Maximum descent angle?

[NY2LA]

On a recent trip, I found myself descending a steep hill. With my lift, fat 34" KO2s, and front bumper mod, the descent seemed very reasonable. Then suddenly, as I neared the bottom, my front right tire plunged into an unexpected soft spot in the ground. This made my descent even steeper and also made me worry about the front end potentially dragging on the earth and preventing the vehicle from safely reaching the level ground that was only several feet away.

I tested reverse to see if I could back out of the soft spot--and, well, that was not going to happen. But I took it slow, and the vehicle gracefully exited the soft spot and cleared its way onto flat ground. I never actually felt the slightest lost of traction or control when going forward, just my own anxiety. But it raised a question: what is a the maximum descent angle of the 200? And with all the mods we do, which can of course alter the angle, how does one know when one reaches a safety limit?

Any perspectives would be appreciated.

 

[Madtiger]

45 degrees for a stock vehicle.

Did you use CRAWL going down? I use that a lot. Keeps my foot off from using the brakes.

Not sure about LC, but in my previous vehicles, reverse gearing is usually the weakest. So avoid powering yourself backwards up a hill. There is risk of grenading your front diff.

 

[RET2]

In jest of course but usually when your buddies are still at the top of the hill laughing?

 

[Lester did that]

45 degrees is correct. 45 degrees is also dead nuts max. That would include any rock or stick that bumps the back to that angle. So if you are on a decent that is 38 degrees and your back rolls over something that pushes you past 45 degrees you could be in a world of hurt.

Reversing is generally not advised on steep grades unless someone is winching you from the back. Stay the course and say a "hail mary"

 

[NY2LA]

45 degrees for a stock vehicle.

Did you use CRAWL going down? I use that a lot. Keeps my foot off from using the brakes.

Not sure about LC, but in my previous vehicles, reverse gearing is usually the weakest. So avoid powering yourself backwards up a hill. There is risk of grenading your front diff.

I did not, because the hill was short.

 

[TeCKis300]

Going downhill, one could go well beyond 45 degrees. To the extent that it would become a controlled roll. Controlled roll in the sense that you can't and don't want to stop (lockup the tires), which is just about the worst thing as that would cause the tires to lose lateral grip. Keeping some lateral grip is important because the moment the vehicle starts to lose that, and begin side-slipping, is when it won't have the longer wheelbase orientation and directional control to its advantage any longer.

Too much manual braking can be dangerous. Using low range and the lowest gear is the preferred wheeling method because it keeps the wheels turning maintaining lateral traction. We have Downhill Assist Control (DAC), which adds additional capability overlaid on low range gears. It's different than human braking because we have a single brake pedal to govern all wheels. DAC has computer control to modulate the braking on each wheel independently to manage whatever grip they do have, avoiding any one wheel from locking up.

Here's DAC in action. Probably not needed but was a good place to practice using it.


Another fun one from Matt's Offroad Recovery channel

 

[bloc]

Plus any lift, larger tires, weight added above the stock CoG, may reduce this number. I say may, because things get complicated if springs are stiffer, different damping, etc. Then we consider things like RTT….

It is reasonable to say the published max angle is for keeping things as static as possible. As Lester points out anything that causes a dynamic shift as we approach that max angle can make things go sideways quickly.

 

[NY2LA]

Another fun one from Matt's Offroad Recovery channel

Wow, that's a nail biter of a recovery.

 

[tbisaacs]

Going downhill, one could go well beyond 45 degrees. To the extent that it would become a controlled slide. Controlled slide in the sense that you can't and don't want to stop (lockup the tires), which is just about the worst thing as that would cause the tires to lose lateral grip. Keeping some lateral grip is important because the moment the vehicle starts to lose that, and begin side-slipping, is when it won't have the longer wheelbase orientation and directional control to its advantage any longer.

Too much manual braking can be dangerous. Using low range and the lowest gear is the preferred wheeling method because it keeps the wheels turning maintaining lateral traction. We have Downhill Assist Control (DAC), which adds additional capability overlaid on low range gears. It's different than human braking because we have a single brake pedal to govern all wheels. DAC has computer control to modulate the braking on each wheel independently to manage whatever grip they do have, avoiding any one wheel from locking up.

Here's DAC in action. Probably not needed but was a good place to practice using it.


Another fun one from Matt's Offroad Recovery channel

You can exceed 45°—and as you point out it's really just a controled slide. I was recently on a single track trail that was obstructed, no bypass so I essentially hopped a switchback. Angle was so steep that seatbelts locked and low oil level warning came on for about 5 seconds. It was scary but me and the truck made it out alive. Would not recommend.

 

[Dan Higgins]

And just to reinforce what @TeCKis300 said and others know - probably you know as well - you want to be pointed down the fall line. If you start to slide and that slide allows the truck to begin to get sideways relative to the fall line it can be best to "let it run" if you can do so safely and straighten it out.

 

[bloc]

Notice in the recovery video what prompted Matt’s slide was the rear tires locking under braking before the fronts. With crawl control engaged this shouldn’t happen on our rigs.. though his tire choice was likely a big factor as well.

 

[04UZJ100]

45 is not the maximum from a tipping over standpoint at all.

45 is the theoretical maximum where the horizontal and vertical component of gravity and resistive tire friction/traction forces are equal in a static situation. That’s why it’s equal for lateral and vertical vehicle movement.

As others said, highly dependent on terrain, kinetic energy etc.

 

[Madtiger]

45 is not the maximum from a tipping over standpoint at all.

45 is the theoretical maximum where the horizontal and vertical component of gravity and resistive tire friction/traction forces are equal in a static situation. That’s why it’s equal for lateral and vertical vehicle movement.

I don’t think that is the case. Different vehicle have different slope capability.

For LC:

 

[Madtiger]

Lexus GX / Prado:

 

[bloc]

I don’t think that is the case. Different vehicle have different slope capability.

For LC:

View attachment 2796413

Those slope angles will likely vary a lot depending on surface, dynamic inputs, toyota legal deciding what can be published vs what the engineers tested for, etc.

Or, it could mean systems like fuel and oil pickups work at that angle, not necessarily that the mechanical/drivetrain/suspension systems can’t handle more.

Think slick rock in Moab vs gravel/rock surface in Colorado.

I can say this.. I’d be nervous AF at 30 degrees side hill, let alone 44. Nuts.

 

[04UZJ100]

I don’t think that is the case. Different vehicle have different slope capability.

For LC:

View attachment 2796413

My point stands, though. Theoretically, the Cruiser can traverse a 45 incline. That does not mean that it will traverse a 45 incline on asphalt or dirt or rocks or …..

 

[bloc]

Wasn’t the same theoretical thinking responsible for widely held beliefs in the 50 or 60s that it was “physically impossible” to run faster than a 10 second quarter mile or something along those lines?

 

[40Man]

Wasn’t the same theoretical thinking responsible for widely held beliefs in the 50 or 60s that it was “physically impossible” to run faster than a 10 second quarter mile or something along those lines?

Especially when Toyota comes out with the animal edition:

 

[bloc]

Especially when Toyota comes out with the animal edition:

I remember wanting one of those things so damn bad. Now I have this lame 200…