>>1580159Not that anon, but I think he is talking about the fact that clinchers hook on to the rim using the pressure created by inflating them.
The clincher system is based on the tire having beads that grip on to the rim's specialized hoops when under pressure. The problem is that road bikes require both lightweight and high pressure wheel systems. Unfortunatelly high pressure clinchers on lightweight rims can be (not are) the cause of failure under hard braking (both because of the forces the rim has to deal with and because of the heat a rim brake causes) and cornering.
The tubular system is more gentle. This is because the tire is using adheasive to stay on the wheel putting much less force to the rim while being able to inflate to even higher pressures.
Basically, in a high speed descending situation, there is a chance that the sidewalls of a clincher rim will come apart due to its lightweight and the forces it has to deal with.
There is also the idea that tubulars might allow you to come to a stop safely in the case of a flat tire since they are glued on to the rim. A deflated clincher tire has nothing to hold it on to the rim and could potentially jump out. This is a theory tho. Chances are that if you get a flat at a high speed descent you are going to eat it anyway.
Lastly, tubulars also have their dangers. If no properly glued on they can come loose (see Beloki's 2003 tdf crash as an example).
