What PSI Should You Run In Your Tires?

Is It Better To Be Aired Up Or Aired Down While Driving In Winter Conditions?

We are going to start a mini series here at My Off Road Radio. This mini series of articles is going to be based on vehicle recovery basics. A lot of it is being designed for informative purposes, to help increase basic recovery knowledge for the members of the NorCal 4×4 Facebook Group.

 

 

NorCal 4×4 is a group based around helping people get home after having a day of fun in their vehicles. Each one of the almost 5,000 members is a volunteer that helps others in the Northern California community recover vehicles at no charge.

The question of airing up or airing down in winter driving conditions, is most easily answered by, “Yes!” This question always seems to be a hot debate among the general public. To air up, or air down, that is the question! But what is the real answer that actually helps people drive safe and get home safe? To answer that, we need to know what conditions you are driving in. So, below, we will go through different types of conditions, and what the general best practices are for each.

Your mileage may vary. Please make sure to always take proper precautions and drive safe for whatever your current conditions are. And remember that winter conditions can change rapidly. Just because they were one way when you started the trail, does not mean that they are the same way as you are coming off the trail.

Winter Driving Conditions

Generally speaking there are two different types of driving conditions. Ones where you have the possibility to get your tires on solid ground, and ones where you don’t.

 

 

In order to find out if you can get your tires on solid ground, you need to measure your ground clearance. In order to do that, take a tape measure and measure from the bottom of your tires, to the lowest hanging part of your vehicle. The lowest hanging part is USUALLY your axle, but it could also be things like skid plates, shock mounts, maybe even an exhaust pipe. This measurement is called your ground clearance!

 

 

Now, you want to measure the depth of the snow that you are in, or will be in. Just take a stick and push it down in the snow until you hit solid ground. If the depth of the snow is greater than your ground clearance, then you have no hope of reaching solid ground with your tires. If the depth of the snow is less than your ground clearance, then you might actually be able to hit solid ground!

Pizza Cutter Tires vs Fat Wide Tires

Now that we know if you are physically able to touch the solid ground with your tires or not, we need to figure out what kind of tire is best for those 2 situations!

Typically speaking, if you can get your tires on solid ground, you will most likely be doing 2 things: driving faster, and driving on pavement.

So, in winter conditions where you can get in contact with solid ground (pavement), it is better to try and do so. Running narrower tires will help cut through the snow, and get you in contact with the ground. Because letting air out of your tires will increase your tire patch (your effective tread width), we also recommend keeping the air in your tires in order to help keep your tires narrower.

 

Photo Courtesy of Expedition Portal Forum

 

For 90% of people that travel during winter conditions, pizza cutters and higher PSI will generally help you maintain traction on the road and thus keep you safe.

But what about those situations where you can’t reach solid ground? If your ground clearance ends up being less than the depth of the snow, it is generally in your best interest to try and stay on top of the snow as much as possible. And the best, easiest, and cheapest way to do this, is to simply let air out of your tires.

 

 

By letting air out of your tires, you increase your tires’ contact patch with the terrain you are on (effectively, it makes your tire wider and longer by increasing the amount of surface area that your tire comes in contact with the terrain with). By having a wider and longer contact patch, you spread out the load and weight of the vehicle. When you can spread out the weight across a larger surface area, you drastically increase your ability to stay on top of the terrain, and not sink down into it. In this case, snow… but the same theory applies with mud and sand too.

So, if you are driving up and over Donner Summit on highway 80 during the winter, you will probably want to keep air in your tires. If you are offroading on a trail, then your best way to retain traction is going to be staying on top of the terrain to reduce rolling friction by sinking down into the terrain.

What PSI Should You Air Down To Then?

That is a good question, and the biggest, most often debated one. Every single vehicle is going to be different. The key component here, is going to be your tires’ contact patch.

A contact patch is the surface area of the tire that is physically in contact with the terrain. The below graph is awesome, because it shows how much a contact patch changes as you let more air out of the tire. It is also really neat because it not only shows the contact patch, but it also shows the amount of pressure that the tire is pushing on the contact surface. As the contact patch increases, it largely spreads the load of the vehicle so that there is less pin pointed pressure pushing down on the terrain.

 

 

If you have a heavier vehicle with big, tall side walls, you won’t have to air down as much in order to increase your tire contact patch. Some F350s with 17″ wheels and 33″ or bigger tires will be able to get away with going down to only 15-20 PSI, because they are much heavier of a vehicle, and have more of a sidewall to flex out as the PSI lowers.

On the flip side, if you have a light weight vehicle, you will need to go much lower on PSI in order to get the vehicle to squish out the tires’ sidewalls. For instance, we have to take the #RunnerCrawler all the way to 8psi before we even start pooching the sidewalls out. And we have to take it down to 4psi to get the contact patches to the point where we feel comfortable about them keeping us on top of the terrain. Most of the time, we snow wheel around 2psi… just because we can!

If you are just trail riding in the snow, and not getting off camber too much, most tires can handle down to 8psi without worry of blowing a bead.

 

 

If you end up on a trail where you are doing a little more extreme wheeling in the snow, and you plan on going off camber a little more often, then most tires are good around 12psi. But if you are going off camber in snow, then you will probably be sliding down a hill very quickly and have bigger problems. Wheeling on sand dunes is where you might have issues with blowing beads if you are down around 8-12 psi.

