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georgelesley's avatar
georgelesley
Explorer
Nov 09, 2017

Tire pressure....again

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?
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  • garyemunson's avatar
    garyemunson
    Explorer II
    Nov 10, 2017
    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's avatar
    bobkatmsu
    Explorer
    Nov 09, 2017
    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's avatar
    Sam_Spade
    Explorer
    Nov 09, 2017
    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's avatar
    georgelesley
    Explorer
    Nov 09, 2017
    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!
  • georgelesley's avatar
    georgelesley
    Explorer
    Nov 09, 2017
    stripit wrote:
    Everyone is guessing without a true weight of what that tire is carrying. The placard is giving tire pressure for the tire they installed to meet the max axle load, nothing more. Weigh it then adjust pressures to meet that load. The unusual wear sounds like a broken belt(steel) inside the tire to me.


    I just looked at the load rating on the tire, it was 4400 lb. i weighed it some time ago at a state hwy station front axle was 6800 which would be ~ 3400 and rear was 12800 which would be ~ 3200. The guys at the station said their scale could not weigh just one side as I wanted to so I could then calculate actual 4 corner weights.

    It appears however we are under the tire load carrying capacity.

    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..
  • WILDEBILL308's avatar
    WILDEBILL308
    Explorer II
    Nov 09, 2017
    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
  • stripit's avatar
    stripit
    Explorer
    Nov 09, 2017
    Everyone is guessing without a true weight of what that tire is carrying. The placard is giving tire pressure for the tire they installed to meet the max axle load, nothing more. Weigh it then adjust pressures to meet that load. The unusual wear sounds like a broken belt(steel) inside the tire to me.
  • 10forty2's avatar
    10forty2
    Explorer
    Nov 09, 2017
    You're going to get sooooo many opinions on this.....both here and through the various "professionals" that you ask. Best answer is to run the pressure recommended by the TIRE manufacturer according to the weight placed on that tire. Set the cold pressure by the manufacturer's chart and unless there's a problem while underway, don't readjust the pressure until the tire is cold once again. Sounds like the tire professional you consulted is defaulting to tell you to run MAX Cold PSI. It's certainly safe to do so, but I've found that the ride is pretty harsh when you do that.

    And yeah, if all the other tires are wearing okay as you have them set, you may just have one bad tire.
  • Jim's avatar
    Jim
    Explorer
    Nov 09, 2017
    Michelin is more interested in a soft ride than tire life.

    WGO is going by their book, which is based on the original tire spec'ed.

    The Tire pro is going by expirience.

    Trust the tire pro.

    Or compromise and put in 105 PSI.

    I think what you're seeing on tire ware is due to an unbalanced load. Take it to a state weigh station when it's closed and weigh all four corners. Get a better handle on it.
  • CapriRacer's avatar
    CapriRacer
    Explorer II
    Nov 09, 2017
    georgelesley wrote:
    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?


    This sounds like a separating belt. If you can get a photo, that would help.

    In the meantime, do not operate the vehicle.

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