Trailer Tire Pressure

gearyg

Petty Officer 3rd Class
Joined
Aug 28, 2006
Messages
84
Just wondering, I need to measure the tire pressure with my boat on the trailer? I am assuming the pressure increases as weight is loaded on them...correct?

Should be the same principal as a car, you don't take the tire off and then take the tire pressure, I just want to be sure....
 

Gary H NC

Fleet Admiral
Joined
Dec 1, 2005
Messages
8,972
Re: Trailer Tire Pressure

Yes,check them with the boat loaded.Run the max pressure listed on the side of the tire.Usually 50 psi...
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Trailer Tire Pressure

It makes no difference if you check pressure loaded or unloaded. It will be the same either way. When a tire shop puts a new tire on a rim it is inflated to its recommended pressure, installed on the balancer, balanced and then put on the car. Pressure is not adjusted again.
 

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,392
Re: Trailer Tire Pressure

Weight and load will increase pressure but by how much I do not know. I have always checked my trailer tire pressures when cold and loaded up.
Just my 2 cents though.
 

ebry710

Ensign
Joined
Jan 29, 2008
Messages
981
Re: Trailer Tire Pressure

The side wall and thread design in conjunction with tire pressure gives the tire is performance. I had gone on the Michelin website for another forum an this is what the Michelin Man says: Be sure to properly check all four tires cold once a month and before a long trip.

Check Pressure Once a Month

* It?s possible for a passenger tire initially inflated to 35 psi (pounds per square inch) to lose 1 psi each month.
* Be sure to properly check all four tires cold once a month and before a long trip.
* Whether you have a full-size or mini spare, make sure that it is properly inflated as well.

Recommended Pressure

If you don?t know the proper inflation air pressure for your tires, what do you do?

Easy. Check at one of the following places on your vehicle:

* In the vehicle owners manual.
* On the vehicle?s door jamb. (Often, a vehicle information placard is located on the door jamb along with the recommended tire inflation pressure.)
* Inside the fuel hatch filler flap. (In some vehicles.)
* The glove compartment door. (In some vehicles.)
o But NOT on the tire. The inflation pressure shown on the tire sidewall is only the maximum tire inflation pressure. In most situations, the vehicle manufacturers recommended tire inflation pressure is shown on the vehicle placard. However, on some older vehicles, the recommended pressure listed by your vehicle?s manufacturer may be shown as two numbers: One for city speed driving and normal load and one for highway speeds and/or maximum capacity vehicle load. Be sure to inflate your tires to the recommended inflation pressure for each type of driving situation.


How to Properly Check Tire Pressure


1. Beware of public pressure gauges at gas stations. They are often abused and unreliable.
2. Purchase a good pressure gauge and check it for accuracy with your Michelin retailer.
3. Check your tires cold ? before you?ve driven even one mile or at least three hours after the vehicle has been stopped.


Inflation Tips


1. Air expands when it?s hot and contracts when it?s cold
2. It?s best to inflate your tires in the morning before the day?s heat.


Valves and Valve Caps


When it comes to proper tire pressure, the tire?s valve is a very important maintenance item. Valves are ordinarily made of rubber, so they can deteriorate over time. Replace them when you buy new tires. At high speeds, a cracked, deteriorated rubber valve stem can bend from centrifugal force and allow air loss.

The valve cap is also an important item. Buy high-quality valve caps that can help contain the tire?s air, should the core of the valve fail for any reason. Valve caps also keep out moisture, which could freeze and in turn depress the valve core, causing air loss. The cap also keeps out dust and dirt particles, which could also interfere with the proper operation of the valve core and cause air loss.
 

jeeperman

Lieutenant Commander
Joined
Aug 2, 2001
Messages
1,513
Re: Trailer Tire Pressure

This advice
"But NOT on the tire."
Could be dangerous if the tires are far from O.E.M.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Trailer Tire Pressure

