Approach and Departure Angles

[Mikestang]

Before I start any suspension mods I wanted to measure the approach and departure angles of my rig in stock form. I know that Toyota publishes values (30* A/ 24* D w/tow hitch) but I wanted real-world numbers. So I grabbed a protractor, piece of paper, pen, and my thermarest (only big, flat item I could find, a 4'x8' piece of plywood would have been ideal) and measured. I took two measurements front and rear and took the average:

Approach: 33.0* (measured 33* and 33*)
Departure: 25.5* (measured 25* and 26*)

There was nothing in the rig, and I only had a 1/4 tank of gas, so I would expect the rear angle to decrease when geared up. I will update this thread as I perform modifications to track the improvements to a/d angles. I'm getting the new tires put on in a few days, and will measure again to see the difference 265/75's make over stock.

[bulldog]

Good to know thx. I'm not sure what exactly is the correct procedure for measuring these angles, but I think it will be interesting to see how it changes as you mod the truck.

Keep us updated.

[jacal]

Good to know thx. I'm not sure what exactly is the correct procedure for measuring these angles, but I think it will be interesting to see how it changes as you mod the truck.

Keep us updated.

I think this is a good discussion to have. How should approach and departure angles be measured?

My personal method was to avoid measuring angles at all, and calculate them from knowing the dimensions of a 90' triangle. Then we just need a reliable method of measurement. We need to select a front and rear "lowest point" that could be used repeatedly.

Perhaps we could email one of the 4x4 magazines? What are some options?



J

[Mikestang]

I found that what appears to be the lowest point may not actually be the limiting factor in the a/d angles, it's tough to look and say, "Yes, that thing will hit before that other thing". I believe your measurement/calculation method would work, but I find that what you calculate and what you physically measure may not, in fact, be the same (I'm an engineer and see first-hand every day that what you calc on paper may not match the real world). I always prefer a direct measurement to something that has been calculated from other measurements.

I took my big, flat object and put it against the tires and propped it up against the first thing it hit (tow hitch in back, plastic bumper cover in front), and measured the actual angle directly. I will perform each subsequent measurement the same way so that my results are comparable to each other. They will not, however, be comparable to a/d angles obtained any other way.

I don't think the actual method of obtaining the angle is that important, as long as when we compare a/d angles we compare values that were obtained the same way, then I think we can have valid discussions about them. We'll also have to consider things like what's in the vehicle when you measure, and how much gas is in the tank. I'll have to remember to only measure mine when I have 1/4 tank and an empty cargo area.

[Dealmaker]

What about making a protractor by bolting two 1"X1"'s together at their ends with a wingnut?? From there, measure from a line at the front of the front tires up to the lowest point and tighten the wingnut to save th angle. From there, overlay a real protractor or a combi-square onto the home-made wood one to determine the angle. A sheet of plywood will be too hard to handle, IMO.

[Mikestang]

The two 1x1s would only hit what is directly in front/behind the tires - it wouldn't account for anything in the middle of the vehicle.

[bulldog]

I think your approah is good, as you keep it consistent you will be able to see and measure the changes as you mod the truck. I would be very interested to see the results as you go along.

[Dealmaker]

chaulk a line between the tires and measure off that line at the lowest point??

The two 1x1s would only hit what is directly in front/behind the tires - it wouldn't account for anything in the middle of the vehicle.

[ToyFamily]

If I were trying to measure this, I would take a sheet of anything (i.e.) wood, metal, plastic. Anything that won't bow in either direction, or diagonally for that matter. It would be at least the width of the mid tire. And an angle finder (they come in a dial or digital). You can find the dial one at Home Depot.

Place the vehicle on level ground.

Then for the front, standing in front of the vehicle, I would slide it along the ground almost butting it up against the tires. Then raise the other end up until you hit anything. The sheet should be hitting the ground, the tire just above the ground and whatever is the limiting factor on the vehicle. Then take your angle finder and measure (running the tool front to back of vehicle or perpendicular to the ground). Make sure the sheet is not bowing due to being placed to far under the tire. There is the Approach angle. Do it the same for the rear to get the departure angle.

Alot of times this angle only comes into play if you are heading straight at or straight off an obsticle and if the obsticle is verticle.

For approaching, the tire clearance comes into play. The distance from the ground to bumper edge near the tire area (from the front view). As well as how far the bumper edge is from the tires front contact area (from the top view). So that the tire can contact from the front or outside. Then driving comes into play by heading a the obsticle at an angle. Increase the angle of approach in most cases maximizes the size of obsticle you can climb. This is limited by trail width and on and on.

If I have confused you in my jumble, think of it this way. In the rock crawling comps as the obsticles got more verticle and undercut we adopted the rice rocket approach. It's an extreme example. Think of when you see a lowered Honda at the mall parking lot. He's got 2" of bumper clearance and there is a 5" speed bump. What do they do.....take it sideways to reduce the angle of the "obsticle".

In most cases it helps for the approach, belly clearance, and departure.

take it for what it's worth, just my own experiences.

and I'm spent.

