How to determine "ground clearance" for a rig?

Air Cooled Nut

Air Cooled Nut

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I see there are roads labeled for high clearance vehicles. What is the definition of "high clearance"? What are the measuring points to determine ground clearance? Is it from the ground to the lower shock mount or to the bottom of the rear diff or simply find the lowest looking point of your vehicle and measure to the ground?
 
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ive always heard and gone with "high clearance" being a minimum of 10" from the ground to the lowest part of the vehicle. I'm sure that can and will be argued...but that's worked for me and generally what I know people to go with.
 
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"true lowest structural element.". Could be the diff pumpkin on solid axle vehicles. For IFS vehicles it would be some part of the frame, maybe low eat part of exhaust. If the shock perches are the lowest point, it should be those, but those should not be the lowest part of the vehicle, but their inboard mounting does seem to get in the way fairly often
 
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Thanks for the input.
The lowest points are at the rear of my vehicle. My pumpkin is 8.5" from the ground, rear shock lower perches are 9.5". Hmm.
I'm the 3rd owner. Truck is shod with 17" rims with a 31.5" or so tire height.
 
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I generally figure 1/2 the tires diameter, less 5" for the diff.
I run 35s, so 17" to the center of the axle/hub, then another 4" or so for most differentials from center to bottom. Airing down costs another inch or so.
Leaves me at 12.
 
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Aah- airing down, I’m reminded of the great debate that was raging back in the 70s in the community about airing down- “ if you air down you lose clearance “ versus “ air down for better traction “ This was back when 31” tires were the gold standard, 33s were considered huge and very rare indeed. As far as High Clearance? Jeeze, I used to get my basically stock 66 VW bug just about anywhere my friend was getting his CJ. In today’s world? In my mind high clearance means no sedans, crossovers, lowrider pickup trucks, etc.
 
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onXoffroad seems to define High Clearance 4x4 Trails as "...4x4 and 6-8" of clearance or greater may be required to travel safely." Well, the "and greater" sure isn't helpful because my truck can clear 8" but not 12" and as we know, size does make a difference. That amount of ambiguity makes route planning a bit challenging.
 
Air Cooled Nut said:
onXoffroad seems to define High Clearance 4x4 Trails as "...4x4 and 6-8" of clearance or greater may be required to travel safely." Well, the "and greater" sure isn't helpful because my truck can clear 8" but not 12" and as we know, size does make a difference. That amount of ambiguity makes route planning a bit challenging.
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What do you drive- I ask because in my case I have plenty of clearance, but I also have a massive 176” wheel base. If you’ve got a short wheelbase CJ on 31” tires or a LC 40 on 31s or a VW squeezing 27” tires can go a lot of places. My brother in law has a Colorado, with 31” rubber and goes a lot of places.
 
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Our ride (same as in my signature):
1000019079.jpg
Front level lift. OEM "off-road" package, which is shocks and a plastic skid plate/engine protection. I replaced the plastic with an aluminum piece. Tires are LT275/65R18....they'll need replacing and I'll be on the Chevy forums regarding what the tallest tire I can get away with. We tow a trailer so I won't be going crazy, needs to be streetable.
 

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Additional info: Canadian truck & we are the 3rd owner. Previous owner used it for hunting and had a bed crane so he could dress the deer. I've been under it and have cleaned out half the Oregon river beds of sand and mud he went thru...or camped in, hard to tell :laughing:

Me? I've been wrenching on classic VWs for decades. Have a '76 Bus with a new transaxle with a Peloquin LSD...hoping to put a Subaru swap in it ($$$ :weary:). I also have a '72 Squareback and my parents were the original owners. I raced a '95 Mk.III Jetta in SCCA Solo-II, EP class, and I'm very proficient with manual tranny (heel-toe, double-clutching, & overall hooligan stuff :smilingimp:). I finally got my grail tool, a 10k Bendpak asymmetrical 2-post lift.

However, this lifted off-road life is totally NOT where I imagined I'd ever be but here I am & it's pretty fun so far! I've attended the last three Overland Expos for ideas & some minor gear.
 
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Air Cooled Nut said:
Additional info: Canadian truck & we are the 3rd owner. Previous owner used it for hunting and had a bed crane so he could dress the deer. I've been under it and have cleaned out half the Oregon river beds of sand and mud he went thru...or camped in, hard to tell :laughing:

Me? I've been wrenching on classic VWs for decades. Have a '76 Bus with a new transaxle with a Peloquin LSD...hoping to put a Subaru swap in it ($$$ :weary:). I also have a '72 Squareback and my parents were the original owners. I raced a '95 Mk.III Jetta in SCCA Solo-II, EP class, and I'm very proficient with manual tranny (heel-toe, double-clutching, & overall hooligan stuff :smilingimp:). I finally got my grail tool, a 10k Bendpak asymmetrical 2-post lift.

