Wilsons Sandbox

> > Chris said its to allow the rotor to expand for heat but I thought it > > referred to the caliper floating back and forth to center itself on the > > rotor. > > Your description is closer to how I see it. > The caliper is reasonably free to slide left and right, mainly I > think to compensate for pad wear since the rotor is rigid.

No, I know the caliper floats, and actually I don't think I've ever seen one that doesn't. If you had pistons on both sides, you'd have to have brake lines running to both, and you still wouldn't have a way to accomodate uneven pad wear unless the caliper could shift. Maybe they do actually do run opposing pistons on high-performance applications, but it's a lot cheaper to just run the piston(s) on one side. I was referring to the disc "floating" as well. Take a look at the picture at http://www.bartels-hd.com/bpp/catalog/brakes.html You can see that there are fasteners between the outer and inner part of the disc. Under braking, only the outer part gets hot, and this can cause the disc to warp, if expansion is constrained by the cooler inner part. However, some discs are still solid, and I think the KLR one is. Can't generate a lot of heat with little brakes... The caliper shouldn't be too big a deal, as long as it's not moved too far away. The bike ain't exactly designed for minimum weight, so the mount probably has a good safety factor. Although, it is a casting, so I'd be careful there. At any rate, I have to pull my guards off, and take a closer look. Keep in mind, I wouldn't build something for someone else that I wouldn't or don't use on my own bike. Chris -- Dr. J. Christopher Krok Project Engineer, Adaptive Wall Wind Tunnel Graduate Aeronautical Laboratories, California Institute of Technology MS 205-45 Phone: 626.395.4794 Pasadena, CA 91125 Fax: 626.449.2677

Every once in a while there is a moment of clarity (or is that parity?)... AHHH HA!!!!! Chris, you're absolutely right. I was thinking horizontally floating, not vertically as it relates to a wheel standing upright. You are also correct in that the KLR and the Ninja 1000 rotors in my hand right now are both completely solid. But Ted is also correct. The brake caliper does shift. I remember this from brake theory in auto shop many many moons ago. The inside pad hits first then "pulls" the opposite side into the rotor. Because disk brakes routinely have only a few thousanths clearance between pad and rotor it's not significant unless you ride the brakes slightly for a long period of time. Jim Jackson II A13 "Gonzo" South Carolina

> > > > Chris said its to allow the rotor to expand for heat but I > > thought >it referred to the caliper floating back and forth > > to center itself on >the rotor. > > > > Your description is closer to how I see it. > > The caliper is reasonably free to slide left and right, mainly I > > think to compensate for pad wear since the rotor is rigid. > >No, I know the caliper floats, and actually I don't think I've ever seen >one that doesn't. If you had pistons on both sides, you'd have to have >brake lines running to both, and you still wouldn't have a way to >accomodate uneven pad wear unless the caliper could shift. >

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Chris Krok wrote: [...]

> No, I know the caliper floats, and actually I don't think I've ever seen > one that doesn't.

Most older caliper designs are of the opposed piston type, with the caliper rigidly mounted. Fron the twin piston calipers in a Mini Cooper S to the quad piston calipers in the 69 Buick Electra, opposed pistons were the way to go in the sixties. Bikes went for sliding piston earlier than cars since the sliding piston caliper could be made a bit lighter and that makes more difference to the unsprung mass on a bike.

> If you had pistons on both sides, you'd have to have > brake lines running to both, and you still wouldn't have a way to > accomodate uneven pad wear unless the caliper could shift.

On all the opposed-piston calipers I've seen, bores in each caliper half are connected through a small port, sealed with an O-ring. so that only one hose is needed. Uneven pad wear is only a problem when the pistons do not move freely enough. The pistons should still self-adjust in the usual manner.

> Maybe they > do actually do run opposing pistons on high-performance applications, > but it's a lot cheaper to just run the piston(s) on one side.

Which is why many calipers are like this these days. Less material and less machined surfaces makes a cheaper but not necessarily better caliper. [...] Mister_T