SRAM replacement hydraulic disc brakes due in April

President Stan Day issues another video update, citing the cause of the recall in some detail

by David Arthur   March 6, 2014  

SRAM HRD front inc disc

SRAM president Stan Day has released a new video outlining the company’s hydraulic disc brake ‘recovery plan’, confirming that the first delivery of replacement brakes will come in the second half of April. All cyclists affected by the recall will be SRAM’s priority.

In his statement Stan has also outlined, in some detail, the exact cause of the problems that prompted the company to recall its entire stock of Red and S-700 hydraulic disc brakes last November, amounting to 19,000 brakes.

Since his last update in January, the company has been examining the cause of the fault, which only occurred during sub-zero temperatures at a US cyclo-cross race. It appears that manufacturing tolerances and a seal design were the cause ot the system being liable to fail in extreme conditions.

In Stan’s own words:

“There are two mechanical issues that enable the brake to ingest air, lose pressure and fail. In the extreme cold air the system seal stiffened and became less complaint which is why we saw the problem multiply in December. the first mechanical issue was that the cylinder bore wasn't’ cylindrical, our manufacturing process parameters did not not adequately control the part fabrication. The result was there was an oval shape to the bore that was beyond what the seal was capable of, especially in the cold when the seal lost its compliance.

“The second issue was that the system created excessive negative pressure in the brake fluid reservoir. When it is controlled, it doesn't’ affect the brakes, when it isn't’ under control, it’s operating outside of the seals capability to compensate, especially in extreme cold. The result was air ingested.

“These two issues, in combination with normal manufacturing tolerance variation, could also allow failure in the system in warm riding conditions. That’s why we asked everybody to stop riding the brakes.

“With our new model year 2015 production, we have fixed both issues, as well as complete a number of normal improvements for a second year production.”

These changes includes an all-new lever body design to improve ergonomics, provides better sealing on all critical surfaces, and drops a bit of weight. Be interesting to how different the lever body shape is, the tall design has divided opinion since it first launched, so maybe they’ve been able to package the internals better?

There’s also a new bleed port design for better sealing and being easier to service. And there’s a new caliper spring to reduce lever travel. Their testing has been updated we well, as Stan says:

“Our test riders thought we had spent enough time with frozen hands and feet for adequate testing. For the new product we have added a battery of laboratory tests and environmental chambers. We’re testing down to -20°C up to 46°C.”

You can keep an eye on SRAM hydraulic updates at the special website they created http://sramroadhydraulicbrakerecall.com/ 

2 user comments

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dear oh dear, what an absolute balls-up ...

posted by Karbon Kev [667 posts]
6th March 2014 - 17:51

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Would those testing temperatures be ambient temps. Assuming if they are the component temperature would be more or less...Ousaveard, you must have a calculation somewhere on this. Wink

posted by Guyz2010 [280 posts]
6th March 2014 - 17:55

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