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Old 04-15-2003, 08:58 AM   #15
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I have been playing with my tire pressure using the method AccessMaster Outlined.

Very neat. It really works.
Last night I checked the pressure before heading home. Ambient temp was about 70deg. Ira, The PO of the Burb, Had told me he was running 55psi in these Michelin tires. This was right in line with the recomendations by GM on the door frame. Problem is these are not the same tires that the truck came off the line with so they probably have different ratings for PSI. The Max cold air pressure on the side wall is 80PSI.

I checked the pressure and according to my gage they were a 56 at the current air temp. Drove the truck 19 miles down the freeway at 65mph. Checked the air pressure and it was reading 64 after heating. SO I went over the 10%. This morning it was 57deg. I checked the tire pressure. Showed just shy of 56 on my gage. I added air till they showed 60psi. Ran 19 miles up the road to work and checked them again. 64psi after heating. Try it again on my way home when it should be about 72 degrees outside. Tomorrow I'll add 2 PSI and see what happens.

Neat trick and did learned something from this. Thanks for passing this on. What I really like is even if the gage is a couple degrees off it doesn't matter. You just need the pressure change after heating.

I'm going to pass this on to another Forum I'm on.
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Old 04-15-2003, 06:54 PM   #16
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Last year while visiting with my sister of 50 yrs., we got into a discussion concerning tire pressure in her Nissan Frontier crew cab truck. I found that she had always filled tires on her Thunderbird, her Nissan Maxima and this Frontier to the pressure stated on the tire rather than on the door sill. And she wondered why all these vehicles always rode stiff. I explained that the tires should not be filled more than this max. rating and since she does not load her truck down, the pressures on the door should be used as guidelines.

My '01 Chevy 2500hd has E rated tires with max. inflation of 80 psi. The door sticker states 55 psi for front tires and 80 psi for rear. Can you imagine how rough that thing would ride if I ran 80 psi front and rear? I run 55 front and rear when not towing and then increase to 70 in the rear when towing. It is my understanding that the 80 psi in the rear would be if you have the max towing weight and tongue weight. It would seem to me that you would lower the rear tire pressure to coincide with the reduction, if any, of towing/tongue weight.

Lastly, my owners or service manual (can't remember which right now) talks about increasing tire psi on the trailer as your weight goes up. I run around 55 psi and this is not the max because I do not load my trailer heavily. I can't see where running the max psi for a trailer not loaded to the max would help rivets stay in place. On the other side, underinflation is not a good thing for trailer tires in my opinion. I would rather slightly overinflate rather than underinflate.
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Old 08-20-2004, 01:02 PM   #17
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Min not Max Pressure?

In trying to confirm everything I've been reading about correct tire pressure, I ran across something about Light Truck (LT) tires I had never seen before:

From http://www.rvknowhow.com/toyotire.html
Quote:
It is important to note that the inflation pressure molded on the side wall of a passenger-car tire is the maximum air pressure for that tire. That is not the case, however for light-truck tires.
The inflation pressure molded into the sidewall of light-truck tire is the minimum (that's right, the minimum) air pressure required for that tire to carry the maximum weight molded into the sidewall of that tire. Using less air pressure means the light-truck tire must carry a lighter load.
While the tire-load rating molded into the sidewall of a light-truck tire should not be exceeded, it is generally recommended that the tire be inflated to the minimum pressure required to carry the load plus an additional 5 - 10 psi. The extra pressure will help the tire run cooler. It also acts as a reserve to offset normal loss of air pressure. But the extra pressure will not add to the tire's load carrying capability. Just keep in mind that the maximum air pressure for a light-truck tire is the minimum air pressure molded into the side of the tire plus 10 psi.
My Load Range C LT tires are stamped 45 psi. After reading the above, I guess I should be running a minimum of 50 psi?

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Old 08-20-2004, 02:41 PM   #18
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Quote:
Originally Posted by tcwilliams
In trying to confirm everything I've been reading about correct tire pressure, I ran across something about Light Truck (LT) tires I had never seen before:

From http://www.rvknowhow.com/toyotire.html

My Load Range C LT tires are stamped 45 psi. After reading the above, I guess I should be running a minimum of 50 psi?

Tom
What the author of that article is espousing is that it is better to overinflate since most tires will slowly lose pressure over time. While 5 lbs. is minimal you do have to be cognative that an overinflated tire is subject to an increased chance of road hazzard damage.

