Can warped discs cause a wobble when NOT braking?
Discussion
Yes. I have this problem at the moment on car, although it's probably a build up of pad material rather than warped discs. I have some judder under braking but also a wobble that starts at around 130 when the discs are starting to rotate fast. The wheels have been balanced very recently on a road force balancing machine (to rule out unbalanced wheels as the cause) so it is almost certainly not the wheels.
In the past in a car with nearly worn out discs and pads I've got the brakes so hot that they start to judder (maybe the discs warping a little??) and at the same time had horrendous (like the car is shaking itself apart) wobble at higher speeds. Once the brakes have cooled down the judder and high speed wobble have completely gone away.
In the past in a car with nearly worn out discs and pads I've got the brakes so hot that they start to judder (maybe the discs warping a little??) and at the same time had horrendous (like the car is shaking itself apart) wobble at higher speeds. Once the brakes have cooled down the judder and high speed wobble have completely gone away.
lord trumpton said:
yes as they would be out of round when warped and introduce additional movement.
No, warped discs simply mean that pad deposits have built up on the disc face, they will not cause a vibration under normal speeds. You could have a balanced wheel that still has a slight buckle, that would cause the wobble. Same with a tyre with a buldge or that has a flat spot.
Lots of 5 series have issues with wobble that many Hunter machines can't sort out.
gizlaroc said:
lord trumpton said:
yes as they would be out of round when warped and introduce additional movement.
No, warped discs simply mean that pad deposits have built up on the disc face, they will not cause a vibration under normal speeds. I had a Honda Prelude that warped it's discs (poor quality, excessive heat caused lateral bending - you could see it when you rotated the disc).
Honda garage who fitted them (genuine Honda parts supposedly...) changed them once, same thing happened again, they refused to change them again.
I had had 7 Preludes before this and never happened before. Suspect the Honda dealer was using crappy non genuine parts.
fwaggie said:
Not necessarily. If they are warped, it will cause vibration during braking and right after braking (as they are pushing the pads away), but after a hundred feet or so, vibration will stop.
Yeah of course they will, but context young man, context. 
He is asking if they will cause vibrations when he is not braking. Hence me saying, they won't at normal road speeds.
Maybe if you get to 120 mph or so they might, but not at normal speeds.
Thanks all.
Discs will be checked for run out this weekend (I suspect they are warped, or more correctly have pad deposits on them) as there is a noticeable shake when applying the brakes lightly which is felt through the pedal and wheel.
Calipers will be checked too, since (I am guessing) is they are sticky, the could keep a small amount of pressure on the disc if they are not retracting properly. There is also a very light squeak when driving from the brakes (on and off with rotation of the wheel) -makes me think the pads are touching the disc in places.
Discs will be checked for run out this weekend (I suspect they are warped, or more correctly have pad deposits on them) as there is a noticeable shake when applying the brakes lightly which is felt through the pedal and wheel.
Calipers will be checked too, since (I am guessing) is they are sticky, the could keep a small amount of pressure on the disc if they are not retracting properly. There is also a very light squeak when driving from the brakes (on and off with rotation of the wheel) -makes me think the pads are touching the disc in places.
Never had a disc cause a wheel judder when not braking. I have had it with wheel balancing (even after being done numerous as some tyre fitters seem unable to properly balance a wheel and one took 3 attempts at 3 different garages), worn suspension bushes, and a bulge hiding away on the inside sidewall.
In answer to your very first question........NO, emphatically, NO. When a car is going along WITHOUT any pressure at all on the brake pedal, the pads are merely "leaning" on the disc. They are under NO pressure whatsoever.
You will ONLY EVER get any influence of the discs and pads on the steering when the brake pedal is applied. They have NO influence AT ALL on the steering until brake pressure is applied.
You will ONLY EVER get any influence of the discs and pads on the steering when the brake pedal is applied. They have NO influence AT ALL on the steering until brake pressure is applied.
datum77 said:
In answer to your very first question........NO, emphatically, NO. When a car is going along WITHOUT any pressure at all on the brake pedal, the pads are merely "leaning" on the disc. They are under NO pressure whatsoever.
You will ONLY EVER get any influence of the discs and pads on the steering when the brake pedal is applied. They have NO influence AT ALL on the steering until brake pressure is applied.
Unless...You will ONLY EVER get any influence of the discs and pads on the steering when the brake pedal is applied. They have NO influence AT ALL on the steering until brake pressure is applied.
The calipers are sticking,
The caliper sliders are sticking or seized,
The hoses are restticting flow back of the fluid,
The pads are not sat correctly in the caliper and are not free to move in/out properly.
But if the wobble is caused by the disk, it is most likely to be uneven run out, possibly a badly seated disc or a hub problem.
stevieturbo said:
One internet article claiming pad deposits, and everyone takes it as gospel saying discs don't warp.
What a croc of s
t.
Have you ever seen a truly warped brake disc? What a croc of s
t.Think about the amount of heat needed to warp those discs.
It is pad deposits. More common with autos as you sit with your foot on the brakes a lot.
My father in law has been running a garage for 40 years and he said he has never seen a warped brake discs. Loads that judder, but break them in again properly and they are fine.
gizlaroc said:
Have you ever seen a truly warped brake disc?
.
Yes. Not a daily occurence, but not rare either..
Not that many garages have a dial run out gauge, and in fairness it is not often needed. But on some cars when you have repeated warped discs ( happened to be a bad batch of well known make discs), you have to check run out after fitting replacement discs (to honour the warranty terms), ensure they are in tolerance, and record them. Then check them after the problem returned.
As for heat. There is (on average), enough heat generated by stopping the vehicle frpm 60 to 0, to boil 500ml of water from room temperature. Do a few repeated stops, and that can be an awful lot of heat in a small area. If that is not cooled by movement of the vehicle it can warp a disc. Not all discs, not every time. But don't assume it never happens.
In this case however, until you eliminate other braking issues, and hub runout etc then I agree it is unlikely to be the issue.
An example of the heat....
Our theoretical car is traveling and generating torque and essentially nothing is happening until the driver steps on the brake. Then a whole bunch of things happen. The brakes must overcome dynamic inertia (the car in motion) and impose static inertia (make the car come to a stop). It does this by changing the kinetic energy to thermal energy or heat -- and it generates a lot. The pads on the smaller car going 60 miles per hour (96.6 kilometers per hour) will reach about 450 degrees Fahrenheit (232.2 degrees Celsius) during an emergency stop.
Edited by Coilspring on Friday 6th September 18:34
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