Opinions on tire pressure

steve76 · 11-08-2017, 02:58 PM

Hello, I have a 2018 Thor Freedom Elite 22FE. Is a class C on Ford E350 Chassis. I have had front end aligned by reputable truck shop and have had SafeTplus installed on front. Question for those who have similar size rig: I am running 85 lbs. all around on tire pressure. Handles o.k. but seems to want to wander in driving lane a little. What are those who have similar size rig recommend for front and rear tire pressures based on their driving experiences? Thank's for any recommendations.

Bob Denman · 11-08-2017, 03:47 PM

The 80 to 90 psi range seems like a good place to start.

Does it feel as if the front end of the rig is "hunting"; or is the back of the rig moving around a bit?
If it's the back: up your pressures a little bit...
Good luck!

cpmath · 11-08-2017, 03:47 PM

I followed the tag on the driver's side door cowl. Have absolutely no problems or steering wander.

steve76 · 11-08-2017, 08:11 PM

Quote:

Originally Posted by Bob Denman

The 80 to 90 psi range seems like a good place to start.

Does it feel as if the front end of the rig is "hunting"; or is the back of the rig moving around a bit?
If it's the back: up your pressures a little bit...
Good luck!

Yes, hunting a very good description of what it feels like. Not a lot but there.

Bob Denman · 11-08-2017, 08:23 PM

I'm not all that sure about how these rigs should feel: I'm still pretty new in mine!

My advice would be to log a bunch of miles on it, and see if you just need some saddle-time to get used to how they go down the road...
There's always lots of advice out there about suspension and steering modifications.
But my Grampa Denman always said: "It's a poor mechanic; who always blames his tools."

blw2 · 11-08-2017, 08:32 PM

It started with getting weights. Ideally the weight at each corner....but I have so far been unable to get that for mine.
You can get the weights of each axle easy enough. Do this loaded to go.
With those weights, you can look on the load/pressure charts for your tires to find where they need to be set.
I targeted a bit more than that, just to add a safety factor to the number I'm quite sure the engineers already built a safety factor into.....
Once I did this, and had my alignment adjusted, it drove noticeable better. very much so....

I was told verbally by tech support at Yokohama that all tire manufacturers use the same standards, so I could find my tire size in Michelin's charts and use that number....
Load & Inflation Tables | Michelin Truck

jpmihalk · 11-08-2017, 08:33 PM

Quote:

Originally Posted by cpmath

I followed the tag on the driver's side door cowl. Have absolutely no problems or steering wander.

This is a good place to start. You may also want to check your tires for max pressure (on the sidewall) as well as either add some air for a stiffer ride or let some out for a softer ride, depending on your preferences.

There are a lot of online resources about RV tire inflation and what is good and what is bad. Most recommend getting all 4 corners of your RV weighed and then inflate the tires on each axle to the highest of the two/four (for duallies.) Don't let dealers or auto shops inflate them to the max sidewall pressure as a default. The tires will heat and pressure will increase as they are going down the road.

Since we are full timing and have almost 17K miles on our Hurricane, we invested in a tire pressure monitoring system (TPMS) to keep track of all of the tires as we go along down the road. But that is for us, you may not feel you need it.

Good luck and enjoy the ride!

jabrabu · 11-09-2017, 02:31 PM

On the Ford E450 chassis, the sticker inside the drivers door says 75 front/80 rear. It's probably the same for your E350. That's what I have used and it has been fine.

As others wrote, ideally you want to use actual weights and adjust accordingly. I haven't had mine weighed yet, but based on weights I've seen from similar units (mine's a 31E so bigger and heavier than your 22FE) the rear should be at the recommended 80 psi, but the front pressure can come down significantly. Based on this, I dropped my front pressures slightly (didn't want to go too far down), so I'm now running 70f/80r until I get it weighed.

As a side note, I bought mine out of state and drove it a long way home. After I got home I checked the tire pressures and they were down around 55 psi. I guess this is how they came from the Thor factory and the dealership didn't adjust them. It drove fine like that and even had a smoother ride, but I think the rears were probably way under-inflated.

JamieGeek · 11-09-2017, 03:22 PM

Quote:

Originally Posted by jabrabu

On the Ford E450 chassis, the sticker inside the drivers door says 75 front/80 rear. It's probably the same for your E350. That's what I have used and it has been fine.

As others wrote, ideally you want to use actual weights and adjust accordingly. I haven't had mine weighed yet, but based on weights I've seen from similar units (mine's a 31E so bigger and heavier than your 22FE) the rear should be at the recommended 80 psi, but the front pressure can come down significantly. Based on this, I dropped my front pressures slightly (didn't want to go too far down), so I'm now running 70f/80r until I get it weighed.

As a side note, I bought mine out of state and drove it a long way home. After I got home I checked the tire pressures and they were down around 55 psi. I guess this is how they came from the Thor factory and the dealership didn't adjust them. It drove fine like that and even had a smoother ride, but I think the rears were probably way under-inflated.

You are probably backwards with your pressures. Since there are dually's in the back the rears don't need as much pressure as the fronts (at least that is the way the chart read out for my Axis).

axis earl · 11-09-2017, 03:52 PM

We had our Axis 24.1 on the E450 chassis weighed at time of the alignment. Recommendation was 65-70 in the rear and 80 in the front. I run 70 in rear, 80 in front and it rolls down the road just fine. Weighing the rig is really the answer to your question.

Tupelo Kid · 11-09-2017, 04:19 PM

Tire info inside my coach calls for 82 cold PSI front and rear.

Chance · 11-09-2017, 05:10 PM

Quote:

Originally Posted by jabrabu

On the Ford E450 chassis, the sticker inside the drivers door says 75 front/80 rear. It's probably the same for your E350. That's what I have used and it has been fine.

.....cut.....

The front "may" be the same for E-350 and E-450, but the rear tires shouldn't be.

Air pressure on sticker has to reflect axle ratings as part of the Gross Vehicle Weight Rating (GVWR), which are different between E-350 and E-450.

Ford has a 5,000-pound front axle option on E-350 which I believe Thor uses on some models, making it the same as E-450's front axle, but the rear axles are not the same.

E-450 has a 9,600-pound capacity rear axle which requires the 80 PSI, while E-350 has maximum of 8,500-pound axle; hence requiring less pressure on sticker.

If actual vehicle weights are significantly lower, some owners lower the air pressure below what is required on sticker. However, since lower tire air pressure can affect handling, they should be careful in doing so.

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