Community Forums

PATRICK49 · 03-15-2021, 06:41 PM

Should I use the tire pressure shown on door plate of my 1999 Holiday Rambler Endeavor (gasser) 36wgs or the pressure calculated using axle weights and chart from tire maker (Cooper Roadmaster) 245/75/R19.5.
Door says 80 all around single and dual. Chart 90 or so
Depending on weight.

richard5933 · 03-15-2021, 06:47 PM

I'd go with the tire manufacturer's chart, based on the weight of the coach, but never lower than the plaque the coach came with.

Lowflyer1 · 03-16-2021, 06:54 AM

Quote:

Originally Posted by richard5933

I'd go with the tire manufacturer's chart, based on the weight of the coach, but never lower than the plaque the coach came with.

Mine is opposite. The plaque on my coach indicates (cold) tire pressures at max axel weights (GAWR). If the actual weight of the axels is lower, then I use the tire manufacturer chart to lower the pressures.
To be more precise, the pressures should be adjusted per the higher corner weights.

JJTL · 03-16-2021, 09:47 AM

Quote:

Originally Posted by PATRICK49

Should I use the tire pressure shown on door plate of my 1999 Holiday Rambler Endeavor (gasser) 36wgs or the pressure calculated using axle weights and chart from tire maker (Cooper Roadmaster) 245/75/R19.5.
Door says 80 all around single and dual. Chart 90 or so
Depending on weight.

Typically the air pressure on the info plate in the coach, is the pressure needed to carry the maximum GVWR (which is based on axle ratings). The coach OEM would have determined this pressure by using the GVWR weight and referencing the tire inflation tables for the OEM tires. The pressures on the data plate should be what is required to carry the max GVWR.

If you weigh your coach and the inflation table is showing a pressure higher than the data plate, this means either your weight is over GVWR or your coach is now equipped with different tires than OEM. If it is equipped with different tires and the pressure required based on you weighing the coach is more than the pressure on the data plate, it would also infer that your new tires have a lower carrying capacity than what came with your coach.

As Lowflyer1 mentioned, usually when you weigh your coach it will be under the GVWR and might give you the option to lower the pressures from the data plate, based on what is needed to safely carry your actual weight (referencing the tire manufacturer's inflation table). Lower pressure, allows for a softer ride. Should be noted, that tires should always be inflated above the minimum pressure listed by the manufacturer.

Either way, something seems wonky. I would check the numbers again.

Note: The above is based on my experience, and how the data plate is written for our coach.

80psi seems low to me. But it might be that I'm more familiar with larger axle ratings.

All the best!
Josh

KanzKran · 03-16-2021, 10:02 AM

Quote:

Originally Posted by JJTL

Typically the air pressure on the info plate in the coach, is the pressure needed to carry the maximum GVWR (which is based on axle ratings). The coach OEM would have determined this pressure by using the GVWR weight and referencing the tire inflation tables for the OEM tires. The pressures on the data plate should be what is required to carry the max GVWR.

In the case of my van, the inflation pressure plate specifically states it applies to the laden condition. And the two axle pressures correspond to the GAWR, though the two GAWR's combined is much more than the GVWR. In short, inflating to those high values makes for a really rough ride, and after getting weighed at a local CAT scale, I can see why - they're both way under their respective GAWRs.

So I've adjusted the pressures down to 10% above the tire table values for the actual loads, which is still much lower than the data plate values. But then, I'm about a ton lighter overall than the GVWR, a ton lighter on the rear axle than the GAWR, and half a ton lighter on the front GAWR.

Oh, and it tracks much better now too, and doesn't wander all over requiring constant steering correction. And it doesn't feel as much like an empty dump truck anymore either.

MSHappyCampers · 03-16-2021, 10:56 AM

I get the recommended pressure from the tire manufacturer's charts and add 5PSI.

Jim Godfrey · 03-16-2021, 11:55 PM

I just do 100 all the way around. The tires can take it and it isn't under pressure. The ride is not too rough 34 ft.. 22,000 lbs 6 wheels. IMO no need to geek out on this, just never be under any rated value

Ray,IN · 05-18-2021, 11:03 PM

For the record, page 2, last paragraph is what Bridgestone/Firestone has to say about tire pressure.

"Find the Recommended Inflation Pressure
Use the RV manufacturer’s recommendation (which you will find on the tire information placard). Never use inflation pressures lower than those printed on the vehicle placard."
reference: https://www.bridgestoneamericas.com/...tires/rv-tires