2020 Cummins IKE pull

Cummins12V98 wrote:

4x4ord wrote:

ib516 wrote:
I'd be surprised if the service brakes are activated without the pedal being pressed. Yes, I know radar (adaptive) cruise control systems do that and so can those pre-collision things, but that's different than a computer dragging the brakes down a grade. How do they know when to "let off" so they don't overheat? Temp sensors in the brakes now? I can't see that being the case.

I think the exhaust brake slowing the truck activates the brakes lights as they are programmed to do.

I am 100% certain that my Ford operates the truck brakes, trailer brakes, brake lights, exhaust brake and transmission shifting automatically when the auto exhaust brake is selected. It works extremely well.

NOT doubting you but why didn’t the Ford slow the load as well as the RAM?

The Ford applies the brakes to slow the truck to "the set point" which is the speed the truck was going at the time the brake pedal or accelerator was last released. after slowing the truck the brake is released and isn't reapplied until the truck accelerates beyond a certain programmed amount. (I don't remember how much it let the truck accelerate before applying the brakes again). Apparently the amount the computer was comfortable allowing the truck to accelerate was more than what Mr. Truck was comfortable with. The Cummins exhaust brake is either capable of holding an extreme amount of back pressure and so it is holding back without a brake application, as you say, or it is reapplying the brakes at more regular intervals to keep the speed more constant.

I think you've said that if you turn the exhaust brake on and let it hold back without utilizing cruise it doesn't hold back the way it does using cruise ..... I think that is the answer to whether cruise employs the wheel brakes or not ..... evidently it does. The other way you can find out is to go down your 14% grade on cruise with 25000 lbs in tow. When you get to the bottom let the truck coast to a stop, then get out and touch your brake rotors. I'd like to see a video showing the expression on your face the instant your finger touches those cold brakes.:)

Amazes me how quiet any of them are, even at full tilt.

srt20 wrote:

IIRC CO requires ALL vehicles to have chains in the vehicle on passes. If you get in a crash and block lanes of traffic without having chains IN the vehicle its a $15xx fine.
I was just on the IKE last week in a truck and trailer with no chains, luckily not snowing. But I was a bit surprised at the signs regarding the chains. I thought it was trucks with trailers that didn't have snowflake tires that required chains.
Lots of darned traffic on that road....There was no way we could go up the west side (side that TFL uses) without getting off the go pedal because of traffic, semis going slow, cars go fast.

I was in a SRW Duramax that easily handled the IKE, of course it had a pretty light load, 6000ish. Had LOTS of brake applications on way down east side because of traffic.

Washington is similar, but if You have a 4X or equal, and get into a wreck, your fault or not, no chains "ON" and with you, its a $300-400 fine ticket. Assuming all others need chains but AWD/4wd. My old dually, and my 96 SW K3500 were both licensed over 10K GVW. So even if I have snowflake tires, "chains required over 10K gvw" I need to chain up, even tho both were 4wd. Altho most LEO's looked the other way..... it could get expensive if something happened. Towing my TT in the winter to the local pass, also required chains when the over 10K chain up sign is out. As I was now at 15-16K literal lbs combined.
Here it is only the actual GVW potential that matter, commercial or private, does not matter. Will assume based on other states I've traveled in, in the winter months, they have very similar laws to Washington as to who has to carry, use at given times.

Marty

4x4ord wrote:

ib516 wrote:
I'd be surprised if the service brakes are activated without the pedal being pressed. Yes, I know radar (adaptive) cruise control systems do that and so can those pre-collision things, but that's different than a computer dragging the brakes down a grade. How do they know when to "let off" so they don't overheat? Temp sensors in the brakes now? I can't see that being the case.

I think the exhaust brake slowing the truck activates the brakes lights as they are programmed to do.

I am 100% certain that my Ford operates the truck brakes, trailer brakes, brake lights, exhaust brake and transmission shifting automatically when the auto exhaust brake is selected. It works extremely well.

NOT doubting you but why didn’t the Ford slow the load as well as the RAM?

IMHO that is the best 19/20 looking RAM HD truck I have seen yet. Not 100% on the black with chrome highlight rings on the wheels. Have not been a big fan of the new look.

ib516 wrote:
I'd be surprised if the service brakes are activated without the pedal being pressed. Yes, I know radar (adaptive) cruise control systems do that and so can those pre-collision things, but that's different than a computer dragging the brakes down a grade. How do they know when to "let off" so they don't overheat? Temp sensors in the brakes now? I can't see that being the case.

I think the exhaust brake slowing the truck activates the brakes lights as they are programmed to do.

I would like to know more about this trailer braking. Not sure if it really exists. I can tell you my brake lights do NOT come on with the exhaust brake.

ShinerBock wrote:

4x4ord wrote:

ShinerBock wrote:

4x4ord wrote:
^^^ So, based on my observation I would say the wheel brakes were largely what was holding the truck back. The computer recognized the need for a downshift to produce more exhaust braking. After the downshift the back pressure and rpm increased to produce the maximum level of exhaust braking the engine was able to do .... the wheel brakes made up the difference.

Nice theory, but owning a Cummins and having been on that road I would have to disagree.

You've been on that road with 30,000 lbs in tow?

No, and neither have you. Although I have been on that road to know it is not 7% grade the whole way through and it varies between 3% and 7%. I have also driven/towed the 6.7L Cummins in other medium duty vehicles both when I worked at Cummins and at my current employer. None of them use the vehicles brakes and yet they apply the same kind of exhaust braking that my truck does at max going down grades when towing.

You're right about the grade being less than 7% for much of the stretch. I think you and I determined on another thread that the average grade is 5.5% .... 2300 ft over 7.9 miles. I believe is is the top mile and a half that is 7%.

I know I can hold back towing 23k, 33k combined on 14% grade locked in 2nd with cruise set so I don’t think it should be an issue towing 30k at 35mph locked in 2nd.

They are about 6k more than me and a much less steep grade so it should be no biggie!

ib516 wrote:
I'd be surprised if the service brakes are activated without the pedal being pressed. Yes, I know radar (adaptive) cruise control systems do that and so can those pre-collision things, but that's different than a computer dragging the brakes down a grade. How do they know when to "let off" so they don't overheat? Temp sensors in the brakes now? I can't see that being the case.

I think the exhaust brake slowing the truck activates the brakes lights as they are programmed to do.

I am 100% certain that my Ford operates the truck brakes, trailer brakes, brake lights, exhaust brake and transmission shifting automatically when the auto exhaust brake is selected. It works extremely well.

I'd be surprised if the service brakes are activated without the pedal being pressed. Yes, I know radar (adaptive) cruise control systems do that and so can those pre-collision things, but that's different than a computer dragging the brakes down a grade. How do they know when to "let off" so they don't overheat? Temp sensors in the brakes now? I can't see that being the case.

I think the exhaust brake slowing the truck activates the brakes lights as they are programmed to do.