However, this lifted off-road life is totally NOT where I imagined I'd ever be but here I am & it's pretty fun so far! I've attended the last three Overland Expos for ideas & some minor gear.
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You didn’t mention speed shifting those crash boxes. I used to almost lift a front tire grabbing 2nd with my 1600 dual port. If you got your Chevy on a high clearance trail those running boards would be toast.
 
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MOAK said:
If you got your Chevy on a high clearance trail those running boards would be toast.
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Aw dang...wife uses 'em to get in-n-out :confounded: I guess I'll see clear of those paths until I can replace 'em with something else. Thanks for the tip!
 
IMHO, absolute the clearance measurements are not nearly as important as knowing how to drive the terrain you’re in for the vehicle that you’re driving. Tire placement, understanding how to approach obstacles, a skilled spotter, recovery skills, and off road experience in general are a lot more important.

Your truck is high clearance in general terms, although if you’re really concerned about it, you really should take those step bars off before they get ripped off or hang you up. Replace them with actual sliders that will make a difference and you’ll be pretty much good to go as long as you know or can learn what you’re doing.
 
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I’ve always wondered about the definition of high clearance, probably a different definition for different folks.

Generally, I think wheel base has a lot to do with the definition, as does tire size. On the Rubicon Trail with my 47 this year, the wheelbase is only 103.5” (I added 25” to the frame) and has 33” tires, and it did just fine…and only has a rear locker. There were others in the group with older CJ5s that were running 31” tires, but because of the short wheelbase, they motored right through the trail.

Driver skill is also a BIG factor…regardless of the rig.
 
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Cj2atruck said:
I’ve always wondered about the definition of high clearance, probably a different definition for different folks.

Generally, I think wheel base has a lot to do with the definition, as does tire size. On the Rubicon Trail with my 47 this year, the wheelbase is only 103.5” (I added 25” to the frame) and has 33” tires, and it did just fine…and only has a rear locker. There were others in the group with older CJ5s that were running 31” tires, but because of the short wheelbase, they motored right through the trail.

Driver skill is also a BIG factor…regardless of the rig.
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Wheel base and ground clearance are not the same the same thing at all. Definition is definition. High clearance. At a stand still how much light between the ground and the lowest structural element of your vehicle.

High Clearance according to the NPS is minimum 8 inches from the lowest structural element - frame, shock perch, diff pumpkin. Not exhaust per se as it is not structural.

And because they say "structural", that means that stupid chin strap at the bottom of your front bumper doesn't count, but you can bet your buttocks if you don't take it off, it will get ripped off.

Tire size can contribute. NPS states they want 15 inch rims. Laugh away but back in the day when cars were on 12's and 13's, a 15 made a difference. And of course, taller rims can take taller tires.

Just remember, for every 2 inches of tire, your car is only raised ONE inch. So if your truck has 8 inches of clearance stock, adding a tire that's 2 inches taller gives you 9 inches of clearance. And, as someone pointed out, you need to account for airing down.

Lift or level, adding an inch here or there sure helps. So, if we add a 2 inch lift at the front coil-over, you now have 11 inches clearance. Just remember to do the same in the rear with a bigger spring block. A 1 inch lift block is really 2 inches tall. You take the existing block out, and the 2 inch tall block for a one inch gain.

Wheelbase...that's just a matter of whether or not you could more easily get "high centered" on a rock or log, or how easily you could turn left or right on a slalom course or weave through trees or rocks. It has nothing to do with static "ground clearance.". But it can determine how nimble your vehicle is.

We all know that skill helps determine whether you will make a climb or trail or fire service road, or not. But that wasn't the question
 
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Official stats for ground clearance for my 2014 GMC Sierra 1500 double cab sle 4x4 z71 with 31.6 in tires is 8.9 inches - officially a "High Clearance" vehicle according to the National Park Service. Add a 2 inch lift and that's 10.9 inches. Add 33 inch tires (an inch and a half bigger than stock, but only 3/4 of an in bigger from rim to outer circumference of the tire so that's 11.65 inches of clearance.

In the case of our trucks, we are talking about the lowest point of the rear diff pumpkin and/ or the lowest part of the front control arms. Or the z71 front skid plate if you also have the z71 package.

If you measure lower than that stock height, the discrepancy may be added passengers, equipment, full tank of gas or even tread wear. So, all of those things will lower your ride clearance, and we don't usually go places without all or most of that stuff, which is why so many people like to "go higher!" After all that lift, you may end up halfway back down to stock height depending how heavy you ride.

So load up, put the ol' lady in there, and the dog, fill the tank, remove that front under-bumper valence and measure at the bottom of the front control arms and the bottom of the rear pumpkin and you will have your real number.

Skill, you will develop. Don't be nervous about stopping (unless you are perched precariously) to take a look under the vehicle (not getting under it) and see, which way should I turn, if at all, to avoid or "clear" this or that obstacle.

The other reason for clearance is scrub brush. Since your exhaust gets so hot, you don't want to park in tall, dry grass and ignite a fire. Much less likely to do that if the grass is a little shorter and your vehicle is a little higher and not touching lower grass
 
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