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SRAM has printed a patent (initially filed final summer season, on June 23, 2021) detailing a suspension fork with an automated venting system, whereby differential strain arising between the ambient atmosphere and the cavity contained in the decrease legs would self-equalize whereas driving. The invention, we think about, would possible change the rider-operated lower-leg strain reduction valves discovered on 2023 Rockshox ZEB, Lyrik, and Pike forks. The auto-venting system would have the very same objective as these bleed valves, however wouldn’t require any enter from the bicycle owner, other than merely driving the bike over uneven terrain. The printed patent doc particulars various separate design ideas (or embodiments) that would every be carried out to attain this new automated operate, a couple of of which we’ll define right here…

SRAM Suspension Fork with Automated Venting

2023 rockshox forks get pressure relief valves on the pike, lyrik and ZEB forks
A strain reduction valve on one of many new 2023 Rockshox forks

Keep in mind when Fox filed authorized motion towards SRAM for using lower-leg bleed ports on their 2023 Rockshox Suspension Forks? The previous claimed that SRAM have been infringing upon their very own patent (#9739331) which describes using valves operable by the rider to equalize strain between the ambient atmosphere and the area within their fork lowers. The valves serve to alleviate strain constructed up contained in the lowers throughout arduous driving (and thus, temperature adjustments), or certainly any strain differential between the 2 environments, as which might additionally come up from elevation adjustments, or touring from one excessive of climate to the subsequent together with your bike.

sram automatic venting suspension fork pressure equalization relief lower leg build up
On this embodiment, a recess on the stanchion is longer than the space between every lip of the k-shaped wiper seal (pink), such that in a compression or rebound occasion, steady airflow between the air exterior the fork and the air contained in the decrease legs (128)

A brand new SRAM patent (US 20020411007) printed December 29, 2022 describes an automated venting system for a telescopic suspension fork that eliminates the necessity for any rider enter, other than driving the bike as regular, that’s. A couple of designs are described throughout the doc, however most appear to middle upon dual-lipped k-shaped wiper seals (pink, in our illustrations) between the decrease legs and the stanchions which are capable of switch pockets of air (168) between the ambient air strain of the skin atmosphere and the air in any other case trapped contained in the fork lowers.

How? By advantage of a collection of dimples, or an annular recess (148, under), positioned on the stanchions themselves.

In these designs, the straightforward telescopic motion of the stanchions relative to the decrease legs throughout compression and rebound occasions would enable an trade of air between the 2 areas, equalizing any strain differential which will exist as the primary Okay-seal passes the dimples. Importantly, in all designs, airflow is bi-directional.

sram rockshox stanchions anular recess dimples air exchange pressure equalization mechanism
Potential recesses (purple) on the stanchions (8) that will create an “air by-pass quantity” between the stanchion’s outer floor and the dual-lipped wiper seal

In fact, if air might be exchanged between the 2 environments, then it stands to purpose that moisture, grime, and oil might, too. The patent describes use of an “air permeable absorbent” materials (inexperienced, in all figures) sitting simply beneath the dual-lipped wiper seal that will forestall any lubrication oil contained in the decrease legs from escaping. This sounds very like a generic foam ring that will be discovered inside any fashionable suspension fork. The doc says this part may very well be made from closed-cell foam, open-cell foam, or a sponge materials shaped from polymer-based supplies. Beneath the air permeable absorbent ring, the patent describes using a standard bushing (blue, in all figures) with a small break up to permit the passage of air between the areas above and under it.

Appears to us from these diagrams that, with a purpose to forestall the stanchion recess from dragging particles down into the lowers, the entire stanchion would have to be protected with some sort of versatile boot. With out that, the recess would merely serve to fill the dual-lipped wiper seal with any particles that ended up on the stanchion, blocking it such that there’d be little trade of air anyway.

Nonetheless, one other model of the automated venting system lacks these dimples, or annular recesses, on the stanchions. To equalize any strain differential, an outlet port is positioned additional down the decrease leg. It presents a pathway for bi-directional airflow between the decrease leg inside and the skin world, with (Fig. 17) or with out (Fig. 18) use of an inlet valve and an exhaust valve (yellow) that may very well be configured to open at respective pre-determined strain differentials. This embodiment appears much more just like the strain reduction valves in use on the 2023 Rockshox forks, although it appears they might equalize any strain variations robotically, with out the necessity for the rider to press a button.

One can think about a situation whereby strain builds up contained in the decrease legs throughout an extended descent, and when it reaches a threshold worth, the exhaust valve is pressured open to permit that strain to “blow-off”. This is able to merely occur whereas driving, so the rider wouldn’t need to undergo any extra undesirable ramp-effects coming from the decrease legs. And due to this fact, they might get way more constant efficiency from the fork, I think about.

For enduro racers at the very least, this may very well be preferable to user-operated lower-leg bleed ports/strain reduction valves. I imply, think about that EWS racers are steadily subjected to hellishly lengthy phases that may typically take greater than quarter-hour to finish, protecting plenty of elevation and measurable warmth build-up of their forks. That stated, with out these user-operated bleed ports, it will not be really easy to equalize pressures ensuing from vital adjustments in elevation.

There may very well be a means round that, nonetheless, significantly within the design that depends upon these dual-lipped wiper seals and dimpled stanchions. If the dimples (and thus air by-pass quantity) have been positioned across the sag zone, the rider would merely have to bounce up and down on the fork a couple of occasions after hopping off the chairlift with a purpose to equalize any strain differential which will have arisen on the journey to the highest.

The place is SRAM going with this?

It’s arduous to say, actually.

It appears the dual-lip wiper seal-dimpled stanchion mixture might necessitate using a fork boot to stop mud, water and grime ingress, lest all of the grime that repeatedly sits on high of our wiper seals get wiped contained in the fork. And we will’t actually see Rockshox happening that route.

Nonetheless, the decrease leg valve with automated exhaust vent appears to be a extra believable design that will be much less more likely to end in contaminants getting into the decrease legs. And, if executed as described by the patent, we reckon it might eradicate that end-stroke ramp impact that always stops riders from accessing the final valuable few millimeters of journey. Going additional, it might even enhance the consistency of a suspension fork’s efficiency on an extended tough descent.

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