Why do transport trucks sometimes have many spare tires hanging from their undercarriage, almost as many tires as those being used? Surely they don’t expect almost all tired being used to break down at once?

Question

Why do transport trucks sometimes have many spare tires hanging from their undercarriage, almost as many tires as those being used? Surely they don’t expect almost all tired being used to break down at once?

In: Engineering

Answer 1

You might be thinking of lift axles – axles that can be raised or lowered depending on the situation.

They affect turning radius, traction, weight capacity and distribution, and to some degree fuel efficiency and of course the tire wear depending on whether they’re raised up or lowered so that the tires contact the road.