Estimating maximum side angle of the LC200 with lift and mods (1 Viewer)

[BloggerL]

I recently asked a question about skids' effects on center of gravity, and folks pointed out their effect is negligible. A bigger question is, how can one estimate the reduction of maximum side angle incurred by lifts, the addition of bigger tires, and rooftop accessories? (I should add the counteracting effect of wheel spacers and such as well.)

We have a nifty angle meter on our display, but I never know quite how to use it since don't really know what my limit is.

 

[grinchy]

This old thread has a now lost attachment that claimed 44 degrees.

What is the max side angle?

What I mean by this, is the angle in which the Land Cruiser can take before flipping over on its side when traversing hills or rocks. :D

forum.ih8mud.com

 

[LTSR]

I had my LC at 30 degrees and i was nervous. in fact too nervous to take a photo of meter on the screen with my phone. maybe i'm not as confident as others who have more time behind the wheel. this is with nothing on my roof, fully stock.

 

[Artie]

This is very timely as I recently went down this rabbit hole after towing my Conqueror over some sketchy stuff and making the mistake of looking in the mirrors.

What I found is I’ll likely get far out of my personal comfort zone before my LC or Conqueror gets to their danger zone.

Therefore, I set my ARB Linx inclinometers to 30° with the alarm at 35°. I ain’t got nothing to prove and don’t see myself towing beyond that… I may follow someone’s lead and find myself pushing my comfort zone sans trailer but if they don’t flip I shouldn’t either.

 

[MCtree]

This is indeed a great post.
I get nervous at 15%. Especially when those degrees are leaning me over a cliff.

@Artie
Do you have a lift or larger tires?
Or anything else that would elevate your center of gravity?

 

[bloc]

While I don’t know the actual number I will say it’s not often as simple as a simple number. Dynamic vs static, is there an overall uphill or down, etc.

Rough guidelines, like knowing 44 is the static limit so set your alarm at 35, can be useful. But with the sheer number of variables I think we’d have a lot of trouble estimating side hill limits with any real precision.

 

[Artie]

This is indeed a great post.
I get nervous at 15%. Especially when those degrees are leaning me over a cliff.

@Artie
Do you have a lift or larger tires?
Or anything else that would elevate your center of gravity?

Yeah, I have 33.7 inch tires, 2 inch lift and Dissent roof rack. Those may be canceled out slightly by bumpers, armor, 40 gallon LRA, and drawers full of crap.

All that being said, I saw some 25° stuff on our last trip a week or so ago but that was mostly pitch and not roll, roll hit 20°. I can’t see searching out 30° plus but it could happen. I need to hit up the local pay to wheel place and get more experience with this truck… I shouldn’t depend on a gauge when the ‘seat of your pants’ gut feeling or ‘pucker factor’ is really what will be dictating proceeding or not.

 

[kcjaz]

While I don’t know the actual number I will say it’s not often as simple as a simple number. Dynamic vs static, is there an overall uphill or down, etc.

Rough guidelines, like knowing 44 is the static limit so set your alarm at 35, can be useful. But with the sheer number of variables I think we’d have a lot of trouble estimating side hill limits with any real precision.

I agree that knowing the static number is 40 something degrees is useful general knowledge but most trucks tip when the incline/off camber situation changes suddenly in a way not anticipated by the driver. You can go from fine to not fine with a bad line causing a lifted wheel situation. Your knowledge of 40 degrees and your inclinometer readout doesn’t help you as it’s too late.

It’s really good to think about how the mods affect things like CG and to think about what the limits are for your truck. While a lift and a lot of weight on your roof rack certainly would reduce your tipping point angle in practical terms I don’t think it really matters. So it goes from 44 to 40. What are you really going to do knowing that? My first LCDC I watched a guy go from fine, maybe 10° of camber, to almost rolling in a heartbeat because of a bad line. It was his internal instinct and reaction that saved him. He just backed off the gas to stop and didn’t panic. Hitting the breaks hard may have allowed momentum to roll him. An alarm suddenly going off might’ve been a bad thing.

 

[bloc]

Not to mention newer cruisers don't have the side curtain airbag cancel button for steep off-camber trails.

 

[OregonLC]

But is that because of better control logic in the latter years? I'd rather have the AI police it than forget to turn the RCSA inhibit back off.

I have to confess... I never use that feature. And there are no 'My Side Airbags Deployed on a Trail' threads that I can remember. Wonder if it was just a liability limiter that Toyota through in because in testing there was a 0.01% chance of occurrence.

 

[bloc]

But is that because of better control logic in the latter years? I'd rather have the AI police it than forget to turn the RCSA inhibit back off.

I have to confess... I never use that feature. And there are no 'My Side Airbags Deployed on a Trail' threads that I can remember. Wonder if it was just a liability limiter that Toyota through in because in testing there was a 0.01% chance of occurrence.

Regulation change was one speculation about why it changed, but that could be another.

I haven’t seen posts about deployments in 200s but there are plenty in tacos and 4Runners, and I vaguely remember something about it happening in a 100 or two..

 

[OregonLC]

there are plenty in tacos and 4Runners, and I vaguely remember something about it happening in a 100 or two..

I suspect correlation to 'hold my beer'...

 

[RET2]

I suspect correlation to 'hold my beer'...

