Air pressure threads?

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Air pressure threads?

Postby regis101 » Tue Sep 22, 2009 11:44 pm

Hello. I searched but didn't find info about tire pressure vs GTW.

An example is the TSC 4 x 8 open floor rated for 1500#. If I know that the GTW is only 1000#, is there any advantage in using a lower air pressure in the tires? Maybe it's a moot point

Thanks,
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Postby clarkbre » Wed Sep 23, 2009 12:14 am

If I'm reading your question correctly, you want to know if running a certain tire pressure will do something good or bad for the trailer...Absolutely!

The way your finished, loaded trailer rides is directly effected by what tire pressure you're running. Running a very low air pressure will make the trailer more likely to wiggle and sway behind the tow vehicle. It will seem very bouncy and squishy and wear the tires on the outer edges. If a high PSI is used, the trailer will ride very harsh. Hitting bumps will make the trailer want to jump. The tires will also be over inflated and wear in the middle.

For even wear and a pleasant ride, there is an optimum PSI.

If you know the weight of your trailer loaded and ready, you're half way there. Take your trailer for example: GTW 1000. If balanced correctly, the tongue should have a weight of 100# and each tire should share the rest of the load at 450# each.

Lets say your trailer has 4.80-12 tires rated at a max load of 750# at 60psi. If you take your trailer weight knowing that only 450# is going to be riding on each tire, it's just a simple math formula.

Take your load per tire (450#), multiplied by the max PSI of the tire (60), divide that by the max load of the tire (750), and you get what should be your correct PSI for maximum ride and wear quality.

450x60= 27000/750= 36PSI

So, in this case, your trailer will perform best with a tire pressure right around 36PSI.

This formula can be applied for any tire as long as you know the max weight, PSI, and the actual weight it will be carrying.

Hope this helps.
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Postby regis101 » Wed Sep 23, 2009 12:25 am

You just explained it all. Thank you very much.
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Postby Steve_Cox » Wed Sep 23, 2009 5:00 am

A simple side note about creating a "softer" ride for a little camping trailer. Since loads are usually much less than a typical cargo bearing trailer the use of radial tires with a less rigid side wall than trailer tires is a possibility. Also you can lower the air pressure in a radial to soften the ride even more where with a trailer tire and it's rigid side wall it isn't such a good idea.
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Postby TPMcGinty » Wed Sep 23, 2009 6:42 am

I use a regular radial car tire on my trailer. Works fine and the trailer only bounces when I hit a large pothole.
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Postby Creamcracker » Wed Sep 23, 2009 7:35 am

clarkbre wrote:If I'm reading your question correctly, you want to know if running a certain tire pressure will do something good or bad for the trailer...Absolutely!

The way your finished, loaded trailer rides is directly effected by what tire pressure you're running. Running a very low air pressure will make the trailer more likely to wiggle and sway behind the tow vehicle. It will seem very bouncy and squishy and wear the tires on the outer edges. If a high PSI is used, the trailer will ride very harsh. Hitting bumps will make the trailer want to jump. The tires will also be over inflated and wear in the middle.

For even wear and a pleasant ride, there is an optimum PSI.

If you know the weight of your trailer loaded and ready, you're half way there. Take your trailer for example: GTW 1000. If balanced correctly, the tongue should have a weight of 100# and each tire should share the rest of the load at 450# each.

Lets say your trailer has 4.80-12 tires rated at a max load of 750# at 60psi. If you take your trailer weight knowing that only 450# is going to be riding on each tire, it's just a simple math formula.

Take your load per tire (450#), multiplied by the max PSI of the tire (60), divide that by the max load of the tire (750), and you get what should be your correct PSI for maximum ride and wear quality.

450x60= 27000/750= 36PSI

So, in this case, your trailer will perform best with a tire pressure right around 36PSI.

This formula can be applied for any tire as long as you know the max weight, PSI, and the actual weight it will be carrying.

Hope this helps.


