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caj13
Senior Nomad
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Airing Down heavy duty tires
OK guys. I run an ex military Landrover 110 ( Tithonis NA 2.5.) I put on Cooper ST's 255 85 16R. huge improvement from the military tires
originally on the vehicle.
The coopers say the max inflation is 63 lb PSI. I run em at 50 PSI, and am happy with that - the stencilled numbers on the truck say 28 up front
and 45 in back, but i assume thats for those military grade tires.
So I'm looking for verification that 50 lbs psi is a good number (like I said, I love the way it goes down the road with these on it)
also guys here swear by deflating tires to deal with washboard, and talk about running 10 - 12 lbs psi.
I suspect that going that low would be pretty hard on the sidewalls, but i suspect it would be an advantage to lower the presures some.
anyone have any experience with deflating heavy load tires (load range D) for washboard?
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bajagregg
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Deflating for offroad driving is the way to go. It's especially helpful in the sand. The important thing is to air up when you are returning to
paved roads. Low inflation is fine for lower speeds in the dirt but will lead to tire damage and failure on asphalt. A 12 volt air compressor is the
way to go. There are plenty of previous posts about this here on the forum.
Traveling Baja for 50 years.
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4x4abc
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50 psi is a very bad number!
do the chalk test first to find out your regular psi number
https://www.youtube.com/watch?v=ojGsavK0Uwc&t=119s
after that we will tell you what to use for washboard and why
Harald Pietschmann
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Maderita
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You are likely to get a lot of wide ranging opinions. Your vehicle is not particularly heavy. Just shy of 4,000 lbs, correct? 50 psi is too high. In
addition to a harsh ride, it will probably wear the center tread rather than even wear across the tread.
My best guess is 35 psi, 40 psi at most, unless hauling heavy cargo.
18-22 psi for washboard dirt roads. The 10-12 psi number that you recall is for sand.
Look up some methods for a chalk or paper under-the-tire test. That will give you accurate info about the actual weight distribution across the tread
surface at a given tire pressure.
Perhaps someone (DK?) will repost that method if you can't find it.
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JZ
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Have Load E Nitto Terra Grapplers on my 3/4 ton. Max PSI is 80. Driving on highways around here put them at 65 front and 70 rear.
Offroad run them at 33-35. The difference in comfort is incredible. We go down to 20 for sand.
Always travel with a compression. One that attaches directly to the battery. This is a good one: https://www.amazon.com/Inflator-Portable-Compressor-MasterFl...
[Edited on 2-24-2019 by JZ]
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David K
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The chalk test is the one true way to determine the correct street pressure for your tires and vehicle.
I had not seen Harald's video link before, but here is the post for my Chalk test on my Tacoma, on the Tacoma World forums: https://www.tacomaworld.com/threads/chalk-test-dynapro-atm-a...
Once you have the correct street pressure dialed in...
You will find that off road (washboard to rocks) is good at about 1/3 the street pressure (or less) and sand at about 1/2 the street pressure (or
less). 3-ply sidewall tires and mud-terrain type tires will need less air in them to achieve floatation on deep sand than do all terrain or street
tires.
For my all-terrain Hankook Dyna-Pro ATM tires on a 4-door Tacoma, 34 psi is the ideal street pressure, and 18 psi is good sand pressure, with 24 psi
my dirt road pressure. The BFG 3-ply tires, many on Baja Nomad run, need to be down to 10 psi max for sand!
On the stock BFGs my truck came with (Rugged Trail TAs), they needed to be down to 15 psi for sand.
Here is a post I made on the difference in deep (Shell Island) sand at 32 psi vs 15 psi (stock tires): https://www.tacomaworld.com/threads/baja-beach-4wd-32-psi-to...
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4x4abc
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here is everything on tire pressure:
http://4x4abc.com/jeep101/soft-sand-deflate.html
it is super important to establish "normal" pressure before doing anything else
do the chalk test
just a number, like 10 psi for sand, might be right for some - will be wrong for many
there is a delicate relationship between vehicle weight (each axle might be different), tire size, volume of air (not psi), and tire construction
(some are stiff, some are flexible, the number of plies is no indication).
Harald Pietschmann
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David K
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Agreed... every tire/vehicle combination is different.
Do the chalk test first to establish to baseline pressure for you.
I gave examples of what works for me with my tires/ vehicle and for me, sand is about 1/2 street pressure but may need to be less... it depends on
temperature and humidity... sand changes based on those two factors. Once, I needed to go down to 6 psi to get out of a sticky situation with a rising
tide and a dead whale blocking my path!
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PaulW
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I will not disagree if tire pressure off road, but for normal driving the pressure should be according to the tire manufacturers tire vs load chart.
Call the tire company and ask for an engineer and get the info and make a chart. Then go get your rig weighed and use the pressure per the chart.
Then when you load teh rig up for a big trip get your new weights at the scale and adjust your pressures.
Been doing this for many years and the result is the best ride as possible and nice even tire wear and long life.
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David K
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I think many here do not keep the tires that often come with the rig we buy, so the chalk test will reveal the correct pressure based on the vehicle
and after-market tires you install.
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4x4abc
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Quote: Originally posted by PaulW  | I will not disagree if tire pressure off road, but for normal driving the pressure should be according to the tire manufacturers tire vs load chart.
Call the tire company and ask for an engineer and get the info and make a chart. Then go get your rig weighed and use the pressure per the chart.
Then when you load teh rig up for a big trip get your new weights at the scale and adjust your pressures.
