jeepstertim

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44°c (111°f) here in Qatar and someone thought it was a good idea to play in the sand. My Gladiator JTR’s first foray into the dunes and it did really well. Aired down to 25psi (think I’d go 18-ish next time) and we didn’t get bogged once, unlike the Tahoe we came across (husband and wife on their own) and F150 (twice) that needed recovery. When we did get stuck, it would always drive out.

I did however find one issue I couldn’t work out. When we had become ‘dug in’ in the sand, the Jeep sometimes felt like the torque converter was slipping. Trying to reverse out of soft sand, I could sit stationary (4hi with diff locks engaged) high engine RPM and I’d get nothing from the wheels, no turning at all, any ideas?

Off Road + was good in the sand but I still had a few failed ascents because the gearbox didn’t shift down in time to keep the RPM up, rather we would slow to almost a halt before it changed down and by that point, it was too late.

A stray metal bar in the sand has given the JTR its first scar (punctured fender) but even that could have been much worse.

I was even impressed with the fuel consumption, 14 mpg in the soft stuff on a 3 hr play and then 24mpg on the cruise home at 60-80mph.

All in all, a very capable sand machine.

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sfurash

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Too bad about the fender, would the Mojave
with the 2.72 to 1 transfer case done better?
I noticed you have color matched fenders which will be a bit of a pain to replace, good argument for the black.
 

ACAD_Cowboy

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My only commentary would be less air for sure. I run 8 to 12 depending on how loaded I might be.
 

ACAD_Cowboy

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So reading through your question again, it sounds like you may need to disengage traction control or try a high gear in low range. All the systems together doing what they each think you want can become confused and start to counter act each other. By detecting and attempting to control some wheel slip the system blithely thinks it's helping. In this case wheel slip is unavoidable and just part of the deal but the system has no sense of it.

I'd rather a speared fender than a speared tire though.

We need more panoramic vista shots BTW.
 

Mastermind

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My only commentary would be less air for sure. I run 8 to 12 depending on how loaded I might be.
The standard we’ve always ran with for dunes is 8 psi in the back - 12 psi in the fronts.

I ❤my JTRD in the sand, but it’s easy to see why the made the Mojave especially for dunes.
 

Terminus33

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Flappy paddles would be good, I seem to need 2 hands on the wheel in the sand!
I've seen rally drivers flying thru single tracks at ungodly speeds with both hands on the wheel working back and forth and when they need to shift just bring that right hand down, smack the shifter and back up to the wheel both hands. I have even started doing this during road driving to get me used to not leaving my had idle on the shifter, of course not having to steer as manically lol.

Flappy paddles are actually really bad for cars that need a lot of steering wheel motion. they are best for close ratio steering gears.
 

aceisback

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So you guys offering sand advice, I’m curious what dunes you’re running? I get Qatar, and two from Michigan, so I’m assuming Silver Lake, but for the Boston and New York folks particularly, what dunes are you running?
Trying to find some folks that run Wranglers and/or Gladiators at Glamis and Dumont. Sold my JK Sahara Unlimited and just don’t see that 3.6L being able to get through those dunes. Getting either a Rubicon Unlimited or a Mojave Glladiator and am really hoping the 3.6 with the eight speed trans is the difference.
Those of you that Jeep in Glamis can you get from the Washes over to the Flagpole via the dunes??? If so I would love to hook up with you and give it a try. I plan on having 35 inch BFG KO2’s.
Don’t want to have to heavily mod it so very interested in what you Jeep duners are doing and where.
 

Bonanza

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Lord did I hate sand in my old JK. Traction control strangled that vehicle, and even with the throttle pinned (in a manual), the computer killed the revs and stuck the Jeep. I've found the gladiator to be a a bit better managed in that department. I thought I almost got stuck once at KOH in "beach sand", but I flipped on the trail control button and slowwwwwwwwwwwwwwwly crawled out of it.
 

ACAD_Cowboy

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So how much air is enough air is tricky. To much pressure and you do not float, to little and you can throw a bead.

I may have posted it previously here, and can if not, a whole paper on calculation of footprint. The reality is there is only one driving factor for contact patch, air pressure. Tire geometry oddly just changes the orientation not total area.

