I have 97 4.6L F150 XLT 2WD with 65K miles. I've noticed when slowing down from about 50-55+ or so, (rather quickly) there's this vibrating that occurs. It's not the brake pedal going back and forth. Just this shaking. I let off the brake and pump it to ease the vibrating, which seems to help somewhat. This vibrating/shaking doesn't happen when I gradually come to a stop. This guy told me I probably have warped rotors. But wouldn't I get the shaking all the time then?

 

Generally, yes.

Over time, your rotors (and/or drums) change chemistry -- the constant heat/cool/heat cycles rearrange the molecules so many times -- and change shape -- and get polished/scuffed so many ways that it is common for **** and dents to appear seemingly out of magic.

Simple things like braking to a stoplight and then sitting there for the 4 minutes while your brake shoes/pads sit on one part of the disc/drum -- while the other part cools rapidly -- causes the opportunity for differences in parallelism (rotors) or concentricity (drums).

Add to this the opportunity for brake pads (disc) to then rub/scuff the resultant high-spots during normal cruising -- and the opportunity (nay: likelihood) of different temperatures and resultant thickness changes then exacerbates the issue for the next stop.

Whacky mettalic structures (visible only to a metalurgist under destructive testing), added to random situations thrown at you over many tens of thousands of miles all add up to differences in metallurgy and size and shape on even the same component.

You can likely 'fix' your problem by trueing-up the parallism of rotors and concentricity of drums -- and/but the trade-off is less material for heat-soak-ability -- so the likelihood of a repeat occurrence becomes greater as the material continues to wear (out).

Bottom line: as long as there are no structural cracks (you can't catch your fingernail in any checking) -- and as long as you can tolerate the annoying shake -- you're better off with having more metal there for that emergency stop than shaving off good (but imperfect) material for the sake of smoothness.

It's really annoying -- but benign.

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Y2K™ Jim

Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"

 

Hey thanks for that very informative answer! Now don't take this wrong, but I gather from your reply that my rotors are indeed warped then? Or at the very least need to be "turned". Or is just better to have them replaced?

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It is better to just replace them. Your rotors are warped internally. By turning them, your are knocking off the high spots, but the internal structure of the metal is warped. It will warp again. It's just a matter of time. I WISH FORD WOULD PUT SOME REAL ****-ING BRAKES ON THEIR VEHICLES!!!!!!!! We have four FOMO products in the drive way and all have warped rotors. 94 Cobra, 95 Sable, 89 Marquis, 00 F150, all warped. It really pisses me off.
The Cobra was so bad when I bought it I didn't want to drive it. Luckily my neighbor turned them for free once I took them off. About 2000 miles later they are warping again. I plan to buy some 99 Cobra rotors made by Brembo, hopefully they are a better material. You could try using some aftermarket rotors such as Bendix or Raybestos, they may be cast from a better grade of iron. I guess I'll have Ford turn my truck's rotors under warranty, then try to warp them again to get a new set.

This is one of my pet peeves..

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Thanks for the reply. Yaa...I was afraid of that. This really *******ing blows! This is twice now. My past two trucks I've had (Dodge Ram Charger and now this Ford) I've had to replace the rotors after 50K. I think I'll try to investagte some aftermarket products.

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97 F150 XLT 4.6L 2WD