiffness.  Hayes says it’s also quieter and has a high Mu (which, for non-physics majors, means high strength to weight ratio…we think a high coefficient of friction, or in layman’s terms, lots of friction between the pad and the rotor…thanks to several reader comments for the correction).

Compared to their Stroker brakes, the Prime has more clamping power for a given amount of lever force.  Or, as this diagram shows, equal clamping power with 18% less lever force.  Translation?  Easier lever feel while getting more power.  And thanks to their mechanical leverage ratio, clamping power increases progressively as you pull the lever, giving you good modulation with bigger top-end braking force.

The bump in power comes from using a bigger 26mm caliper piston (versus 24mm on their Stroker Trail) while using essentially the same master cylinder in the lever.


Hayes will launch with two models, the higherend PRO and mid-level EXPERT. The chart below shows the differences:


Target weights for the PRO is 385g, and it’ll retail for $209/wheel.  The EXPERT comes in at $179 and will have a black color scheme (weight TBD).  These prices put make them highly competitive for fully featured (powerful, reach and stroke adjust, etc.) brakes, and Hayes says they’ll run all the way up the line to big, heavy freeride and all-mountain bikes and still have plenty of power.

They start shipping to distributors end of May, available to all beginning of June.  We should get a test set to review some time in April or May…stay tuned.

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14 years ago

Actually, in engineering, Mu typically refers to the coefficient of friction between two entities.

14 years ago

Notice the lack of bleed nipple on the caliper? And notice the screw in the middle of the banjo fitting, a la avid… New bleed system on the way?

14 years ago

FYI: mu is the coefficient of friction

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