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I am experiencing some pulsating while braking in my 99 Ford Escort. After removing the wheel and inspecting the discs they both look like this.

warped rotor?

Are the lateral lines something that could cause the pulsation I am experiencing? Do these need to be replaced or just resurfaced?

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It very difficult to say if a rotor is warped by visual inspection. The tolerences involved are very small in the .004" range. That is about the thickness of 3 or 4 human hairs. My recent experience (if you are doing your own repairs) is to replace rather than resurface. The thickness of used and resurfaced rotors may exceed the minimum allowed thickness, however they seem prone to quickly warping after being reinstalled. When you take the cost of having the rotors machined versus the cost of new ones it often isn't cost effective to reuse them. There are of course exceptions on vehicles with very expensive rotors but the average front wheel drive hubless rotor is pretty inexpensive.

  • In general it's hard to tell by visual inspection, but the rotor in OP's photo is so warped that I can't imagine you could drive at all with it. – R.. Sep 24 '13 at 3:57
  • R - that doesn't look like warping. I don't know what it is, as they are weirdly damaged. Definitely replace. – Rory Alsop Sep 24 '13 at 15:06
  • I thought that was normal. That's what all of mine look like (and I don't have any pulsating on any of my cars at the moment). – Brian Knoblauch Sep 24 '13 at 16:29
  • It actually looks like cracks. – kyle_engineer Nov 29 '16 at 20:19
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Best bet replace you don't need to do a brake job twice. For about $60 for the both rotors and $18 for the pads you will come out ahead. Just make sure you break in the new pads. Don't use excessive braking or hard braking the first 200 miles and you should get at least 50000 miles of trouble free braking unless the calipers mess up.

  • Follow the brake pad manufacturer instructions for bedding in of pads. Some require an initial round of very hard braking. – Brian Knoblauch Sep 25 '13 at 11:55
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99.9% of rotors do not warp. The pulsation is caused by improper bedding procedures that leave deposits in spots on the rotor that changes the friction characteristics. If not addressed early, will create a molecular change in those spots to cementite which is pretty much a permanent change in the friction characteristics and is best remedied by a new rotor. The deposits and change to cementite is not visible to the eye so...the good news is that most new rotors don't cost that much more than turning anyway. For details Google the stop tech article using terms brake rotors warp cementite.

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if you decide to replace pads and rotors bed them in.Correct procedure to be found on Bendix website.While there check out BENDIX general CT stealth advanced technology (ceramic) disc pads.Even with standard rotors they are exceptional.With slotted rotors they work well offroad too

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Are the lateral lines something that could cause the pulsation I am experiencing?

Yes.

Do these need to be replaced or just resurfaced?

They need to be replaced. Either the rotor has rusted out from the backside along the "lateral" lines, or pad imprinting has caused rust to concentrate along the edges of the imprints.

Either way, your braking response will vary throughout the rotation of the disc, causing pulsation feeling.

Escort discs are cheap. Replace them. Check the new ones for parallelism, and when installed, runout.

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