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Topic: Retarder discussion (split from Re: Fuel economy difference between 350hp and 450hp Cummins?) (Read 499 times) previous topic - next topic

Retarder discussion (split from Re: Fuel economy difference between 350hp and 450hp Cummins?)

Keep the retarder off unless you are on flat land and unless you NEED the retarder use the service brakes.  pc

 
S/W Houston 95" U320C SE/40' 
Build #4778  Cummins M11
Repairs & Covered RV Parking (BAO)
PPL is close..

Re: Retarder discussion (split from Re: Fuel economy difference between 350hp and 450hp Cummins?)

Reply #1 –
"Keep the retarder off unless you are on flat land and unless you NEED the retarder use the service brakes."

Why?

best, paul
1999 U320 40' 1200 watts on roof. 12cf AC/DC Cold plate fridge/freezer. VMS 240 CL Honda Element

Re: Retarder discussion (split from Re: Fuel economy difference between 350hp and 450hp Cummins?)

Reply #2 –
Quote from: Paul Smith –
"Keep the retarder off unless you are on flat land and unless you NEED the retarder use the service brakes."
Why?
best, paul
Service brakes need to be used to make sure all components are working and nothing is binding. Minimal use may be the reason some calipers stick and helper springs are needed.

Using the retarder on all downgrades does not keep the driver in touch with the ability of the service brakes to stop the vehicle. How well do they work and how many times can you apply the service brakes before fade becomes a factor? Constant retarder use can mask a brake problem. Operators need to be aware of service brake capabilities in case of a retarder malfunction.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Retarder discussion (split from Re: Fuel economy difference between 350hp and 450hp Cummins?)

Reply #3 –
Thanks! I was reading it in the context of fuel economy. And did not see the connection.

Apart from pressing hard on the service brakes every day when we start out, we do seen to need to do it from time to time every day to avoid carless autos.

On respectable downgrades I try to find the sweet spot between:

Speed

Selected gear

Fluid temps

Service brakes

and not use the retarder.

It looks like more than one of us is going to get our hand slapped with a ruler for going off-topic ;o)

best, paul
1999 U320 40' 1200 watts on roof. 12cf AC/DC Cold plate fridge/freezer. VMS 240 CL Honda Element

Re: Retarder discussion (split from Re: Fuel economy difference between 350hp and 450hp Cummins?)

Reply #4 –
Quote from: Pierce & Gaylie Stewart –
Service brakes need to be used to make sure all components are working and nothing is binding. Minimal use may be the reason some calipers stick and helper springs are needed.

Using the retarder on all downgrades does not keep the driver in touch with the ability of the service brakes to stop the vehicle. How well do they work and how many times can you apply the service brakes before fade becomes a factor? Constant retarder use can mask a brake problem. Operators need to be aware of service brake capabilities in case of a retarder malfunction.

Pierce

Ditto

I think the retarder is best in tight traffic at speed as the service brakes are cold normally. 

And big hills of course.

Common problem with brakes made for heavier rigs than our coaches.

Old marquis with gillig bus chassis glazed the brake drums a lot. Coach never warmed up the brakes
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Retarder discussion (split from Re: Fuel economy difference between 350hp and 450hp Cummins?)

Reply #5 –
Around town, I keep the retarder on a mid-range setting.  This way it engages lightly before my foot travels from the accelerator to the brake pedal, giving me a slight head start on braking.  It also allows me to modulate speed easily.  I use service brakes mostly for the final stop, so they do get exercised.  And there are enough idiots around that they get exercised HARD more than often enough.

On downgraded, I use the retarder along with downshifting to try and keep my speed where I want it without using the service brakes.  That being impossible in traffic, I do occasionally use the service brakes moderately to bring the speed down where I want it, then continue with the retarder.  Since so much of my driving is in California, I can practically guarantee one or two HARD uses of the service brakes as  I come up on someone doing 30 with no room to pass, or better yet, a truck doing 25 pops right in front of my bumper from the right lane.  This happens two or more times on each pass of the Grapevine, where I try to maintain a speed around 55 limited to the same two lanes where trucks are limited to 35.

