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Old 09-08-2009, 06:00 AM   #18 (permalink)
Frank Lee
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Quote:
Originally Posted by MechEngVT View Post
Calipers have no mechanism to spread the pads away from the disc after brake actuation. Many caliper designs have o-rings on the slides in an attempt to prevent knock-back where rotation and flexing of the disc (or wheel bearing) will push the pads away from the disc.
I'd say the retraction accomplished via the deformation of the square-profile piston seals qualifies as a "mechanism". Yes in the past it wasn't much of a retraction but lately I've seen tidbits about lower-drag calipers on the new "high fuel economy" versions of domestic pickups. Are they really any better than what was standard, oh, 15 years ago? Here's a bit of info on what makes for a lower drag disc system: Classroom manual for automotive ... - Google Books

I've never run anything (car/truck/motorcycle/tractor/off-road toy) hard enough to experience "knock back". I would hope that's just a racing thing. I suppose those anti-knock back O-rings function the same way as the caliper piston seals?
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