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OK guys, let me run some ideas past y'all.
About 9 months ago I replaced my scored front rotors because the car was shuddering during high-speed braking - and I mean high-speed, out on the empty stretch of I95 between me and Fredericksburg you can go from 90 mph cruising to dead stop in several seconds due to the saturation of morons along that corridor. Needless to say, in that kind situation I need very reliable brakes. So I changed the rotors with Brembos.
At the time, I took my father's advice to leave the pads alone. They still had a good 1/4" of material left. Braking was smoother...for a while.
I replaced the pads a few months ago with PBR semi-metallic and still had plenty of material left on the old pads, but my rotors - much less than a year old - were already scored like the last ones.
Pause for questioning: could this be because I did not replace the pads, thus wearing the same pattern from the old rotors into the new ones?
So now I've got brake shudder again in the front end; pedal does not pulse much under my foot - does ABS affect how much I could feel this? - but the front end does a verticle shimmy and the steering wheel shakes up and down. They might even pull a bit to one side during hard braking.
I borrowed my cousin's runout gauge but haven't gotten around to using it, but I'm guessing that I've got some flat spots on the rotors causing this - I think I can faintly feel the brakes catch and release with very light pressure at low speeds.
SO, I guess what I'm asking is - do you guys have similar rotor problems on your 240's?
Do you replace pads every time you replace rotors? Do I need to replace those new PBRs to make sure I don't transfer the scoring from the rotors to a new set? Would it be safe to use a table top belt sander to remove some material from the pads (with a respirator and dust collector, of course) so that I had a fresh, flat surface on them wihtout throwing out a nearly new set of pads?
One more ponderance: I was told my rear rotors are very thin by a shop wanting to replace them. Again, I haven't measured yet, but is it possible that thin rear rotors cause the fronts to do more work, thus generating more heat and brake problems? Thin or not, they are clean and smooth and I have no rear end braking shudder - should I replace them with the fronts?
Thanks folks!
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