Wrong gear

I'm with you on your observation about suggested speeds for descending grades. I think they were developed for descending without Jake's, in which case 17 mph would be a reasonable maximum speed with some brake application, either snub braking or continuous light braking at about 10 psi.

My theory about why drivers end up with smoking hot brakes, with end results being a trailer fire, is they firmly believed the adage to never shift going down a grade. IMHO that is one of the most dangerous pieces of advice a driver can follow. If you are on an unfamiliar route you are bound to get into situations where down shifting is necessary to maintain control.

Even on familiar routes you might come around a curve and see a permitted heavy load crawling along at 10 mph. What's the plan? Are you going to stay in the same gear and stand on the brakes for the next 20 minutes while threatening to stall the engine? That's idiocy. Downshift already! The big problem is if you haven't PRACTICED downshifting on a downgrade you might get into panic mode. Practice. Practice. Then practice some more.

 

The 17 and less are the old defensive speeds for trucks with neurtured jakes or none at all. If you tried it with your jake off at 15 or less you will find the resistance of your engine and very disciplined spending of your air supply plus your thermal build up on your brake pads etc will decide victory or defeat in flames and death.

Lepton1 made some good points as well. Some of which has been forgotten because I have not had to worry about that for some time. If you want to make me scared, hand me a tractor with no jake, a shaky pre 62 brake system and a 18% drop for several miles and tell me take off. (62 and earlier had no spring cans) Ima come offen that at 2 mph. It will be a while. If it's raining or snowing etc YAHOO. let's go because I know i can cool off them brakes.

 

Yup, no shortage of drivers who do not know how to brake, I can go either way, slight pressure all the way down or stab braking, But today the engine brakes a pretty skookum,

 

Here again, when these actions were put into practice the tractor/trailers and there brakes were not what we have today. You take an old B series with a 4x4 or 5x4 and they did not down shift so well. Todays trucks are a whole different thing, so in today's trucks I completely agree with you, And I still stop and hook up brake lines before backing under trailers. Old habits die hard.

 

Me too. Once the milk tanker actually bounced off my hook and backed away from the tractor. I had to chase it with the tractor until mental 2+2 = set trailer brakes you dummy... got it stopped. (No landing gear in sight, we used blocks.)

 

Yup, spring brake a mighty good idea...

 

We didnt have those. Just single cans back there. What a trailer it was...