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John M
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Registered: 9-3-2003
Location: California High Desert
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Why lowering tire air pressure really works
This link is found on the "Expedition Portal" site. In the relatively brief article the author explains his take on the benefits and why's of lowering
air pressure when off-road. It may not be just as you think (if he is correct). As you read through the article, it refers to a couple of photos that
didn't come through on the link, but they are easy to imagine.
John M
https://expeditionportal.com/the-lowdown-off-road-tire-press...
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TMW
Select Nomad
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Location: Bakersfield, CA
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Sounds good to me. Whether it is wider or longer as long as it works.
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gnukid
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John M ima ask you don't you want higher pressure on the roads and lower pressure on the dirt?
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4x4abc
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here is everything you need to know about airing down (start with the driver)
http://4x4abc.com/jeep101/soft-sand-deflate.html
http://4x4abc.com/jeep101/soft-sand-turn-straight.html
http://4x4abc.com/jeep101/soft-sand.html
Harald Pietschmann
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BajaMama
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Mood: Got Baja fever!!
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Yep, all vehicles in our 4x4 club air down, then air up before and after runs. I just got a mini compressor so maybe I'll air down for the long haul
out the road to Punta Chivato (kidding, never need to before...). But yes, more surface contact is the key.
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John Harper
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Quote: Originally posted by BajaMama  | | Yep, all vehicles in our 4x4 club air down, then air up before and after runs. I just got a mini compressor so maybe I'll air down for the long haul
out the road to Punta Chivato (kidding, never need to before...). But yes, more surface contact is the key. |
I aired down on the miles of graded roads in the Copper Basin of Idaho. It just makes the truck ride softer and not have a tendency to "skitter"
around (as shown in 4x4abc's attachment).
John
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4x4abc
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I found that on Baja dirt roads reducing tire pressure from around 30 psi to20 psi will completely eliminate the risk of flat tires.
Going up in pressure would increase the risk of flat tires.
Always think of a fully inflated birthday balloon - a coarse finger nail will make it explode. A limp balloon does not even react to something sharp.
Harald Pietschmann
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David K
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I greatly reduced flats from sharp rocks at 20 psi, down from the 34 psi street pressure. My air pump connects direct to the battery (MV-50) and
only takes 2.5 minutes to refill each tire, which is 3 times quicker than the pumps that plug into the cigarette lighter.
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4x4abc
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anything smaller than an MV-50 is not worth having.
Main reason - when you most need them, cheap plug in compressors will have quit working.
Harald Pietschmann
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BajaNaranja
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Registered: 9-10-2006
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Keep in mind that ideal tire pressure for offroading depends on a few other factors, like:
Weight / load: A Ford F350 with a cab over camper will have a tremendous amount of weight compared to a Toyota Tacoma, and ideal air pressure for
offroading has a lot to do with weight on tires. So 20-30 psi may be a good round about target to try for most light vehicles, but if you are dealing
with heavy load, slowly decrease pressure and watch sidewall deformation.
Type of tires: All terrain or off road tires often have beefier sidewalls with additional tire plys and are much heavier, versus street tires which
are constructed to be lighter and to provide greater fuel efficiency on the highway. Obviously an all terrain or off road tire, with a beefier
carcass, is going to absorb a lot more abuse and handle lower air pressure better in an off-road setting than a street tire.
Type of terrain: There are plenty of roads in Baja where there's jagged lava rock embedded in dirt; might not want to expose too much sidewall in such
areas, as lava rock can slice sidewalls with ease. Versus pure sand, where lower tire pressure is better.
As always, take on advice while exercising your own judgement, and ask a saltier vet for their take, if in doubt.
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David K
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Agreed, a % of the street pressure for deflation amount may be a better way to cover both heavy truck tires vs light truck or car tires. For example,
30% for dirt roads and 50% for deep sand.
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AKgringo
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Check your tire pressure gauge as well! I have found significant differences in readings when I compare them against each other.
The PSI will also change a bit with temperature and sidewall flexing.
If you are not living on the edge, you are taking up too much space!
"Could do better if he tried!" Report card comments from most of my grade school teachers. Sadly, still true!
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JZ
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Registered: 10-3-2003
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| Quote: Originally posted by AKgringo | Check your tire pressure gauge as well! I have found significant differences in readings when I compare them against each other.
The PSI will also change a bit with temperature and sidewall flexing. |
Use the gauge on your dashboard.
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msteve1014
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| Quote: Originally posted by JZ | | Quote: Originally posted by AKgringo | Check your tire pressure gauge as well! I have found significant differences in readings when I compare them against each other.
