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Old 05-19-2015, 02:34 PM   #15
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Originally Posted by Re-Pete View Post
Can anyone post links to a thread/s on how to weight a TT (Airstream) including the individual tires? I've not done this before, and am a bit intimidated by the process.
If for any reason you need individual tire loads, weigh everything as Howie described. After you get your ticket, you can go back across the scales slightly to the right, leaving all of your curbside wheels off the scales. Subtract left wheel weights from from axle weights and you will have rt wheel weights. Of course that only works at scales without obstructions on the right hand side of the platforms. I have seen some scales where you would have to hang off of the left, and some that are curbed in where this won't work at all. Reweighs are usually only 2 or 3 dollars.
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Old 05-19-2015, 02:37 PM   #16
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Originally Posted by HowieE View Post
...Most of use generally weight the axles of the TV empty and then weigh them and the trailer while hitched. This lets us know how the hitch is transferring weight. There are 3 plates at the scale and you can position your rig to weigh the TV axles and the trailer at the same time.
HowieE,

I didn't realize how these scales are set up. Now I get it.

Thanks
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Old 05-19-2015, 03:06 PM   #17
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Thanks for all of the good info here. I'd like to pass something on that I picked up from another forum member. Google Earth. It's the best for getting a nice overhead and sometimes even a good street level view of just about anything. I've used it to check out campgrounds. This time I used it to check out weigh scales near me. Now I feel very confident in what I can do when I get there.
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Old 05-19-2015, 03:18 PM   #18
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I also use 80 psi on my Michelin's. Again I have a very heavy 30' slide out unit and feel from a load standpoint alone, the 80 psi that I do is warranted. I've had belt separation on the original D and replacement E ST tires, even though I have towed no faster than 65 mph and have kept pressures up to recommended specs on those tires.

We have a couple of guys here on the forum who are tire professionals who work in the industry. They both have noted that in a tandem or tri-axle mode, LT tires are operating in a different environment that they usually do on a 4 wheel truck. LT tires don't have the same construction as an ST tire which have side walls built to resist the lateral forces incurred when used on a trailer. While they both encourage weighing your trailer, they also note that additional air pressure may be justified to stiffen up those sidewalls on LT's. Tires should have a minimum reserve of 15% of their max load capacity (based on weight capacity of the tire inflated to proper pressures).

Unfortunately I have seen no conclusive evidence here on the forum that LT tires perform better with load related pressures vs. inflating to maximums on the tire itself. I do know in the case of my van (that uses the same size tires as my Airstream), the manufacturer (GM) recommends lower than maximum air pressure dependent upon load. For example top end recommendation for my front tires for my van under max load is 55 psi with the rears at 80. .............


Jack
For example top end recommendation for my front tires for my van under max load is 55 psi with the rears at 80.

Jack, look at your front Axle max gross. Compare that with the weight your tires will carry at 55 psi. I think you will find they are the same. GM's PSI door sticker for the tires will either match the axle or be max sidewall, which ever is less. I think it's called litigation PSI.
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Old 05-19-2015, 03:25 PM   #19
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I think it's called litigation PSI.
It is the same as to how many keys, on you key ring, you can hang from the ignition key.
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Old 05-19-2015, 03:47 PM   #20
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Quote:
Originally Posted by Howard L. View Post
For example top end recommendation for my front tires for my van under max load is 55 psi with the rears at 80.

Jack, look at your front Axle max gross. Compare that with the weight your tires will carry at 55 psi. I think you will find they are the same. GM's PSI door sticker for the tires will either match the axle or be max sidewall, which ever is less. I think it's called litigation PSI.
Yep, and it's a good example that tires with higher load capacities can run successfully and safely at lower pressures. I think that's the point that many espouse to relating that if the load is less, there is no need to run maximum PSI.

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Old 05-19-2015, 04:33 PM   #21
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The recommended tire pressure for the 16 inch replacements is 70 PSI.
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Old 05-19-2015, 05:01 PM   #22
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Where did 70 PSI come from? Airstream recommends 80 for ST or LTX E rated. They have the most liability at stake.
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Old 05-19-2015, 05:17 PM   #23
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Where did 70 PSI come from? Airstream recommends 80 for ST or LTX E rated. They have the most liability at stake.
Guskmg
That's what happens when I use my tablet to post. I hit "8", but "7" showed up.
It is supposed to be 80PSI.
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Old 05-19-2015, 05:40 PM   #24
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When I switched to 16" Michelins two years ago, I got very confused about all the recommendations on best pressure to run!

In the end I settled on 75psi as it seemed a good average of what everyone was running and I liked the fact that it was little below the tires max rating.


Seems to have worked fine for me so far on two cross country trips and a few shorted ones and I will probably stay with it!

I'm not seeing any real wear pattern at all on the tires yet that would indicate either under or over-inflation for this application, and in fact they still look brand new!

