tire pressure vs ride

Hi CapriRacer,

I've been driving it since 2009 and did a tire and wheel upgrade (thank you for your help at that time) because although I was below the GAWR's, I was over limit for the tires on the driver's rear. I'm now below the limits for the tires.

No, the makers do not care about balance. It is patently stupid of them to design having the battery bank, two fresh water tanks and two waste tanks all on the driver's side.

As I said before, I have deliberately done a "stand on the brakes" stop.

CapriRacer wrote:


2 thoughts:

First what did the vehicle tire placard say about GAWR's. How do the values you obtained compare to the GAWR's?

Second, I would recommend against applying the brakes too suddenly until you figure this out.

Also, have you weighed things with normal tank fillage?

And lastly, surely there must be something that can be moved to improve the weight distribution. Why did they design it this way? Don't these people care about how badly off center things are?

pianotuna wrote:
Hi CapriRacer,

Because I wanted "worst case" numbers, the weights were taken with all tanks full. All the water tanks are on the driver's side as is the battery bank. There is little I can do to change this. The "extra" water amounts to 550 lbs. (66 gallons US).

I do not have trouble with tracking or stopping, even if I "stand" on the brakes. I will be moving the generator to the front and will attempt to favor the passenger's side.

Currently I have the pressures set at 80 for the rear and 65 for the front.

Ride is rough so, so I'd love to lower the fronts in hopes of making the ride less rough.

2 thoughts:

First what did the vehicle tire placard say about GAWR's. How do the values you obtained compare to the GAWR's?

Second, I would recommend against applying the brakes too suddenly until you figure this out.

Also, have you weighed things with normal tank fillage?

And lastly, surely there must be something that can be moved to improve the weight distribution. Why did they design it this way? Don't these people care about how badly off center things are?

Hi CapriRacer,

Because I wanted "worst case" numbers, the weights were taken with all tanks full. All the water tanks are on the driver's side as is the battery bank. There is little I can do to change this. The "extra" water amounts to 550 lbs. (66 gallons US).

I do not have trouble with tracking or stopping, even if I "stand" on the brakes. I will be moving the generator to the front and will attempt to favor the passenger's side.

Currently I have the pressures set at 80 for the rear and 65 for the front.

Ride is rough so, so I'd love to lower the fronts in hopes of making the ride less rough.

My Ford F-250 door label calls for 50 psi front and 70 psi rear. Max tire pressure on tire is 80 psi, which is to be used if you are at maximum load. I have used recommended pressures for 9 years and never had a tire problem.
If I used the 80 psi in the front tires, they would be over inflated by 60%, and make for a very harsh ride.
Vehicle MFG put those recommend pressures there for a REASON.

pianotuna wrote:
Hi,

I don't have a good understanding of tire pressure vs ride.

I have been using what is on the inside of the driver's door.

i.e. 65 lbs front and 80 rear.

Should both front tires be inflated to the same number if they have different loads?

Driver's front is 2007 lbs, Passenger's is 1720 lbs.

Does ride improve as pressure is lowered?

Should the rear duals all be inflated to the same pressure?

Driver's rear is 5534 lbs, Passenger's is 5181

First, you need to figure out why there is such a difference left to right and do what you can to even things out. Those numbers sound out of bounds and I think you could be headed for trouble in an emergency.

Yep, thought that was you, PT. You must be haulin' watermelons or something back there! Or does it have a really short wheelbase?

Suspecting it was you, I looked at Michelin's tire pressure chart for larger size 16's than Class C's usually have. You're at max for the rear and yes, the front pressure comes up 45 for the weights you furnished.

I'd suspect that the ride at 45-PSI might make your front end tracking a little wobbly. I can promise you that MORE pressure than the front axle weight calls for is Not Good on a Ford E-Series chassis 1992 or newer. GawRonTeed. That said, we headed out into cool (relatively speaking, summer in Georgia mountains instead of Florida...) and that effectively lowered our front tire pressure. I aired up to the chart requirements, and tracking was much better driving home than it was on the way up.

So, what I'm now suggesting is get the front tire pressure within 5-PSI of what the chart wants. You're showing 45 on the chart...try 50.

Why should both front tires be the same brand at the same percentage of wear and at the same pressure?

Regardless of any other benefits or detractions if and when you need to stomp on the brake pedal all this nitpicking pays off with a vehicle that does not pull to the right or left.

It doesn't take much imagination to see the consequences of having the rig end up being where it shouldn't.

Hi j-d,

They are 235/85r16

The pressure to use for a given scale weight depends on the tire size.

If you have the 225/75R16E that's common on Class C, then 55-front, and even at 80-rear your rears are overloaded.

But I don't remember every member's postings. If you've upsized your tires, then very possible the 45-front you quoted is correct. Still, with 10700 pounds on the rear, even if the tires will carry the load at 80 PSI, the rear axle's overloaded by half a ton or so.

I run 70 lbs. on the front and keep the rear duallies at 80. Most of my miles are highway/interstate and they run fine with that.. also improves mileage when not under-inflated.