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When to Air Down/Up Mountain Trails

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Discussion starter · #1 ·
Ok, my jeep is running on 35'' BF Goodrich Mud-Terrain T/A KM2. Max pressure cold-35psi. Here in Kansas i lower it down to 15 psi when needed. Here are a few questions

1. When what situation/scenario would i need to lower my tire pressure when on mountain trails?

2. Would it be best to lower my tire pressure going into the trailhead or wait till the obstacle (never know whats around the switchback) :rolleyes:.

3. Is 15 psi ideal tire pressure for mediocre rock crawling/trail riding.

THANKS IN ADVANCE, GREATLY APPRECIATED!!!!!! :wavey:
 

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#2 ·
Typically we air down as soon as we start wheeling for the day. Not only is your traction much improved, but your ride will be much softer. Because of this I air down whether we're riding simply green trails or doing something more difficult.

As far as pressure, how wide is your rim? If you're running an 8" wide rim, I would suggest trying 8-12 psi.
 
#3 ·
I agree with airing down from the start. I run my 33" duratracs at 12-14 psi from trailheads... Even if it's just a dirt road for a while.

Duratracs are only a 2 ply sidewall and I dare not go much lower than 12 psi. They flex quite well as it is.
 
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Discussion starter · #6 ·
Ok, thanks. What kind of air compressors do you guys use? Ive been looking at the VIAIR 400P Portable Compressor. Price isnt a huge deal, just not wanting to spend an arm and leg for something i might only use 5 times a year. BUT when i need it i want it to work :)
 
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#7 ·
Personally not a fan of the 12V compressors. Currently I'm using a CO2 tank; it's fast, cheap, and works great.

In my 98, I converted my A/C compressor into an air compressor and used that as an OBA system. It worked great and was fast. In the 04 that I currently have, my A/C works pretty well and I would like to keep it intact, thus the reason I have the CO2 tank right now. Eventually once I get the time, I want to get a York compressor from the junkyard and use it for an OBA compressor. But for now the CO2 tank works very well and is quite fast so I'm not in a big hurry.
 
#8 ·
geiman said:
Personally not a fan of the 12V compressors. Currently I'm using a CO2 tank; it's fast, cheap, and works great.

In my 98, I converted my A/C compressor into an air compressor and used that as an OBA system. It worked great and was fast. In the 04 that I currently have, my A/C works pretty well and I would like to keep it intact, thus the reason I have the CO2 tank right now. Eventually once I get the time, I want to get a York compressor from the junkyard and use it for an OBA compressor. But for now the CO2 tank works very well and is quite fast so I'm not in a big hurry.
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What vehicles would have a York compressor?
 
#10 · (Edited)
For most 35" tires, your normal street pressure should be 24-26 psi. 35 psi is excessive for that size tire carrying a vehicle the weight of a Wrangler. Keep in mind the air pressure molded onto a tire's sidewall is NEVER the correct street pressure. That pressure is only the tire's maximum safe air pressure to be used if the tire was forced to carry its maximum safe weight. Since the Wrangler weighs no more than about 50% of the tire's maximum safe weight, the sidewall air pressure should never be what the tire is inflated to.

For airing down, air down as soon as you're ready to start on the trail. 15 psi is barely airing down, you'll get better traction and the tires will be less likely to be damaged if you air down to lower pressures. For an easy trail, 12-13 psi is fine. For a really tough trail, 10-11 psi. For extremely difficult trails, 7-8 psi is common. My 35" MT/Rs are seldom higher than 10 psi when offroad and 7-8 is pretty common if the trail is tough.

Air back up to 24-26 psi before you hit the highway. Highway speeds with deflated tires will heat them up which can cause a tire failure. My TJ never sees speeds faster than 20-25 mph when the tires are aired down which helps keep them from overheating.
 
Discussion starter · #11 ·
Jerry Bransford said:
For most 35" tires, your normal street pressure should be 24-26 psi. 35 psi is excessive for that size tire carrying a vehicle the weight of a Wrangler. Keep in mind the air pressure molded onto a tire's sidewall is NEVER the correct street pressure. That pressure is only the tire's maximum safe air pressure to be used if the tire was forced to carry its maximum safe weight. Since the Wrangler weighs no more than about 50% of the tire's maximum safe weight, the sidewall air pressure should never be what the tire is inflated to.

