🚙 What is Rotational Inertia?

Rotational inertia is how much a spinning object resists changes in speed. The heavier and larger something is — like a wheel/tire combo — the harder it is to speed up or slow down.

When you lift your truck and throw on bigger tires (like going from stock 30” to 35”), you’re making the brakes work a lot harder — not just to stop the truck, but to slow down those spinning wheels.

📈 What Happens When You Go Bigger?

Stock setup:
• 30 inches in diameter
• 65 lbs per wheel/tire

Upgraded setup (35s):
• 35 inches in diameter
• 87 lbs per wheel/tire

Because inertia scales with the square of the radius and the mass, your braking demand increases by about 50–70%.

🔢 Braking Effort Formula

Use this formula:
New Effort ÷ Stock Effort = (New Weight × New Radius²) ÷ (Stock Weight × Stock Radius²)

Example:
Stock: 65 lbs, radius = 15"
New: 87 lbs, radius = 17.5"

➡️ That means your brakes need to work about 82% harder just to do the same job.

🧠 Why This Matters

• 🚨 Longer stopping distances
• 🔥 Brake fade under heavy use
• 🚙 Poor towing & off-road control
• 💸 Faster wear and potential failure

🛠️ Real-World Tip

If you’re running 35s or larger (especially with a lift and heavier wheels), consider:

• ✅ Larger rotors
• ✅ Multi-piston calipers
• ✅ High-friction brake pads

Want to learn more? Call our experts at (716) 775-6700 to talk about your specific build.

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