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Old 06-07-2021, 10:10 PM   #1
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THOR #12231
Lets talk Tire Pressure.... Yet Again

Lets talk tire presure .... Yet Again.

I was thinking about this last year when I had my blow out on my 2017 Axis (E450 chassis) so I changed what PSI I run now.

I know everyone knows about the Suggested Tire Pressure from the Thor wall sticker (75 F and 80R on my ride).

And I know you can go to the tire manufacture website for the optimal tire pressure for any given load (weight) for your exact tires (80 PSI max on my tires). That way you can get a little better ride if your lighter or if you want to max out your payload etc.

And yes I have scaled out both the front and rear of my RV.... The front was about 500 # BELOW the max (with me on the scale next to the drivers seat) and the rear was like 1200# BELOW the max weight recomended for my chassis with full load / fluids.

Thats not what this tread is about.


Should I go with a Little higher pressure in my front than Thor recommend if I cannot tell any difference?

I been running 76 front and 78 in the rears for about a year - feels the same.

I do have a TMPS now....(should have done it sooner.)

But now Im thinking 78 F / 78 R (cold tire pressure of coarse)

So my reasoning is this.... Since I cannot tell the differance from 72 front and 75 rear when I jumped to 76 F and 78 Rear last year just stick with something closer to my max tire pressure..... It has to help a little with wear and MPG not to mention lower tire HEAT (so that has to be good right?).

I would never run more than the Max pressure on the sidewall.

Plus if you get a leaking tire (Fast or slow) it would give me more time to pull off the road safely?

What do you guys think? Since I dont feel like my ride confort has changed just run 78 psi in all corners? Perhaps even 78 Front and 80 Rear?

I dont need to know WHAT tire pressure to run (I have tried them all) im just wondering if running max or close to max pressure all the time would have any NEGATIVE effect (esp in the front since THor recommend 75 psi). So far I cannot feel any change in handling or comfort so why not go to 78 in the front anyway?

Should I factor in the road heat will add a few PSI to my tires so run 78 max all the way around? or perhaps 77 all the way around?

Any thought on this subject?

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Old 06-07-2021, 11:12 PM   #2
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Having a higher than required pressure in tires, other than the "feel" which you are comfortable with, may result in higher tire wear in the center of the tire.
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Old 06-07-2021, 11:30 PM   #3
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There is only ONE way to figure ideal tire tread meets the pavement.
Tire. Chalk. Pressure. Test.
Look It up on youtube or the internet.

Everything else within the minimum maximum is
religion,
speculation
and
'my dad ran xxxpsi in his 65 gto' ghost stories.

Your more air gives it more time to go flat theory isn't conclusive. More psi might make the hole theoretically 'bigger' as psi pushes out more air...per psi.

What doesn't leak at 60psi may leak at 75psi.

My 3/4 ton truck with michelins runs at 38psi.
My neighbor with the same tires runs his at almost 80psi.
His truck rides like shit.
My truck rides like a dream.
I'm not really interested in tire longevity.
Mine don't cup, his doesn't run the center out.

I did the chalk test
He read the door frame and sidewall.
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Old 06-08-2021, 12:52 AM   #4
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I tried every recommendation I heard or read about that fit my coach, and I could NEVER detect an improvement. In fact with front tires 2 psi higher than the rear it was a harder ride for me. I put all of my tires at 82 regardless of weight just like the Mfg and Yellow sticker recommends. I did buy a TPMS and it nice that it confirms I have 82 psi every time I get in coach, but I have ZERO confidence that it will actually warn me in time to get off freeway during a blowout. Gradual air loss, yes but I don't see that short of changes in psi related to temperatures
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Old 06-08-2021, 02:36 AM   #5
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Quote:
Originally Posted by 16ACE27 View Post
Having a higher than required pressure in tires, other than the "feel" which you are comfortable with, may result in higher tire wear in the center of the tire.
Well the tires says "Max 80 PSI" on the sidewall and all of the tires bulge out on the bottom so im feel safe to say thats not going to happen.

