[VincentVega]

far less than 575 feet from 55 mph. Like substantially less than a third of that distance.

I'm far from an expert, but I dont think the stated distance is too far off. I found this...

Keep your distance from the car ahead – stopping time and distance is up to four times more for an RV. Never tailgate (good advice even in a car!)

Read more: http://campingrving.suite101.com/article.cfm/rv_insurance_safety_tips_for_drivers#ixzz0NtBfqRYw

That said, if the rider did try the brake check he got what he deserved.