How to determine safe limits for sidehill driving?

[Sabre]

On a recent trip in our Montero, my wife and I started up an old 4x4 road on a grassy slope. It soon became apparent that the left side of the trail was getting lower and lower with respect to the right, and the trusty Montero was taking on more of a port list than we were comfortable with. So here's a general question: how do you determine, for your specific vehicle, what a safe angle for sidehill travel is?

We could obviously do some trial and error experimentation, but we're not too keen on actually EXPERIENCING the tipping point! What do others do about this? I can set up the little app in my phone to give me a warning about such angles, but how do we determine whether we're just being overly-cautious or whether we're being too casual about approaching the rollover scenario?

I fully understand the physics of the question, center of mass, etc. I'm more interested in the practical, real-world situation. How do you guys know when to back down?

 

[rayra]

Practice. Do it often enough to get a feel for it. There is no fixed value, and if you get close and get distracted looking at a tilt gauge or by a hysterical spouse, you're probably gonna roll it. Just find some berms and roadside slopes to practice on and get a feel for the how steep is too steep for your vehicle and learn to recognize such turf by eye so you stay the hell off it.

eta and better yet, save your crazy hill-climbing for disposeable / solo vehicles, and not your daily driver. Most folks start out doing it on moto bikes or ATVs, where the worst outcome is a bent handlebar or axle and some scrapes and bruises. I got mine in spots like the high desert in SoCal and Buttercup dunes.

And that's another thing. You learn how with an audience, so you have people to help when it goes wrong.

 

[Hilldweller]

When your wheels come up on one side you went too far...
I was leaning last weekend more than I ever did before. My shotgun rider knew more about my Jeep's capabilities than I did and said, "you'll be fine".
It helps to have a Yoda along, someone wiser than yourself.

 

[UK4X4]

You can add, speed momentum, vehicle loading and tyre bounce into the equation too..

they all come into effect, in Colombia we had a lot of off camber and mountainside trails, on three seperate occasions people rolled their trucks behind me, on sections I'd just driven over.

Similarly equiped trucks, experienced drivers...as you close on driving to the limits of the vehicle, the risks become higher.

There are so many more incidental conditions involved than just physical vehicle lean and a little dash board inclinometer

 

[KevinsMap]

Learning

... when I was learning, my Dad tied what was essentially a plum-bob (a weighted vertical line), draped over the centre of the rear-view mirror so that the friction of the string on the mirror frame dampens the motion. Instructions; when it points at your either the driver or passenger enough to easily notice, you are getting dicey. Take care! When it swings around wildly, you are hot rodding off-camber; fun maybe, but not smart for a beginner still learning limits. So it also teaches you "Go slow; easy does it best".

Going uphill, only the top of the mirror frame dampens the movement, going downhill it is dampened top and bottom - So, it is a bit more sensitive going uphill. How well does it work (?): it is not that easy to "see" 5 degrees of tilt (perfectly safe), whereas 20 degrees just looks scary on this setup! So yea, it works.

You can see that it is a "Relative" teaching aid - no meter, numbers, or gauge... except it makes you gauge your surroundings. It also helps you judge true vertical when you are the one tilted. That is not intuitive for almost everybody, when sitting down. It must be learned... and the movement of the plumb gives you constant, easily assimilated feedback.

My spouse is a wiz at this; awesome at sensing relative position; she is my most trusted spotter.

Gauges can help, but if you use them right from the start, you grow dependent on them. I do not use them.

Edit added: you will need to fiddle with the line length and the weight; these two parameters adjust the speed of the swing relative to the string friction... the sensitivity. Use the minimum weight suitable for purpose. Tie it well above and ever so slightly in front (towards the front bumper) of the mirror frame, which is the damper. The line should be thick, coarse cotton for friction, and the weight positioned well below the bottom of the mirror; with the mirror as background, the thick cotton line is very easy to see at a glance.

 

[Sabre]

Excellent feedback from everyone...thank you very much! I need to calibrate my butt....

 

[Rebellion]

If You Can Do This Then All Is Fine

 

[Buliwyf]

Just go slow and keep all four wheels on the ground.

One of the taller trucks actually ratchet strapped his up hill suspension, up, in one nasty spot to level the truck some. Stupid, but it helped.

 

[4x4junkie]

Something I've noticed is the tires on the uphill side will start to lose traction if the weight on them gets dangerously low (this if you have two open diffs/selectable lockers unlocked... those with limited slips/full (auto) lockers need not apply).

