Flat-tyrey charger

Nearly 2 years ago I bought a 2005/55 BMW 535d M Sport. I have been very happy with it except for the run-flat tyres. On the inside of the near-side rear and the near-side front, blisters have appeared and then grown into bulges which make the tyre unsafe so that it has to be replaced even though it has done less than 10,000 miles and still has plenty of tread on it. I am told that this is because I have driven over speed humps and cushions and into pot-holes. During my lifetime I have driven about 600,000 miles and have never had this trouble with conventional tyres. I have taken the matter up with BMW United Kingdom and they consider run-flats are better for my car than conventional ones. I am thinking of replacing all 4 tyres with conventional ones and wonder if you agree with this. I think that this will be cheaper and a lot safer in the long run as to examine the inside of tyres is difficult.

Asked on 3 October 2009 by

Answered by Honest John
Metre wide, chamfered edge speed cushions are a relatively new phenomenon devised not to impede the progress of fire engines and large goods vehicles. They were very briefly and inadequately tested by the TRRL in 2004, but never tested for their long-term effect on car tyres. Actually it's a no brainer to realise that if a car straddles a speed cushion with both inner sidewalls on the chamfered edges of those speed cushions, the combined forces are bound to damage the inner shoulders of the tyres. Since this is hidden damage, cars could be driven with tyres about to blow out completely unbeknown to the driver. So Honest John's life-saving 3 point plan of action is:-

1. Every motorist should regularly inspect the inner shoulders of their

2. Never straddle a speed cushion. Drive one wheel over and one wheel on the flat surface of the road, alternating from hump to hump where possible.

3. 46 deaths in 2007 were directly attributable to blowouts and many more may have been. Since the numbers of speed cushions have risen since 2007, the number of deaths caused by tyre damage by them must also have increased. Campaign to have these vicious, car destroying obstructions removed before they cause any more death crashes due to tyre blowouts.

(The good news about runflats is RFT3s coming in the autumn, which offer the ride quality of conventional tyres with the capability of running flat for up to 50 miles without damage.)
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