Since we seem to have a debate on whether there is an increase in tire pressure loaded vs unloaded I actually ran a test. Using a digital tire gauge I took three measurements loaded and three unloaded on the left front wheel of my truck. There was not one bit of difference with the wheel off the ground than on the ground. The readings were idential right down to the "tenth" of one PSI. Ignoring altitude and temperature, once a given amount of pressure is inserted in a tire, the only way that pressure can change is to change the "volume" of the tire. Although a tire changes its shape as its loaded, its volume remains essentially the same. So what causes blow outs you ask? Simple -- tire failure due to underinflation and the resultant heat causes structural failure. Overloading likewise causes heat build up which again results in structural failure which is due only in part to an increase in pressure caused by the excess heat. I proved my point so now someone can run their test! Data is good! :)
 

Outsider

Lieutenant Junior Grade
Joined
Apr 24, 2007
Messages
1,022
Re: Trailer Tire Pressure

o But NOT on the tire.

I looked all over my trailer and can't find recommended tire pressures anywhere ... except on the tires! Besides, I've not heard of Michelin ST tires.
 

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,392
Re: Trailer Tire Pressure

Since we seem to have a debate on whether there is an increase in tire pressure loaded vs unloaded I actually ran a test. Using a digital tire gauge I took three measurements loaded and three unloaded on the left front wheel of my truck. There was not one bit of difference with the wheel off the ground than on the ground. The readings were idential right down to the "tenth" of one PSI. Ignoring altitude and temperature, once a given amount of pressure is inserted in a tire, the only way that pressure can change is to change the "volume" of the tire. Although a tire changes its shape as its loaded, its volume remains essentially the same. So what causes blow outs you ask? Simple -- tire failure due to underinflation and the resultant heat causes structural failure. Overloading likewise causes heat build up which again results in structural failure which is due only in part to an increase in pressure caused by the excess heat. I proved my point so now someone can run their test! Data is good! :)

Great info and true. I just tried your test and agree that any difference is miniscule. Theoretically though when more load is applied on an inflated structure the pressure within the inflated structure will increase. At the other end of the spectrum try the same test with a balloon and add weight. You will see the pressure increase. So in a boat and trailer application it will make so little difference that it is not recordable with normal test equipment.
Point taken.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Trailer Tire Pressure

Did you actually measure the pressure in the balloon? :) No data! Because of its elasticity and therefore ability to change its volume, I suspect you would not be able to detect any difference in pressure. Unlike a tire, a balloon has no belts or cords to help retain its shape so it would seem it would be impacted less by outside forces than a tire with very stiff construction yet we proved there was no difference (at least that a gauge calibrated to tenths of a pound could detect). I will do another test tomorrow. I just took delivery of a pontoon that has wide oval tires (load range E so folks don't panic) and which are inflated to 90 PSI. I'll post the outcome. If there was as much as a 5% increase in loaded vs unloaded pressure, I should be able to detect 1/2 pound difference in pressure. Since my guage is calibrated to 1/10th, a 1% difference should show up as 1/10 difference in pressure. Geez -- are we anal or what. The poor guy asked a simple question and we are picking nits again. But by golly banter sure is fun.
 

ebry710

Ensign
Joined
Jan 29, 2008
Messages
981
Re: Trailer Tire Pressure

o But NOT on the tire.

I looked all over my trailer and can't find recommended tire pressures anywhere ... except on the tires! Besides, I've not heard of Michelin ST tires.

I have never hear if Michelin made a trailer tire and I don't think I'd buy it, but the point is that that manufacturer only recommends check their tires monthly and before a long trip. It is probably for the same reason that Silvertip found, tire pressure doesn't change much. I fact when I used drive a bobtail commercially I never worried about checking tire except at the start of any leg of the trip ...... unless I though I was overloaded. Even when my wife has me check tire pressure on her car, I rarely see much more then a 3 pound change between the summer fill and winter...... my van tires I only check when they look low or before vacation.:)
 
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