I would venture the clenching butt cheeks meter is more accurate.

 

[bloc]

Pretty innocuous movement can cause it too. One example on a GX470

 

[TeCKis300]

I recently asked a question about skids' effects on center of gravity, and folks pointed out their effect is negligible. A bigger question is, how can one estimate the reduction of maximum side angle incurred by lifts, the addition of bigger tires, and rooftop accessories? (I should add the counteracting effect of wheel spacers and such as well.)

We have a nifty angle meter on our display, but I never know quite how to use it since don't really know what my limit is.

At its most basic, a picture of the critical angle looks like this. It's going to be the relationship of the cars center of gravity, relative to a vertical line from the tire shoulder. Once the COG crosses over center of the vertical line, it goes over.

To earlier points, there's more at play. The COG will move with suspension compression of the loaded side, causing COG to lean that way (which is why I drew it off-center). KDSS may help minimize lean in this scenario, increasing resistance to roll by maybe a couple degrees. So could stiffer springs.

Intuitively, anything above the COG datum like lifts or RTT will raise the datum and cause it to more easily cross over center. So could any gear in the car as it would likely be above the datum. Skids potentially could lower that to your point. And yes, wider track with wheel spacers can help.

I'd bet the critical angle is over 40°

 

[OregonLC]

Pretty innocuous movement can cause it too. One example on a GX470

I wouldn't say that was benign at all. That would have been some pretty serious head toss inside the vehicle. I wouldn't have expected an airbag deployment on that trail, but it would have been a jolt.

But for the purpose of this discussion, I think it illustrates two things: 1) it's not just angle, it's rate of roll and 2) one would need to have RCSA inhibited on virtually every run to prevent the risk of that type of deployment. Hopefully current sensor technology and Airbag control logic has it sorted out enough now so that risk is eliminated.

 

[BloggerL]

At its most basic, a picture of the critical angle looks like this. It's going to be the relationship of the cars center of gravity, relative to a vertical line from the tire shoulder. Once the COG crosses over center of the vertical line, it goes over.

To earlier points, there's more at play. The COG will move with suspension compression of the loaded side, causing COG to lean that way (which is why I drew it off-center). KDSS may help minimize lean in this scenario, increasing resistance to roll by maybe a couple degrees. So could stiffer springs.

Intuitively, anything above the COG datum like lifts or RTT will raise the datum and cause it to more easily cross over center. So could any gear in the car as it would likely be above the datum. Skids potentially could lower that to your point. And yes, wider track with wheel spacers can help.

I'd bet the critical angle is over 40°

View attachment 3090875

"Once the COG crosses over center of the vertical line, it goes over." -- This is the best summary of the situation I've heard yet.

 

[Markuson]

Not that this is news…but…
-The calculation is massively worsened by movement on uneven terrain and over/around obstacles. The closest I came to rolling wasn’t because of the angle, but was because of inevitable movement while navigating it. Near the limits (or even well below them), even the slightest bump/bounce effect can put you over.

We don’t drive on the smooth, cement bamkes of flood channels like in the movie Grease… We drive at crazy angles in rocky, or slippery, bumpy stuff…while moving, turning & sliding/stopping.

Those “critical numbers” go right out the window when you intfoduce, bumps and slips/side-slides (often followed by a catch, or a “stop” point within the slide.

Numbers may help get someone in the ballpark, but like most objects in super-varied motion, you’d better develop a FEEL for it…

By the same token, I’ve driven far beyond the tip angle… because of intentional speed & motion in a power turn (think roller-coaster) . At speed and with intention, you can defeat roll-over angles, but bogging down in soft sand means down you go.

An example are the crazy formations just outside of Capital Reef… If you STOP in the turn at the top of these, you roll. But if you power through and don’t bog down, you’ll exceed the roll angle just fine as you continue the turn.

This second camera angle is deceiving. The angle is as steep as shown in the first pic as its the same spot, but I was alone and had set my phone on the ground for this…so it flattened the look. But you can certainly defeat max angle with speed and turns, just as you can roll at lesser angles with sketchy bumps, etc.

I don’t think this is news to anyone here… Just noting that there’s a lot more than angle numbers ti think about.

 

[BloggerL]

Pretty innocuous movement can cause it too. One example on a GX470

Great vid. I wasn't thinking about airbags so much myself, but it's this kind of unexpected sideways dip that's been on my mind. There are a lot of resources and discussions on this and other sites about "vertical issues," but it's hard to find much on "sideways issues"

 

[bloc]

I wouldn't say that was benign at all. That would have been some pretty serious head toss inside the vehicle. I wouldn't have expected an airbag deployment on that trail, but it would have been a jolt.

But for the purpose of this discussion, I think it illustrates two things: 1) it's not just angle, it's rate of roll and 2) one would need to have RCSA inhibited on virtually every run to prevent the risk of that type of deployment. Hopefully current sensor technology and Airbag control logic has it sorted out enough now so that risk is eliminated.

My phrasing could have been better. Yes a head jerker, but because of the terrain there was little risk of going over or actually needing the airbags. Not that the vehicle could have known that.. which is why I feel there are limitations on how good movement/force-sensor based RSCA control logic can get and still do the job.

I’m glad I have my button..