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Warped Rotors: Myth or Fact?

Old 09-18-2010, 10:55 AM
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Warped Rotors: Myth or Fact?

Does true rotor "warp" occur in the sense that we use it (i.e. like when you left your record on the dashboard of your car on a hot day) or is it myth?
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Old 09-18-2010, 12:01 PM
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You can over heat them at the track to the point there is excessive run out... Not likely to happen in most street riding.
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Old 09-18-2010, 04:28 PM
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I have only seen it a few times on OEM parts, and you really, really have to work for it... But I have seen it several times on thinner/lighter than stock race rotors... Less common now though when all nutters started using wave rotors instead to reduce weight...

I'd say 9 times out of 10 it's just surface transfer instead...
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Old 09-18-2010, 04:36 PM
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It's very common in cars/trucks, and once they're machined they'll warp faster.

About 20 years ago the Auto Body/Paint instructor at my old school went up to SF in his Buick Regal to visit his son over Spring Break. When he got there his brake pedal was pulsing like crazy, and it scared him, so he went to a gas station in The City. The mechanic said, "You're from LA (anywhere in SoCal to a San Franciscan) aren't you? And I'll bet you came over The Grapevine to get here. You've got warped rotors." He told him it was safe to drive back home. The next week he brought it into my Brake and Suspension class, and we measured .010" lateral runout on one of the rotors...the most I have ever seen. We were able to machine them without going under the minimum thickness spec. The next year he repeated the trip...came to me and said, "Well, I did it again." We had to put new rotors on it that time.

I've seen as little as .0015" lateral runout cause severe vibration (shaking the whole front end) under braking at 50mph on a 4Runner with fixed calipers.
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Old 09-18-2010, 05:17 PM
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I warped rotors on the Hawk GT a couple of times. That was when I was using the single 6p PM caliper on a stock F2 solid rotor in the mountains around Asheville, NC. I switched to a fully floating rotor and it held up fine.

The original Buells have a reputation for warping rotors, too. My brother warped one on his S3 after a lot o hard riding in West Virginia.
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