 

 

One of the best and least expensive ways to let air out of your tires is with an ARB EZ Tire Deflator. These tools will pull the valve core out of your tire’s valve stem, and keep it safe within the tool. That way you can let air out of the tires as fast as physically possible, while not risking losing your valve core. It also allows you to check the PSI during the process with one little swipe of the gauge sleeve.

ARB EZ Tire Deflator – $38.00

 

 

 

Your other option is a MORRFlate 4 Tire Off Road Inflation Deflation Kit. The MORRFlate connects to all 4 of your vehicle’s tires, and then lets air out of them evenly, and airs them up evenly. It automagically equalizes all of the tires’ PSI. And, is good to go right out of the box. No more pulling valve stems. No more squatting to check PSI over and over. No more moving hoses between all your tires. Just take the MORRFlate out of the box, attach it to your valve stems, and let it do its thing.

The MORRFlate 4 Tire Off Road Inflation Deflation Kit comes in 2 sizes, and is a universal fit to your tires. If your on board air source is not located in the middle of your bumpers, then there is also an optional MORRFlate Lead to connect your air source to the MORRFlate or MORRFlate +.

MORRFlate 4 Tire Off Road Inflation Deflation Kit – $169.99

MORRFlate + 4 Tire Off Road Inflation Deflation Kit – $189.99

MORRFlate Lead for Off Road Tire Inflation Deflation Kit – $24.99

 

What About Getting Air Back In Your Tires?

The only downside with airing down, is that you need to air back up after you are done playing! If you are wheeling in California, then it is state law that if you buy gas at a gas station, they have to let you use the air pump free of charge. So, find a gas station near your trail and go gas up after your adventure. While there, you can air up your tires too.

 

 

Or you can be spiffy and get an air compressor. We highly recommend the Smittybilt 5.5CFM compressor. We have had ours for 3 years now and it has seen a LOT of use. It still goes strong and airs up all 4 of our 36×13.50×15 Iroks in under 15minutes from start to finish. It is also enough to reseat beads with the combined use of a strap. And at just under $150, it performs almost as well as the ARB Twin Compressor, but only a fraction of the cost.

 

 

Or you can look into a Powertank if you want something with enough pressure to reseat beads and run air tools, all in one great bundle. The only down side to Powertanks are that you have to refill them once you use them. Most people get roughly 12 vehicle’s worth out of 1 tank.

 

 

Or if you want to be really classy, you can hook up an onboard air system. Viair has an awesome dual compressor 100% duty cycle X’Treme on board air system. It comes as a complete kit and has great reviews and ratings from users. For those looking for something a little less extreme, and maybe not running air tools 100% of the time, Viair also makes a single compressor 100% duty cycle on board air system, at almost half the price of the X’treme duty system.

 

 

ARB also has different on board air options. Most people get the ARB Twin Air Compressor as it boasts a staggering 6.16CFM of airflow, which is enough to reseat beads or run air tools with the addition of an air tank.

Or, if you want to be crafty and test your ingenuity, you can create your own on board air system with a Smittybilt 5.65CFM compressor, a craigslist air tank, some electrical wiring, a properly rated fuse, some air tubing, air fittings, and a PSI cutoff switch for a fraction of the cost of the Viaire or ARB systems.

On Board Air Options For Your 4×4 Off Road Vehicle

Smittybilt 5.65 CFM Compressor – $150.00

Powertank On Board Air Off Road Bundle – $510.00

Viair X’treme Duty On Board Air System – $420.00

Viair Constant Duty On Board Air System – $280.00

ARB Twin Compressor 6.16 CFM – $500.00

 

That’s it for this installment of recovery basics! On the next article due up, we will cover traction aiding devices! Should you use chains in the snow? What about those traction boards? Mud Terrain vs All Terrain tires? Cardboard (wait, what?)?

 

Thank you for reading! Feel free to leave any comments or questions below! If you want to keep in touch with us when we add new content, join our newsletter! We do special offers that only show up in the newsletter, so make sure you sign up below!

You can also join the community forums and ask questions and see what adventures everyone else is up to!

 

Join the Off Road Ham Radio Community!

 

Also, if you don’t have your Ham Radio Technician License, head over to our Online Ham Radio Class and study up! Remember, 15% of your registration goes back into keeping our trails open!

And, of course, don’t forget to check out our MORRFlate 4 Tire Off Road Inflation Deflation Kit!

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4 Comments

  1. Dean H ; KM6RNW

    Tyler, I have most of the types of tire deflaters available and have found that the cheapest and fastest one is an air inflation chuck disconnected from the inflation line. Simple and fast no worries about losing the valve stem valve core. It evacuees air as fast as removing the valve core.

    1. Nice! That ARB Ez Deflator does the same thing… keeps track of the valve core for you, lets air out as fast as possible! We are developing our own tire inflation and deflation system here at MORR, it is affectionately called the MORRFlate. You will be able to inflate and deflate all 4 tires at the same time, check all 4 tire pressures from 1 location. No more having to squat next to the rig to keep checking tire pressures and moving from tire to tire. The design is done. The patent is pending. Once all of the parts come in, we will start the selling and marketing!

  2. Dean H ; KM6RNW

    Tyler, I pirchased a boa feng 5 watt radio from a dealer in my home town at 3x the on line cost thinking that I would get some help when I needed it.
    Well…… he did program in 39 channels but I have yet to receive any sound from any, or get a reply from cq.
    The cd’s that came with the radio all are in Chinese. At least that’s what I got.
    So how do I go about getting out or what options do I choose from the manual I down loaded.
    Clue less with my bf5watter.

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