Here’s the thing: many of your surprise expenses aren’t surprises at all. Look at your life from a broader view. You know tires don’t last forever (set something aside each month for auto maintenance).
Assess my budget for what is NOT being budget. Which months are extra spending months. Set back some money for yearly clothing and shoes. Enough money for gadgets? How much have I spent on gadgets last year? Entertainment money? Out of town money?