For airing down, air down as soon as you're ready to start on the trail. 15 psi is barely airing down, you'll get better traction and the tires will be less likely to be damaged if you air down to lower pressures. For an easy trail, 12-13 psi is fine. For a really tough trail, 10-11 psi. For extremely difficult trails, 7-8 psi is common. My 35" MT/Rs are seldom higher than 10 psi when offroad and 7-8 is pretty common if the trail is tough.

Air back up to 24-26 psi before you hit the highway. Highway speeds with deflated tires will heat them up which can cause a tire failure. My TJ never sees speeds faster than 20-25 mph when the tires are aired down which helps keep them from overheating.
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Thanks, Jerry!
 
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#13 · (Edited)
NikeSwimming said:
If you don't have an on board air compressor, would it be okay to air down then air up after the trail at a gas station?
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If you can keep your speeds down to around 20-25 mph while driving to the gas station, yes. Driving faster than that on tires that are aired down will cause them to get hot, possibly hot enough to fail.

I would just buy a compressor or C02 tank. One thing to know, cheap air compressors that scream how they can get up to some high air pressure like 200 psi will take forever and a day to get four tires refilled. Cheap air compressors don't put out enough air volume (air volume is king, not air pressure!!!) to make airing up tires anything but an agonizingly slow torturous process.
 
#14 ·
Yes of course, the only downside is being able to get to a gas station. If you air down to 10PSI, you shouldn't drive over 20-25MPH on the hard road, and even that is pushing it. The other downside is whether the air is free or not. If it's not free, the compressor is typically very slow and you will have to pay multiple times to fill up all four tires. I did that once or twice before deciding enough was enough and I just got a CO2 tank.
 
#16 ·
Just found this thread and love the advice! I run 31 inch bf all terrains. Where can I get a co2 tank and which is the best? I don't air down when I wheel only because there are no nearby gas stations and I don't have a compressor. Any advice and help welcome thanks guys :)
 
#17 ·
I found mine locally. I'd first check Craigslist and get in touch with your local beverage shop. Restaurants use CO2 bottles for various things, and that's how I got mine. You're local beverage supplier will typically refill those bottles for restaurants, and they may have a few used ones laying around.

ebay is also a good place to look for used tanks. Other than that, look around online. The beverage factory usually has decent prices on new ones:

20 lb. Aluminum Co2 Tank | BeverageFactory.com

Keep in mind that's a 20lb tank; you might not want something that big. It's the size I run since I found one so cheap locally, but it does take up a lot of room. Of course with the bigger tank you can go longer between refills. Just something to keep in mind.
 
#18 ·
geiman said:
Keep in mind that's a 20lb tank; you might not want something that big. It's the size I run since I found one so cheap locally, but it does take up a lot of room. Of course with the bigger tank you can go longer between refills. Just something to keep in mind.
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How many fill ups does that 20lb tank last you? I homebrew, so I'm thinking it'd make more sense to drag my CO2 out and get a hose adapter.
 
#19 ·
To me, a 20 lb. C02 tank would be too big to lug around, I'd go with the more common 10 lb. size which is much easier to store and carry. How many refills you can get depends on your tire size and how far you air down. For my 35" tires and 10 lb. C02 bottle, I can air all four of them from 8 to 24 psi around five times or about 20 tires worth.
 
#20 ·
Jerry Bransford said:
To me, a 20 lb. C02 tank would be too big to lug around, I'd go with the more common 10 lb. size which is much easier to store and carry. How many refills you can get depends on your tire size and how far you air down. For my 35" tires and 10 lb. C02 bottle, I can air all four of them from 8 to 24 psi around five times or about 20 tires worth.
Click to expand...
Dang, I could probably get 3 kegs and 4 fillups off one 10lb can. That's not too bad.

Thanks for the estimate.
 
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