I understand the math (no problem) but it's stated in the HF manual that the tires must be inflated to 60psi.....there is no mention of changing the pressure to reflect the load....there have been instances of individuals on this board who have had tires disintegrate when they run them at less than 60psi......
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Postby Arne » Wed Sep 23, 2009 7:48 am

I run my h/f 1800# tires at 40# psi.

One way to check if there is too much squirm in the tire sidewall is simply to feel it.... if it is too hot, you have too much squirm and that is not good.

I compare how my t/d tires feel to how my car tires feel. My trailer tires are cooler, so I'm not concerned... also, I've run this type of t/d tire at 40# for over 30,000 miles and have never had a failure.

my t/d weighs 1,100#
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Postby clarkbre » Wed Sep 23, 2009 9:35 am

Creamcracker wrote:
I understand the math (no problem) but it's stated in the HF manual that the tires must be inflated to 60psi.....there is no mention of changing the pressure to reflect the load....there have been instances of individuals on this board who have had tires disintegrate when they run them at less than 60psi......
Philip


The HF manual may say 60psi; however, it says that so when the trailer is fully loaded and the manufacturers GTW is at its maximum you dont have a tire blow out.

Our camping trailers are completely different beasts. For the most part the builder knows close to the final weight, balance, and gear load of the trailer. Adjusting tire pressure, axle location, and tongue length are all part of building and "tuning" the trailer to fit our needs. I guarantee your HF manual doesn't advise moving the axle position and/or altering the frame but it's a very common practice here on this board.

I have a Redtrailers utility trailer (almost identical to HF) and always run a tire pressure of 50psi. It rides like crap when it's empty but when it's got a weighted load it rides very nice.

In the cases where tires have disintegrated, it's easy for someone to blame it on tire pressure...it's the easiest way out. But, in the end, there are always factors that lead to operator error.

I would question everything relating to a tire blowout:
Was the trailer loaded, weighed, and tire pressure calculated?
When was the last time the tire pressure was properly checked?
How many miles were on those tires?
Were the tires rotted or cracked from sitting out in the weather?
What speed was it going when they came unglued? Some trailer tires have a 55mph limit.

"Nope, it was just tire pressure!"...Then why wasn't it addressed before the operator hit the road?
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Postby Creamcracker » Wed Sep 23, 2009 10:25 am

clarkbre wrote:
Creamcracker wrote:
I understand the math (no problem) but it's stated in the HF manual that the tires must be inflated to 60psi.....there is no mention of changing the pressure to reflect the load....there have been instances of individuals on this board who have had tires disintegrate when they run them at less than 60psi......
Philip


The HF manual may say 60psi; however, it says that so when the trailer is fully loaded and the manufacturers GTW is at its maximum you dont have a tire blow out.

Our camping trailers are completely different beasts. For the most part the builder knows close to the final weight, balance, and gear load of the trailer. Adjusting tire pressure, axle location, and tongue length are all part of building and "tuning" the trailer to fit our needs. I guarantee your HF manual doesn't advise moving the axle position and/or altering the frame but it's a very common practice here on this board.

I have a Redtrailers utility trailer (almost identical to HF) and always run a tire pressure of 50psi. It rides like crap when it's empty but when it's got a weighted load it rides very nice.

In the cases where tires have disintegrated, it's easy for someone to blame it on tire pressure...it's the easiest way out. But, in the end, there are always factors that lead to operator error.

I would question everything relating to a tire blowout:
Was the trailer loaded, weighed, and tire pressure calculated?
When was the last time the tire pressure was properly checked?
How many miles were on those tires?
Were the tires rotted or cracked from sitting out in the weather?
What speed was it going when they came unglued? Some trailer tires have a 55mph limit.

"Nope, it was just tire pressure!"...Then why wasn't it addressed before the operator hit the road?


Anyone else want to chip in on this...at the moment I'm not convinced ...especially based on other previous comments...
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Postby dh » Wed Sep 23, 2009 6:18 pm

Creamcracker wrote:
clarkbre wrote:If I'm reading your question correctly, you want to know if running a certain tire pressure will do something good or bad for the trailer...Absolutely!

