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2350 Tire Pressure

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Doneworking

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2350 Tire Pressure
« on: April 16, 2015, 07:29:07 am »
OK, I searched the forum and read some information about tire pressures.  

Here is my question:  on a Phoenix Cruiser 2350 Ford 350 with slide and fully loaded (water, gear etc) what tire pressure are you using?  

The sticker shows 75 front, 65 rear.   Now, I know to be technical each axle should be CAT weighed and to be really technical each of the surface contacts should be weighed separately.   I just need to know this:  what pressure do folks with this specific unit use?  65 rear seems low to me and 75 front seems high, both by five pounds or so. 

This question is really specific to Ford 350s.  I have owned 450s in the past but this is my first 350.  The tires are new MS2 thanks to the recall.

Paul

« Last Edit: April 16, 2015, 07:31:32 am by Doneworking »
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Ron Dittmer

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Re: 2350 Tire Pressure
« Reply #1 on: April 16, 2015, 08:15:48 am »
Our 2007 2350 E350 (NO slide), I set tire pressure to 65-70 in front and 60-65 in rear.  Visually the tires look a little under-pressured.  As an experiment, I once pumped the tires to max which then they looked right but the ride was horribly rough.  A trip taken a few years ago when we did not tow our Jeep Liberty, I added 5 psi in all tires to 75f/70r to improve fuel economy.  The ride was a compromise.  The trip average fuel economy was near 11 mpg.  I concluded I should have let some air out of the tires to enjoy the ride better and forget about fuel economy.  I am surprised how 5psi can change the ride significantly.
« Last Edit: April 16, 2015, 08:17:48 am by ron.dittmer »
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TomHanlon

Re: 2350 Tire Pressure
« Reply #2 on: April 16, 2015, 09:29:52 am »
Very interesting. You two are putting less presure in the rear than in the front. Are you sure you don't have this backward? (WH)

My E450 calls for 75 front and 80 rear. I run about 5 lbs less because I weighted the coach and used the Michelin charts.
« Last Edit: April 16, 2015, 09:35:12 am by TomHanlon »
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Ron Dittmer

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Re: 2350 Tire Pressure
« Reply #3 on: April 16, 2015, 10:24:07 am »
Tom, The sticker PC-USA placed on my rig states 65f/60r, I assume because of the weight ratio verses quantity of tires.  So I maintain that relationship.
« Last Edit: April 16, 2015, 10:26:05 am by ron.dittmer »
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Doneworking

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Re: 2350 Tire Pressure
« Reply #4 on: April 16, 2015, 10:24:43 am »
Tom, I bring this up because yesterday I was getting ready for a trip and checking tires.  I had my front end realigned at a great local tire shop last week (independently owned, AAA Certified, two RV bays.....owned by the same family for fifty years).   When I checked my tires yesterday, which I meticulously do on all of my vehicles, I was shocked when I started at the back and got 65 on the dual.  I thought I had a leak!  Then I checked all the rears and got 65 exactly.  Checked the front:  75.   So, I checked the PC sticker on the driver's post and sure enough, that was what was on it.  Like you, I have always done the exact opposite.   I don't know if the pressure is set that way because it is an E350 and is different than an E450 or not???   The local guys just matched the sticker.  They know RV folks are always pretty anal about their personal preferences, and with good reason:  rig specific experience.

I have used 65 front and 75 rear since I got the PC about 18 months ago.  So, I asked the experts here.  65-75 was what I used on my previous Class  B (two front and two back and weighed out at almost 8800 on a Chevy 35 modified chassis) and that is what I have used on my previous two E450 Cs.

Ron's comments are really inline with the local tire guy's setting and the PC post.   Interesting about Ron's experience with the ride quality at the lower pressure.  

I am going on a short trip for a few days and will drive only about 600 miles round trip, mostly Interstate, so I am going to pop the rears down to 65 and just see how they handle.  Ron is on target again: those babies look a little underinflated to me, but so do all low profile car tires.  You just can't go on looking anymore.

I carry three things always regarding tires:  a good (and old so made in Ohio) trucker's gauge, a 110v compressor I can run from the genset and an infrared thermometer with which I check tire heat after driving a while.  I use the thermometer  to detect any internal tire problem that may not show up on a pressure check.

I will look forward to others comments and maybe a consensus will develop.   There has been a bunch of postings over the years on rv.net about this question but I am interested in PC specific responses and particularly focused on the E350.  

