Tire pressure

[Labaree]

I've read many times in this forum how important it is to maintain proper tire pressure in your trailer tires. My question is when on the road if in need of air (cold) where do get your air? Do you carry a air compressor,stop at service station after driving several miles. Does anyone use nitrogen rather than compressed air? Thanks in advance for ideas, thoughts.

[AWCHIEF]

First off nitrogen is a waste of money for trailers. Science and cost does not justify it's use. I and many others carry a small DC compressor and/or 120AC unit. I don't think it is really that important what the brand or cost is. You can get excellent reliable inexpensive compressors from Harbor Freight especially when on sale and 20% off coupons.

[SteveSueMac]

I carry a Viair 450P compressor that a wise forum member (Robert Cross) helped me convert to run off my 7-pin plug in my truck.

[CBWELL]

Get an inexpensive compressor, but a good tire gauge. I carry an extra long heavier duty 12 volt cord for the longer run from my truck outlet. Only used it once, but sure saved a lot of hassle. Chris

[rd tighe]

We carry a 12 vt compressor you can get one at harbor freight inexpensive. A little slow ,just have a nother cup of coffee gain patience

[rd tighe]

Search results for: '12volt conpresser'

[jcanavera]

I carry a small 12 volt compressor. Never had to use it on the road, but it's there if needed. Note those compressor plugs usually go in the cigarette lighter. Run them long enough and that plug can get hot enough to melt the plug. If you need significant air, find a station that has air. One thing to be aware of is that some stations have pumps that many not have enough power to get to higher pressures. Until I bought a high power pump for home use, only one gas station in my local area could fill my 16" Michelin LT's to 80 psi. The local QT and other convenience mart stores may not have pumps that can reach that pressure.

Jack

[Tireman9]

If you follow "best practice" and are inflating your tires to the pressure on the tire sidewall that is associated with the max load you should not need more than a couple of psi to "top off" your tires say once a month.

Tires should loose no more than one to 2 % a month. If you see faster then you need to investigate, find and repair the cause. I have a number of posts on my blog with the label "valve" that provide examples.

An alternative to carrying a compressor might be.
1. Measure your CIP with your digital gauge and record the number of psi needed in each tire.
2. Assuming you are not under-inflated for the measured tire load, i.e. are between your minimum inflation based on load and the tire sidewall pressure you can drive to the nearest service station.
3. Measure your hot inflation and add the number of psi needed in #1 above plus 1psi
4. Next morning confirm you now have your correct CIP.
NOTE if you are below the pressure needed to carry the actual load then you need to add air before driving anywhere.

The above is why you need to know your actual tire loads even if you are running the tire sidewall pressure to lower your Interply Shear force.

[Nomad518]

I carry two Honda 2000 generators and a 110v compressor. If I need air on the road, I can fire up a generator (my compressor will run on one of the generators). If I need air when connected to shore power, there's no need for the generator to power the compressor. My compressor is a 150lb pancake style purchased at Home Depot. It's more than I need, but it works fast. The compressor has a tire gauge built into the valve just like you would find at a gas station.

[Hiho Silver]

And some of us have both, a small 110v compressor (+ Honda 2000) and a small 12v, that's what I carry.



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[53flyingcloud]

So, what actual "tire pressure" do you normally use ?? Thanks~

[Hiho Silver]

Originally Posted by 53flyingcloud

So, what actual "tire pressure" do you normally use ?? Thanks~

I use 68 in my Michelins, 16". Seems like most guys use more though. I have a 27 FC, and don't want to stiff of a ride, so less pressure, but I'm not a tire expert.


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[Tireman9]

Originally Posted by 53flyingcloud

So, what actual "tire pressure" do you normally use ?? Thanks~

Your absolute minimum pressure should be the pressure needed to carry the actual load on the tires.
Few RVs have the load split evenly between axles PLUS the load on any one axle is seldom split 50/50 side to side.
You can't estimate this and can only learn by either using individual tire position scales or following the various published guides on how to calculate tire loading.

The minimum pressure needed is the pressure published in the Load/Inflation tables.

Now if you want to lower the Interply Shear forces that are trying to tear the tire structure apaart you should run the pressure molded on the tire sidewall that is associated with the tire Max load capacity.

If you don't understand "Interply Shear" and why higher is bad for tires, I suggest you Google
Interply Shear RV tire
to learn more


Before you say you don't need to check your weight you need to remember that a majority of RVs have one or more tire and/or axle in overload.

Until you confirm your actual load the minimum inflation I would suggest in trailer application is the inflation shown on the tire Placard.