The way your finished, loaded trailer rides is directly effected by what tire pressure you're running. Running a very low air pressure will make the trailer more likely to wiggle and sway behind the tow vehicle. It will seem very bouncy and squishy and wear the tires on the outer edges. If a high PSI is used, the trailer will ride very harsh. Hitting bumps will make the trailer want to jump. The tires will also be over inflated and wear in the middle.

For even wear and a pleasant ride, there is an optimum PSI.

If you know the weight of your trailer loaded and ready, you're half way there. Take your trailer for example: GTW 1000. If balanced correctly, the tongue should have a weight of 100# and each tire should share the rest of the load at 450# each.

Lets say your trailer has 4.80-12 tires rated at a max load of 750# at 60psi. If you take your trailer weight knowing that only 450# is going to be riding on each tire, it's just a simple math formula.

Take your load per tire (450#), multiplied by the max PSI of the tire (60), divide that by the max load of the tire (750), and you get what should be your correct PSI for maximum ride and wear quality.

450x60= 27000/750= 36PSI

So, in this case, your trailer will perform best with a tire pressure right around 36PSI.

This formula can be applied for any tire as long as you know the max weight, PSI, and the actual weight it will be carrying.

Hope this helps.


I understand the math (no problem) but it's stated in the HF manual that the tires must be inflated to 60psi.....there is no mention of changing the pressure to reflect the load....there have been instances of individuals on this board who have had tires disintegrate when they run them at less than 60psi......
Philip


They put that in there so they don't get sued.

Some other charms from HF manuels:

"An automatic drip oiler should be installed between the air supply and the tool" (Paint Gun)

"Unplun this device before making any adjustments" (Cutting Torch)

"Make sure the engine is off and the battery disconected when installing this auto accessory" (Trailer Lights)

"This tool will cut best at the rate for which it was designed" (Mig Welder)
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Postby Larwyn » Wed Sep 23, 2009 6:31 pm

I got one of those 110 pound Russian anvils from Horror Fright a few of years ago. The book warned that I should not carry it by the cord.
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Postby caseydog » Wed Sep 23, 2009 6:54 pm

I have a lot of tire experience form running cars on a race track.

1. What causes tires to fail most often is heat, which happens when a tire not inflated enough for it's load.

2. On a 600 pound trailer, you will not need a lot of pressure to keep the tires running at a safe level of heat. The more your TD weighs, the more air pressure you will need.

I live in Texas, and I run my TD tires at 25 pounds. They are regular car radials, not trailer tires. My TD weighs about 600-700 pounds.

60 pounds in trailer tires is going to be really bouncy. I think 36 pounds is high, personally. I run 36 pounds on my 4,200 pound Audi. I used to run my Tractor Supply utility trailer in the 22 pound range, just to try and take some of the bounce out of it.

If your TD weighs in at less than 1,000 pounds, you should be able to run at 30 pounds or less. Just monitor the heat. If your tires get hot (not a little bit warm, but HOT) after a 20 mile drive on the highway, add air.

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Postby Creamcracker » Wed Sep 23, 2009 8:51 pm

I want to revisit this with the figures from my trailer when I'm not addled from working......it does certainly bounce around and lower tire pressures would certainly help that....I have the HF trailer 90154 with a weight capacity of 1,450.......my trailer weighs 820lbs with atongue weight of 60lbs...how does that compute?
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Postby Mauleskinner » Wed Sep 23, 2009 9:42 pm

Sounds like what we're going for here is the optimum "shape" of the tire...it's designed to be "not quite perfectly round, with a relatively level tread surface".

Too high a pressure for the weight of the trailer, and it's "perfectly round, with a bulging tread surface". Rough ride, and you only get to use 1/3 of the tire's tread.

Too low a pressure for the weight of the trailer and it's "too big a flat spot on the bottom". Excessive flexing of the sidewall, generating heat and likely to cause failure.
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Postby mechmagcn » Wed Sep 23, 2009 11:08 pm

I'm with CD on this one, my TD has 15" radials to match the TV and I only run 20-22 PSI. I really think the trailer rides better than the truck :oops: Plan on hitting the scales when I leave out for vacation next month, I'll let everyone know what it weighs.
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