FWD car. Trying to check for warped rotors. Wheel doesn't spin by hand. (rental, brakes)
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The wheel won't go more than 3 " because the transmission is engaging. The wheel will turn with pressure.
But even if the wheel did free spin, you can't check for warped rotor just spinning it. As an example, if the pads are normally 1/8" from the rotor but the warp is 1/16th, you wouldn't detect it. A warped rotor is checked with a dial gauge.
With one qualifier, presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification, in more than 40 years of professional racing, including the Shelby/Ford GT 40s – one of the most intense brake development program in history - I have never seen a warped brake disc. I have seen lots of cracked discs, (FIGURE 1) discs that had turned into shallow cones at operating temperature because they were mounted rigidly to their attachment bells or top hats, (FIGURE 2) a few where the friction surface had collapsed in the area between straight radial interior vanes, (FIGURE 3) and an untold number of discs with pad material unevenly deposited on the friction surfaces - sometimes visible and more often not. (FIGURE 4) In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures.
The wheel won't go more than 3 " because the transmission is engaging. The wheel will turn with pressure.
But even if the wheel did free spin, you can't check for warped rotor just spinning it. As an example, if the pads are normally 1/8" from the rotor but the warp is 1/16th, you wouldn't detect it. A warped rotor is checked with a dial gauge.
I know I have to use a dial gauge. Saw on youtube.
The opinion of one engineer isn't going to convince me that rotors don't warp, as I have managed to warp the rotors on a rental Impala driving it down the Continental Divide, and I owned a Escort that had the flimsiest rotors in history-contact with any road spray while they were warm would induce wheel juddering warpage immediately.
How to believe-that guy or my own lying shaking steering wheel?
Back to the OP-if you aren't feeling the warpage in your wheel, don't worry about it. And remember that some slight degree of warpage is fine and helps push the pistons back into the bores of the calipers when you release the pedal.
The opinion of one engineer isn't going to convince me that rotors don't warp, as I have managed to warp the rotors on a rental Impala driving it down the Continental Divide, and I owned a Escort that had the flimsiest rotors in history-contact with any road spray while they were warm would induce wheel juddering warpage immediately.
How to believe-that guy or my own lying shaking steering wheel?
Back to the OP-if you aren't feeling the warpage in your wheel, don't worry about it. And remember that some slight degree of warpage is fine and helps push the pistons back into the bores of the calipers when you release the pedal.
Slight warpage is not necessary to make the pistons retract.
Over time slight warpage turns into greater warpage and is not good.
Spinning the rotors like that won't accomplish anything. If you get pedal pulsation or steering wheel shimmy when applying the brakes, chances are the rotors are warped.
Some cars are more prone to warping rotors than others but some steps to minimize the chances it'll happen:
-Always torque lug nuts to manufacturer specs.
-Prevent lateral runout by cleaning off any rust or debris from the wheel hubs and studs when installing new rotors.
-Apply the brakes early and smoothly. Jack rabbiting from light-to-light then slamming the brakes only increases wear-and-tear.
-Clean and lube brake pads and caliper slide pins with appropriate grease.
Back to the OP-if you aren't feeling the warpage in your wheel, don't worry about it. And remember that some slight degree of warpage is fine and helps push the pistons back into the bores of the calipers when you release the pedal.
Quote:
Originally Posted by mclasser
Spinning the rotors like that won't accomplish anything. If you get pedal pulsation or steering wheel shimmy when applying the brakes, chances are the rotors are warped.
Some cars are more prone to warping rotors than others but some steps to minimize the chances it'll happen:
On the highway, when slowing from 65 to 40, I feel some vibration in the steering wheel and pedal. I'm not sure if it's the ABS engaging. When I double brake to disengage ABS, I still feel a little vibration.
Not enough vibration to lose control of the car though.
Also, during traffic when slowing from 40 downward, I sometimes also feel vibration.
Weird thing is, on local streets when I'm going 40-45 and brake, I don't feel any vibration.
Not sure why it happens on the highway but not city.
Also, I've never flushed the brake fluid since new, and I have 100,000 miles on the car now.
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