brakepad-to-rotor distance

[subliminally incorrect]

so i've put aout 1000km on my car so far and i drove up to waterloo from hamilton and then to scarbourough last thanks giving weekend. for me that was quite an experience as i've never driven on ontario highways to that extent.

anyhow i had to brake a lot when i was going through the 401 and i noticed that my front disk brake pads are now conical shaped as opposed to the flat shape it should have.

i also noticed that the space between the rotors and the pads on all four wheels is very minimal when im parked (maybe its because my parking brake is on?). its rather odd as i notice on other parked cars it isnt like this. i'm not sure if it was like this when i first left the dealership.

now that ive noticed this i get a sneaky suspicion that my brakes are rubbing on my rotors when im driving, thus slowing me down a bit.

can anyone confirm whether or not this is normal?

[kaval]

Conical shaped? As in the edges of the pad are beveled? What you're describing sounds normal to me unless I'm not interpreting what you've said properly.

Do you feel the car pulling to one side while driving? Since your car is new, the pads have a lot of material on them. It may look like they are contacting the rotor when you're not breaking but it should be okay.

[sas]

Not enough info.
Conical shape, one wheel one pad, one wheel both pads, all pads of front wheels?
Also you need to check, how disks on both sides are worn.
Conical, it really has to be checked.
About minimal space, it is normal but wheel have to spin easy.
Photos could be weeeery helpful.
If car on warranty and dialer is not far, better to ask him.

[subliminally incorrect]

Conical shaped? As in the edges of the pad are beveled? What you're describing sounds normal to me unless I'm not interpreting what you've said properly.

Do you feel the car pulling to one side while driving? Since your car is new, the pads have a lot of material on them. It may look like they are contacting the rotor when you're not breaking but it should be okay.

yahi do notice a bit of drift to the right when driving on a straight flat road, albeit minor. i'll post some photos tommorow

[Noisy Crow]

yahi do notice a bit of drift to the right when driving on a straight flat road, albeit minor. i'll post some photos tommorow

Most roads have a slight crown to them, so drifting to the right on a two or four-lane road is normal. You need a centre lane on the 401 or something like that to be sure.

[mazdas3sporte]

i notice that my pads might be close to my rotors too, and i do get the car going a very very slight bit to the right, i thought i was being paranoid so i ignore it... iam gonna have a look 2moro.

[Fobio]

I have 3 things to say...

all brake pad edges are beveled or tapered as kaval says...that's the way they're made...last I saw flat oem pads on my own car, I believe was on a 1998 car...

ontario hwy road-surfaces are bad...they're potholed and rutted...this may cause a slight pull left or/and right depending where you drive, accentuated by wider/more aggressive tire setup and suspension upgrades...

these same shitty ontario hwy's are sometimes bad enough to f'up your alignment...about $60 to fix your alignment...

I'm also interested in knowing if our pads are spring back from the rotor or not...I'm pretty sure they're not...

[SL3VIN]

it is normal for the brake pad to seem like its touching the rotor. also slight drifting on any road is normal since the roads are angled to prevent pooling of water.

[Wild Weasel]

Brake pads should be in contact with the discs at all times.

They're not like drum brakes, which have springs to pull the shoes away from the drums when you let off the brakes.

Discs work based on whether or not there is pressure pushing them against the rotors. Without pressure, there is no friction. They stay right beside the rotors.

If there WAS a discernable space between the pad and rotor, that would mean that the rotors have high spots that are forcing the pads away, and would need to be turned or replaced.

[subliminally incorrect]

Brake pads should be in contact with the discs at all times.

They're not like drum brakes, which have springs to pull the shoes away from the drums when you let off the brakes.

Discs work based on whether or not there is pressure pushing them against the rotors. Without pressure, there is no friction. They stay right beside the rotors.

If there WAS a discernable space between the pad and rotor, that would mean that the rotors have high spots that are forcing the pads away, and would need to be turned or replaced.

so youre saying that when i apply my brake pedal, it's the rotors that move and come in contact witht he brake pad and not the other way around?

[kaval]

so youre saying that when i apply my brake pedal, it's the rotors that move and come in contact witht he brake pad and not the other way around?

The caliper will open and close based on pedal input, pushing the pad against the rotor. The rotor is secured to the hub (either by two screws, or when the wheel is put on), so it does not move in and out.

Fluid flows through the brake lines and forces the piston(s) to press the brake pad against the rotor. Then when you let go of the pedal, the fluid backs itself up and the pad pulls away from the rotor. This is why if you're pulling to one side, sometimes it can be a seized caliper.

[Wild Weasel]

so youre saying that when i apply my brake pedal, it's the rotors that move and come in contact witht he brake pad and not the other way around?

Actually, for the most part, nothing really moves there. Like I said... it has to do with the pressure.

The pad is always in contact with the rotor, but since the rotor is spinning parallel to the pad, there is no friction.

If you want to get really technical, then the tiniest of bumps and grooves on the rotor and pad will have forced the two the tiniest bit apart, but that's mostly irrelevant here.

