Measuring your car's brakes to tell if you need a brake job
Cooley On Cars
Your car's breaks, they sure are important.
So why is it so annoying when the shop calls and says you need new pads again, and maybe new rotors or disks, and now the price is starting to really get up there and you just start to wonder, do I need them now?
Here's the easy way to convince yourself whether or not.
You're currently the brake job.
The most commonly replaced part of the brakes is the brake pads is a brake pad right here.
It's an abrasive wearable material.
hard but wearable on a metal backing plate, okay.
These are used And they're pressed by a hydraulic piston to clamp onto the disk and that creates the friction slows your car.
So a lot of heat and force takes place on these guys but they do where it says it's pretty thick right there.
That's a lot of material right eventually that wears down to One, two, three millimeters and that's when you need to start to replace these.
The other thing is that your car's weight, the way you drive it, and your terrain are going to make the interval for you to get new brake pads.
Very different from someone who has different terrain and driving habits even in the same car.
And you might just say, wow, my neighbor gets breaks down every 40,000 and I need them every 8,000.
What's going on there.
There are a lot of variables.
So you might want to check these yourself and check your disks as well.
Those are the things you see behind your alloy wheel.
Big round, shiny metal disc, or a known as a rotor.
And that's what pads clamp on to, of course.
Now sure, they're made of heavy duty metal, but they do wear because these brake pads are basically grinding on them all the time.
When those disks get too thin, they can dissipate heat less well, that may cause brake fade during heavy braking.
[SOUND] They may also take a little bit of a warp very slight but just enough for the car to have a little bit of a shimmy or a wobble under braking and you might feel it pulse back in the pedal as well.
This is the world of why you need pads and rotors as the job is called.
Here's how to go in there and prove it to yourself.
Okay, now our car is in the air.
It's all secured and we've cracked these lug nuts because you don't wanna do that while the car is in the air.
I puts too much force on this wobbly jack and threatens to drop it down to the Jack Stan which is there for safety, we don't want that to happen.
And let's get our lug nuts off, you can speed that up a lot using a socket attachment on an electric drill.
Okay, wheels off and now we can get down to seeing the guts of our brake system which is pad that fits inside this thing, the calliper which we saw a minute ago.
And then over here we've got of course the rotor or disc as it's called.
First I need a couple of special tools.
Those tools are called callipers.
They're for measuring the thickness of something especially kind of like this, when you need to grab the outside of it as opposed to ballparking it with a tape measure which you can do, but we're talking about some pretty fine measurements on the thickness of pads and thickness of rotor.
So that's why callipers used to be really expensive nowadays.
I got these for under 30 bucks this pair and there's another one here that I paid not even $20 for and these are going to do two different things.
This one has long sort of outside fingers.
That's gonna allow us to go to our disc or rotor and grab it from both sides.
See, put the disk in there.
And measure that thickness and get a digital reading up there.
The other caliper which is more of a traditional type has these little points right here you can see I'm gonna use that hopefully I can get that in there and match that to the thickness of the pad material.
And then read that number off the display here.
Again, not terribly expensive.
I think you're thinking I'll grab, I'll go buy two tools just to verify my need for a brake job.
You'd be surprised how handy it is to have calipers around the shop if you do any kind of mechanical work at all, let's go measure.
Okay, so first I'm going to take this long reach caliper with these funny long fingers on it.
Here's why you want that I'm going to zero it out.
So I get an accurate measure, I go over here, because I have those long fingers that reach kind of around something, I'm able to go over here and measure that disk.
And I can see it's 28.25 millimetres and I'd go check that against the spec, either in a service manual or you can google it from a reliable source of Specifications on your car.
Why I want those unusual fingers on there, is because as this disc where's, the shoulders at the top are gonna remain at factory thickness because the disc doesn't touch the very edge.
It wears what's called the swept area.
This shiny part here, if I took this regular caliper I tried to measure my rotor like so all I'm going to measure is the shoulder.
I'm not going to get down to the more worn swept area down here.
I'm going to get a false measurement that tells me my rotor hasn't worn at all, just because the very top edge hasn't.
But this caliper allows me to reach past that.
Into the area where the actual friction occurs and get a true measurement.
That's why I got two kinds of calipers.
All right now my other caliper here I use that to measure my pad because this doesn't really have the right fingers if you will to do that.
I want these little tiny ones.
Now this is where it gets a little tough.
You may not be able to really get these down to the pad where I want to spread these to go, the thickness of the soft part of the pad, the part that wears and not pick up the metal backing plate that we saw so I can reach in here.
Yeah, it's tough.
I can't really get clearance on this particular Car, because the top of this tool gets in the way.
So here's a trick.
I get a business card, nice thick piece of cardstock and a flat blade screwdriver.
Here's what I do.
I take this thing and I lay it right up against the face of the rotor disc.
And then, with the screwdriver, I just carefully Go in there, and i score this guy.
So it's right along.
There we go.
So now i've got a line that i made the corresponds to the thickness of my material.
Is it exactly perfect?.
Is it close enough for service?.
Now i can take a really good tape measure or in this case, i will take my caliper Zero it out.
And when I measure that I've got a nice, fat, what is that?
Almost nine millimeters of pad.
Now, on this car, at this moment, this happens to be a fresh brake job.
So, I have lots of rotor with almost no shoulder up here, and nice thick pads.
You might find that your pads are down three millimeters or less, that's generally.
Are you starting to think about replacing brake pads and certainly by the time you get down to one millimeter tend to get them out of there.
So roughly one to three is your think about it zone.
But check the specs on your car and it'll vary a lot more for rotors.
That's less easy to ballpark across makes and models.
Okay, so we've measured up the right front in this case now you got to go over and do the left front, right?
Not necessarily, unless you're doing some very strange driving, like going around a track one way all the time, or if something's wrong with the pressure in your brake system, the brakes on either side of an axle should wear pretty pretty closely to each other.
I'm not gonna go measure the other one, it's gonna be about the same zone as this that either needs replacement or doesn't.
I'm not trying to split hairs here.
Now, if you're comparing breaks from front to back, that's a whole different story.
Front and back.
Brakes are like different universes.
The fronts were way faster than the rear on just about any car.
So in that case you would want to go pull a rear wheel as well, but if you're being told us just a front brake job you need I've done enough here to verify that I do or don't need that.
Okay, so that's it.
It's a little bit of work I gather most people aren't going to do this but if you're watching this video you probably are inclined to do so.
Now you know how to check your brakes to make sure you're not being rock when they say you need a whole new set of pads and rotors across left and right maybe even the whole car.
There aren't that many shops that are going to try and **** you over.
I just haven't run into that many in my life.
I hope you don't either.
But there are some cars.
I'm looking at you German brands that go through pads and sometimes rotors so fast, you'd swear they're pulling your leg.
This is something you might want to do once or just twice to find out okay, that car in my terrain the way I drive Does go through breaks that fast and then at least you know.
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