Recently fitted new marathons to the trusty steed and went for a spin today. (Third time out on the new tyres) After about 4 miles noticed the rear wheel rubbing and within a few seconds locked up. Climbed off to investigate and the tube exploded blowing the tyre off the wheel. I was outside a pub and people came out to see what the bang was. I had two spare tubes with me fitted one and continued. About 5 miles further on same thing happened but this time to the front wheel. So is it: Me incorrectly fitting/pinching two tyres or faulty tubes? The tubes were blown wide apart they are called Impac and came with the marathons.. I had inflated to 4 bars by the way.