If you need to do some mechanical work on one or more of the brake calipers in a car, you will want to know what size Allen wrench (also known as a “hex key wrench”) is needed for the job.

A size ⅜” inch or 9 millimeter Allen Wrench is sufficient for most General Motors vehicles, including Chevy and Ford vehicles. However, this may not apply to every car make and model, so you will need to find the answer from an authoritative source, such as the owner’s manual.

Allen wrenches effectively unscrew and replace brake calipers, so finding the right size will spare you from unnecessary difficulties in the process. Read on to learn more!

The Right Size Allen Wrench

Fortunately, Allen wrenches or keys are not difficult to find and come pre-made in various sizes. You will find them available at almost every major hardware and auto retailer, such as:

The Home Depot
Lowe’s
NAPA Auto Parts
ACE Hardware
Many others

The right size Allen Wrench for the brake caliper on a Chevrolet or Ford make vehicle is typically going to be ⅜ inches or 9 millimeters but may in fact vary depending on the model.

Size Variation Issues

It is important to remember, however, that not all brake caliper bolts are the same size, so the proper size of Allen Wrench may vary. In these cases, it will be important for you to consult the owner’s manual of your vehicle if you plan to work on it yourself. On the other hand, a competent auto mechanic should be able to identify the correct size and proceed from there.

You should also be aware that there are numerous instances in online auto forums of people asking what correct size Allen Wrench to use and receiving varied responses; as such, it would perhaps be prudent to take these with a grain of salt unless you can independently verify the information.

What are the Different Sized Allen Wrenches

Allen Wrenches come in various sizes, starting with ⅛ inch, then 3/32 inch, 7/64 inch, 5/32 inch, 3/16 inch, ¼ inch, and the largest size, 7/64 inch.

There are also two kinds of Allen Wrenches: Imperial and Metric. Imperial models use the inch measurements, as you are most likely to find in the United States. Metric models, meanwhile, will be found in the United Kingdom and other countries that use the metric system of measurement.

It should be noted that if you are having difficulty finding the right size to use for a brake caliper or any project for that matter, you might find it useful to start with the middle wrench and go from there.

The Torque Factor

When you go to replace a brake caliper, you will need to know how much torque is required for the caliper to stay in place.

According to the retailer AutoZone, you may need to apply as much as 113-pound feet of torque to screw the caliper bolt in. Given that a human being cannot apply this much pressure manually, a wrench drill may come in handy.

When Should You Replace A Brake Caliper?

This question depends on how much wear and tear your vehicle has undertaken and other factors. Auto Smith recommends that the brake calipers on a vehicle be changed either after 10 years or between 75,000 and 100,000 miles.

If you are unsure of the condition of your brake calipers, you can consult your mechanic for advice. Additionally, there are some valuable YouTube videos on the topic, such as the following:

If you choose to have an auto shop replace the brake calipers, you can expect it to cost at least $500-600 and likely much more once additional fees are factored in.

What Are the Best Allen Wrenches?

If you are shopping for an Allen Wrench set and want to know the most highly recommended brands, here are a few:

Obviously, these are just a small handful of the sets available, so you can do your own research or visit a local retailer to find the best deal for you.

Conclusion

As you can see, the right size Allen Wrench is 9mm or ⅜ inches for some brake calipers, but this is not a universal rule, and you should consult an owner’s manual or other authoritative sources to know exactly what size you will need. Good luck!

What Size Allen Wrench Is Needed For Brake Calipers?