Paul
« Last Edit: April 16, 2015, 10:27:37 am by Doneworking »
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Barry-Sue

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Re: 2350 Tire Pressure
« Reply #5 on: April 16, 2015, 12:10:07 pm »
Paul

The E350 has the front axle rating of 5,000 pounds and a rear axle rating of 8,500.  If you take the maximum weight limits for each axel and use them to determine tire pressure from the Michelin Tire Load Table you would find the maximum that the front tires need to be inflated to is 75 pounds and the maximum the rear tires need to be inflated to is 65 pounds.

We had a 2008 2350 with slide on an E350 and I inflated our tires to 55LBS/65LBS.


Barry
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Doneworking

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Re: 2350 Tire Pressure
« Reply #6 on: April 17, 2015, 11:07:36 pm »
Well, I think I will play with this on our upcoming short trip.  I will keep the rear at 65 where the tire guy put it when the alignment was done last week, and I will put the front at about 65 and drive a couple of hundred miles. Then, I will drop the 65 to 60 and see if I can detect any ride difference.   This will be interesting.   We will be driving less than 600 miles total and so it will be easy to feel any significant difference.

Thanks for all the input.  This is really counter intuitive for me, but am going give it a shot.  One thing about it:  it is easy to let it out and put it in and air is cheap (if you carry your own compressor :)(:)

Paul
« Last Edit: April 17, 2015, 11:10:27 pm by Doneworking »
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Ron Dittmer

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Re: 2350 Tire Pressure
« Reply #7 on: April 18, 2015, 10:19:44 am »
Paul, I think you have a very good plan, adjusting along the way.
« Last Edit: April 18, 2015, 10:21:51 am by ron.dittmer »
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Doneworking

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Re: 2350 Tire Pressure
« Reply #8 on: April 25, 2015, 09:26:36 am »
Here is the results of my tire pressure experiment outlined above in my earlier post.  We drove from Oklahoma City over to NW Arkansas to a state park, mostly on an interstate highway, then on twisting mountain roads in the Ozarks for about a hundred miles total, then back to OKC mostly on a turnpike.  So, we traveled on a variety of roads.  We traveled with our fresh water tank full, quite a bit of stuff and so were fairly well loaded.  Driving speeds were between 65-70 on the interstate and pike and in 40s mostly on the mountain roads.  

Tire pressure wise, I tried a few variants and ended up with 65 psi on all six tires.   I must say, for the first time since we bought our PC about 19 months ago from the first owner who put a little over 7000 miles on it, it really drove much smoother than any other pressure combo I have tried.  The difference between 75 psi in the rear and 65 really made a significant difference in the ride, and reducing the fronts to 65 also improved the handling and ride.  I was very pleased with change in ride after settling on 65 all.  

I don't know about a 450 chassis, but the 350 really was greatly improved with this pressure.  Rough roads were simply much smoother with 65 psi vs 75 on the rear and 70 on the front.  I am really going to watch for any wear patterns on the tires, which are new due to the MS recall and replacement with MS2.  

Paul
« Last Edit: April 25, 2015, 09:28:33 am by Doneworking »
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Ron Dittmer

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Re: 2350 Tire Pressure
« Reply #9 on: April 25, 2015, 05:33:58 pm »
Paul, Thanks for sharing your results.

I concluded nearly the same with our rig, though 5 more psi up front.  I don't think our conclusions would be a perfect match because our 2350 is a 2007 with a softer front suspension along with not having a 400 pound slide out.  Considering those differences, I think we agree.

With regards to thread wear, with around 27000 miles to date, our back tires are wearing perfectly.  Our fronts are wearing evenly inside to outside, but we have a slight chafing or scalloped thing going on.  Because it is relatively minor and evenly formed across the threads, I really am not concerned.  By the time it gets serious, the tires will be replaced due to age.

Strange tire wear can happen from a few long driving days if the conditions are right.  For example, you can ruin your front tires just from driving across the Great Plains during a very consistent strong cross wind the entire time.  Turning your steering wheel to compensate puts excessive wear on the outside of one front tire, and the inside of the other.

By some people's standards, our 8 year old tires are already too old, but I want to get at least another 4, pending their thread and side-wall condition.  The rig is always stored in a dark garage so they stay fairly well preserved.

It's good to know we are in line with each other with tire pressure.  Thanks Again!
« Last Edit: April 25, 2015, 05:44:22 pm by ron.dittmer »
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