The Times of London has a handy table of the numbers of cars burned during each day of the French riots. Tim Blair and Mark Steyn have called this metric the Car-B-Q. A graph showing the numbers of cars Car-B-Qed against day is shown below.
Two inflection points immediately jump out. The first occurs on Day 6 when the car burnings really took off after trending flat for the previous 5 days. I think this represents the missed opportunity to deal with the riots at an early stage, either with large concessions or large crackdowns. I don't think it mattered which as long as the authorities acted decisively, which they didn't, because this was the period when the French government stood paralyzed like a deer in headlights.
The second inflection point is Day 11, when the graph appears to be flattening out. Appears because Day 11 is also the day in which the modality of the disturbances began to change from Car-B-Qs to arson against churches, schools and buildings combined with shooting attacks against police officers. But clearly it may be the case that the French riots may be running out of steam and therefore susceptible to the countermeasures the government is now putting in place. Let's wait and see.