Lowering tire pressures

[wa8yxm]

Thanks for the update on Smart Tire..

Some facts: The proper pressure for the weight on the wheel means that the full width of the tread is in contact with the road and wears evenly. This spreads the load across the full width and thus maximizes tread life. It also maximizes control in situtations where you need it.

Too much pressure (IE: the pressure on the sidewall if you are not carrying maximum load) means the center of the tire is in contact with the road, but not the sidewalls. This can cause a loss of control when cornering epically on other than clean dry pavement, it also means the tread life is reduced.

That said, Most RV tires do not wear out that way.

Too little pressure means the center is NOT in contact, more wear on the edges of the tread, more flexing of the sidewalls making more heat which can kill a tire, and a tendency for the tire to roll on corners, another bad thing.

So when Mr. D says the pressure on the sidewall is the MINIMUM pressure for the MAXIMUM load.. yes it is, it is also the maximum COLD TIRE pressure for the maximum load, in short it is the only COLD tire pressure for the maximum load.

And if you are not loaded to the MAX, then it's too much.

That simple.

[freebirdbus]

Originally Posted by trackman

Low tire pressure means more heat to the tires and greater chance of blowout. Also of concern is the mileage goes down with the tire pressure

First, Thanks for all of the responses. I have driven trucks and RV's a long time and am aware of proper inflation pressures.

Second, My original question was if the threshold where a tire develops damage from driving with less than the recommended maintenance pressure has changed from 80% to less than that. Anyone know?

[slickest1]

I think it would depend on the weight being carried. If your coach is maxing out the weight of the tires then even 10 lbs less would start to be a problem.

What I don't understand is people thinking they get a better ride on less air in their tires, and yet can drive down the road with a flat or a low tire and not know it, unless they have a tpm. Flame suit installed.

[FastEagle]

Original tire selection for your Motor Home tires is done in accordance with DOD regulations by the vehicle manufacturer.

Here is the one of the references used in the overall process. Pay particular attention to S5.3.1 because that is where the vehicle manufacturer is directed to set the recommended (CORRECT) tire pressure (s).

http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=571.120

FastEagle

[Mr_D]

Originally Posted by freebirdbus

First, Thanks for all of the responses. I have driven trucks and RV's a long time and am aware of proper inflation pressures.

Second, My original question was if the threshold where a tire develops damage from driving with less than the recommended maintenance pressure has changed from 80% to less than that. Anyone know?

I don't think it's changed any. Michelin still says 80% or more low is considered to be "run flat".

[Fiesta48]

I'm lightly loaded. If I run more than the minimum tire pressure (70-75 in the front, 80 rear) the ride and handling are terrible. Tires may wear a little faster, I may get a tiny bit less MPG, but at 5k miles a year, they will rot out long before they wear out. Blow outs are rare.

[Fossilhog]

Originally Posted by corvettec3

A month ago I had a blowout on one of my rear duals and did not hear or know about it until I went to install a tire monitoring kit. After that I decided to replace all six tires. When the technician was here installing the new ones I asked him what tire pressure he was using and he told me 100 psi. I told him that the sticker inside my driver door specified a recommended pressure of 70 psi. He said "If I left here knowing that you only had 70 psi in the tires on that rig, I would not sleep well tonight. It would just be a diaster waiting to happen and that if you were running 70 psi before then that is why you just had a blowout." So I am running 100 psi all around. The rig certainly rides and handles nice with those pressures.

I often wondered about that 70 PSI on the door. I checked the other day and I'm running 90 PSI and the backs just look low. I'm going up 10 lbs.

[Sky_Boss]

Originally Posted by Fossilhog

I often wondered about that 70 PSI on the door. I checked the other day and I'm running 90 PSI and the backs just look low. I'm going up 10 lbs.

UMMMM....get your rig weighed!

Don't go by looks because they can deceive. Get 4 corners if at all possible and follow the tire charts. If you can't get 4 corners then divide the axle weight by 2 and then add about 5-10% for the probability that one corner of an axle weighs more than the other and use that with the tire pressure chart.

[Fossilhog]

I've been told that for awhile now but no where near me to get it done.

[Sky_Boss]

Originally Posted by Fossilhog

I've been told that for awhile now but no where near me to get it done.

Go to almost any truck stop that has a CAT scale.

CAT Scale Locator | CAT Scale

I know that these are not in your back yard but I would load up your rig like you would travel, passengers, cat, dog, food. Include full fuel and the amount of water you normally carry when you travel. Keep this as a base line.

[Dutch Star Don]

freebirdbus......I understand what you want to do and I'm sure it's tough getting beat up, but no matter what percentages you're looking at, it's really not a good idea to go under that minimum. It may not initially cause damage, but there will be a hot day where you're running down the interstae and you overheat those tires and blow one.

Like one poster stated, you often don't notice a few pounds in air pressure either way, not worth the risk.

Have you looked at the condition of your shocks and thought about changing to a good quality shock?

[koda59]

Please correct me if I am wrong. Looking at my tires it says max pressure at max weight. Is that correct or are my tires miss stamped. Reading statement earlier that said minimum pressure for max weight. I am a little confused.

[Mr_D]

Originally Posted by koda59

Please correct me if I am wrong. Looking at my tires it says max pressure at max weight. Is that correct or are my tires miss stamped. Reading statement earlier that said minimum pressure for max weight. I am a little confused.

What brand and size tires?

[koda59]

Mr D I have Toyo tires that are 245/70/19.5.