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Maverick71 · 05-30-2021, 04:46 PM

This is a rather open ended broad question. I have a 2020 tiffin phaeton 40IH and this is my first class A diesel pusher. I’ve learned a lot regarding driving style over the past year but have yet to find my comfort zone when it comes to proper breaking procedures. As a newbie, I’d like to get some opinions on appropriate ways to use the air breaks in all conditions, street, city, highways, hills, etc. especially a crash course on engine breaks, preventing glazing or overheating and Especially how others crest a hill and start the downgrade.

Much appreciated

Brett

Oregonpharme · 05-30-2021, 04:57 PM

You have a good coach with excellent braking systems. My recommendation is read the manual and practice. It also does not hurt to find a trucker that is willing to discuss how they use their air brakes for pointers if you are hesitant.

Like any system, maintenance of the air brake system is critical to long life and performance. Air brakes are a far cry above hydraulic brakes for performance and consistent operation of heavy vehicles, but do require attention to air pressure, not riding the brakes at any time, and very deliberate use. You do not fiddle faddle around tapping the brakes to maintain speed, but apply them only when needed.

Bigd9 · 05-30-2021, 05:35 PM

You will get a LOT of answers to this question! Just remember to do what feels right to you.

I really don't do much different between braking our Honda and the motorhome other than allowing a lot more distance between me and the other vehicles around me. I use the exhaust brake when needed going down hills. I don't believe in the "theory" go down the hill in the same gear as you go up.

Bottom line, get to know your coach, and drive it responsibly ....and enjoy the ride!

richard5933 · 05-30-2021, 05:54 PM

You've forgotten the single most important aspect of your braking system in your initial question(s). The one aspect that can save your a$$ more often than any other thing with regard to braking.

Space.

How much space are you leaving between you and and next vehicle? At all times - not just when it's convenient. It's even more important when things make it not convenient, like when some punk in a souped up compact car insists on being between you and the vehicle in front of you.

Back off and leave enough room to come to a complete stop if need be. Someone moves into your buffer zone? Back off and create another one.

Why? Today I had a perfect example. Cruising through rolling hills between St. Louis and Springfield MO. I was following a compact car down a fairly steep grade (marked 'steep grade') which ended at the bottom on a fairly sharp curve. I was a hundred yards or so behind him, with the engine brakes (Jakes) easily maintaining my speed without having to touch the service brakes.

As we approached the bottom of the hill he had a tire disintegrate. He maintained control, but rather than pull onto the should he just turned on his hazards and quickly slowed to about 5mph. The left lane was occupied and I had no where to go.

Slamming on the brakes helped, but we were still closing in on him. Luckily my air horn managed to convince him of the wisdom of using the shoulder to stop. Otherwise, all bets would have been off. Amazing how fast even a large distance can close in a situation like this.

Always leave a larger buffer than you think necessary. Best technique you can practice as you learn to brake your rig safely.

dfuelman · 05-30-2021, 06:02 PM

I will offer this when it come to braking and climbing hills, What ever gear your transmission uses to climb a grade, you want to use one gear lower to descend the same grade. Use the lower gear in combination with your engine brake to keep your speed down with as little use of the air (foot) brakes as possible. Once you get to the bottom of the hill, shift into high gear and turn off or release your engine brake and continue with your trip.

Mile Marker 42 · 05-30-2021, 06:03 PM

Practice and trial and error is what will work. Understanding how everything works is needed as well.

Skip426 · 05-30-2021, 06:14 PM

Engine brake , what equipment do you have ? 2 or 3 stage engine brake , or just an exhaust brake . Some Cummins engines could have either .

Watch your uphill speed and consider your slowest uphill speed is your control speed for the downhill ; lost track of lowest uphill

crest at 45 MPH . Remember you can speed up any time you MAY NOT be able to slow down without smoking the brakes ( or loosing brakes all together ).

Can you add engine and transmission info to you post and confirm engine ( 2/3 stage ) brake or exhaust brake , for better info.

Theturboman · 05-30-2021, 06:21 PM

I may have a different approach then many but I do not leave the exhaust brake on (only when I need it) as I approach a downhill decent and start to accelerate I turn on the exhaust brake to help slow the coach and if it continues to accelerate I watch the RPM's and when I get to 2700-2800 I turn it off and use the brakes with a few aggressive presses to slow it down then I re- apply the exhaust brake and continue the process. This way I never stress out the engine on RPM's or the brakes but this is just me

Bigd9 · 05-30-2021, 07:33 PM

Exhaust brake: In general with my coach and toad I have found any down grades greater than 7% I need to apply the coach brakes every once in a while to keep the down hill speed down. Any grade less than 7% the exhaust brake usually keeps things under control. Remember, each coach can be different.

But then there are road grades like this one that take special attention:

SKP Kirk · 05-30-2021, 07:50 PM

Dutch Star Don · 05-30-2021, 09:37 PM

The Tiffin brochure says the 40 IH has the Powerglide chassis with either the 380HP or 450HP with a compression brake.

