Just weighed the MH

[jc55]

I've read time and time again how important it is to know the exact weight of your motorhome, in order to get the correct tire inflation pressure. I was able to get the Vectra weighed , thanks to some local road construction going on. The scale was a drive on scale for trucks, so there was no way to weigh each corner of the mh, but I was able to get the weight of the front axle, the rear axle and then the total. The mh is a 34' Winnebago Vectra, with 454 gas. The total weight of the coach with 3/4 tank of gas(80 gallon tank) and same for fresh water, was 15,920 pounds.
Front axle weight was 5360 pounds and the rear axle weight was 10,520 pounds. Is this weight ratio normal?  Now when I look up tire inflation charts, do I divide the front and rear weights in half, in order to get the weight for each wheel. The tires on the mh are Toyo M120 8r x 19.5. I am currently running the tires at about 87 to 90 psi. This time of year, there can be a substantial change in tire pressure due to the temperature changes... warm days.. cold mornings and evenings.
Jim

 

[Alaskansnowbirds]

Jim,

Yes on the front axle. Take the axle weight and divide by 2.

On the rear take the axle weight and divide by 4. I'm assuming you have duals on the rear axle.

 

[Gary RV_Wizard]

Yes, that is a common weight distribution for your type of motorhome.

It is rare that the weight on an axle is equally divided on all tire - usually one side is heavier than the other.  A generator or a slide room, for example, usually adds quite a bit of weight on just one side.  After dividing by 2 or 4), add a "fudge factor" to allow for an imbalance. I would suggest adding  10-15% to the calculated weight. Then, whatever slot that falls into on the inflation table, go one slot further up to give some more margin. Much better to be a bit overinflated than even 1 psi under-inflated.

 

[jc55]

Thanks Don and Gary
I'm glad I asked and glad you answered. I didn't think to divide the rear weight by 4 and i wasn't sure how much to add as a safety factor. A great help
Thanx again to both of you.

Jim

 

[scottydl]

Front axle weight was 5360 pounds and the rear axle weight was 10,520 pounds. Is this weight ratio normal?

Very similar to mine last year when I weighed it (and our coaches are similar vintage)... 5840 front axle, 10,460 rear axle, total weight 16,300 pounds.  That was fully loaded before a trip and my GVWR is 17,000.  I keep my tires inflated at their max of 80psi, but that's on 16" LT tires and not the larger 19.5" that you have (and I wish I did) which should have a higher weight allowance.

 

[Backdraft161]

If you are concerned about PSI changes, try having nitrogen put in all tires.

Works for me.

 

[PatrioticStabilist]

I weighed mine, if I inflated the front tires per the Michelin chart they would have only 70 pounds.  I think my tires exceed my requirements.  The truck tire folks said they are way underinflated like that and will ruin the sidewalls, that is the lowest weight Michelin recommends for these tires by the way.  So I do about 82 in the front and around 90 in the back.  I have to watch as overinflating for my wieght makes the motorhome more unstable in my opinion, its hard to arrive at the correct weight or seems to be for mine. The max pressure allowed in these is 120 psi, they are 19.5 inches.

 

[scottydl]

I weighed mine, if I inflated the front tires per the Michelin chart they would have only 70 pounds. . . The truck tire folks said they are way underinflated like that and will ruin the sidewalls, that is the lowest weight Michelin recommends for these tires by the way.

If your tires are Michelin's and you are using the appropriate inflation chart (which I'm sure you are), then it seems like Michelin would  know more about the correct PSI than the truck tire folks who probably install dozens of different makes/models of tires and may unfortunately give blanket advice across all brands.  If 70psi is within the operating range given by Michelin, I can't see how the sidewalls would be ruined.

 

[BernieD]

I agree with Scott. I've had too many tire installers try to give me the standard line regarding mounting and tire pressures. They give a one size fits all answer and argue if you disagree no matter how wrong they are. It is easier to train them using the sidewall or GVWR pressures than to teach them how to go about getting it right.