1. #1
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    Default Engine Brake/Retarder with ABS

    I've been wondering,

    It has always been taught and recommended to disengage engine brakes and retarders on rigs in slippery conditions to prevent loss of traction/skidding. With ABS essentially standard now, is this still necessary? If I understand correctly, ABS activations cut off engine brakes and retarders through the engine ECM. If this is the case, why do we need to disengage these auxillary braking devices?

    Additionally, is a heavily loaded fire apparatus with a full water tank even capable of skidding with the force of an engine brake on a slippery road (not accounting for ABS)? I had heard in the past this was more of an issue with light in the rear end situations, such as a tractor bobtailing without a trailer or an empty water tanker.

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    Engine brakes and retarders are not part of the braking action, meaning they have no influence or effect with the actual brakes at the wheels.

    ABS systems reads signals from the wheel sensors, and nothing else. Therefore they only control the brakes. But, if there is a problem to throw an ABS MIL, it will turn off the retarder, but not an engine brake.

    You should always disengage any retarder/jake brake on slippery conditions. Reason is the engine or retarder will significantly slow the rear wheels enough to cause a slide. Even though the retarders work with the brake pedal, they are also controlled by air pressure switches. These switches activate the retarder before the brakes even think about moving. Therefore they need to be disengaged.

    edit: Also with the retarder and ABS. With the retarder working, and going into a slide because of it, the ABS wheel speed sensors will not pick up the slide. Reason being is your braking action at the wheels are not causing the slide, and the wheel speed sensors are not reading a possible ABS event. The slide is caused in the driveline, not the brakes themselves.

    I'm off to work, and this is a quickie reply, so If I missed something, someone should be able to expand on the above.

    FM1
    Last edited by FIREMECH1; 07-17-2009 at 12:29 PM.
    I'm the one Fire and Rescue calls, when they need to be Rescued.

    Quote Originally Posted by EastKyFF
    "Firemens gets antsies. Theys wants to goes to fires. Sometimeses they haves to waits."

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    I have to disagree on this using an engine or exaust brake on snow and ice is safer than hitting brakes. If your engine brake causes you to slide then you surely are not going to slow down by hitting your brakes. We deal with snow and ice 7 months of the year here and we always use our engine brakes and it helps. If your not using it in the winter you are only cheating yourself.

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    We use a combination of the Telma Retarder and Wabco ABS. We ran into this problem in 1994 when our rigs were delivered with off switches and signs to disengage the retarder when roads were wet. After much correspondence Spartan authorized removal of the switches and placards after the ABS manufacturer and Telma agreed that the ABS would cut the Telma out on any wheel lock up. We have run 3 rigs for the last 15 years in all sorts of conditions with the Telma engaged and no issues.

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    Interestingly enough youve reminded me that as a loyal fan of the show Ice Road Truckers, they show the drivers using Jake brakes in place of service brakes to avoid loss of control.

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    Seen it go both ways.If you're a EXPERIENCED heavy driver you can use the Jake sparingly to help slow down.I've also see it put our 44,000# Engine right around sideways on level ground on a snowy road. There's a reason the Mfgs are telling you to shut it off.I can control air brakes easier than I can predict the Jake action. But then,I've only been driving in the s**t for forty years. T.C.

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    engine brakes that activate when the accelerator are released such as the jake brake would be a problem. In situations where you just want to remove artificial accelerating and braking forces this thing will turn on the second you let off the gas.

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    Quote Originally Posted by Pa6050
    I have to disagree on this using an engine or exaust brake on snow and ice is safer than hitting brakes. If your engine brake causes you to slide then you surely are not going to slow down by hitting your brakes. We deal with snow and ice 7 months of the year here and we always use our engine brakes and it helps. If your not using it in the winter you are only cheating yourself.
    Where did anybody say what you quoted in red????

    You're also missing the point of the original poster. He included ABS.

    Even in a slide with a jake brake, you should use your brakes if it is equipped with ABS. The control module will give back some control in braking, and minimize the slide, and possible loss of control.

    For the quote in blue: Not all compression, jake, or exhaust brakes are the same. Some are very aggressive, and some are mild mannered.

    The bottom line is, you need to know your truck, what it has, how it works, and nothing beats experience.

    FM1
    I'm the one Fire and Rescue calls, when they need to be Rescued.

