Can I Put Smaller Tires on My Car?

Using smaller tires can mean big gains or big trouble.

Tire size can make or break any aspect of your car's performance from acceleration to fuel economy. However, many newer cars aren't as happy with rubber changes as older ones.

Potential Gains

Smaller-diameter tires can increase acceleration by reducing the drivetrain's effective gear ratio, which allows your engine to exert more torque per revolution. Shorter tires also get your car lower to the ground for reduced aerodynamic drag and increased fuel economy and high-speed stability. Narrower tires can increase fuel economy by offering reduced rolling resistance, but only to a point.

Drawbacks

Narrower tires will reduce braking, acceleration and handling performance. Shorter tires will likely increase fuel consumption by keeping revolutions per minute (rpm) higher at cruise speed, and any aerodynamic gains aren't likely to offset the fuel consumed by this additional rpm.

Considerations

Your car's electronic control systems don't know or care about the width of your tires, but using tires of differing diameters can cause serious problems. Your antilock brakes, stability control and traction control systems are calibrated with the assumption that all four tires are the same size. Using shorter tires on only the front or rear will send all of these systems into fits and ultimately cause system failure.

References

• Intellichoice: Tire Basics
• AJ Design: Gear Design Equations and Formulas Calculator
• AA1 Car Library: Anti-Lock Brake Systems