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Hayes Prime Disc Brakes – Poppet Cam Contact Stroke Adjustment Unveiled

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Hayes has officially pulled the wrapper off the final details for their new Prime hydraulic disc brakes.  Shown in cutaway view above, the Poppet Cam is (as suspected) a stroke/pad contact adjustment, but the Poppet valve hides some big flow tech inside the master cylinder.

Externally, the Poppet Cam Dial will move rotate the cam (rust-colored doodad in the cental close-up image) to move the poppet valve in relation to the piston, giving you control over where in the stroke the lever starts making pad contact.  Combine this with the reach adjust, and you can fine tune the feel and position of your levers quite a bit.  We’ve reviewed the Stroker Grams and the “Top Hat” lever reach adjustment dial is great.  Both adjustments are tool-free.

Internally, the main piston is hollowed out and the whole assembly has 5x greater oil flow than their Stroker, allowing for quick movement of fluid to compensate for heat and pad wear.  Hayes claims this eliminates any lever pump caused by heat buildup, and it’ll automatically adjust for pad wear to keep contact and force the same throughout use.  This “open bath” design also increases durability since it doesn’t require the traditional rubber seal movement over port holes inside the master cylinder.

Hayes has a few videos on the Poppet Cam page that show some of these features better than words.  We featured Bikerumor-Exclusive power/leverage charts here, and more tech details and pics of the Prime are here.

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