Run-flat tires have reinforced sidewalls that let you drive 50 miles at 50 MPH after a puncture, eliminating the need for an immediate roadside change.
The tradeoffs are significant. Run-flats cost 30–50% more than conventional tires. They ride harsher because the stiff sidewalls transmit more road feel. They wear faster. And they usually can't be repaired — even a small tread puncture means full replacement.
Run-flats are popular on BMW, Mini, and some Mercedes models. The manufacturer sometimes deletes the spare tire to save weight and trunk space, making run-flats the only option.
If you have a run-flat-equipped vehicle and want to switch to conventional tires, you'll need to add a spare and tools to the trunk. Conversion is possible but reduces the run-flat 'safety net' the original design provides.
Mounting and balancing run-flats requires specialized equipment that not every tire shop has. Call ahead.