Brian.
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Old 05-19-2015, 07:35 PM   #25
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Tire Pressures and Tire Temperature

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Originally Posted by Msmoto View Post
Having just installed new 16" wheels on my 2015 Serenity, along with the Firestone Transforce LT225/75R16, I am attempting to decide on the correct tire pressure and how to determine this.



In ambient temperatures of 80 F, at no time was the tire more than warm. Even with 30 - 40 mph sideways gusts of wind over several hundred miles, the tires and wheels remained only warm to my hand, never hot enough to prevent touching.



My question is, can one determine the correct tire pressure based upon how arm the tire gets in use? It would seem to me, if the tire were under inflated, it would become much warmer, way to hot to touch. Correct inflation would result in the coolest running temperature.



Mine are at 65 PSI currently and I am thinking this is the correct pressure, but would like the experience of others with 16" wheels/tires.

You're looking to set a numerical baseline. If you wish to be thorough, then, with full fuel and the truck loaded for a long trip, make three passes across a Cat Scale. The trailer should also have full propane and fresh water plus gear/supplies for extended travel.

Pressure tires to sidewalk max on TT and the Dodge to within door placard numbers.

Search and use the Ron Gratz chart ( I've posted it several times here [originally from a 2010 thread at Woodalls] and it allows for an examination of WD loads.

If the hitch needs adjustment, then this is the time to do it.

The final check is to weigh the combination with corrected WD applied, wheel by wheel. Same day as the above. The truck will probably show individual weights as equal across each axle

The TT will not.

The reference to use is the Bridgestone and RV Safety Foundation pdf at that companies website titled How To Weigh an RV.

This will entail a good number more passes across the scale. The re weighs are cheap.

If the across axle weight discrepancy is large, it may be worth trying to shuffle the weight around. On the axle or within a foot or two. Avoid the trailer ends.

The ideal is no more than about .85 of sidewall maximum per tire.

Check the tire pressures when cold the next morning. Drive 1-1.5/hrs steady state (cruise control) and have a preambles stop at an Interstate parking area or rest area with a long runway . . use as little brake as possible to come to a full stop.

Assuming bearing and brake adjustments were properly made, one is looking to see a pressure rise of 10% or less in all tires. 5-7% is ideal.

With WD at a good point, with tire pressures at recommended numbers, and if any changes necessary are made

you now have the numerical baseline from which to make further changes if you deem them worthwhile. A default setting.
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Old 05-20-2015, 06:34 AM   #26
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Well, lots of good comments. Lots of not so good comments. So I'll add mine.

The one thing no one has said is: After you've gone through all the weighings and the charts and the calculations and come up with a number, how can you verfiy that is correct? The pressure build up test.

Set your cold pressures. Drive on the freeway for 45 minutes to an hour, then measure the pressures. You should get no more than a 10% build up. If you get more than 10%, you need to add air. If you get more than 15%, you need to take immediate action - driving slower, add load carrying capacity( more air, higher load range, bigger tire).

If you are UNDER 10%, then drive another 45 minutes to an hour. It takes about an hour and a half to get the tires to stabilize, that's why 2 readings. An early one to prevent going too far, and to see where you are headed - and a second one to get a final reading.

Please note: Freeway driving means open country - and the speeds you normally tow. If you've done your homework, this should just be a confirming test - or if you suspect you have a problem, this might confirm it for you.
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Old 05-20-2015, 10:05 AM   #27
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Well, lots of good comments. Lots of not so good comments. So I'll add mine.

The one thing no one has said is: After you've gone through all the weighings and the charts and the calculations and come up with a number, how can you verfiy that is correct? The pressure build up test.

Set your cold pressures. Drive on the freeway for 45 minutes to an hour, then measure the pressures. You should get no more than a 10% build up. If you get more than 10%, you need to add air. If you get more than 15%, you need to take immediate action - driving slower, add load carrying capacity( more air, higher load range, bigger tire).

If you are UNDER 10%, then drive another 45 minutes to an hour. It takes about an hour and a half to get the tires to stabilize, that's why 2 readings. An early one to prevent going too far, and to see where you are headed - and a second one to get a final reading.

Please note: Freeway driving means open country - and the speeds you normally tow. If you've done your homework, this should just be a confirming test - or if you suspect you have a problem, this might confirm it for you.
That is one of the best posts i have seen. Gets noted here and a Thanks to you
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Old 05-20-2015, 12:40 PM   #28
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CarpiRacer, does this mean that if we run our Michelin 16" LTX tires on our Airstream at 60 psi, rather than the 80 psi maximum pressure indicated on the sidewall, that is a correct pressure if it passes your pressure test procedure?

That seems to be in conflict with another tire engineer who has recently cautioned here that any tire used on a multi-axle travel trailer with lowered pressure is more likely to experience tread separation from sideway scrubbing when turning the trailer, so we should always use the maximum sidewall indicated pressure.

Or are you suggesting we should always use the maximum sidewall indicated pressure, and then use your pressure test procedure to ensure it is enough? I suppose the two tire engineers would be in agreement then?

The correct tire pressure for our Airstream remains unclear to me.

cheryl
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