    Quote Originally Posted by EastKyFF
    "Firemens gets antsies. Theys wants to goes to fires. Sometimeses they haves to waits."

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    So are we saying that if a rig has ABS and the driver actually controls the engine brake manually (via the switch) then its pretty safe to say its do-able? I always turn the engine brake to medium or low when its rainy or snowing, and I think I have a pretty good sense of my rig. Am I doing the right thing?

    I am also unsure I understand how the engine brake or retarder won't cause wheel sensors to pick up a slide/traction loss through the ABS/ATC systems.

    I also failed to mention we have ATC, how does that factor in?

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    NFPA 1901 requires that anytime the brake anti-lock system is activated, all auxiliary brakes are automatically disengaged. Therefore if you skid for any reason, they (almost) instantly turn off. But don't let that fool you into using them in rain or snow. Once you'll started skidding, it may be too late. You want to avoid the skid altogether.

    The real reason for not using auxiliary brakes in rain/snow is that you can't determine how much force an auxiliary brake applies to the wheels, and when applied there's a significant imbalance in braking force between the front & rear axles.

    The trans-retarder is either on or off. Granted some trucks have different settings, but 99% are not user adjustable.

    Same thing goes with a Jake, some offer the option of only 2 cylinders of operation, but still, it's either 2 cylinders on, or none at all.

    Service Brakes on the other hand, are designed to be applied at almost infinitely variable rates. I can just barely touch them, or bear down on them all the way, or anything in between. Plus, the service brakes are designed to operate (somewhat) equally on all wheels, to prevent one wheel from skidding while others are still turning.
    Last edited by txgp17; 07-18-2009 at 01:50 PM.
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    Quote Originally Posted by MG3610
    So are we saying that if a rig has ABS and the driver actually controls the engine brake manually (via the switch) then its pretty safe to say its do-able? I always turn the engine brake to medium or low when its rainy or snowing, and I think I have a pretty good sense of my rig. Am I doing the right thing?
    That is where experience comes in, in both driving and knowing your rig, and what it is telling your ***. I can't say if your doing the right thing or not. I don't know what rig you have and what it's capabilities are, etc. In short of that, follow the manufacturers recommendations.


    Quote Originally Posted by MG3610
    I am also unsure I understand how the engine brake or retarder won't cause wheel sensors to pick up a slide/traction loss through the ABS/ATC systems.
    Engine brakes and retarders work through the drivetrain, and do not have speed sensors tied into the ABS/ATC. BUT... The ABS/ATC wheel speed sensors can shut down the retarder when a lock up event is about to happen, and goes into ABS mode. ATC is for acceleration spin control at any powered wheel with a speed sensor. I don't have experience with the engine brake rigs with ABS to say that they work the same or differently through the ABS module to the ECM. We use Telma's as our auxiliary braking.

    Quote Originally Posted by MG3610
    I also failed to mention we have ATC, how does that factor in?
    ATC systems uses the same wheel-speed sensors as the ABS. The sensors measure differences in rotational speed to determine if the wheels that are receiving power have lost traction. When ATC determines that one wheel is spinning more quickly than the others, it automatically "pumps" the brake to that wheel to reduce its speed and lessen wheel slip. It is not used when braking.

    FM1
    I'm the one Fire and Rescue calls, when they need to be Rescued.

    Quote Originally Posted by EastKyFF
    "Firemens gets antsies. Theys wants to goes to fires. Sometimeses they haves to waits."

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    I am far from the experienced heavy vehicle driver that many here are, so I believe these systems were designed with "me" in mind. Very often apparatus drivers have the majority of their large vehicle driving experience in a firetruck, nothing else. This means, most likely we'll fall back on our normal "automatic responses" when faced with a driving scenario.

    That being said, my first reaction upon encountering a slippery section of road where I'm concerned with maintaining control will be to let off the accelerator. If this engages the auxiliary brake when equipped the immediate slowing may cause a more rapid deceleration than intended. Some obvious examples are coming to a portion of road that is covered in standing water, coming down a hill and seeing black ice ahead, slush grabbing the tires when changing lanes, etc.

    As with most systems, they're designed to cover the widest range of potential driver, in the fire service we probably represent the greatest range of any group.

