What Size Allen Wrench Should You Use for Brake Calipers?

If you’re trying to replace your brake calipers, in many cases, you’ll need an Allen wrench to get the job done. The exact size you’ll need for your brakes depends on the specific car you own. In addition, some cars use bolts that are compatible with a Torx wrench instead of an Allen wrench.

Allen vs. Torx 

Allen and Torx are two types of screw/bolt socket designs. The Allen socket, also known as the hex socket, has been made since about 1910, while the Torx socket has been made since 1967. The name “hex socket” comes from the fact that the sockets have six sides (they’re hexagonal).

The Allen socket design is commonplace across a variety of screws and bolts, and Allen screws/bolts are used for a wide range of applications, from building and furniture construction to automotive use.

Allen sockets and Allen wrenches have a lot of advantages that make them so popular. Allen wrenches are incredibly easy to manufacture since they’re just a small piece of hexagonal steel with a 90-degree bend. 

Because Allen wrenches are so cheap and easy to make, this makes them perfect for products that require assembly, since the manufacturer can include the correct size Allen wrench with their product.

Allen sockets are less likely to cam out because they have six sides.Camming out refers to when the torque needed to turn a screw is greater than the torque being applied to it, which can cause the wrench to slip out of the socket. Camming out repeatedly can strip the screw and damage the wrench.

Torx sockets, on the other hand, more closely resemble a six-pointed star. As such, they’re also referred to as “star bits”. The main difference between Torx sockets and Allen sockets is that the design of the Torx socket is intended to resist camming out even more than Allen sockets.

It’s a bit complicated to explain, but basically the design of Torx sockets gives them a greater resistance to the radial force that occurs when torque is applied to the screw. Not only does this prevent the wrench from slipping out of the socket, it stops both the screw and the wrench from becoming damaged.

The design of Torx sockets also allows you to apply more torque than an Allen socket to a screw with the same sized head. The advantage of this is that it allows you to apply the same amount of torque to a smaller screw, which can be useful if you’re using a screw in a place where there isn’t much room to accommodate the screw head.

Given the significantly different design of these two sockets, you shouldn’t try and use an Allen wrench to tighten a Torx screw or vice-versa, unless you want to mess up your screws and your wrench. 

How to Replace a Brake Caliper

Knowing what tools to use to change a brake caliper is one thing, but actually changing your brake caliper is another. Let’s go over the proper procedure for changing a brake caliper now.

Removing the Original Caliper

  1. Jack up your car and remove the wheel in front of the caliper you want to work on. It’s best to only remove one caliper at a time since you’ll probably end up spilling a little brake fluid when replacing your calipers, and working on one caliper at a time will help you spill less.
  2. Locate the two bolts on the back of the caliper and remove them. This is where you’ll be putting your Allen/Torx wrench to use. Some calipers may require a ratchet screwdriver for this. Once you’ve removed the bolts, rock the caliper back and forth to loosen its grip on the brake pad.
  3. Now you need to disconnect the brake lines from the calipers. Use a line wrench to remove the brake line fitting from the frame, and use a rubber cap to cover the metal brake line. You should have a container or a towel handy to catch any brake fluid that spills out when you do this.
  4. Once the caliper has been removed from the brake disc, you can remove the brake pads from the caliper bracket. The pads may have clips that hold them in place.
  5. Unscrew the two bolts that secure the caliper bracket, and remove it from the brake disc. Now you’re ready to install the new caliper. 

Installing the New Caliper

  1. Attach your brake lines to the new caliper. Make sure the holes in the brake lines line up with the intakes on your caliper.
  1. Bolt the caliper bracket back onto the brake disc and slide the brake pads on.
  2. Install the new caliper on the bracket so that it fits over the brake pads, and reattach the bolts that secure it in place. If you’ve done everything right, you should now have a brand new, fully functional brake caliper!


When replacing your brake calipers, it’s important to have the right equipment for the job. You don’t want to start replacing your calipers only to discover that none of your wrenches are up to the task.

In addition, replacing your brake calipers can be a bit of a challenge if you don’t have much mechanical experience, so if you’re not totally comfortable with changing your calipers yourself, we’d suggest just taking your car into the shop to have this done.