Nick

[Joel]

we adopted the rice rocket approach

:rotflmao:

[Mikestang]

My measurements are not as accurate as I would like them to be, but I suppose they show a order of magnitude difference that mods make. Here's the results with my 32" tires:

Stock suspension w/31" tires:
Approach: 33.0*
Departure: 25.5*

Stock suspension w/32" tires:
Approach 34.0*
Departure 27.0*

Based on my measurement technique and protractor, I'm thinking I probably have a fudge factor of +/- 1*, so given that I would say that there is no discernable difference from stepping up one tire size. That's to be expected, given the very small change in tire radius (.5") that affects the angles.

[ToyFamily]

this is a good place to post pics showing the function of these angles.

http://www.shrockworks.com/Forum_Images/4runner-gen4-fb27.jpg http://www.shrockworks.com/Forum_Images/4runner-gen4-fb24.jpg http://www.shrockworks.com/Forum_Images/4runner-gen4-fb26.jpg



Nick

[Mikestang]

Approach, before and after. (http://www.mikestang.com/approach-angle.htm) Before the only way I could climb this was at such an angle that it would lift diagnol wheels off the ground. Now I can drive pretty much straight up it without hiting anything except the tow hitch.

http://www.mikestang.com/user/image/bumperstocktest01.JPG
http://www.mikestang.com/user/image/bumpermodtest03.JPG

http://www.mikestang.com/user/image/bumpermodtest04.JPG

[bulldog]

Great comparison pics. Have you had time to remeasure the angles again?

Would love to see how things improve as you go down your mod list.

MAybe we all can stop by your house onde day and you can measure the trucks :bigok: :guitar:

[Mikestang]

I haven't remeasured yet. As soon as I'm down to 1/4 tank of gas I'll try and remember; I just filled up today.

[ToyFamily]

pics are worth a thousand words...nice, makes me smile :bigok:

[expat]

Mike - did you ever get around to measuring the approach angle with the bullbar and stock wheels/tires?

So far I understand you measured 33 in stock form.

Thx
Mark

[expat]

Has anyone finally measured their approach angle with the bullbar, AT or MT tires, and a suspension lift?

[Mikestang]

Mike - did you ever get around to measuring the approach angle with the bullbar and stock wheels/tires?

Not yet, but I actually planned to some time this weekend while I'm crawling around underneath it.

[expat]

Not yet, but I actually planned to some time this weekend while I'm crawling around underneath it.


Will the measurement you take this weekend be with stock tires? Did you do your first measurement with stock tires (I thought so?)?

[Mikestang]

I measured 1st w/stock tires, then with 32s, and next will be 32s + s/w bumper. Except I realized that my protractor is at work, so I won't be able to find out the actual angle until I go back in on the 3rd.

[expat]

Hmmm...you got me confused.

What I need is two measurements...

1. approach angle with stock tires no bullbar
2. approach angle with stock tires and bullbar (preferably no winch, but whatever)

Can anyone provide these details?

Thx
Mark

[Mikestang]

1. approach angle with stock tires no bullbar
2. approach angle with stock tires and bullbar (preferably no winch, but whatever)

1.
Approach: 33.0* (measured 33* and 33*)
Departure: 25.5* (measured 25* and 26*)

2.
I will have 32s for this measurement; however, I did measure the difference between stock tires and 32s and it was negligible for the level of detail I am able to obtain (pen, paper, protractor), so I think my # will be close enough.

[Mikestang]

Stock suspension w/31" tires:
Approach: 33.0*
Departure: 25.5*

Stock suspension w/32" tires:
Approach 34.0*
Departure 27.0*

Stock suspension, 32" tires, Shrockworks front bumper:
Approach 38.0* (measured 37* & 39*)
Departure (not measured, no change)

The measurement with the bumper is to the front tow hooks. Since they're pretty small and it may be unlikely that they would be the limiting factor in most approaches the actual approach angle is probably a bit higher.

I plan to install my lift this weekend, so I'll try to remeasure again soon.

[bulldog]

Thx Mike!!! Very interesting info. I would guess that the overall approach angle is probably 40+ degrees if the tow hooks are ignored. SO with a lift you should be in the 45+ range. WIll be interesting to see your results as things progress.

[expat]

Perfect! Thx Mike.

[Mikestang]

For my last measurement with the lift I found out that my flat measuring device was not wide enough for me to get both rear wheels up to the tow hitch, so I had to improvise with it. After seeing the result (28*) I can say that that measurement is bogus, it should be more on the order of 32* or so. If I come across something else to use to measure it I probably will, but basically this concludes tracking the increase in these angles.

Stock suspension w/31" tires:
Approach: 33.0*
Departure: 25.5*

Stock suspension w/32" tires:
Approach 34.0*
Departure 27.0*

Stock suspension, 32" tires, Shrockworks front bumper:
Approach 38.0* (to tow hooks)
Departure (not measured, no change)

Donahoe front c/o's, Deaver rear coils (2.5"/30%), 32" tires, Shrockworks front bumper:
Approach 41.5* (to tow hooks)
Departure 32* (assumed)

[bulldog]

Very interesting, thx Mike.

I will definitely need to take mine down late this year for measurement :D

[Mikestang]

My method was crude, so not entirely accurate, but it gives the general relative difference each of the mods make. It would be interesting to see how others' measurements compare.