You're kidding...Right?

[wjschill]

Just had new TOYO tires installed on our recently purchased Tiffin 36LA gas m/h. (2014)

They seem to ride a bit harder than the ones replaced. I see the installer set all tire pressures at 110 psi.

Now, I read that I should weigh all four corners to adjust each tire to the proper pressure. But, before I do so, fill the gas, propane, water, black and grey tanks, plus put in all our gear, tools, dogs, cats, and any people that might ride with us, before weighing.

Then add 5% for road temps, cold or hot.

I did weigh the rig for the front and rear axels, but surely there's some kind of average to stay within the safety factors.

So, flame me, scorch me, inform me....Please.

First time motorhome owner, just looking for answers.

Thanks in advance,

Skip

[4x4van]

Weigh fully loaded, with full fuel, LPG, fresh water (empty black/grey).

As others have said, 4-corner weighing is the best (although both ends of the axle should be set at the same pressure; use the higher of the 2). If you can't do 4 corners, then weigh each axle, and use 55% of that number (to account for variation in side-to-side weight; mine is actually about 54%/46% biased to the driver side). Find the tire manufacturer load chart and use it based on your actual weights. Some suggest to add 5-10%, but IMO that would really depend on where your weights fall in the chart; if your weight is close to the top of one of the sections, then bump up. If it is just barely into that section, then stay where the chart says since you already have some buffer. Hope that's clear.

If you haven't weighed your rig, then you can use the tag on the driver's side interior wall or door. That will give the pressures required for YOUR rig at YOUR max GVWR. Never use the number on the tire sidewall, as tires can be used on many different vehicles of different weights.

[mountainkowboy]

They did the same to ours. At 80 psi, the lowest recommended pressure for the size...I can't reach that weight...it would put me over GVWR and axles weights....lol.

[LouLawrence]

Lower pressure is NEVER correct if you don't have your weights and you haven't checked the charts!

[2oldman]

johnhicks wrote:
DO NOT pay any attention to well-meaning suggestions to lower pressure or whatever someone else uses.

Admonishment duly noted, but if you want a smoother ride, lower pressure helps.

[johnhicks]

DO NOT pay any attention to well-meaning suggestions to lower pressure or whatever someone else uses. Consult Toyo's chart and set your pressures accordingly, perhaps adding a few percent to account for cold-temperature changes. It may or may not be lower than 110psi; fwiw according to Toyo's chart I need 105psi in front and 110psi rear, so 110psi certainly can be the correct presure. The installer did the right thing since weight was unknown.

[pianotuna]

wjschill wrote:


Now, I read that I should weigh all four corners to adjust each tire to the proper pressure. But, before I do so, fill the gas, propane, water, black and grey tanks, plus put in all our gear, tools, dogs, cats, and any people that might ride with us, before weighing.

Then add 5% for road temps, cold or hot.

Welcome to the forums!

Wheels on the same axle need to have the same pressure.

Enjoy your travels!

[Sandia_Man]

If you have already done axle weights as you stated in your OP you are close enough number wise to adjust according to inflation charts. Every time we got new rubber on any of our RVs over the last 3 decades tire installer always put max psi as stated on sidewall, no real biggie as I would adjust psi to my preference. On our towable RVs we ran close to max psi, on our motorized RVs we run approximately 20# below max psi.

Sure, it would be nice to attempt to get your coach weighed on each corner believing you have the exact weight every time you hit the road, but real world numbers will never be that precise. How much water do I have in each tank, or did I purchase too much at walmart that tire inflation needs to be adjusted, come on folks on a 22K# rig a few hundred pounds in either direction is meaningless.

[wjschill]

OP here.

My wife is still "stocking" the mh. When she runs out of room, I'll get it weighed and use the tire chart.

Thanks for all your input....Very helpful...

Skip

[JoeH]

wjschill - I see you are in Texas.... if you want to do it right, get a 4 ( or 6 if tag) corner weighing. Escapees RV Club will do it for you. They are in Livingston and will weigh and give advise regarding your questions. It's $45.

[Tom_Barb]

wa8yxm wrote:
My class A liked 115 PSI

Ours likes 100 PSI cold,

[wolfe10]

I will go with tire manufacturer's recommendations rather than "do it yourself" evaluation. Do it yourself ASSUMES everyone is equally qualified to make these important safety decisions. NOT TRUE. Heck, it is hard enough to get most drivers to stop ignoring their "low tire" warning light.

They pay their engineers to do this for you!

[wa8yxm]

My class A liked 115 PSI

But there are ways to tell... One is to use a powder Flower Chalk both good

Dust the road in front of the tire and note the tracks

FULL width even pressure.... GOOD
edges not well pressed. Lower pressure
Center not pressed.. increase

Or chalk the tire drive a bit and note where the chalk is worn off
Center not worn more pressure. edges less. all evenly worn excellent.

But scaling is the best

Though I like to do every wheel separate and set accordingly.

Many do the axle/2 method. both seem to work.

ONE fact.. You will not wear the tread out...

Why is inflation important?

Too low the side walls flex generating heat and KBOOM you also have less control (Spin outs are easier to do), Trailers can sway more.

Too high and you have less control over the vehicle.

[dodge_guy]

Don’t add for temp variations. That’s already built into the recommended cold inflation pressure. I run my fronts at 80 a d the rears at 95. Weighed and adjusted per Michelin’s chart.

[wildtoad]

options:

1) Use the tire pressure on the RV manufacturers label in the mh, usually near the drivers seat.
2) Use the gross axle weights provided by RV manufacturer, and look in the tire manufacturers manual.

If you still have issue with the ride:

1) Get the coach weighed and use the real axle weights to determine tire pressure.