Fermi estimate of a big San Jose auto dealer's yearly tire volume

Estimate how many tires a single large car dealership in San Jose, California buys in one year. Talk through your assumptions and your arithmetic. ```hint Follow the tires A dealership does not buy tires for their own sake. List every part of the business where a tire ends up on a car, and ask which of those the dealer actually pays a tire supplier for. ``` ### Clarifying Questions - Does "large dealership" mean one high-volume franchised store, or a dealer group with several locations? - Do tires that arrive already mounted on new cars from the manufacturer count as dealer purchases, or only tires the dealer buys separately from suppliers? - Should the count include tires the dealer fits to used cars it reconditions for resale, or only tires sold to service customers? ### What a Strong Answer Covers - A clear definition of what counts as a tire purchase, with an explicit call on factory-mounted tires on new cars. - A breakdown of where the dealer's tires go (customer service work, used-car reconditioning, minor uses), each with its own equation. - Labeled, round assumptions for the drivers that matter: sales and service volume, tire life under local driving conditions, and the share of replacement demand the dealer wins. - Arithmetic that is easy to follow, a sanity check from an independent angle, and the range implied by the least certain assumption. ### Follow-up Questions - Which assumption moves your answer the most, and what single figure would you ask the dealer for to pin it down? - How would the estimate change for a dealership of the same size in a city with snowy winters? - The dealer wants to sell 20% more tires next year. Which lever in your model would you pull first, and why?