When you press the brake pedal, pressure is applied to the inside pad and, since the caliper floats over the rotor, that pressure is transferred to the outside pad as well, through to the rotor, producing friction. That friction produces heat, and the car slows down.

Nothing has "moved" but now there's pressure being applied.

Same as if you put your hand against the wall, and then start pushing on it. Your hand, and the wall, don't move... but you can certainly vary the amount of force applied, right?

[Wild Weasel]

Fluid flows through the brake lines and forces the piston(s) to press the brake pad against the rotor. Then when you let go of the pedal, the fluid backs itself up and the pad pulls away from the rotor. This is why if you're pulling to one side, sometimes it can be a seized caliper.

This is not really true.

Hydraulics don't work on the movement of fluid, so much as in the change in pressure which is uniform throughout the entire fluid.

The fluid does not "suck back" and pull the pad away. The pedal adds and relieves pressure in the fluid.

[kaval]

This is not really true.

Hydraulics don't work on the movement of fluid, so much as in the change in pressure which is uniform throughout the entire fluid.

The fluid does not "suck back" and pull the pad away. The pedal adds and relieves pressure in the fluid.

Thanks for correcting me! :d

[Walrus]

This is not really true.

Hydraulics don't work on the movement of fluid, so much as in the change in pressure which is uniform throughout the entire fluid.

The fluid does not "suck back" and pull the pad away. The pedal adds and relieves pressure in the fluid.

This is not really true.

A liquid is not compressible. Hydraulics do work by the movement of fluid. You are moving the piston in the caliper a small amount (a few thou) but moving it none the less, by moving the fluid in the brake lines a small amount.

[subliminally incorrect]

Actually, for the most part, nothing really moves there. Like I said... it has to do with the pressure.

The pad is always in contact with the rotor, but since the rotor is spinning parallel to the pad, there is no friction.

If you want to get really technical, then the tiniest of bumps and grooves on the rotor and pad will have forced the two the tiniest bit apart, but that's mostly irrelevant here.

When you press the brake pedal, pressure is applied to the inside pad and, since the caliper floats over the rotor, that pressure is transferred to the outside pad as well, through to the rotor, producing friction. That friction produces heat, and the car slows down.

Nothing has "moved" but now there's pressure being applied.

Same as if you put your hand against the wall, and then start pushing on it. Your hand, and the wall, don't move... but you can certainly vary the amount of force applied, right?

thanks for clarifiying, i understand now. its just that i was comparing my brakes to my uncles neighbour's lexus ls250 one day and his/her brake pads had about a 2 cm gap between the rotor and brake pad. whereas mine were right up next to the rotor.

so there is SOME contact/friction on the rotor-to-brakepad interface on calibrated/tuned brakes. it's just that its not enough to impede on the freedom to rotate. thus, this is normal and i shouldnt be worried.

thanks for your responses guys. i'm sorry to be such a noob. :bang

[Wild Weasel]

This is not really true.

A liquid is not compressible. Hydraulics do work by the movement of fluid. You are moving the piston in the caliper a small amount (a few thou) but moving it none the less, by moving the fluid in the brake lines a small amount.

You are putting pressure on the pistons, but not necessarily moving them except by the amount of pad that you are wearing off in the braking process.

This inability of the hydraulic fluid to compress is what gives the system such tremendous force. When pushing in the piston in the master cylinder, you are creating a huge pressure in the fluid which is transmitted uniformly throughout. Sure, anything that can move will move, but the fact that nothing can really move is what causes so much pressure to be put on the pads against the rotors.

When you release that pressure, there is no force pulling them back away.


thanks for clarifiying, i understand now. its just that i was comparing my brakes to my uncles neighbour's lexus ls250 one day and his/her brake pads had about a 2 cm gap between the rotor and brake pad. whereas mine were right up next to the rotor.


This is impossible under normal circumstances. Either you weren't looking at it right (weren't seeing the pad and only looking at the caliper itself or something) or the pads were just changed and the pedal hadn't been moved.

Hell, even with brand new pads you wouldn't get a 2 cm gap.

Yeah... I think you were just looking at it wrong. But now you understand. :)

[subliminally incorrect]

You are putting pressure on the pistons, but not necessarily moving them except by the amount of pad that you are wearing off in the braking process.

This inability of the hydraulic fluid to compress is what gives the system such tremendous force. When pushing in the piston in the master cylinder, you are creating a huge pressure in the fluid which is transmitted uniformly throughout. Sure, anything that can move will move, but the fact that nothing can really move is what causes so much pressure to be put on the pads against the rotors.

When you release that pressure, there is no force pulling them back away.



This is impossible under normal circumstances. Either you weren't looking at it right (weren't seeing the pad and only looking at the caliper itself or something) or the pads were just changed and the pedal hadn't been moved.

Hell, even with brand new pads you wouldn't get a 2 cm gap.

Yeah... I think you were just looking at it wrong. But now you understand. :)

yah this was at 8 am or so, and there were lots of shadows from the sunlight, so it might be at most a 1cm gap.