Disc Brakes Getting Hot On One Side?

#1 Sticking Caliper Piston

This is probably the most common cause behind hot disc brakes on one side.

The caliper piston is the part inside your brake caliper that pushes the brake pads against the rotor when you hit the brakes. It’s hydraulic, meaning it works using brake fluid pressure.

Now, here’s the thing: sometimes this piston gets stuck. 

It might be because of corrosion, dirt, or worn-out seals. When it sticks, the pad doesn’t pull away from the rotor properly after you stop braking. 

So what happens? Constant rubbing. 

That rubbing creates friction. And friction = heat.

Imagine walking around with your shoe constantly brushing against the ground. Your foot would heat up real quick. That’s pretty much what’s happening to your brake. 

One side is basically always “on,” even when it shouldn’t be.

Also Read: Why Is My Car Beeping When Parked?

#2 Frozen Or Corroded Caliper Slide Pins

These little guys don’t get a lot of attention, but they play a big role. 

Slide pins let your brake caliper move smoothly when you brake. They ensure that the caliper applies even pressure to both brake pads.

But here’s the problem: they’re metal, and they live in a very unfriendly environment. Water, salt, dirt… it all builds up. Over time, they can rust or get gunked up. 

Once they freeze or corrode, the caliper can’t slide like it should.

And that means one pad might stay in contact with the rotor while the other doesn’t. Or the caliper clamps down unevenly. Either way, one side ends up dragging. 

More dragging, more friction, more heat. 

And just like that, one disc brake is hotter than the others.

#3 Collapsed Or Blocked Brake Hose

A blocked brake hose is another reason why your disc brakes are getting hot on one side. 

Your brake hoses carry fluid from the master cylinder to the calipers. When everything’s working right, fluid flows in when you press the pedal and flows back out when you let go.

But sometimes the hose gets damaged. 

It can collapse or get clogged up. So fluid can go in and push the caliper piston out, but can’t come back out properly. The piston doesn’t fully retract. And guess what that means? Yep, the brake stays partially engaged. 

Again, more friction and more heat on that side.

Also Read: Whirring Noise After Engine Off

To the naked eye, everything might look fine. But inside that hose, it’s a mess. This kind of issue can drive you nuts because it’s not super obvious, and it mimics other brake problems.

#4 Parking Brake Mechanism Sticking

If your car has a rear disc brake system with an integrated parking brake, this one’s for you. 

Over time, the parking brake mechanism can get sticky. This happens a lot if you don’t use it regularly. Rust, grime, or just wear and tear can cause the mechanism to not fully release.

And when it doesn’t let go all the way, the brake pads drag. You’re driving around with your parking brake kind of halfway on. 

That’ll heat up one side of your brakes in no time.

This issue is more common in areas with a lot of moisture or salt on the roads. 

So if you live where winters are nasty and salty roads are the norm, keep this in mind. A stuck parking brake can be easy to overlook but makes a big impact.

#5 Wheel Bearing Issues

Sometimes it’s not the brake system itself. 

A worn-out wheel bearing can cause uneven rotor movement. That can make the brake pad on one side rub more than it should.

It’s not super common, but it happens. 

A failing wheel bearing can wobble the wheel slightly, creating just enough movement to cause the brake pad to touch the rotor when it shouldn’t. Again, you end up with that dreaded heat on just one side.

Another clue? You might hear a grinding or humming noise while driving. That’s your bearing crying for help.

Also Read: Car Makes Popping Noise When Accelerating

Risks Of Driving With One Hot Brake

Now, you might be thinking: “Okay, it’s just a little heat - how bad can it be?”

Unfortunately, it can be pretty bad.

For starters, heat messes with brake parts. Your rotor can warp if it gets too hot, and once that happens, you’ll start to feel vibrations when braking. 

Then the pads wear unevenly, and suddenly you’re replacing stuff way sooner than you planned.

More importantly, though, it affects how your car stops. 

If one brake is always grabbing more than the others, your car can pull to one side during braking. That’s dangerous, especially in wet conditions or in a panic stop.

And let's not forget about the fire risk. It’s rare, but brakes can actually catch fire if they overheat badly enough. Usually, you'll notice smoke and a burning smell before it gets to that point - but still, not worth testing.

How To Diagnose The Problem

So now that you know what could be causing the issue, the next step is figuring out which part is actually acting up. You don’t need to tear the whole thing apart right away, there are a few quick checks you can do to narrow it down. 

These can help point you in the right direction:

1. Listen while driving. Squeaking could mean dragging pads, and a humming or growling sound might hint at a bad wheel bearing.
   
   
2. Jack up the car and spin the wheels by hand. If one doesn’t spin freely or feels like it’s dragging, something’s sticking.
   
   
3. Check brake pads for uneven wear. One pad looking way thinner than the rest means a stuck caliper.
   
   
4. Inspect the rotor. A blue or scorched look usually means it’s been overheating.
   
   
5. Try compressing the caliper piston. If it’s hard to push in or doesn’t stay in, that could be a stuck piston or bad hose.
   
   
6. Test the parking brake. Make sure it fully releases and isn’t hanging up on one side.

These quick checks won’t solve the issue by themselves, but they’ll definitely help you zero in on what’s wrong, so you can fix it before it turns into a bigger headache.

Bottom Line

If your disc brakes are getting hot on one side, it’s usually a stuck caliper or something closely related. Slide pins, hoses, even the parking brake can all play a role. 

And while it might seem like a small problem at first, it can wear out parts fast, and even become a safety issue.

It’s not something you want to ignore.

The good news? It’s usually fixable without a full brake system overhaul. 

Sometimes it's as simple as cleaning and greasing some pins, or replacing a hose. But if you're not sure or don’t want to mess with it, a quick visit to a mechanic can save you a ton of headaches.