Perhaps at 90 + psi that might be an issue.

Besides im only like 500 # from my max payload on the front axle so instead of the 75 psi that thor recommends (for Front axel) im thinking 78 would be a better choice for me?
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Old 06-08-2021, 02:40 AM   #6
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Originally Posted by dkoldman View Post
I tried every recommendation I heard or read about that fit my coach, and I could NEVER detect an improvement. In fact with front tires 2 psi higher than the rear it was a harder ride for me. I put all of my tires at 82 regardless of weight just like the Mfg and Yellow sticker recommends. I did buy a TPMS and it nice that it confirms I have 82 psi every time I get in coach, but I have ZERO confidence that it will actually warn me in time to get off freeway during a blowout. Gradual air loss, yes but I don't see that short of changes in psi related to temperatures
Ok, Well I think you have the F53 chassis..... right? So you have the 19.5 inch rim?

Im running the E450 Chassis with 16 inch rims.

So your at the lower end of your tire pressure where Im thinking of running the higher end of mine.

Did you check your weight at a CAT scale to confirm your in a good range for your use?
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Old 06-08-2021, 02:53 AM   #7
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Originally Posted by ducksface View Post

Your more air gives it more time to go flat theory isn't conclusive. More psi might make the hole theoretically 'bigger' as psi pushes out more air...per psi.

What doesn't leak at 60psi may leak at 75psi.

I did the chalk test
He read the door frame and sidewall.
Yeah I see what your saying but its not like im trying to push more PSI than what the manufacture shows as max.

I always go with what the door jam says (or sometimes 2 psi more). But I think like the RV is a much different then the famliy car.

Nothing will help you with a blowout. But with the TPMS you have the tire temps as well.... perhaps that would warn you in time? Perhaps.

I wish I had the TPMS when the old valve stem was leaking (unscrewed itself like 2 turns). When I left home all of the tires were perfect but then 3 hours later I stopped for a break and I check around the RV and found one of the rears was totally flat. I didnt even know it... she drove fine. So I figured the Valve stem was leaking for 2 + hours and I tore apart the inside of the sidewalls. I tighten the Valve stem, filled with air....It held fine..checked after 20 miles.... all was well for one more hour ..... BANG!!! the tire blew...scared the crap out of me. I will never go without TPMS ever again. Since then I installed a spare tire so I dont have to wait 4 hours again.
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Old 06-08-2021, 03:20 AM   #8
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Originally Posted by Long & Winding road View Post
Ok, Well I think you have the F53 chassis..... right? YES So you have the 19.5 inch rim? YES

Im running the E450 Chassis with 16 inch rims.

So your at the lower end of your tire pressure where I m thinking of running the higher end of mine.

Did you check your weight at a CAT scale to confirm your in a good range for your use?
No, and I concede I am guilty, but I no we don't come any where near the carry capacity and the Goodyear pressure ranges are in alignment with a reasonable estimation of weight. But it crapshoot anyway in my opinion. i.e. I leave town with full tank of gas, full tank of water, with plan to dump the black and gray tank I am going to heavy when you consider all of my other normal stuff, but I am not going to adjust my tires when I get down to low tank of gas, dump black & gray tank etc.

With all that said, I had a chance to get a CAT weigh at a Loves in West Texas or New Mexico? We were resting a couple of hours and I was right next to CAT scales One day I may do, but I am 100% we are NEVER anywhere close to being overweight in our RV.