[m.hony]

65# of pressure in the tires per the placard on the side of the trailer-
I have TPMS on the trailer tires, too.
Small 12 volt compressor- takes a long time but gets the job done- even a high pressure bicycle pump-
Another option if you can find it is service stations with air or tire shops/repair shops.

[A W Warn]

Originally Posted by 53flyingcloud

So, what actual "tire pressure" do you normally use ?? Thanks~

There is a placard on both of my trailers that says Airstream recommends xx psi. I consider that the minimum tire inflation pressure, since Airstream based that recommendation on GVWR of the trailer and the tires that came originally on the trailer.

On the sidewall of the tire there is a maximum inflation pressure for that specific tire. I inflate my tires to, or just under, that maximum.

My understanding is the higher the pressure the better (for the tire), without exceeding the maximum limit of either the tire or the wheel.

[Tireman9]

Originally Posted by A W Warn

There is a placard on both of my trailers that says Airstream recommends xx psi. I consider that the minimum tire inflation pressure, since Airstream based that recommendation on GVWR of the trailer and the tires that came originally on the trailer.

On the sidewall of the tire there is a maximum inflation pressure for that specific tire. I inflate my tires to, or just under, that maximum.

My understanding is the higher the pressure the better (for the tire), without exceeding the maximum limit of either the tire or the wheel.

The "Maximum" inflation can be misunderstood. In reality that is the Minimum pressure needed to carry the Maximum stated load. Each type tire i.e. P, LT, ST has it's own wording. I covered this in detail on July 3 2015 on my blog on RVTireSafety

You are correct about the advantages of running higher pressure to lower the Interply shear forces in tires.

[A W Warn]

@Tireman
A hypothetical question:
Assume two tires are of the same size, one D rated the other is E rated. Both are inflated to exactly the same pressure, that is below the maximum inflation for either.

Does one of tires have the ability to carry more or less load when at the equal inflation pressure?

I think I know the answer, but do not recall that I ever heard this question asked or answered before.

Thanks!

[CapriRacer]

Originally Posted by A W Warn

@Tireman
A hypothetical question:
Assume two tires are of the same size, one D rated the other is E rated. Both are inflated to exactly the same pressure, that is below the maximum inflation for either.

Does one of tires have the ability to carry more or less load when at the equal inflation pressure?

I think I know the answer, but do not recall that I ever heard this question asked or answered before.

Thanks!

In case Tireman9 doesn't respond right away:

No matter what the load range, a tire's load carrying capacity is directly related to its inflation pressure - that is Load Range D and Load Range E tires operated at the same pressure perform the same.

And just for the folks who are going to struggle with this: There may be an ever so slight improvement using a higher Load Range - BUT - it is so small, it is undetectable in practice.

[Tireman9]

Originally Posted by A W Warn

@Tireman
A hypothetical question:
Assume two tires are of the same size, one D rated the other is E rated. Both are inflated to exactly the same pressure, that is below the maximum inflation for either.

Does one of tires have the ability to carry more or less load when at the equal inflation pressure?

I think I know the answer, but do not recall that I ever heard this question asked or answered before.

Thanks!

Well Capri got to the computer first so I guess he wins.

It might help to understand that answer if you think of a tire for what it really is. Just a container of pressurized gas. It is the pressurized gas that supports the load.
Many time people do not understand what physical differences there may be in tires that appear to be the same except for their Load Range.
There are a number of tests tires must pass and the conditions of the tests are based on the Max load capacity at the appropriate pressure for that load.
These tests include the ability to stay seated on the wheel and another may measure a tire's ability to resist a tread puncture of a special 3/4" dia steel rod.
Sp lets assume we run a tire company and have a LR-D tire already in production and want to add a LR-E. We do the testing and discover our prototype which is based on the LR-D construction passes all the tests except maybe the tread puncture test. So the best thing for us to do in that case would be to increase the strength of the belts.
If however our prototype passed all the tests except the bead test we would need to change the strength of the bead wire. The bead is the band of wire that retains the tire on the wheel.
So depending of test data a tire company will modify prototype constructions to provide the strength required to deliver satisfactory performance. These changes may be minor in some cases and major in others with no way to predict the changes or see them by simply looking at a tire.

Note the above are just two of the dozens of tests a tire must pass but I limited the number to make the answer easier to understand.

[Cyclist]

I carry a 12 volt compressor but have never used it. I use a bicycle pump to add the occaisional couple of pounds - usually requires about 25-30 strokes per tire. I think of it as exercise doing push-ups and has the added benefit of amusing the neighbours.