52 replies to this topic

[wicked1]

 I've done some googling about this already, and it seems there is no good answer for any vehicle.. ( A slight bump could bounce the suspension and easily push the vehicle over the limits, even if you knew what the limit should be)  But..  I'm sure more people than me have put a lot of thought in to this situation..

What do you think the max lean angle is for a truck w/ a FWC on top?  Has anyone here tipped? 

I'm not offroadng for the sake of offroading in my camper rig, but I do want to get down the sketchy roads to the unoccupied areas.  I definitely went beyond my previous comfort zone on this trip, and had no issues. 

 

I've got a little tacoma w/ fleet flatbed, and go down some small jeep roads, a full size truck couldn't get down, and a lot of these roads get pretty off camber. 
And everything about the modifications of the truck raise the CG.. Flatbed is higher CG than a standard bed.  The lift raises the CG.  But then big wheels/tires/suspension add weight down low.  And then obviously the heavy camper on top and over the cab. 

 

I guess I'm just looking for a little general discussion about what other people are comfortable with.
Thanks!

[Jon R]

It’s going to be different for different configurations. It might be better to research methods for determining vertical cg position of a vehicle. The only way I can think of to positively determine tipping angle involves a scale and some truck tilting shenanigans, which I doubt a scale facility has time or inclination to let you perform. Once you have the cg height and track width you can calculate it from there.

However, a more practical approach is to assume a cg height that you are positive is higher than the actual cg height could possibly be, and calculate the angle for that cg height. I would also suggest assuming a lateral offset of the cg of 6 inches from the centerline and calculate for the worse direction with that assumption. In addition, don’t use the outside of the tires for track width - use the center line of the tires. You’ll probably be surprised at how large the tipping angle is even with those conservative assumtions.

And in high school you thought you’d never use trigonometry!

[Jon R]

Here’s an example ballpark estimate of STATIC tipping angle for my 3500hd with Grandby:

Raw data/estimates:
Bed height above ground 35 inches
Conservative estimate of truck cg 6 inches above bed floor
Truck weight 7600 lbs
Grandby cg estimated 36 inches above bed floor
Grandby weight 1800 lbs
Track width between tire centerlines 66 inches

Calculations:
Combination cg height = 35in+6in+(1800/(7600+1800))36in = 47.9 inches

Tipping angle if cg on centerline = 90 degrees - inverse tangent of (cg height / 1/2 track width) = 90 - inv tan (47.9/33) = 90 - 56 = 34.5 degrees

For tipping angle to worst side if cg is 6 inches to one side, do the same calculation but subtract 6 inches from the track half-width = 29.4 degrees

I could draw a diagram but I’m watching the KC/Bengals game right now.

Edited by Jon R, 02 January 2022 - 09:04 PM.

[wicked1]

Thanks a lot!  Math isn't my strong point, so having your calcs above really helps. 
Next, I need a meter in my truck to measure the angle..  As it is, I have no idea what angles I've been to.  (I know, my phone will do it, and I have a digital level I could use).

[Vic Harder]

This is a great topic.  Jon R's calculations give us a conservative 30* tipping angle.  I think my puckerer would be all puckered out by the time I hit 30* 

 

I've seen some pictures/videos on this site where folks had their rigs on some crazy angles.  I suppose we could compile those here and superimpose some lines on the pictures to calculate what angles they survived.

[Jon R]

Again, that’s for my huge, heavy 3500hd crew cab long bed truck, with a camper that is less than a quarter of the weight of the truck, and withstock suspension and wheels/tires. Folks with raised suspensions, big tires, and a heavier camper on a half ton may get a significantly different result.

I agree Vic there’s no way I would ever sidehill that truck at 30 degrees. My display system has an inclinometer in it. Maybe I’ll keep an eye out for a good spot and see how 20 feels.

Edited by Jon R, 02 January 2022 - 08:43 PM.

[pvstoy]

I have a built in tilt meter that if I get too much leaning I hear some accelerated breathing and see body reaction.  It's time to pick a different line.

 

My gal is always willing to get out and walk and as she departs there is always the encouraging words, "If your going to die you're going to die alone"  I can remember a couple times she got out and walked along with a thunderstorm/rain pounding down.

 

Even with the calculations there is real world surface conditions and speed factors.  You maybe well under the roll over point calculations but with truck heading down hill/ side slope, just one bounce of the rear tire can bring it over. Not to mention many different surface type and conditions adds a value to your consideration.  

 

Add some physics along with trigonometry. Every situation will have it's own safety limits.

[Jon R]

Agreed. That was why I capitalized STATIC in showing an estimate of the static tipping angle. A little momentum in the wrong direction can make a big difference.

Edited by Jon R, 03 January 2022 - 12:43 AM.

[okiedavid]

Again, that’s for my huge, heavy 3500hd crew cab long bed truck, with a camper that is less than a quarter of the weight of the truck, and withstock suspension and wheels/tires. Folks with raised suspensions, big tires, and a heavier camper on a half ton may get a significantly different result.

I agree Vic there’s no way I would ever sidehill that truck at 30 degrees. My display system has an inclinometer in it. Maybe I’ll keep an eye out for a good spot and see how 20 feels.

 

My inclinometer showed 19 degrees on my half ton with a Hawk on the back once and I thought I was going to have to change my shorts after. It's super scary. As others have mentioned, it would not be so bad if you were stopped, but when moving, bouncing over rocks, etc., it's an extra layer of stress. Also, I've done it with around 8 degrees down and 14 degrees angled, again not fun. I try to stick to moderate trails at most, but sometimes they get washed out and that's where the sweating begins. Honestly, I think a couple of times I've just been lucky, not a good strategy to depend on luck. But hey, I didn't buy it to decorate the driveway. 

[pvstoy]

Thanks Jon R for sharing some calculations.  Since retiring I have not sat down and done any calculations for much. I guess when I was retiring Sage had a signature line "Work is none of my business". Been that way ever since.  You're retiring soon, your going to like it!

 

Cheers,