The Daily Telegraphs motoring agony aunt Honest John has been tacked again on the issue of run flat tyres (the second time in a week).
This time a reader wanted to know his opinion safety and performance.
Q: I have a BMW 525d, which was supplied with runflat tyres as standard. I am not impressed with claims by the manufacturer that they are fitted for safety reasons. Has anyone carried out independent tests on ride quality of these tyres compared with conventional tyres and comparative all round performance? J.H., Mersham
A: I have carried out safety tests involving blow-outs of these tyres at 80mph while cornering. I have also been in the great danger of replacing an offside rear wheel with a blown-out conventional tyre on a motorway hard shoulder. Because of their stiffer sidewalls, runflats generally have the ride quality of the next lower profile, by which I mean a runflat 245/45 R17 will feel more like a conventional 245/40 R18. The ride quality can be shocking on 19- and especially 20-inch wheels.
Oliver Hall, Operations Team