My process is to check my tires before towing and making sure they are at max inflation, rather than assume that the extra 5 lbs. of air has addressed any shortfall. In my experience on most trips, tire pressure is the same on return, as it was upon original departure. The only variance I have seen is when I changed altitudes or if there was a significant temperature difference between my two endpoints. In those cases I make the adjustment necessary to get the tires to cold inflation pressures before departing.

Personally adding 5 lbs. extra is just a crutch to avoid monitoring your tires for proper pressure.

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Old 08-24-2004, 03:46 PM   #19
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Airstream recommends 55 lbs cold and a 65# valve, per a response I received from their on-line support last spring.
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Old 08-24-2004, 03:53 PM   #20
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Quote:
Originally Posted by davidp
Airstream recommends 55 lbs cold and a 65# valve, per a response I received from their on-line support last spring.
That recommendation would be based on a specific trailer. Tires with different load ranges are inflated to different pressures.

I would not inflate my LR C tires to that pressure since the tire indicates 45 psi (although I have yet to convince myself if this is "max"). What is the load range on your tires?

Tom
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Old 08-24-2004, 05:54 PM   #21
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tires

My old suburban called for all 4 tires inflated to 50 psi. My new Sub door sticker says RR at 80 psi at load, and FF 55 psi. They're the same tires, front and back. I didn't realize you could have such a wide range on them. When I rotate them their inflation depends on where they're located I guess. Am I reading this right? Thanks.
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Old 08-24-2004, 07:05 PM   #22
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Quote:
Originally Posted by Tin Hut
...When I rotate them their inflation depends on where they're located I guess. Am I reading this right?
Yes. Loads are usually carried on the rear axle; Higher than necessary pressures (in the front tires) result in a rough ride, For example, my Suburban has load range E tires rated at 80 psi max.

For tooling around town, the door sticker says, "44 psi front, 60 psi rear". But for towing, the sticker indicates, "44 psi front 80 psi rear".

But, for any type of trailer, I would expect the tire(s) pressure to stay at the rated pressure located on the tire for all tires. Anything less would cause the tire to heat up unncecessarily, and anything more is outside the tire maker's "realm of responsibility".

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Old 08-24-2004, 07:33 PM   #23
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I've always just put in the amount of air indicated on the sidwall of the tire at cold PSI. It seems that the manufactuer would have already determined the safety for heated tires PSI. Always heard that you need to keep the tires fully inflated because they will run cooler and last longer. Never heard what happens if you over inflate except that you run the risk of a blowout.
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Old 09-09-2004, 05:23 PM   #24
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This remains a hot topic. Lots of misinformation out there, even from the guys who mount tires for a living.
I just put new tires on my coach and had the guys shaking their heads in disbelief as I had them lower the air pressure from 90 psi to 65 on my 6 rear tires. Once the tires heated up the pressures ran 72. Which is just perfect considering the hot weather we run in down here.
For those of you who have inflated the tires to the point that they are the same pressure after you have been running at freeway speeds as they are when cold, you can lower the pressure and get a better ride and will be less likely to have an tire failure due to an impact.
Which would you rather run over a sharp object, a balloon that is full of air almost to the bursting point, or one that is about 75% inflated? Which would you rather ride on?
Proper air pressure depends on the amount of work the tire has to do. This is a function of load and speed. The tire is designed to flex basically in the center of the sidewall. Too much pressure causes it to flex very close to the tread area ... not good ... Too little air causes it to flex close to the rim ... even worse. Always error on the side of over inflation if you must error at all. An under inflated tire will heat up and come apart, an over inflated tire usually just rides rough... it is more vulnerable to impact damage ... but tires really can take a beating and usually keep on going.
A detailed explanation is in my post dated 4/11/03. I hope this helps.
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Old 09-09-2004, 05:37 PM   #25
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Quote:
Originally Posted by AccessMaster
...A detailed explanation is in my post dated 4/11/03. I hope this helps.
I understand your points. Could please give me a link to the post or a few more key words to search on?

Thanks,
Tom
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Old 09-09-2004, 05:37 PM   #26
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After reading my post I realize that claiming 72 to be just perfect does not make sense unless you read my earlier post that explains that a 10% pressure build up is acceptable from cold to hot.
The earlier post explains how to determine the correct tire pressure for you.
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Old 09-09-2004, 05:39 PM   #27
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Quote:
Originally Posted by tcwilliams
I understand your points. Could please give me a link to the post or a few more key words to search on?

Thanks,
Tom
The post is earlier in this same topic. Page 1.
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Old 09-09-2004, 06:28 PM   #28
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Oops - I misread thinking another thread

Thanks for the followup.

Tom
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