Good Sam Club Open Roads Forum: I weighed my rig. Need help with math
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 > I weighed my rig. Need help with math

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Octaneforce

Long island

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Posted: 03/16/20 05:01pm Link  |  Quote  |  Print  |  Notify Moderator

So i got my 30ft class a weighed today. With me in it, it weighed 13,060lbs total, 8400lbs rear, and 4660lbs front.

Now i know i should have fully loaded it but i didnt have the time or energy. With the basic math i did, Id say in fluids, gear, and people, I’ll add about 1500lbs, mostly on the rear axle.

I did this because i want to order coil springs from supersteer to replace my crummy front airbags. The springs im torn between come 4400-4900lbs or 5000-5300lbs. Im leaning towards the 5000lbs springs. All i need is 2 additional passengers and I’ll be beyond 4900lbs

My other question is how to calculate my tire pressure. My tires say 3525lbs at 110psi single and 3305lbs double. I keep my tires at the recommended 110psi and my coach rides like a brick. Id like to run less psi but im not sure how to extrapolate the numbers to determine my minimum psi needed.


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Posted: 03/16/20 05:05pm Link  |  Quote  |  Print  |  Notify Moderator

The 5-5300# for sure.


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rk911

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Posted: 03/16/20 05:38pm Link  |  Quote  |  Print  |  Notify Moderator

without loading it as you would for travel...food, fuel, fresh water, lp, supplies, pets, clothing, people....you're just guessing and your guess is as good as mine. why not just assume your axles will be at max load..gross axle weight rating (GAWR)? of course that'll also be a guess. do it the right way.


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KD4UPL

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Posted: 03/16/20 07:08pm Link  |  Quote  |  Print  |  Notify Moderator

You need to locate the load inflation chart for your tires, probably from the manufacturer's website. Then, you can determine the proper psi for your scaled weight.

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Posted: 03/16/20 08:23pm Link  |  Quote  |  Print  |  Notify Moderator

I'd go with the 5000/5300 springs. In order to determine the correct psi for your tires, we'd need the tire size. You've already given your estimate of your weights. To be more accurate though, I'd wait until I was ready to go camping and have the coach weighed then. I usually weigh mine at a Flying J when I fuel up. $11 and you have accurate axle weights. Then simply look at the chart and air up or down accordingly. I've linked the chart below. Airing to the max will jar your teeth.....Dennis

Inflation tables


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way2roll

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Posted: 03/17/20 07:50am Link  |  Quote  |  Print  |  Notify Moderator

The proper way to get weights is to load your rig for travel - fuel, water, food, people, clothes, tools, chairs, bbq, the list goes on and on. Why?, because that's your actual weight when you travel and that is what matters for being over/under and determining proper PSI. You just wasted your time and now you are guessing - which you could have done without weighing it. Why bother to do it if you aren't going to do it properly?


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Posted: 03/17/20 08:28am Link  |  Quote  |  Print  |  Notify Moderator

way2roll wrote:

The proper way to get weights is to load your rig for travel - fuel, water, food, people, clothes, tools, chairs, bbq, the list goes on and on. Why?, because that's your actual weight when you travel and that is what matters for being over/under and determining proper PSI. You just wasted your time and now you are guessing - which you could have done without weighing it. Why bother to do it if you aren't going to do it properly?
X2 Then use the mfg load inflation table for your tires.

Actually the "best" way is to weigh all 4 corners, then use the weight for the heavest side on a axle to set the psi for all tirea on that axle. You could have a side to side weight problem that can be corrected by moving cargo.


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Posted: 03/17/20 03:55pm Link  |  Quote  |  Print  |  Notify Moderator

Most truck scale locations do not want to mess with RV's to check each wheel / corner. But nearly all have the front / rear / tag weight capability.
I make a first weight run of the total rig and then do it again with one side off of the scale. Simple subtraction will get the weight for the wheels of the side that was not on the scale.


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Octaneforce

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Posted: 03/18/20 04:38pm Link  |  Quote  |  Print  |  Notify Moderator

Hey sorry for the delay. Things are crazy around here.

Anyway i appreciate the replies. The tag in my coach says 14,800 gross and 65psi for all the tires. 65 sounds a little low to me. The tire size is 8r19.5

rk911

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Posted: 03/18/20 05:19pm Link  |  Quote  |  Print  |  Notify Moderator

Octaneforce wrote:

Hey sorry for the delay. Things are crazy around here.

Anyway i appreciate the replies. The tag in my coach says 14,800 gross and 65psi for all the tires. 65 sounds a little low to me. The tire size is 8r19.5

even assuming that tag is accurate...a big assumption...you still don't know what you actually weigh on each axle.

brand of tire? and the complete size from the sidewall?

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