“Brake caliper bolt stuck” and “caliper mounting bolt stuck” aren’t phrases I’ve ever heard people actually say. But thanks to Google, those combinations of words are likely why you’re reading this. People in the U.S. googled those two phrases, or other very similar ones, over 100,000 times in the past year. Which means the problem of having a stuck caliper bolt is something bugging a lot of people. Stuck or frozen caliper bolts are one of many problems that comes from reusing old parts during a brake job, rather than replacing them. — Motor City Mitch
A few years ago, I was driving down a neighborhood street near my home, when a dog darted in front of my car. I hit the brakes and, a moment later, heard a scream to my right. I looked and saw a large man running towards me from his driveway. He ran around the front of my car yelling and slammed his hands down on my hood.
As it turned out, his dog (and my hood) were fine. But the next day I decided to look at my brakes. I wasn’t sure, but in the turmoil, I thought I’d heard them squeak. And when I looked, I saw fluid at the base of my right front wheel. That led to me trying to remove my calipers and, eventually, heading to see Dave, the mechanic at the Sunoco station a block away. It was my introduction to “caliper mounting bolt stuck.”
For this reason — stuck caliper bolts — Carlson recommends replacing them anytime you replace your calipers. Doing so makes sense. Your brakes are a system that is put under enormous pressure and over months and years. Eventually, things wear out and rust. And it’s not just calipers and rotors and pads, but the nuts and bolts — the hardware holding things in place.
What Caliper Mounting Bolts Are and Aren’t…
First, a word about what we’re not talking about…
- We’re not talking about bolts on drum brakes. (This is strictly a disc brake conversation.)
- We’re not talking about “caliper pin bolts, or lock bolts, which hold guide pins in place on a floating caliper. (These bolts get stuck too, but that’s another problem.)
- Nor are we talking about bleeder valves, bleed screws, banjo bolts or anything that holds on brake lines or lets you breed the brakes.
What we are talking about are what you see above — the bolts which hold calipers onto your car or truck. Remove them and your calipers fall off. Plain and simple. They’re often called “caliper bracket bolts” because they attach to the part of your caliper called the bracket, and hold it tight to the spindle or steering knuckle.
Now a word about torque, the twisting force that tightens a bolt.
Because caliper bolts MUST stay on, they need a LOT of torque. AutoZone, for example, recommends 113 pound feet of torque. To put that number in perspective, the average person can (according to NASA) apply about 15 pound feet with a bare hand. A heavy-duty drill can create up to about 45 pound feet of torque — “pound feet” being a way torque is measured. (There are other ways, such as newton meters, that I won’t go into here. Some people say “foot pounds” instead of “pound feet,” which is both close and understandable, but technically not correct.)
If you’re wondering how to measure torque, a good way is to use a torque wrench. Here’s a wonderfully clear two-minute video about torque wrenches, if you want or need to learn more, by the YouTube mechanic Chris Fix…
Brake Caliper Bolt Stuck?
So you’ve got a stuck caliper bolt. It may be old or rusty or overtightened. It may an original bolt that you or someone reused when they replaced a caliper. In any case, it’s stuck: what do you do?
For starters, when you’re dealing with a front wheel, it’s nice to be able to turn it right or left. That can make it easier to get at things, particularly these bolts. So unlocking your car’s steering wheel, while keeping the car off, will let you do that.
Once you’ve found the bolts, it’s really handy to have a breaker bar. A breaker bar is a long wrench-like bar that doesn’t ratchet. Using it with wrench-style sockets, you can pull up or bear down on the handle to create a great deal of torque.
Generally one to two feet long, breaker bars give you length and the length gives you leverage. Often it’s enough leverage to “break” a stuck caliper bolt free when it’s been tightened to 100+ pound feet of torque.
Below is a breaker bar and socket my mechanic was using to loosen a caliper mounting bolt on a GMC Sierra.
Extending Breaker Bars
A breaker bar and socket may not be enough. The “caliper mounting bolt stuck” you’re dealing may be old or rusty. It may have been over-torqued in the first place. Or it may be you have an older vehicle, and the calipers were replaced but not the bolts.
A helper bar or cheater bar can give you even more leverage. Basically, this is a piece of pipe you fit over your wrench or breaker bar to give you more length. And with that added length, you’ll be able to apply much more leverage and torque on the stuck bolt.
In the following one-minute YouTube video, Nick Stageberg puts a 3-foot galvanized pipe on a one-foot breaker bar. He’s loosening a lug nut rather than a “brake caliper bolt stuck” — but the idea is the same either way. He’s got, as he puts it, “a tough nut.” And he explains it well.
“Archimedes said, ‘With a big enough lever, I can move the world,” Stageberg said in the video. But that’s not the only way to go at a “brake caliper bolt stuck.”
Using a Wrench
There’s a different way to go that doesn’t involve a breaker bar.
Eric the Car Guy is a YouTube mechanic who’s created hundreds of videos and has over a million subscribers. In making the video below on “How to Diagnose and Replace a Bad Brake Caliper,” he ran into two tough caliper bolts.
At the 12-minute mark, he encounters two rusty bolts, which he calls “fasteners.” And they’re rusty and stuck enough that he sets aside his breaker bar for a wrench that gives him an ultra-tight fit on the bolts.
His wrench extends off camera but it appears to be at least 12 inches long, and perhaps a few inches more. “I like long wrenches,” he says. “They really help leverage.” He hits down on the wrench and, on the second bolt, switches to his ratchet. “Instead of hitting on my wrench, I’m going to hit on my ratchet — it’s got a soft end on it.”
“Personally with rusty fasteners,” he adds, “I prefer that impacting motion. But I’ve also had people make comments that it’s a bad thing because can cause damage and carpal tunnel and those kinds of things. So, weigh the risk and make your own choice.”
Here’s the video, starting at the point where finds the rusty bolts:
I’ll add that Eric has another video about replacing brake parts — getting rid of squeaky brakes by replacing brake hardware). And along that line of thinking, Carlson recommends replacing these bolts if you’re replacing a caliper. Again, it just makes sense.
He’s Got the Jack
What if a wrench or breaker bar and the strength of your hands and arms isn’t enough?
One thing you some people do is put a car jack underneath a breaker bar or pipe and just jack it up. What they’re basically doing is letting the weight of the their car or truck do the work. It’s one way to take torque to a whole new level.
There’s a 40-second YouTube video of Gabriel Cannon doing exactly that.
“So we have a socket, we have some leverage, and we have a jack stand,” Cannon says. “All we’ve got to do is tighten up that jack stand.”
The bolt begins loosening at the 26-second mark.
There is more to talk about — from impact wrenches to torches — but I’m going to stop here.
I will say that replacing caliper mounting bolts is a good idea when you’re replacing calipers. It makes the brake job complete, so you’re not relying on “brake caliper bolt stuck” to bear the pressures of braking.
Because when a dog darts in front of your car, with a screaming owner right behind, you want your brakes at their best. Life turns on a dime.