Been doing this for many years and the result is the best ride as possible and nice even tire wear and long life. |
need to get front and rear weighed separately
Harald Pietschmann
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caj13
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Ok guys did the chalk test, but I used white shoe polish, the liquid stuff in a squeeze bottle. had to drive back and forth 10 times, but it
worked fine. Based on that, I am going to run 38 up front and 42 in the rear and see how i like that on the road.
also, Lbs are kind of useless comparing, because my 3 air guages show a 10 % variance between them, so I guess use one guage and just go with
those numbers for the unit.
Thanks for the Info David and Harald, helped alot
[Edited on 2-25-2019 by caj13]
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4x4abc
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the chalk test is the quickest most accurate information you can get on "normal" tire pressure.
If the tire manufacturer will provide a weight/pressure chart - great
but they are not too responsive.
here again:
"normal" for around town and a quick freeway trip
+ 10 psi for prolonged and fast freeway trips
1/3 down from "normal for easy off road (dirt road)
2/3 down from "normal" for mud, sand and snow - and demanding off road (like widow Maker)
1/2 down from the last number for emergencies (like what David described)
for super demanding steep climbs (they rarely happen, but they do) - use 2/3 in the rear and "emergency" in the front (due to the vehicle's weight
shift)
Harald Pietschmann
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4x4abc
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tip for gauges - use the ones that cover your range only
a gauge from 0-100 will not be very accurate around 10 psi
I carry a 0-60 gauge for every day driving
and a 0-30 for off road
make sure you use the off road gauge up to 30 psi only
it blows up when used with higher pressures
Harald Pietschmann
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caj13
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| Quote: Originally posted by 4x4abc | the chalk test is the quickest most accurate information you can get on "normal" tire pressure.
If the tire manufacturer will provide a weight/pressure chart - great
but they are not too responsive.
here again:
"normal" for around town and a quick freeway trip
+ 10 psi for prolonged and fast freeway trips
1/3 down from "normal for easy off road (dirt road)
2/3 down from "normal" for mud, sand and snow - and demanding off road (like widow Maker)
1/2 down from the last number for emergencies (like what David described)
for super demanding steep climbs (they rarely happen, but they do) - use 2/3 in the rear and "emergency" in the front (due to the vehicle's weight
shift) |
Thanks for that Harald.
With the 2.5 NA diesel in this beast putting out a whopping 62 horsepower, and the vehicle weighing 4500 lbs, and having the aerodynamics of a brick
turned sideways, Fast Prolonged Freeway trips are just a wet dream! runs forever, at 62 mph, if i want more speed i would need to Thelma and Louise
it over a cliff!
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Phil C
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Wow, has anyone calculated for wind speed and temperature ?
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tobias
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| Quote: Originally posted by 4x4abc | the chalk test is the quickest most accurate information you can get on "normal" tire pressure.
If the tire manufacturer will provide a weight/pressure chart - great
but they are not too responsive.
here again:
"normal" for around town and a quick freeway trip
+ 10 psi for prolonged and fast freeway trips
1/3 down from "normal for easy off road (dirt road)
2/3 down from "normal" for mud, sand and snow - and demanding off road (like widow Maker)
1/2 down from the last number for emergencies (like what David described)
for super demanding steep climbs (they rarely happen, but they do) - use 2/3 in the rear and "emergency" in the front (due to the vehicle's weight
shift) |
I am going to bookmark this one.
So if my chalk test gives me 45 PSI as optimum then I would be running 15 PSI in sand and 7.5 PSi in emergency situations ?
I am guessing I run the risk of losing the bead on my 30 inch BFG KO2s at 7.5 so best to be cautious.
Very cool stuff and good to have in my back pocket for those off road excursions. I have found my AWD express van is pretty capable in the sand at 20
PSI and would love to see what it does down at 15.
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4x4abc
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losing you bead depends on 3 factors:
A. the height of the hump built into your wheel (they vary - the higher ones are better)
B. the tightness of the bead of your tire (the innermost cable next to the wheel)
B. your driving style
when aired down to 10 psi or less be gentle on your steering - any radical direction changes put a ton of side load on your tires - that's when they
pop off
drive ver big rock in a straight line - steering and climbing will likely result in a popped bead
I have done extreme low pressures and extreme trails (Rubicon daily) for 30 years - lost a bead maybe 3 times
sure you can spend $$$ on beadlocks - or just be careful
Harald Pietschmann
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4x4abc
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caj13 - your truck should be lighter in the rear than in the front (engine) - thus 48 psi seems high - are you sure?
Harald Pietschmann
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mtgoat666
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| Quote: Originally posted by caj13 | OK guys. I run an ex military Landrover 110 ( Tithonis NA 2.5.) I put on Cooper ST's 255 85 16R. huge improvement from the military tires
originally on the vehicle.
The coopers say the max inflation is 63 lb PSI. I run em at 50 PSI, and am happy with that - the stencilled numbers on the truck say 28 up front
and 45 in back, but i assume thats for those military grade tires.
So I'm looking for verification that 50 lbs psi is a good number (like I said, I love the way it goes down the road with these on it)
also guys here swear by deflating tires to deal with washboard, and talk about running 10 - 12 lbs psi.
I suspect that going that low would be pretty hard on the sidewalls, but i suspect it would be an advantage to lower the presures some.
anyone have any experience with deflating heavy load tires (load range D) for washboard? |
When changing tires to non-spec tires, Use load inflation tables to find proper tire pressure. Any good tire shop will have a copy.
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