UK4X4 is 100% right, dynamics play a huge role also. Go 0.5MPH over something, and you'll probably be OK, but at 2 MPH, that rock sticking up a mere 2 inches could be enough to send you over onto your side when your uphill tire bounces over it.

 

[AFBronco235]

You also need to pay careful attention to tire pressures, especially on the "downhill" side. You're main concern will be sidewalls coming off the rim. I've done it a few times and its NOT FUN. We've all seen the stunt of driving a car on two side wheels, but when that is done, the tires are usually at least double the usual tire pressure. So if you have lowered the pressure for the terrain, like mud or sand, that can cause your tire to easily come off the rim in this type of situation.

As for a tiltometer, I've found that those globe style compasses make pretty good cheapo meters. They won't tell you precise measurments, but if you draw a line around the "equator" as a base "0", it can give you some idea of how tilted you are. Its also a LOT safer than dangling a heavy weight on a string from your mirror, which can bounce and swing around.

As far as how far is too far, it really is a trial and error thing, since its constantly changing with how much gear you have in the vehicle, to include passengers. The lower you keep your gear though, the further you can tilt though. That why you'll see people holding straps or even hanging off the uphill side of serious rock crawlers.

 

[KevinsMap]

Its also a LOT safer than dangling a heavy weight on a string from your mirror, which can bounce and swing around.

Which is why we never used a heavy weight ;-) It worked, for both my brother and I; no injuries...

 

[Hilldweller]

Something I've noticed is the tires on the uphill side will start to lose traction if the weight on them gets dangerously low (this if you have two open diffs/selectable lockers unlocked... those with limited slips/full (auto) lockers need not apply).

UK4X4 is 100% right, dynamics play a huge role also. Go 0.5MPH over something, and you'll probably be OK, but at 2 MPH, that rock sticking up a mere 2 inches could be enough to send you over onto your side when your uphill tire bounces over it.

There's a video somewhere of a JK flopping off the side of Blackbear because he went a little too fast over a small bump. Good relevant advice.
Slow. Slow. Slow.
Have your passenger look out the window if that's the uphill side.
If you're losing it and have an option, steer downhill (lengthening your wheelbase).

 

[craig333]

Probably my least favorite thing. When my butt puckers its too steep. I also have on other method for determining when its too much. When the dog wants out

 

[eggman918]

Probably my least favorite thing. When my butt puckers its too steep. I also have on other method for determining when its too much. When the dog wants out

The dogs judgement wont help us as when the trail is rough enough that the vehicle speed is less than ~10 mph the dogs like to run beside or in front of the the truck...............might they be smarter than we are???

 

[RoyJ]

From my 45+ years of experience, experiments and educating and my clients. With my years of educating, this is what my clients get. I teach with the KISS method.

............

It is worth going to a certified 4X4 Driving Class. The best are members of the I4WDTA this is a world wide association. It is 1000 times every dollar spent on the education. They have the highest standards for all educators in the world.

All very good points Frenchie.

People are often surprised at how stable OEM trucks and SUVs are, just about all of them can reach the 45 degree tilt point. Like wise, on flat ground with sticky tires, just about all OEM vehicles can hit 1.0g of cornering (steady state) without rolling. And people wonder why their trucks don't come with 3" lift and big tires stock...

Problem comes with modified and loaded vehicles.

I'm anal about center of gravity, and hence why I'm highly against the "safari look" fully laden roof rack. When I pack, the only thing that goes on my roof is my RTT. Every other heavy item sits in the absolute lowest location - on the floor, where the removed rear seat used to be. This includes my deep cycles, water, jerry cans, and misc recovery items. A sleeping platform is then built over the heavy items for the lighter stuff - fridge, sleeping bags, clothes, chairs, food, camp chairs, etc.

Even my spare tire is in the factory location, because a 70 lbs tire, with a 30 lbs carrier, sitting 4' off the ground, raises COG much higher than 1.5' off the ground. My expedition driving is mostly to get to places, and not technical off-roading. There's never been a situation where I can't get the spare out of the factory location. I'm not building a JK on 40s to rock crawl or mud bog.

The efforts pay off. My fully laden Explorer feels pretty much stock, because the 800 lbs of payload sits at or even below normal COG, offsetting the RTT. I can travel side grades very comfortably, as well as highway curves. And this is with BOTH sway bars permanently removed!