Off-road questions from a guy with not a lot of off-road experience... (transmission and air compressor content)

[DanF.]

Are there any pros/cons to crawling along (+/-5mph) in 1st gear with OD off? (automatic gearbox)

 

Next, is there a guide to how much I should air-down with stock-sized tires? I'm thinking about going down to 20psi as a starting point, and see how that works.

 

And, does anyone have any experience good/bad with the Viair 88P Portable Air Compressor? My wife is demanding an Xmas present suggestion (she didn't think rolls of crisp $100s was appropriate) and I pulled this out of thin air. Are there better options in the sub-$100 category?

 

 

I've been exploring a lot of the class VI roads nearby, and realized that I don't really know what I'm doing other than trying to be safe and not break anything or tear up the ground.

 

Thanks .

 

 

[hawairish]

OD only controls whether the truck goes into 4th gear (the overdrive gear), so it's got no impact on low gears/speeds.

 

PSI depends more on the terrain. Can't say I've seen a compelling article about specific PSIs to use, though. Ideally, you want a PSI that 1) increases surface contact with the obstacle and 2) reduces the risk of puncture by the obstacle. The size of the tire is less important than construction, type, and condition of tire. The tricky part is finding the balance.

 

Since you spend some time at the beaches, 25psi is probably suitable. Maybe higher for wet/packed sand, and lower for dry/loose sand...and lower for hot/dry/loose sand (accounting for operating temps, not "cold" temps). For rockier or bumper conditions, where rocks or branches can puncture tires, under 15-20psi is ideal...lower end for sharp obstacles, higher end for just dirt roads to improve ride quality. Be mindful of changing conditions, too...driving on a low PSI that is good for rocks probably isn't good for that mile stretch of dirt road in between.

 

You should definitely carry an air compressor in any case.

 

I don't have experience with the Viair pump, but in terms of quality, their primary industry focus is air, so I'd expect them to be good. I use the cheap MF-1050 (among variants) that everyone else raves about, and it's earned its keep.

[rgallant]

I have had a Via air 90 (?) for about 4 years get used a few times a year has stood up well. Airing down is very much a terrain issue, I almost never air down, but I am on the West Coast and most of the roads are hard pack dirt, gravel or stone.

 

Be aware of though I have seen more torn tires on trucks that air down and are aggressive on the gas, when they are on sharp rock. So adjust your driving accordingly.

 

Your last line is says it best and remember the road ends where you say it does.

Getting out and walking for 5 or 10 minutes can save you hours of digging, if in doubt walk down the road and see what it looks like.

Line is everything look for the easiest way, not the "coolest" way.

More gas is rarely the the best solution to any problem.

 

Finally beacuse this drives me nuts, be prepared to walk out, have good foot wear, a warm jacket and long pants even in summer. Just toss it all in a day pack with some water and energy bars and always toss it in the truck or just leave it in there. If you travel with otheres they should be equally prepared to walk.

[XPLORx4]

RE: Driving in 1st gear

As mentioned by Hawairish above, O/D on/off does not even factor into the transmission shift logic until higher vehicle speeds, so the toggling of O/D on or off is irrelevant. At 5mph, you're not really even locked in gear anyway. There is significant slipping of the torque converter (no risk for damage by overheating) at low engine RPM and speed, no matter what position the transmission selector is in.

 

Pros: instant engine torque available, speed directly proportional to accelerator pedal movement. Less wear on transmission at slow speeds (tranny does not try to shift out of 1st at higher speeds or lower throttle input).

Cons: Max speed is RPM-limited to about 35-40. Lower fuel economy. Potentially less comfortable ride for passengers if you don't modulate throttle smoothly. (Vehicle will tend to lurch forward and backward more easily with varying throttle input. While you depress the accelerator pedal, brace the side of your foot against the transmission hump while driving on rough terrain.)

 

RE: Airing down on stock tires

You didn't say what kind of tires you have. Again as Hawairish commented, tire size is not as important as tire type when determining how much to air down.The degree to which you air down depends on the tire construction, tire wear, tire tread, weight of your rig, and the terrain you'll drive on. If your tires are highway-tread with weaker sidewalls, airing them down too much on rocks could risk a sidewall puncture. In softer terrain such as sand, you can air them down without fearing sidewall damage. I run all-terrain and mud-terrain load-range-E tires on my rigs, and my preferred PSI for airing down on mixed terrain is 16-18psi. For dry, firm sand, I would go down to about 10-12psi. For highway tires (eg. Dueler HL) I might go 18psi on rocks, 12psi on sand.

You'll want to watch how much the sidewalls bulge out at lower pressure. In my opinion, 20psi is actually still pretty high, especially for sand. More info here: http://www.off-road-outdoors.com/tire-pressure.html

You can also find a plethora of useful information if you google "airing down tires".

 

RE: christmas wish-list items for your rig (in order of importance)

Recovery and emergency gear (ex: tow strap, shackles, receiver hitch, come-along hand-winch*, tree-saver strap, battery cables, paracord rope, leather gloves, first-aid kit)

Airing down and airing up equipment: tire pressure gauge, compressor, and automatic tire deflators, such as these: https://www.amazon.com/Staun-SCV5-Tire-Deflators/dp/B00QBPBLWY

I have had very good experiences using this MV50 compressor (I have two, one is hard-mounted under the hood of my Pathy (pics here, and the other is still portable.) https://www.amazon.com/Industries-MV50-SuperFlow-12-Volt-Compressor/dp/B000BM8RT8

 

*I used to keep a come-along in the rear cargo under-carpet storage bin, even after I'd installed an electric winch in my bumper. I used it a couple of times, the most critical being after I lost traction ascending a steep muddy slope, and the rear slid sideways towards a tree as I tried to back down. I had to attach the electric winch to a tree up ahead, then attached the come-along to the rear hitch to pull the back end squarely onto the trail as I then reversed the electric winch to get down the hill.