What this means is finding the low pressure failure point beyond which you are either throwing a bead or stressing the tire cords aka oxbowing the sidewall.
 

MrJeep

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Neat post. 24 on the highway is the most impressive stat here. Must be the flat land! I have noticed people tend to lose beads in the 12-13 range and lower more easily. Less an issue in sand than if there are pesky rocks looking to separate the bead in a turn.

On your converter slipping issue, what eventually solved the problem? Shifting the transfer case back and forth or the tranny? Be curious to know your transmission temps next time you do this.
 

ACAD_Cowboy

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Okay, so as promissed.

https://www.boeing.com/assets/pdf/commercial/airports/faqs/calctirecontactarea.pdf
Boeing Document #C1-APC-96-a072

Calculating Tire Contact Area
The tire contact area for any aircraft tire is calculated by dividing the single wheel load
by the tire inflation pressure. If the load is expressed in pounds, and the tire pressure in
pounds per square inch, then the area is in inches squared. The same thing works with
kilograms and kg/cm2 - the result will then be in square centimeters.
The shape of the footprint area is usually understood to be a 1.6 ellipse (as referenced
in the US Corps of Engineer's S-77-1 Report), wherein the major axis is 1.6 times the
minor axis. The calculation to solve for the minor axis is .894 times the square root of
the contact area. Note that the major axis runs parallel to the normal direction of motion
of the aircraft, and the minor axis is perpendicular to the major axis.

Example: 777-300 Main Gear Tire Contact Area
For this case, use the maximum taxi weight of 662,000 lbs configuration of the
777-300 as shown in Figure 7.2 “Landing Gear Footprint - 777-200/300” and
Figure 7.3 “Maximum Pavement Loads - 777-200/300.” Figure 7.2 provides the
main gear tire pressure of 215 PSI. Figure 7.3 shows the V(mg) per strut /
maximum load at the static aft center of gravity for this airplane configuration of
313,900 pounds. Given that the 777-300 has six wheels per main gear as shown
in Figure 7.2, to calculate the contact area first determine the load per tire
(313,900 / 6 = 52,317) then to calculate the contact area, divide the load per tire
by the PSI (52,317 / 215 = 243.3 in2 contact area).
The footprint area is a 1.6 ellipse determined as follows:
Minor axis is .894 x square root of the contact area (0.894 x sq root of 243.3 =
13.94 inches minor axis)
Major axis is 1.6 x minor axis (1.6 x 13.94 = 22.30 inches major axis)

So lets say we have Gladiator loaded to 6250lb at 30psi, 15psi & 8psi

6250lb / 4 tires = 1562.5lb per tire (yes I know, this is discounting weight distribution, go corner weight your own rig and do you own math)
1562.5lb / 30psi = 52.08333"^2 contact area
1562.5lb / 15psi = 104.1666"^2 contact area
1562.5lb / 7psi = 195.3125"^2 contact area

minor axis = .894 x sqrt (contact area)
@30psi = 6.451889052
@15psi = 9.124346372
@8psi = 12.49402982

major axis = 1.6 x minor axis
@30psi = 10.32302248
@15psi = 14.5989542
@8psi = 19.99044772

So...
30psi = 10.32 X 6.45
15psi = 14.60 x 9.12
8psi = 20.00 x 12.50

That's a pretty dramatic increase in contact area that oddly enough has nothing to do with the actual size of the tire. Tire size and subsequent load rating should then be the determining factor for how long and how well any given tire performs in this situation. To take a look at it in very basic terms Load = Patch and Patch should be physically limited by tire carcass dimensions; you should not have contact patch wider than the physical tread width. Which is a long way of saying contact patch determines tire size and not the other way around.

Or even another way, load dictates how much air pressure you can tolerate via tire deformation; the larger the patch gets, the less sidewall you have supporting the load AND the more work an incorrect part of the tire is doing.
 

ShadowsPapa

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Flappy paddles are actually really bad for cars that need a lot of steering wheel motion. they are best for close ratio steering gears.
They always seemed to be in the way on one of the prior Jeeps my wife had. She kept wanting me to cut them off.
Imagine what a guy driving a race car at 150-200 mph does when he needs to shift........
 
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