Do You Really Need Brake Pads and Rotors at the Same Time?
This is probably one of the most common questions we get when quoting a brake job.
“If my brake pads are worn out, why do I need rotors too?”
It is a fair question. Brake pads and rotors are two separate parts, and technically, they do not always have to be replaced together.
That being said, about 90% of the time, we do not recommend reusing the old rotors.
Here on PEI, rust and corrosion usually make that decision for us.
The rotors may still technically pass a motor vehicle inspection, but that does not always mean they are a good surface for a brand-new set of brake pads. There is a difference between something meeting the minimum inspection standard and something being worth reusing for another few years.
What Happens When You Put New Pads on Old Rotors?
Your brake pads squeeze against the brake rotors to slow the vehicle down. For the brakes to work properly, the surface of the pad needs to make good, even contact with the rotor.
When a rotor is new, the surface is smooth and even.
After a few years of PEI winters, road salt and moisture, that surface is usually not so smooth anymore. It becomes rusty, rough, scored and uneven.
Putting a new brake pad against that old rotor is a bit like rubbing it against a cheese grater.
The old rotor starts wearing away at the new brake pad almost immediately. Instead of getting the full life out of the new pads, you may only get around half the life you should have.
You may also end up with brake noise, uneven braking, vibration or a pulsating brake pedal.
So while replacing only the pads may save some money today, it can cost you more when the brakes need to come apart again much sooner than they should.
The Rotors May Still Pass Inspection
This is where some confusion comes from.
A rotor can technically be thick enough to pass inspection and still not be in good enough condition to reuse.
Every brake rotor has a minimum thickness. A technician can measure the rotor and confirm whether it is above or below that specification.
But thickness is only one part of the inspection.
We also need to look at the amount of rust, scoring, pitting, heat damage and whether the rotor is wearing evenly.
A rotor might technically be above its minimum thickness, but if the surface is heavily rusted or full of grooves, it is not going to be kind to a new set of pads.
That is why we may recommend replacing a rotor that still technically passes inspection. We are not only asking whether it is legal today. We are asking whether it makes sense to reuse it for the life of another set of brake pads.
PEI Is Hard on Brake Rotors
Light surface rust is normal.
You may see rust on the rotors after a rainy night or after your vehicle has been sitting for a few days. Usually, that light rust cleans off after a few stops.
The problem is deeper rust and corrosion.
PEI vehicles deal with damp weather, winter salt and plenty of moisture. Over time, rust begins building up around the edges of the rotor and across the braking surface.
The inside of the rotor is often worse than the outside. You may look through the wheel and think the rotor does not look too bad, but the back side can be heavily rusted and flaking apart.
Once that happens, the rotor is not going to provide a clean, even braking surface.
What Is Rotor Scoring?
Rotor scoring is simply grooves worn into the surface of the rotor.
Some light marks are normal, but deeper grooves are a problem.
They can be caused by worn-out pads, debris getting between the pad and rotor, seized brake hardware or a sticking brake caliper.
If you install new pads against a deeply scored rotor, the pads have to wear themselves into those grooves before they can make proper contact.
That leads to faster wear, poor braking contact and often quite a bit of noise.
Why Do Brakes Pulsate?
If your steering wheel shakes or your brake pedal moves up and down when you brake, the rotors may be uneven.
People commonly call this a warped rotor. Sometimes the rotor has actually changed shape, but more often the issue is uneven thickness or uneven brake-pad material on the rotor surface.
Either way, new pads will not fix it.
If the rotor is causing the pulsation, the rotor needs to be replaced or, in certain cases, resurfaced.
Why Will Shops Not Warranty Pads on Old Rotors?
Most repair shops will not offer the same warranty on brake noise or brake-pad life if the customer chooses to reuse old rotors.
The reason is pretty simple.
A shop can install the pads correctly, use good-quality parts and do everything right, but it cannot guarantee how those pads will perform against an old, rusty and uneven rotor.
Old rotors are more likely to cause noise and they will usually wear the pads out faster.
That does not mean the pads were defective or installed incorrectly. It means the new pads were put against a surface that was already worn out.
If we are going to stand behind a brake job, we want to know the new pads are being installed against a clean and proper braking surface.
“Back in the Day, People Turned Rotors All the Time”
They did.
Years ago, resurfacing rotors, or “turning” them, was a normal part of a brake job.
Older rotors were often thicker and had more material available to machine away. Rotors were also expensive and labour was cheaper, so it made financial sense to pay someone to resurface them instead of replacing them.
That has changed.
Modern rotors are often thinner and do not have as much extra material. By the time the first set of pads is worn out, the rotors may already be close to their minimum thickness.
Replacement rotors have also become much more affordable, while labour costs have increased.
By the time a technician removes the rotors, measures them, machines them and confirms they are still thick enough to use, it can cost just as much or more than installing new rotors.
Rust and pitting are another issue. A rotor may technically have enough thickness left, but there may be so much corrosion that machining it does not make sense.
Like a lot of things today, many modern brake parts are designed to be replaced rather than rebuilt or reused. Whether we like that or not, that is the reality.
Can Rotors Ever Be Reused?
Yes. It does happen.
If the rotors are still thick enough, smooth, wearing evenly and have very little rust or scoring, they may be reasonable to reuse.
We also need to make sure they are not causing brake pulsation and that they have enough material left to last through another set of pads.
The brake calipers, sliders and hardware also need to be working properly. There is no point reusing a good rotor if a seized caliper is going to destroy the new pads anyway.
The problem is that, in PEI conditions, we simply do not see rotors in reusable condition very often by the time the pads are worn out.
So, Do You Really Need Rotors?
Not every single time.
But most of the time, yes, replacing the pads and rotors together is the better repair.
It gives the new brake pads a smooth surface, helps prevent noise and vibration, and gives you the best chance of getting the full life out of the new parts.
A rotor can technically pass inspection and still be a poor choice to reuse. Saving money by keeping an old rotor does not help much if it wears out the new pads and you have to pay for the same repair again.
At JustJoes, we inspect the complete brake system and explain what we find.
If the rotors are genuinely in good enough condition to reuse, we will tell you. If they are heavily rusted, scored or too worn, we will explain why replacing them makes more sense.
The goal is not to sell you parts you do not need.
The goal is to repair the brakes properly, get the full life out of your new pads and keep you from paying for the same job twice.