The PSI will also change a bit with temperature and sidewall flexing. |
Use the gauge on your dashboard.
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Too funny. I just got an email telling me my tires are low.
New trucks, huh?
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JZ
Elite Nomad
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Registered: 10-3-2003
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Mine gives you the instantaneous length of your tire footprint. So you can tell how much air to let out.
Unfortunately, it doesn't yet have a button to deflate to said pressure/length - yet.
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4x4abc
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here are the rules for tire deflation:
off-road (meaning leaving pavement) 1/3 less than street pressure
if street was 30, now it is 20
mud, sand and snow 2/3 less than street pressure
if street was 30, now it is 10
emergency (about to get swallowed at Malarrimo) 50% less than mud, sand and snow
if MSS was 10, now it is 5
if you have tires with a low aspect ratio (like 275/50 or 285/30) have a tow truck follow you
if your tires do not have a light truck designation (like LT275/70 etc) avoid dirt roads in Baja - short stretches like around
Chapala are OK when driven carefully.
I know you all have your personal buts, ifs and whens - but they dot affect theses rules.
And no, your tire will not come off the wheel when at low pressures like 10 or 5. Beadlocks (metal rings that bolt your tires to the wheel) were
invented for drag racing and serve a purpose there. Then the competition offroaders discovered them. Because they drive like maniacs, they need them
too.
You will only need them if you combine 10 psi with donuts at the beach.
No sane driver will ever need beadlocks.
However, they make you look semi professional.
Harald Pietschmann
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JZ
Elite Nomad
Posts: 9268
Registered: 10-3-2003
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| Quote: Originally posted by 4x4abc | here are the rules for tire deflation:
off-road (meaning leaving pavement) 1/3 less than street pressure
if street was 30, now it is 20
mud, sand and snow 2/3 less than street pressure
if street was 30, now it is 10
emergency (about to get swallowed at Malarrimo) 50% less than mud, sand and snow
if MSS was 10, now it is 5
if you have tires with a low aspect ratio (like 275/50 or 285/30) have a tow truck follow you
if your tires do not have a light truck designation (like LT275/70 etc) avoid dirt roads in Baja - short stretches like around
Chapala are OK when driven carefully.
I know you all have your personal buts, ifs and whens - but they dot affect theses rules.
And no, your tire will not come off the wheel when at low pressures like 10 or 5. Beadlocks (metal rings that bolt your tires to the wheel) were
invented for drag racing and serve a purpose there. Then the competition offroaders discovered them. Because they drive like maniacs, they need them
too.
You will only need them if you combine 10 psi with donuts at the beach.
No sane driver will ever need beadlocks.
However, they make you look semi professional.
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Looks good except for the 1/3 off for general dirt driving. We typically run 34 on E load tires. Where it is 60-65 on the street. So closer to 45%
less.
[Edited on 10-9-2018 by JZ]
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4x4abc
Ultra Nomad
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I always like individual adjustments
Harald Pietschmann
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4x4abc
Ultra Nomad
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by the way, lowering tire pressure does not increase traction
in fact, you have the same traction with deflated tires as with 100 psi (less weight per square inch, but more of it vs more weight per square inch
but less of it)
weight increases traction
ever follow a loaded logging truck down the mountains?
you will have a hard time following him
lotsa pounds per square inch
lotsa traction
so the advantage of lower pressure in sand is less resistance
the "hill of sand" you are running against is smaller with less pressure
thus less resistance
on dirt roads the advantage is increased flexibility
the tires now mold around ground contours
like a flexible hand grabbing outcroppings during mountain climbing
the larger footprint also guarantees more points to hold on to
so more tire pressure gives you more traction (per square inch) but a smaller footprint and thus less opportunity to grab the ground
that is why we opt for less pressure
on the negative side:
rolling resistance goes up, with it gas consumption
ground clearance will be reduced
side wall is more exposed and less talented drivers might have side wall nicks (most likely right rear)
why right rear?
like in real life, people tend to avoid problems - they steer around them
in a car that usually works fine for the front tires
but since the rear tires follow a different path, one of the rear tires will get bruised
right rear because it is the farthest away from the driver and the most difficult to place (left rear in Australia)
the way out?
take on problems!
drive o
ver the obstacle - you are always telling your friends how much ground clearance your truck has - use it!
ingrown rocks on a trail or dirt road signal their danger to all drivers way ahead
they always have a very black side
blackened by bruised side walls
once you spot them, it is your chance to behave differently
you probably won't - but at least you read about it
Harald Pietschmann
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JZ
Elite Nomad
Posts: 9268
Registered: 10-3-2003
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Biggest benefit of airing down is a MUCH more comfortable ride.
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