What size Allen wrench do you need to change front brakes on a 2001 GMC Sonoma?

The size of the Allen wrench (hex key) needed to change the front brakes on a 2001 GMC Sonoma will depend on the specific caliper design. There's no single definitive answer. You might need multiple sizes.

You'll likely need at least one Allen wrench to remove the caliper mounting bolts. These are typically either 7mm or 8mm. You might also need a smaller Allen wrench to remove the caliper bleed screw if you're replacing the brake fluid.

It's best to:

1. Consult your owner's manual: This is the most reliable source for specific information about your vehicle.

2. Look at the caliper bolts themselves: Before you start, visually inspect the caliper bolts to identify the size of the Allen wrench needed. Take a wrench with you to the truck and try it out.

3. Use a wrench set: A set containing both 7mm and 8mm (and possibly other sizes) will ensure you have the right tool.

Don't attempt brake work if you're unsure of what you're doing. Brake failure is extremely dangerous. If you are unsure, consult a qualified mechanic.