One of the reasons for me buying a Foretravel was the retarder, and I intend to use it.  My brakes are exercised well enough.  I also give them a few hard applications while stopped before starting a trip.  This makes sure they are moving freely.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: Retarder discussion (split from Re: Fuel economy difference between 350hp and 450hp Cummins?)

Reply #6 –
Quote from: Paul Smith –
Thanks! I was reading it in the context of fuel economy. And did not see the connection.

I've split the retarder posts off from the 350/450 fuel economy topic to avoid further confusion.
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Retarder discussion (split from Re: Fuel economy difference between 350hp and 450hp Cummins?)

Reply #7 –
What Tom Lang described seems to make the most sense to me, using the transmission, retarder, and service brakes in combination. It also depends on a lot of other factors, e.g. the terrain, traffic, weather as to whether the retarder is used. I rarely use the service brakes (except in an emergency) until the last 200 feet of a normal stop.
Royce & Denise, MC #17410
'01 U320 4220 ISM450 Build #5895 SOLD
Toad: '10 Honda CR-V

Travel makes one modest. You see what a tiny place you occupy in the world. - Gustave Flaubert

Re: Retarder discussion (split from Re: Fuel economy difference between 350hp and 450hp Cummins?)

Reply #8 –
Quote from: pocketchange –
Keep the retarder off unless you are on flat land and unless you NEED the retarder use the service brakes.  pc

I agree and use mine that way normally.  Leaving my home I have a steep downhill that with the retarder on at the third position and the trans set for 1-6 the engine does not automatically downshift.  retardation is fairly low.

I see I need to manually downshift the engine so the retarder works better?

I normally leave the retarder off at this point probably because of the low effect and agressively ride the brakes down the hill to warm them up and remove and rust or glaze off the rotors.  Couple of hundred yards they warm up and are ready to go.

At 32.000 to 35,500 the weight is light enough to not quickly warm the brakes up if needed in an emergency as others have noticed and posted.

I prefer the disk brakes as they have almost limitless stopping ability.  Fun to use them hard.  Especially if you had driven older rv's that normally lacked the braking reserve these have.

But on a crowded freeway with close traffic I do turn on the retarder at maybe the second position. 

Adds the initial braking effect the cold brakes lack.  Probably why Foretravel used the retarder originally. 

Fire trucks I think are 45k weight.

Had my electric/electronic guru move my joystick up to the middle position in the second row up from the rear and the retarder button is next to it on the drivers seat side.

I had a brake pad dragging issue on our first trip and it happened a second time on a subsequent trip.  Hard application of the brakes retracted the shoes enough upon release to not drag.

Reading the meritor service instructions I noted test when you add the clay based lubrication you are supposed to remove a plug on the top of the caliper so you do not overfill the reservoir and cause the pad to drag on the rotor.

It also mentions needing lube one or two times in the life of the pads in total. 

Never heard anyone mention removing the plug while lubing the calipers. 

So my operation might be an unconscious way to not have any pad dragging.  Hard and off retracts the pads for sure.  Especially after adding the helper springs and having the cummins guys flush the calipers and use the correct grease.  I doubt if they pulled the vent plug although. 

Sometimes I forget why I do things a certain way but no drag this way and the warmed up system allows strong hard stops on top of the retarder.

Had a fed-ex truck stop short at 65mph in front of us in New Mexico.  150 yards maybe?

Whoa Nellie.  Easily  stopped well short.  Warm brakes and retarder.  Impressive. Almost came out of the seat. 

"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Retarder discussion (split from Re: Fuel economy difference between 350hp and 450hp Cummins?)

Reply #9 –
"I prefer the disk brakes as they have almost limitless stopping ability. Fun to use them hard. Especially if you had driven older rv's that normally lacked the braking reserve these have."

I'm always impressed at how the disk brakes stop 35,000 lbs. If you tell them stop, you do.

Sometimes I look to see if our Honda is abut to pass us. ;o)

best, paul
1999 U320 40' 1200 watts on roof. 12cf AC/DC Cold plate fridge/freezer. VMS 240 CL Honda Element