Iced over roads- Settings for traveling in such

[Baron von Teuchter]

CDSVT, you’re right, the systems are not connected and it’s not an intuitive principle but think about what the CDL actually does. It makes the front and rear props turn at the same speed and, more pertinently to this discussion, accelerate or decelerate at the same rate.

Think of the props being locked together. If you have no rear brakes at all, just fronts, when you brake the calipers will bite the front discs, slow the front axle and the front prop and the CDL will then slow the rear axle. It’s the same thing, using the CDL automatically makes your braking force 50/50 no matter what the brake bias is.


As always, I’m not an expert but this is my understanding and it seems to make sense. Always willing to learn

Like I said above, if you’ve got some snow and ice experiment with it

 

[cdsvt]

It’s the same effect if you fail a hill climb without CDL. You can be on the brakes but can still roll back. Engaging the centre lock (if you have one) will stop this.

Robert Pepper did a good video explaining it here

View: https://youtu.be/QCPlK5CJ9uI?si=AoH26AYlYImFiFJ3

I watched this. I'm not questioning observed behaviors. The behaviors people are attributing to brake bias have nothing to do with brake bias and nothing to do with a connection between braking systems and center differential locks.

 

[cdsvt]

CDSVT, you’re right, the systems are not connected and it’s not an intuitive principle but think about what the CDL actually does. It makes the front and rear props turn at the same speed and, more pertinently to this discussion, accelerate or decelerate at the same rate.

Think of the props being locked together. If you have no rear brakes at all, just fronts, when you brake the calipers will bite the front discs, slow the front axle and the front prop and the CDL will then slow the rear axle. It’s the same thing, using the CDL automatically makes your braking force 50/50 no matter what the brake bias is.

We are defining brake bias differently.

I understand what you are saying though. Thank you for the explanations.

 

[Tom D]

AFAIK the ABS is not completely switched off when locking the CDL it's just changed. Locking the axle lockers turns it off completely..

 

[Tom109]

I see your point but on ice and hard packed snow I personally find esp and abs less useful - they’re too intrusive

I use Offroad mode all the time, but center lock is important if you do this in low traction conditions.

 

[Krabby]

I do like how the yanks call it 'freedom' measurements. You're wrong, but it still makes me smile

On a related note, do you guys call inch worms 2.54 cm worms?

 

[CrazyOldMan]

On a related note, do you guys call inch worms 2.54 cm worms?

Unless they’re Australian, in which case they call them something mind-bending like “snoggy poggers,” and their version can jump 18 feet (5.4864 meters) and spit an alkaline venom that dissolves flesh off your bones.

 

[255/85]

When you lock the CDL it turns off automatically

I didn't think that was correct but it makes sense that ESC would have to be off. Locking the CDL does illuminate the "ESC Off" light in the telltale.

By locking the CDL the front axle can only lock up if the rear does too this is essentially sending some of the braking performance from the larger front brakes to the rear axle. Because the front axle can't lock as easily the ABS can spend more time in the grab position and less time letting go.. ( all of this happens many times a second )

In older 2wd/4wd systems without ABS/ESC it has always seemed easier to get into a spin/slide when in 4wd. Yes, 4wd will get you moving easier but tap the brakes too hard and everything breaks free at once. I was taught to drive in snow and ice with these systems without using the brakes at all... if possible. That also means no sudden high rpm down shifts.

If locking CDL leaves the ABS functioning to some degree but eliminates ESC (so that I can use the brakes more and plan ahead a little less) when is the ESC Off button designed to be used? I don't think I've ever been able to get it to come on even when triple locked.

 

[bemax]

I remember well when I drove with my Defender on an icy road in the woods nearly 20 years ago.
I thought it would be a good idea to lock the CD.
I was really feeling relieved when I came to the snow and ice free main road because the car behaved so silly in the corners of the small icy gravel road with a mountain to the left and the steep falls to the right.
Sit took me some time to understand that it was not my car that acted unnormal but that I just made a mistake by locking the CD in those conditions.
Also it was really icy I had no big issues with the grip of my tyres. But with the diff locked I got tension in the drive train which killed the traction in the corners of.
So I learned my lesson well.
Use the locks when you don’t have traction and leave them when you don’t need them. They can make things worse if applied at the wrong time.

 

[CrazyOldMan]

I remember well when I drove with my Defender on an icy road in the woods nearly 20 years ago.
I thought it would be a good idea to lock the CD.
I was really feeling relieved when I came to the snow and ice free main road because the car behaved so silly in the corners of the small icy gravel road with a mountain to the left and the steep falls to the right.
Sit took me some time to understand that it was not my car that acted unnormal but that I just made a mistake by locking the CD in those conditions.
Also it was really icy I had no big issues with the grip of my tyres. But with the diff locked I got tension in the drive train which killed the traction in the corners of.
So I learned my lesson well.
Use the locks when you don’t have traction and leave them when you don’t need them. They can make things worse if applied at the wrong time.

This is sound advice in my opinion - especially for those not used to icy or snowy conditions. OP is in TX and is dealing with an unusual ice storm. They had one several years ago where a number of people died. They just don’t have the systems or infrastructure for it. I wouldn’t overcomplicate this. A number of us in the US who are daily drivers in snow and ice (Alaska, Wisconsin, Vermont, upstate New York) are basically saying “hey, you’ve got a 4WD - let it do its job, go easy, nothing sudden, stay as far away from others as possible.” I wouldn’t seriously recommend that someone not frequently driving on ice worry about locking and unlocking the center diff based on whether the asphalt looks dry or slick. I’m not going to see any temps above 10F for the next 8-10 days. Dallas will be up to 42 by Tuesday. Honestly, my best suggestion is to stay home and drink your way through all of your bourbon. I guess if you’re Methodist, you’re SOL. Hot chocolate, I guess? I’m happy to sponsor anyone interested in converting to Roman Catholicism (for the booze - Bavarians and Austrians, back me up on this). Stay safe, all you warm weather compadres in the US dealing with this mess.

 

[Rupert]

Thanks for al the honest feedback. I did what I heard (for the most part) and left it all as though I were having a normal day of driving. I did, however, take it slow, relaresed the accelrator way in advance and let the vehicle downshift on its own at stops. Traction was very good, I had to punch it to try and get them to spin. Tomorrow morning will be ten times worse as sleet and frozen rain are plummeting the earth tonight.

Thanks again to all.

 

[CrazyOldMan]

Thanks for al the honest feedback. I did what I heard (for the most part) and left it all as though I were having a normal day of driving. I did, however, take it slow, relaresed the accelrator way in advance and let the vehicle downshift on its own at stops. Traction was very good, I had to punch it to try and get them to spin. Tomorrow morning will be ten times worse as sleet and frozen rain are plummeting the earth tonight.

Thanks again to all.

Good luck to all of you down there - looks nasty and I know a lot of people will also be without power.