My TPMS system is basically a sophisticated digital tire pressure system
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Old 06-08-2021, 03:35 AM   #9
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IMHO & the method I used, right or wrong, on 1 ton dually tow vehicle & 16.5k lb 5th wheel was to run all the tires at or very near, no more than 5 lbs less, the max load rating printed on the sidewall, never had rv or truck tire issues & all 10 tires wore evenly.
Running at lower pressures increase temperatures & for every psi below that max inflation you also decrease the load carrying capacity on the tires.
Motorhomes are built on truck chassis in order to carry heavy loads so a stiffer ride is to be expected, if you want a cushy ride get a luxury car.
Again in my opinion, worth .02 cents or less, weighing RVs then adjusting each tire for the load on each tire is a waste of time. Every time you add/remove weight you need to reweigh & readjust tire inflations on each tire??? What a PITA!
If the max psi is 80 then running at 76 & 78 should be fine & would be my recommendation for that .02 cents.
If inflated to the max it's not necessary adjust inflation to account for increased pressures due to increased temperatures, the tire manufacturers have taken that into consideration when manufacturing.
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Old 06-08-2021, 01:16 PM   #10
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Thanks Travelin TX.

Yeah 76 / 78 looks to be a sweet spot for me... But I might try 78 / 78 to see how it feels.

I would not adjust tire pressure for every single load unless I knew I was max out on my weight.
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Old 06-08-2021, 02:01 PM   #11
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The tire manufacturer chart is what I follow. They spend $$$$$ figuring out those specs. It is way more than comfort and feel: wear, traction, side wall support.
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Old 06-08-2021, 03:59 PM   #12
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The tire manufacturer chart is what I follow. They spend $$$$$ figuring out those specs. It is way more than comfort and feel: wear, traction, side wall support.
Speaking of the manufacturer's chart, mine says 60psi for the front tires. Right now (from the dealership) they are at 80. Would anyone go as low as 60?
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Old 06-08-2021, 04:04 PM   #13
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My chart minimum is 80 max 120: if it said min 60 then yes. My front is 10,000 and rear 19,850. 22.5 inch. What size tire?
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Old 06-08-2021, 04:16 PM   #14
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Class C. 225 75R 16
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Old 06-08-2021, 04:22 PM   #15
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So you have the about the same psi as my 30,000 pound Diesel Pusher. I stick with the manufacturers charts.
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Old 06-08-2021, 04:37 PM   #16
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Speaking of the manufacturer's chart, mine says 60psi for the front tires. Right now (from the dealership) they are at 80. Would anyone go as low as 60?

NOPE!
IMHO 60 is too low, wouldn't do less than 75.
The manufacturer may have spent $$$ on research, but I/we are spending the $$$ on replacing the tires not the manufacturer.
So run them at whatever pressures suit you, but not more than imprinted on the sidewall!
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Old 06-08-2021, 04:45 PM   #17
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Thanks Travelin TX.

Yeah 76 / 78 looks to be a sweet spot for me... But I might try 78 / 78 to see how it feels.

I would not adjust tire pressure for every single load unless I knew I was max out on my weight.
Doubt you'll notice a bit of difference in a couple pounds!
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Old 06-08-2021, 05:12 PM   #18
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Originally Posted by waynetaylor55 View Post
Speaking of the manufacturer's chart, mine says 60psi for the front tires. Right now (from the dealership) they are at 80. Would anyone go as low as 60?
THat has to be Wrong.....Most Class C's show around 75 psi. If they said 70 I might try it but 60 has to be wrong IMO.
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Old 06-08-2021, 05:13 PM   #19
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Doubt you'll notice a bit of difference in a couple pounds!
I bet your correct. I might try 78 front but I think perahps 76 front and 78 back would be spot on for me.
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Old 06-08-2021, 05:18 PM   #20
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Originally Posted by HMCSW View Post
The tire manufacturer chart is what I follow. They spend $$$$$ figuring out those specs. It is way more than comfort and feel: wear, traction, side wall support.
This is true but to me those charts are telling you the suggested pressure for a give load per axle. That way you dont ruin a tire and are safe on the road.

They dont want you at at 65 psi but maxed out on each axle.

But if your lighter than what they show your fine to use the higher PSI IMO.

Keep in mind I'm only talking about a few PSI in my case. 75 suggested from Thor but im runnig 76 now thinking of going to 78 front and 78 rear.

So its nothing dramatic.
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