What size thread is a GM caliper bolt?
There isn’t a single universal thread size for GM caliper bolts; it depends on the model and year. Common configurations you may encounter include 7/16-20 UNC or 1/2-20 UNF for front caliper mounting on many GM cars, while some newer or heavier‑duty GM models use metric sizes such as M12x1.75. Always verify the exact size for your specific vehicle using the GM service manual or the correct parts catalog.
Common thread sizes you may encounter
The size of GM caliper bolts varies by platform and generation. The following patterns cover many GM models, but always confirm with your vehicle’s documentation or a parts specialist.
- Front caliper mounting bolts (to knuckle/bracket): 7/16-20 UNC is common on many GM passenger cars and light trucks from older generations; some trucks and SUVs use 1/2-20 UNF.
- Caliper-to-bracket securing bolts (caliper adapter to caliper): Often the same size as the mounting bolts (7/16-20 UNC or 1/2-20 UNF on heavier vehicles), but some platforms use metric fasteners depending on year and region.
- Caliper guide pins (sliding pin bolts): Typically metric, such as M8x1.25 or M10x1.5, depending on the model; these are separate from the mounting bolts and are critical for caliper alignment.
Note: GM’s global platforms and modern vehicles may switch to metric fasteners on some lines. Always cross-check with the specific service information for your VIN to ensure correct size and torque.
How to identify the exact size for your GM vehicle
To ensure you use the correct thread size for your caliper bolts, follow these steps tailored to your exact GM model and year.
- Consult the official documentation for your vehicle» GM service manual or the GM parts catalog using your VIN to confirm the bolt size and thread pitch for the caliper mounting bolts.
- Physically inspect the bolt: note the thread count in a given length, diameter, and whether the bolt appears imperial (inches) or metric (millimeters).
- Measure the major diameter and count threads per inch (for imperial) or use a thread gauge (for metric) to identify the precise size (for example, 7/16" with 20 TPI or M12x1.75).
- When in doubt, replace with a GM‑approved bolt of the same size and grade, and torque to the specified value in the service manual.
Understanding the exact size is essential not only for fitment but also for proper torque and safety, as brake components operate under critical loads.
Practical tips and caveats
- Always verify the thread size for your specific vehicle by cross-referencing the VIN, model, and year in GM’s official manuals or catalogs.
- Do not rely on visual estimates alone; incorrect thread size can lead to cross‑threading, brake system failure, or reduced braking performance.
- When replacing caliper bolts, ensure you use the correct bolt grade and length as specified for your GM model.
In short, GM caliper bolt thread sizes are not universal. They vary across generations and platforms, with common imperial sizes like 7/16-20 UNC and 1/2-20 UNF appearing on many vehicles, and metric sizes such as M12x1.75 on others. Verifying the exact size for your car through official GM documentation is the best practice.
Summary
The thread size of a GM caliper bolt depends on the model, year, and platform. Common configurations include 7/16-20 UNC or 1/2-20 UNF for mounting bolts, and metric sizes like M12x1.75 on some newer models. Always consult the vehicle’s service manual or GM parts catalog for your exact VIN to ensure correct size and torque.
