Community Forums

DebiT · 05-26-2019, 02:09 PM

Although I've towed boats in the past, I'm new to towing a trailer.* Next week I'll be practicing with my new tow vehicle and new to me Casita, and want to ask about a downhill freeway grade that will be part of most of my trips.

When I used to drive our old Class A RV down this grade, I would often shift out of "OD" into regular D, using the engine to brake the rig a little.* My new Durango has regular drive, and then an option to shift into manual, which would then allow for a downshift.* Which is better, to do that, or to use my brakes, thereby of course using my trailer brakes, even if I end up using them quite a bit while going down the grade?

I hope this question makes sense.* I thought it would be good to ask for advice rather than start experimenting at 55 mph!

1st-tt2018 · 05-26-2019, 02:19 PM

Downshift will be better in the long run....best to not melt your brakes...but dont be afraid to use the brakes of you need to.

1bigmess · 05-26-2019, 02:26 PM

Brakes work by using friction against energy. Friction creates heat. Heat reduces braking efficiency. It's a vicious cycle.

The very best plan for going down hill is to not need to use the brakes at all. This way, you have one hundred percent of your available braking power at the ready in case you really need to stop, and you really need to stop Right Now.

This certainly isn't practical in every situation, but it's The Very Best Plan.

If you must use your brakes to maintain a speed you like, stab braking is the method recommended because it gives the brakes some time to cool between applications of friction.

In my mind, if I find myself stab braking quite a bit, I'll use the brakes so I can downshift again and see if that means I use the brakes less.

My attitude may be much more aggressively safer than others, but I've been in enough situations of "I think I have to stop right now" that I want all the braking power I can get to be ready when I need, and not hope that if I need it I will have enough.

twinboat · 05-26-2019, 02:27 PM

Downshift to maintain speed.

Use your brakes to get the speed down, if it gets to fast, and down shift more.

DebiT · 05-26-2019, 02:34 PM

Thanks, all, this makes sense. Basically what I used to do before, probably even more important with a trailer behind me.

So great to have places to go to ask questions. What did we do before the internet?

Rhagfo · 05-26-2019, 04:31 PM

Quote:

Originally Posted by 1bigmess

Brakes work by using friction against energy. Friction creates heat. Heat reduces braking efficiency. It's a vicious cycle.

The very best plan for going down hill is to not need to use the brakes at all. This way, you have one hundred percent of your available braking power at the ready in case you really need to stop, and you really need to stop Right Now.

This certainly isn't practical in every situation, but it's The Very Best Plan.

If you must use your brakes to maintain a speed you like, stab braking is the method recommended because it gives the brakes some time to cool between applications of friction.

In my mind, if I find myself stab braking quite a bit, I'll use the brakes so I can downshift again and see if that means I use the brakes less.

My attitude may be much more aggressively safer than others, but I've been in enough situations of "I think I have to stop right now" that I want all the braking power I can get to be ready when I need, and not hope that if I need it I will have enough.

????
I assume you are speaking to best practice for the OP. Your signature states 2014 Ram CTD, you have an exhaust brake, you should never need the service brakes on normal hills up to about 7%, just drop a gear or two.

1bigmess · 05-26-2019, 04:42 PM

Quote:

Originally Posted by Rhagfo

????
I assume you are speaking to best practice for the OP. Your signature states 2014 Ram CTD, you have an exhaust brake, you should never need the service brakes on normal hills up to about 7%, just drop a gear or two.

Yeah, general advice for a general question. I don't tell people to drive the way I do because I don't assume everyone can or should drive like I do.

Someday, that exhaust brake I bought this pickup specifically for might decide to take a day off. I'm ready for that if it should happen.

sirtate · 05-26-2019, 07:01 PM

One more thing to remember is; slow down.

Remember highschool physics?

E=1/2mv2

The amount of kinetic energy in an object is equal to one half its mass time the square of its velocity...

So...

If you want to slow down from 70mph to 50, you have to dissipate the energy in the form of heat.

Mass is the same in both cases, let's call it 2.

So half of 2 is 1... (Makes the rest of the math easy)

70*70 is 4900.
50*50 is 2500.

You need to dump 2400 units of energy to slow down those 20mphs.

That's almost the same as *stopping* from 50!

Try it using proper measures and units, you'll get better results, but the difference is the same...

So, instead of running at 60mph, and snubbing at 70 down to 50. Try starting at 40 and running to 50 before dumping your speed.

wingnut60 · 05-26-2019, 08:29 PM

Believe he said he is towing the Casita with a Durango? Starting down slow and never letting speed gain more than about 10mph using brakes/gearing is probably best way.

shane_the_ee · 05-26-2019, 09:00 PM

Does it have a “tow/haul” mode? Start there as most modern vehicles with a tow/haul mode will pick the right gear to maintain a given speed and you won’t have to try and figure it out on your own. Which is a good thing now that there’s 8 or 10 gears from which to pick...

DebiT · 05-26-2019, 09:43 PM

Doesn't have a tow mode, but I understand now. Same as what I was used to with big class A rig. Wasn't sure if trailer, with trailer brakes had different "rules". Laws of physics still the same I guess, keep speed reasonable using gears

Jshopes81 · 05-26-2019, 10:15 PM

You guys are referring to snub braking. Stab braking is hitting the brakes almost to the point of lockup. Thats what it seems like anyway. I like snub braking. A search engine browse will explain it well.

grindstone01 · 05-26-2019, 10:31 PM

Downshifting is good, but do not over rev the motor into red line or you will be looking for a new motor. Most likely you will need to use your brakes to keep things under control, just try not to ride the brakes.

bross · 05-27-2019, 08:58 AM

I'll just parrot what others have said. I never use my brakes on down hills, unless as stated to slow enough to drop to a lower gear. With our Canyon Star, 26,000lbs, Ford F53 chassis and V10, that would mean 1st gear, hazard flashers on, staying in the slow lane with the big rigs on anything over a 6-7% grade. That gas V10 is a revver, so it could be turning 4500-5000rpm on some descents just to maintain 25mph.

Now with our TT and F-150 I just use tow-haul mode and it easily maintains a safe speed using the gears in the transmission, rarely do I need to intervene.