Tire pressure....again

[georgelesley]

OK guys, I am thoroughly confused. Our right front tire has recently, in the past several hundred miles, started wearing on the outside. First thought was alignment, but the wear pattern is not typical of toe in toe out wear. This is about a 1/2” well defined wear groove from the edge towards the center of the tire. It isf maybe 1/8” deep then normal tire. In my experience alignment manifests itself with a even, tapering wear pattern

I did not feel any cupping,or other wear on any tire, including the one in question. Next week I am taking it to a truck tire shop for alignment check and repair if needed. The alignment guy asked what pressure I was running. I told him 90 , which is what WGO prints on the placard inside.

He suggested 120 would be much better. I just chatted with someone on the Michelin website, gave them the corner weights, tire size (22.5 235/80 Michelin XRV), and they recommended 70!

OK so whom do I believe, a professional tire guy who says 120, or WGO which says 90, or the tire manufacturer who says 70?

Hint: since the problem is new, and all other tires are OK and the tpms shows similar temps and pressures on all when running, I am inclined to stay with 90. Monday when the mechanic looks at it I will not be surprised if he finds a mechanical issue.

What am I missing here?

[Jim]

You might consider those air foil, air spoilers for the back of your RV to help stabilize it in both winds and from passing semi's. I put them on last spring and really think they help. A lot. I always keep my 22.5 tire pressures up over 100 PSI to reduce wear and noticed a slightly higher incidence of road wander during winds. After installation of the spoilers noticed that wander was reduced. I wrote a product eval and posted it to my blog if you're interested. Articles content and conclusions are entirely my own...V-Spoilers Product Evaluation

[georgelesley]

Well the answer is in on the tire wear problem. I took it to a Goodyear truck tire shop in Springdale, AR. The manager Dan looked at the tires in front and pronounced both are just starting to show normal wear considering they are four years old. He said no alignment is needed but did suggest I up the pressure to 105 (110 is max on the sidewall). I had him do that. He said I could lower back to 90 if it was too harsh riding but he expected we would find little difference

He also said it would stop or slow down the edge wear which makes sense. He also felt the higher pressure would make it more stable on the road because of less sidewall flex. That also made sense to me.

Having driven it several hundred miles now, I have mixed feelings about the higher pressure. Ride quality seems the same. Steering response is quicker, which is to be expected. Passing trucks and side winds seem to affect the coach more than before however. Both DW and myself felt the difference. Probably because of smaller tire contact patch and less sidewall flex to absorb sideways force. For now, I will leave it alone, but may drop the pressure back a bit. We will see.

In summary, I highly recommend the Goodyear truck tire shop in Springdale, AR, just off I-49 exit 73. I went there expecting an alignment or maybe mechanical work and told Dan so. He could have easily sold me such but did not. Because on his honesty I had him do an oil change and straighten the steering wheel which as many here know is a problem on Ford 53 chassis. The price he charged for the work was very fair.8

[wa8yxm]

The only way. THE ONLY WAY to determine the proper tire pressure is with a scale.


First: you go to Mitchlin and download the inflation chart for your tires

THEN you scale it. ALL 4 Corners.. (Remember there are two charts one for duals one for singles) You can find instructions for weighing elsewhere on teh forum or I can type 'em out for you.. Or you can contact www.rvsafety.com and follow the links there and they come out.. Charts in hand.

From the load placed on the tire. you determine the inflation.. Mine is 115PSI same tire.

[WILDEBILL308]

Paul, welcome to the forum. If you add your coach to your signature it will help to get better answers when you have questions.
Your coments on weight are the reason it is important to weigh your coach so you can run the right preshure for the load.
Bill

[Sam_Spade]

Blutoyz wrote:
He does have experience OTR with large trailers as well as 30+ years in the trade so I will trust his recommendation.

The considerations for tractor-trailers are different than those for an RV......or at least they should be.

One size does NOT fit all.

During those 30 years of experience, it appears that he has had NO training, which is not unusual for a tire changer. Not trying to be nasty here, just trying to get things into perspective.

I would lean heavily toward what the tire manufacturer and RV maker says because they have a good bit more expertise and thousands of years of combined experience.

What you have decided to believe defies good logic.

[MotorhomeExperi]

Hi everyone, just joined the forum and was browsing around to see what everyone was talking about when I ran across this thread on tire pressure.

Just remember George, because someone is a "tire professional" doesn't mean he knows what he's talking about. In my opinion, 120psi is overkill, will make your coach ride like hell and wear the center of your tire.

If you haven't been having issues at 90psi, and this doesn't sound like a low pressure issue, why not stay at 90psi. As one of the other gentlemen said, a pic or two might help shed some light on the problem.

When I bought our coach a year and a half ago all the tires were at 90psi, which I thought was high and the coach seemed to be riding rough. The chart next to the driver's seat and the owner's manual called for 80psi. I dropped them to 80psi and it rides better, has no wear issues and hasn't had any other problems to speak of.

We've done 18,000 miles with them over the past 11 months.

All of these guys are correct about weight being a factor, but if you aren't way over weight, which you don't want to be anyway, go with what the motorhome manufacturer recommends, not what some tire guy thinks it should be.

