||On Tue, 19 Oct 2004 01:56:10 -0700, "Harold & Susan Vordos" || wrote: || ||>
||>> >
||>> >
||>> >Uh huh! It takes almost no error to end up with lumpy brakes. If the ||>> >disc does so much as flutter when it's running on the bearings, it will ||>be ||>> >noticeable when the car is driven, even if the faces are parallel to one ||>> >another. Turning them in two setups is asking for problems. The ||>very ||>> >best scenario is to get them running true to the bearings, and cut both ||>> >sides while set up. I'd be interested in hearing how they turned out, ||>too. ||>> >
||>> >Harold ||>> >
||>> It is difficult to do in 2 setups, but certainly not impossible for an ||>> experienced machinist with half decent equipment. ||>> That said, a proper rotor lathe makes the job a lot easier ||>>
||>> A very small amount of runout, as long as the surfaces are parallel, ||>> is not a serious issue, as the calipers are designed to "float" and ||>> this will absorb a couple thou of runout - but you want as little as ||>> is physically possible. Some cars are much more sensitive to runout ||>> than others, but all are more sensitive to vatiations in thickness. ||>
||>Yep. Exactly my point. Not sure what you might consider an experienced ||>machinist, but I started working in the industry in '57, aero-space stuff. ||>I ran my own commercial shop for years, sub-contracting primarily from the ||>same industry, so I know the difference between a thou and a tenth, and I'm ||>here to tell you that any deviation from "perfect" shows up in your pedal, ||>much the same way extended use can, and usually does. Been there, done ||>that. I had a thou or less runout when I turned the disks for a '77 ||>TransAm, one side at a time, several years ago. I used a commercially rated ||>engine lathe (Graziano). I ended up making a mandrel to do them over. One ||>thing I discovered is that the floating caliper helps, but does not ||>eliminate the lumpiness. It's ultra critical that the surfaces be ||>parallel, and dead perpendicular is almost as important. The loaded caliper ||>doesn't float as easily as you might imagine, what with the force of the ||>braking being applied against the pins. You *can* feel the resistance in ||>the pedal, which translates into lumpiness. ||>
||>Harold ||>
||What makes them squeal like banshees? I got a brake job at the dealer ||in town, and I swear I could drop all pedestrians to the ground to ||either side, covering their ears in agony, by playing the brakes. I ||never looked, but I'll bet the discs looked like an LP. I switched to ||another dealer and had them install new rotors with ceramic pads to ||end the horrendous noise. || ||Pete Keillor
As the manufacturers have experimented with non-asbestos pad formulations, there have been some premium products on the market that have shown a tendency to squeal if the installation was anything less than perfect. Squealing almost never has anything to do with the way the rotor is turned. Compound and weight of the pads, along with the age of the clips and springs, and the amount of wear of the caliper contact surfaces all interact to produce squeal. Building a pad that lasts over 40K miles, has good grip, and doesn't squeal *ever* is almost a black art. Having said that, Wagner and Raybestos premium ceramic pads are as good as it gets currently. Texas Parts Guy