Some basics.....until you get use to how powerful your engine brake is (depending on your weight and if you're towing a toad), you need to start down each grade at a reasonable speed (50-55) and see how well your engine brake holds you back. This will very with the steepness of the grade. On a 4% grade, your engine brake should do well. When you get into the 5% - 6% grades, you may have to start out a little slower or use the foot brakes. Learning how well your coach will descend a hill, could take you MANY trips before you can judge how much braking is needed and at what speed. So again start out slow.

If the coach starts to gain too much speed, you want to "stab" the brakes hard, bring it under control and continue down. NEVER ride them. It may take a couple of good stabs to make it to the bottom. Again, a learning process.

Your engine brake quits operating around 15 mph, so don't be surprised if it suddenly shuts off. When you use the engine brake, the Allison transmission will start downshifting. Your transmission keypad will change to the number "2", the gear the transmission is eventually trying to slow down and achieve. If on flat ground, with the engine brake on, your coach will eventually slow down to second gear and the engine brake will turn off at 15 mph.

People have varying opinions on using the engine brake at other times, like flat ground. Some turn it off and only use it in the hills. I leave mine on all the time, as my coach will operate with the engine brake switch on, (not the engine brake engaged) while using cruise control. I fell that in an emergency stop, I want all the braking power available and don't want to be fumbling for the engine brake switch.

During slower speeds, like 45 mph in light traffic, you can keep the engine brake switch on and control it's use by keeping light throttle pressure. There will be times where you're traveling 45 mph or so, but have to get on and off the throttle due to traffic. With a little practice you'll learn to keep a SLIGHT amount of pressure on the throttle, which will keep the engine brake from engaging, without having to turn it off. This is another technique you can earn and practice.

Around town....I know many use their engine brake every time they stop, figuring that they're saving their foot brakes. If you do this constantly, you end up lightly using your foot brakes for the last few feet before you stop. This will eventually glaze your disc and drum brake pads, leading to squealing.

When in stop and go traffic or around town, having the engine brake on can be annoying when it downshifts abruptly. Your foot brakes will stop well in slower traffic.

Some like to downshift the Allison on a grade to 5th gear and then engage the engine brake, making the downshift occur earlier. Just another technique.

Over the years, I've had three diesel pushers. My first was a 2005 Monaco Diplomat with a 400 ISL and an exhaust brake. I could crest any grade out west at 55+ mph, but with the exhaust brake, I had to slow down to 45 or 50 mph when descending the other side, as my exhaust brake would not hold me back. I mention this because many like to say that you descend at the same speed you crested the hill, I find this never applied, in that coach or my current coach. My current coach is a dog on the hills and often tops them at 40 - 45 mph, but my 3 speed engine brake can take me down the same hill at 55 - 60 mph and hold me back without using the foot brakes.

So.......there is no magic formula and people use different techniques depending on their engine size, coach weight, towing or not towing and if they have an exhaust brake or an engine brake. So you need to experiment, which will eventually give you the ability to look at a grade and know exactly how your coach will behave.

I'm sure other will add their experience and why they do things a certain way. Try all of their techniques and pick the ones that work best for you.

Mr_D · 05-30-2021, 09:42 PM

Quote:

Originally Posted by Skip426

Engine brake , what equipment do you have ? 2 or 3 stage engine brake , or just an exhaust brake . Some Cummins engines could have either .

Watch your uphill speed and consider your slowest uphill speed is your control speed for the downhill ; lost track of lowest uphill

crest at 45 MPH . Remember you can speed up any time you MAY NOT be able to slow down without smoking the brakes ( or loosing brakes all together ).

Can you add engine and transmission info to you post and confirm engine ( 2/3 stage ) brake or exhaust brake , for better info.

Cummins ISB and ISC will all have exhaust brakes. You don't get enging brakes till getting to the ISL, ISM and ISX. Even then some ISL's had an exhaust brake.

Bigd9 · 05-31-2021, 05:29 AM

I don't think this has been mentioned here, but this is something to remember. If you let the coach go too fast downhill with the exhaust brake on, the transmission may upshift to keep the engine from over revving. When this happens it can be scary as the braking power suddenly is greatly reduced. Know your coach, transmission and engine parameters.

Maverick71 · 05-31-2021, 07:32 AM

Thanks to everyone who has given me your 2cents on this topic, it’s been very helpful. I’m always amazed at how little a dealer will instruct a new buyer on certain very key driving components. Common sense goes a long way but so to does experience. I learned rather quickly after glazing the breaks driving from my home to the highway through several poorly timed traffic signals how NOT to lightly feather and use the breaks. Still grappling with where to keep my RPMs with the engine break on as I start to descent a grade. I’m headed over Donner summit tomorrow in Northern California so I’ll put the advice to the test.

Thanks again