Tire pressure

[mikern]

on our 2016 ventana le 4037 i have not had a chance to weigh the coach 4 corners yet
dry 29700lbs gvwr 36400 lbs
very little cargo at this time full water and fuel
125 psi it rides rough
do u think it would be okay to run 100 for now
michelin X® MULTI Z - 275/70R22.5

thanks

 

[Webz]

Without knowing your actual weight, it is pretty much a guess. IMHO
You can get in the ballpark by using a CAT scale at a truck stop. At least you will know how much weight is on each axle. And for some that is sufficient.

 

[Tnedator]

I would go to a CAT scale and weigh (make sure you have your axles on different scales. Then, for each axle, multiple by .53. So, if you came out at 9300lbs on the front axle, 9300 x .53 = 4,929 and use that as the weight for both tires on that axle. Do the same with the other axle, then look up the PSI in the Michelin load chart.

The .53 is recommended when you don't have a four corner weight, as typically one side is heavier than the other, so it's about the best option you have short of a four corner weight.

 

[Rich W.]

My weights are as follows:
DF 5,750
PF 5,350
DR 10,050
PR 9600
For a total of 30,750

Using the chart from the publication below, and using the high side of each axle, I should be able to safely run 100psi in the rear, and 105psi in the front, I added 5psi to each front because I’d rather run a little firmer that softer for tire condition reasons. So my current pressures are 100psi rear, 110psi front.

You probably weigh more than 30,750 and as I said, I’m fudging on the high side for my pressures. But for guestimating your pressures in lieu of weighing I wouldn’t go below 105psi for the rears and 115psi for the fronts. Once you weigh the coach you’ll probably be able to lower it 5psi all the way around becuase you are probably not at 34,000lbs loaded. But…5psi less probably wont get you any perceivable improvement in ride and that 5psi may keep your tires cooler.

All this probably sounds like a definite maybe (because without weighing it is) but I would say that 125 is higher than necessary and high enough to contribute to a rougher ride.

In case you dont have the chart:

https://www.michelinb2b.com/wps/b2bcontent/PDF/RV_Tires_Brochure.pdf

 

[mikern]

thanks for the info

mike

 

[mikern]

I would go to a CAT scale and weigh (make sure you have your axles on different scales. Then, for each axle, multiple by .53. So, if you came out at 9300lbs on the front axle, 9300 x .53 = 4,929 and use that as the weight for both tires on that axle. Do the same with the other axle, then look up the PSI in the Michelin load chart.

The .53 is recommended when you don't have a four corner weight, as typically one side is heavier than the other, so it's about the best option you have short of a four corner weight.

i got to weigh the coach on axles only
as per michelin load chart
115 fronts and 95 rears psi
a very noticable difference in ride for sure
they had the fronts set at 131 max pressure for the mult z tire

thanks everyone

 

[Rich W.]

Since you don’t have individual weights on the rear, I’d run them at 100psi until you can do 4 corner weights. Note that I’m 450lbs heavier on my drivers side rear which puts me into the next higher tire pressure column, even though my pass side rear weight is low enough for 95psi. Also check the clearance between the duals. I seem to recall 1.5” minimum. Lower pressure will of course reduce the spacing.

When you get four corner weights, don’t interpolate - just go to the next higher pressure. So in my case, at 10,050 Im much closer to the 95psi column (9,950) but over by 100lbs and the next higher level, 10,370 is 100psi, so per the Michelin recommendation, thats what I run. Your coach is heavier than mine by at least 1700lbs, so I would think your TP would be at least as high as mine.

What were your axle weights?

 

[mikern]

Front 11464
Rear 19599

 

[Rich W.]

Front 11464
Rear 19599

So since you don’t have four corner weights, using the total axle weight x .53 (thank you Tnedator) you end up with 10,387 so I definitely run 100 in the rears until you have weights for both side. Even if you divide by two and multiply by 1.03, you’re still at 10,093 which puts you in the 100psi column. Also with four corner weights you’ll probably find you can run 110 in the fronts.

 

[Scotttkd2]

Mkern......My Kountry Star appears to be a lot heavier in the front (13600 on the Cat scale) and uses the same 275/70r22.5 size tires, I have to run them near max 130psi cold to cover that weight. I am concerned that is not the best idea to have engineered a design that relies on running a tire at the very top of its load range. Am looking at the possibility of fitting the 295/70r22.5 for the added margin, but no idea yet on clearance. Glad you got it sorted out!