Service Brakes w/ Retader, Panic Stopping

[davidbrady]

Sounds good Chuck and Ernie. There's also the fact that the jake disengages at 15 mph leaving braking to a stop entirely up to the service brakes. Then there's the issue of making sure the retarders are turned off on slippery roads to avoid possible loss of drive axle traction and loss of control. All of this adds up to me turning on the retarder when I need it and off the majority of the time, which I also agree is what skilled truckers do. The transmission retarder will bring the bus to a complete stop, but the added braking provided by retarders is far from smooth and linear. Retarder braking power is dependent upon engine speed and gear selection. If a Prevost's service brakes are a finely tuned system with each axle doing it's proportional amount of braking, then additional drive axle retarding upsets this balance. I've looked at the many NHTSA braking test for transit buses and semi's and all braking requirements are based on service brakes alone. The service brakes need to get the job done in an emergency, the retarders need to get the job done on long descents - two different requirements satisfied by two different systems. Some may thing the bus stops faster when using the retarder along with the service brakes, but I think that's an illusion. The retarder on my H3 makes my service brakes feel like they're power boosted, but I'm sure w/o the retarder I can achieve maximum braking power and minimal stopping distances by pushing harder on that pedal. If you can't stand on the service brake pedal with the required force, then the driver is the limiting factor. There are lots of myths perpetuated in the Prevost community and I think this is one; be careful out there.