Wilsons Sandbox

Hey KORG!!! Folks, I need a little technical information. What exactly is a floating disc brake system and how do I tell by viewing it on the bike what kind it is? 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. I'm bowing to his expertise but I'd like to know more about how it all works. Chris and I are going to look into modifying a sport bike rotor and caliper to work on the KLR and I'm heading to the salvage yard at lunch tomorrow with an old worn out KLR disk and mounting studs for comparison. What the heck should I look for? As usual, thanks in advance, Jim Jackson II A13 "Gonzo" South Carolina _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com Share information about yourself, create your own public profile at http://profiles.msn.com

Jim Jackson wrote: [...]

> What exactly is a floating > disc brake system and how do I tell by viewing it on the bike what kind it > is?

The KLR front brake is a perfect example of a floating caliper setup. The caliper works like a hydraulic G-clamp, only one side of the caliper has pistons in it. A non-floating caliper has pistons on both sides.

> 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. As the KLR inside pad wears, the caliper has to slide over to take up the "slack". The piston will move out to automatically adjust as well.

> I'm bowing to his expertise but I'd like to know more about how it > all works. > Chris and I are going to look into modifying a sport bike rotor and caliper > to work on the KLR and I'm heading to the salvage yard at lunch tomorrow > with an old worn out KLR disk and mounting studs for comparison. What the > heck should I look for?

The disc is the easy part. It doesn't need to be real thick and heavy. It may help if it is flat like the KLR disc so you know it will clear the fork and the spokes. Mounting the caliper gets tricky. It's not just a matter of adding an adapter plate. You have to take into consideration the forces on the caliper mounts. The stock mounts on the fork leg have a certain diameter of disc in mind. The stock caliper would normally put compressive force on both mounting holes on the fork leg. Adding a badly designed caliper adapter could end up putting compressive force on the top bolt hole and tension on the bottom hole which may be enough to ultimately fracture the lower bolthole. The bigger the modified oversize rotor you use, the further away the new caliper location has to be. In theory you could make a 15 inch rotor and a huge long caliper adapter bracket. The braking would be great but I bet you would end up ripping a chunk out of the fork leg. I trust MAP did some testing when they devised their oversize rotor and caliper kit. Mister_T

Mr_T, Thanks (again) for your input! It's greatly appreciated and please keep it coming.

> >The disc is the easy part. It doesn't need to be real thick and >heavy. It may help if it is flat like the KLR disc so you know >it will clear the fork and the spokes. >

That's what I was thinking. I know from automotive studies that the braking power gets better from a larger diameter rotor, more caliper pistons (simple hydraulics) and/or from a larger total surface area of rotor contact. Ideally we could mount a same-sized rotor with wider surface area and appropriately bigger caliper and not have to worry about it. The larger the diameter the greater the torque forces on the caliper (exponentially?). Also, more fluid moving around in the caliper means more travel in the brake lever right?

> >Mounting the caliper gets tricky. It's not just a matter of adding >an adapter plate. You have to take into consideration the forces on the >caliper mounts. The stock mounts on the fork leg have a certain diameter of >disc in mind. The stock caliper would normally put compressive force on >both mounting holes on the fork leg. >

Been thinking about that too. There are two approaches I can think of off hand. Engineers, please correct me where I am wrong because I know I am somewhere here... Approach one will mount to the old holes with the caliper further out from rotor centerline, same spot otherwise. This places extreme forces on the mounting bolts in ways it twern't intended to be applied so we'd have to have some sort of bracket that distributes that force to the fork tube itself. Not exactly pretty. Can the fork handle that? Second approach is better and that is to engineer the bracket to mount the caliper at an angle from the original bracket such that the braking torque hits evenly on the original bolts holes. If the current brakes can lock up the front tire (done that) then the mounting holes are strong enough to handle this. I'm just not nearly good enough at geometry to fig'r out where the caliper should go. Makes sense? What am I missing? Thanks again T, Jim Jackson II A13 "Gonzo" South Carolina _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com Share information about yourself, create your own public profile at http://profiles.msn.com

I wrote:

> > Jim Jackson wrote: > [...] > > What exactly is a floating > > disc brake system and how do I tell by viewing it on the bike what kind it > > is? > > The KLR front brake is a perfect example of a floating caliper setup. > The caliper works like a hydraulic G-clamp, only one side of the > caliper has pistons in it. > A non-floating caliper has pistons on both sides.

Whoops! I just struck me that my answer was not quite correct insofar that it didn't answer the actual question. A floating disc and a floating caliper are not the same thing. A floating disc is mainly in two parts, the friction surface and the mount. Between those parts are small dowels that allow a bit of play, floating discs can actually rattle as you ride the bike. The play lets the disc move sideways a bit. Floating discs are most often used on fancy sportbikes as the floating design is less likely to warp in non-helpful ways under hard use. You would not normally use floating discs with floating calipers as only one of the two need to move. Floating discs tend to cost more due the greater number of precisely machined parts that go into one disc. Mister_T

> I just got back this morning from two and a half days on the OR > BCDR, during > ____ > > Is this the ride where a DR rider died? and another in his party > critically > injured? > > Kurt

I haven't heard about that. Certainly there are a few places where going off the road would be Very Bad Thing. And of course, there is the usual quota of rocks and branches and other hard or pointy objects that you wouldn't want to develop a close personal relationship with. When I was in Glacier a couple of years ago there was a fellow who took one step backward to get a better picture and fell off a cliff to his death. So neither the BCDR nor just a DR is needed to waste your life. Dreas