What Car? Q&A - Should I take run-flat tyres of my BMW?

Q: My new 520d has come with run-flat tyres. The dealer has offered to change this option to regular tyres with a spare if I wish.
What are the pros and cons and what would you advise?
Ger Kidney

A: Run-flat tyres have stiffer sidewalls so that they can, as their name suggests, continue to run when deflated.

Unfortunately the stiffer construction means the ride is a little more uncomfortable than on a car fitted with conventional rubber.

BMW says it develops cars to use run-flat tyre specifically, however, so if you switch it claims it won't handle as well. You'll also lose some boot space to the spare wheel if you go for standard pneumatic designs.

Although we'd be tempted to try conventional tyres for added comfort, it would be very expensive to revert back to the costly run-flats if the handling did deteriorate signficantly.

We'd be more than happy to live with the ride of a 5 Series on run-flats, so all-in-all we'd leave them be.