Being a front tire though, I would want to know what the problem is before driving it and putting yourself and passengers at risk.

Have an amazing day and safe travels!

[WILDEBILL308]

CapriRacer wrote:

georgelesley wrote:
...... UPDATE. As a result of this thread, I just examined the tire again very closely. We have driven about 320 miles since I first noted the wear. Now the “sharp groove” pattern has rounded a bit with no other wear issues on the tire. One more telling thing that should narrow it down a bit, is that today I also examined the left front tire and found the same wear just starting on BOTH the inside and outside of that tire. Same width 1/2” or so but not nearly as deep. Running my fingers over it maybe the new is 1/16 or less

Sorry I did not check all of this today before posting. I wanted the manufacturers recommendation before Monday at the shop and was blown away by three completely different numbers. Monday should tell the story at the shop. Will advise..

Still sounds like a belt separating. That photo would be very helpful to sort this out.

Oh and those tire load charts? They are MINIMUMS!! If you are getting wear on both shoulders, it just might be that the tires are under inflated.

I always run +10% or just 10lbs over what the chart says. This protects you if temps change as you don't want to run under inflated.
Bill

[Blutoyz]

I read and read to figure this out...My pal and mechanic has a shop that I had do my pre-trip service and he set all the tires at the sidewall max cold pressure.

I questioned it since reading all of the discussion on here and he told me it is better to run at this pressure than not. He did say I could drop 5# or so for comfort up front (95# now) since I am not close to max load on these tires. He does have experience OTR with large trailers as well as 30+ years in the trade so I will trust his recommendation.

[CapriRacer]

georgelesley wrote:
...... UPDATE. As a result of this thread, I just examined the tire again very closely. We have driven about 320 miles since I first noted the wear. Now the “sharp groove” pattern has rounded a bit with no other wear issues on the tire. One more telling thing that should narrow it down a bit, is that today I also examined the left front tire and found the same wear just starting on BOTH the inside and outside of that tire. Same width 1/2” or so but not nearly as deep. Running my fingers over it maybe the new is 1/16 or less

Sorry I did not check all of this today before posting. I wanted the manufacturers recommendation before Monday at the shop and was blown away by three completely different numbers. Monday should tell the story at the shop. Will advise..

Still sounds like a belt separating. That photo would be very helpful to sort this out.

Oh and those tire load charts? They are MINIMUMS!! If you are getting wear on both shoulders, it just might be that the tires are under inflated.

[wolfe10]

garyemunson wrote:

The camper mfg pressure would yield even weight distribution across the tread and the tire should wear out in an even fashion.
Too much pressure for the load will cause the tire to wear in the center of the tread.

I AGREE IF, REPEAT IF EACH AXLE IS LOADED TO ITS GAWR. THE PSI ON THE GVWR PLAQUE IS CORRECT PRESSURE ONLY IF THAT IS ACTUAL WEIGHT OF THE HEAVIER WHEEL POSITION ON THAT AXLE.

[garyemunson]

Pressure on sidewall is max cold pressure recommended by tire mfg with a full load also matching sidewall data.
Pressure on camper placard is what camper mfg recommends with full load the camper is rated for.
The camper mfg pressure would yield even weight distribution across the tread and the tire should wear out in an even fashion.
Too much pressure for the load will cause the tire to wear in the center of the tread.
Too little pressure for the load will cause tire to wear on the outside edges and may overheat the tire and lead to failure at speed.
Tire pressure should always match the load although in the real world, that can be tricky.
More pressure (as long as it does not exceed mfg max cold pressure) is more desirable than less but makes for hard ride and center tread wear.
Never 'bleed' air from hot tire even if pressure is above sidewall numbers. Remember, sidewall max is cold. Mfg expects tire pressure to increase with temperature. Tire set at max cold pressure will never increase pressure to the danger point while running unless the tire is grossly overloaded.

[bobkatmsu]

My experience was the WBO said 90 lbs. the Michelin dealer that I bought the tires from said 100 lbs. I was not happy with the way the motor home rode at either setting. Before I went on a 5 month trip, I had it weighed and consulted the Michelin charts and followed their recommendation of 72 lbs. I put 7600 miles on the trip, it never drove better and there was no evidence of any unusual wear on the tires.

[Sam_Spade]

Some specific tires wear funny.
Maybe you should have asked Michelin if the ones you have are known to do that.

I wouldn't blindly believe EITHER of the recommendations you got.

The "professional" tire guy probably believes that "max on the sidewall" for everything is the right thing to do....because he really doesn't know any better.......and the Michelin person on the phone was probably just looking things up on a chart and might not even know what a truck/RV tire really is.

[georgelesley]

WILDEBILL308 wrote:
Like 10forty2 said you will get a lot of opinions.
Question, have you done a alignment on your coach, lately? You indicated you had your 4 corner weights right? Are you using the highest weight on a axel to set the tire pressure for that axel?
This is the latest inflation chart I could find.
http://www.michelintruck.com/reference-materials/manuals-bulletins-and-warranties/load-and-inflation-tables/#/
Bill

Boy it sure looks like the Michelin CS was right? Why then does WGO say 90??? Monday will be interesting!