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    Does any remember the "Wet" - "Dry" Road Condition switches that some trucks use to have on the dash? When the switch was in the Wet position it was suppose to limit the braking pressure to the front axle. If I remember right the switches were done away with in the latter years and had to be disabled.

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    Quote Originally Posted by rpierce View Post
    Does any remember the "Wet" - "Dry" Road Condition switches that some trucks use to have on the dash? When the switch was in the Wet position it was suppose to limit the braking pressure to the front axle. If I remember right the switches were done away with in the latter years and had to be disabled.
    I remember them very well. Since they limited air pressure to the steer axle, they reduced braking power by a proportional amount. It was thought that by doing so the chance of losing control of the vehicle due to locking the steer axle brakes would be reduced or eliminated. Also, many if not most tandem axle tractors had no front brakes at all for the same reason.

    D.O.T. concluded that the risk of crashes due to lockup of the steer axle brakes was minimal compared to the risk of crashes due to reduced braking power. They outlawed the "Dry Road/Slippery Road" valves and required front brakes on all tandem axle tractors. My memory is a bit vague, but I believe that its one of the few times that D.O.T. required retrofitting rather than just saying, "From this date forward vehicles shall be equipped with....."

    Stay safe out there, everyone goes home!

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    Wet-Dry switches - we had one that worked on our 1969 International-Young engine all the way up to 1996 when she was retired. The old-old school drivers still swore by using it right up to the day she ran her last call.

    Because we grew up with a rig that had a manual transmission, we were taught using the comparison that the Jake Brake on our Ladder was similar to downshifting the IH pumper. Simply, if it wasn't a condition we would want to downshift the pumper, then turn the Jake off. This was a very aggressive Jake though - one that would put you against the windshield just by letting off the gas at 50mph.

    I've learned over the years when and how to work with the Jake and how to let if work for me. In rain or snow, I set it to Low unless we're out running the highway, then I just leave it on high. Ultimately I guess it depends on the experiance level of the driver. The less you use the Jake, the more you have to get in the service brakes - are you really gaining anything here?
    FTM-PTB DTRT

    Everything I state on here is to support and aid my fellow firefighters. Everything I post is my opinion only, and in no way should be taken as an official opinion of any Company, Department, or Municipality I represent... oh and this includes Pierce Mfg, as so their legal department has advised me; since they apparently also invented the right to control "Free Speech".

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    Quote Originally Posted by FIREMECH1 View Post

    ABS systems reads signals from the wheel sensors, and nothing else. Therefore they only control the brakes. But, if there is a problem to throw an ABS MIL, it will turn off the retarder, but not an engine brake.



    FM1
    I have only worked on trucks with WABCO or Bendix ABS, every one of them cut the engine brake off, sometimes that was the problem I was working on. I have even checked 'em on a ice covered hill behind one of the shops I worked at. You get a burp of engine brake, you start to feel like you are going to loose control and then your engine brake cuts off. If you happen to be lucky and have ATC, WABCO will pulse the correct brakes and stop your slide. On the older systems this was done by the reterder relay, then they went to J-1922, today it is done over J-1939. This is the same for engine brakes, exhaust brakes, xmission retarders and telmas. Your wheel sensors pick up the difference in wheel speed. If you start to slide, your wheels are rotating at different speeds. If you are more comfortable with the brakes off because of the conditions you are in, turn 'em off.
    The A/C is not cold enough, the warning lights are not bright enough, siren is not loud enough, the C.D. player skips every time we jump a curb, cab doors only open to 89.5* and it's been like this since day one!!!!

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    Quote Originally Posted by evtrandy
    If you happen to be lucky and have ATC, WABCO will pulse the correct brakes and stop your slide.
    Since when has the ATC been part of the braking solution in a slide???

    I don't mind being quoted, but please make sure you read ALL my posts on this subject before taking my "quote" out of context.

    The quote you have me in, is referring to the fact, that if the ABS is showing a MIL (Malfunction Indicator Light), that it automatically disengages the Telma retarder. Whether or not it does the same with engine brakes, I can't say, and I noted that on post #11.


    FM1
    I'm the one Fire and Rescue calls, when they need to be Rescued.

    Quote Originally Posted by EastKyFF
    "Firemens gets antsies. Theys wants to goes to fires. Sometimeses they haves to waits."

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