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Old 06-06-2013, 09:57 AM   #1
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New Michelin tires, seem unstable.

I just put on all new xrv 255/80 22.5 tires replacing my xze's which turns out they were about 15 years old... So after replacing I went from a very straight driving coach to feeling like I am slithering down the street like a snake, having to constantly correct steering.

I have read sometimes you have to run the tires to get them worn in.

Secondly, the sticker on the coach called for 255/80's on the duals and 275/70's for the steer tires. Which would allow for a lower pressure at a higher load. My coach puts the steer tires right at the max weight load at the highest pressure.

I asked the tire installer about this and had him look at the label and he said there won't be a problem, the tires sizes are so close they are technically the same. I assume the tire guys are correct, they have way more experience than I do...

Would this narrower tire or pushing the maximums, or wearin cause this steering issues that I am experiencing?
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Old 06-06-2013, 10:13 AM   #2
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Someone posted a week or so ago that they were told their tires had to "wear in" before they would be stable. I've never heard that line, and never experienced it. The only time I had unstable ride was when I was sold inadequate tires for my vehicle with the assurance they would be great ...the sidewalls were too flexible, handling was poor, and they did not last long before I had belt separations. You say your steer tires are at max weight load at highest pressure ...which I presume means they are inflated to the max sidewall pressure. Is that calculation based on actual weight of the front axle? ...or on the max axle capacity? If the tires are over-inflated for the load they are carrying, handling can be poor/erratic. The other factor is load range, which you did not mention. The same size tire can come in different load ranges ...G, H etc. I suspect your probably calls for H or higher. If you run a lower rated G where you should have an H, you will have to run higher pressures for the weight, and the sidewall will flex more which downgrades handling and causes premature failure/blowout.
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Old 06-06-2013, 02:20 PM   #3
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Quote:
Originally Posted by bobioknight View Post
I just put on all new xrv 255/80 22.5 tires replacing my xze's which turns out they were about 15 years old... So after replacing I went from a very straight driving coach to feeling like I am slithering down the street like a snake, having to constantly correct steering.

I have read sometimes you have to run the tires to get them worn in.

Secondly, the sticker on the coach called for 255/80's on the duals and 275/70's for the steer tires. Which would allow for a lower pressure at a higher load. My coach puts the steer tires right at the max weight load at the highest pressure.

I asked the tire installer about this and had him look at the label and he said there won't be a problem, the tires sizes are so close they are technically the same. I assume the tire guys are correct, they have way more experience than I do...

Would this narrower tire or pushing the maximums, or wearin cause this steering issues that I am experiencing?
It may be your inflation pressures. With the 255/80s if you are maxed out then you should be running 110 psi on the steer tires. If your drive axle is rated at 20k then you need 110 psi there also. If your drive axle is lighter then adjust accordingly. The tire guy lied to you. The 275/70 tires on the steer axle would carry the rated axle weight at 90 psi. That's a significant difference.
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Old 06-06-2013, 02:52 PM   #4
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Hi bobioknight,
Re check the front axle actual weight you are carrying and adjust the tire pressure accordingly. I have 275X70X22.5 XZE2 and run 95 PSI carrying 12K lbs.
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Old 06-06-2013, 07:13 PM   #5
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Yup, ensure tire pressure is correct for the actual weight of the coach, then go from there if the problem persists.
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Old 06-10-2013, 02:45 PM   #6
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Quote:
Originally Posted by AFChap View Post
Someone posted a week or so ago that they were told their tires had to "wear in" before they would be stable. I've never heard that line, and never experienced it. The only time I had unstable ride was when I was sold inadequate tires for my vehicle with the assurance they would be great ...the sidewalls were too flexible, handling was poor, and they did not last long before I had belt separations. You say your steer tires are at max weight load at highest pressure ...which I presume means they are inflated to the max sidewall pressure. Is that calculation based on actual weight of the front axle? ...or on the max axle capacity? If the tires are over-inflated for the load they are carrying, handling can be poor/erratic. The other factor is load range, which you did not mention. The same size tire can come in different load ranges ...G, H etc. I suspect your probably calls for H or higher. If you run a lower rated G where you should have an H, you will have to run higher pressures for the weight, and the sidewall will flex more which downgrades handling and causes premature failure/blowout.
X2 on the tires having to "wear in" I have never experienced that either.
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Old 06-10-2013, 04:15 PM   #7
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If the coach calls for 275's, take it back to the dealer and insist on the 275's, the height (diameter) of the 2 may be very close, but I bet that the load ratings are higher on the 275's. Ask the dealer if he will cover all liabilitys from a blowout.
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Old 06-11-2013, 12:21 AM   #8
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The xrv are for RV only and made with a softer sidewall. The xze are made for truck like a dump or 18 wheelers where a softer ride is not the idea. I agree with checking axle weight and finding out what tire psi. I would say the man that put the tires on just wanted to sell you what he had on stock. Not what you should be running. So if you want xrv tires make sure you get the ones made for front axle weight (load rating etc....).
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Old 06-11-2013, 09:43 PM   #9
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Remember that the tread depth is 31/32 of an inch. What your feeling is called "tread squirm" Your old tires probably did not squirm.When I first got Bridgestones on the drive axle I thought something was wrong with suspension.
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Old 06-11-2013, 09:56 PM   #10
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Quote:
Originally Posted by AFChap View Post
Someone posted a week or so ago that they were told their tires had to "wear in" before they would be stable. I've never heard that line, and never experienced it. The only time I had unstable ride was when I was sold inadequate tires for my vehicle with the assurance they would be great ...the sidewalls were too flexible, handling was poor, and they did not last long before I had belt separations. You say your steer tires are at max weight load at highest pressure ...which I presume means they are inflated to the max sidewall pressure. Is that calculation based on actual weight of the front axle? ...or on the max axle capacity? If the tires are over-inflated for the load they are carrying, handling can be poor/erratic. The other factor is load range, which you did not mention. The same size tire can come in different load ranges ...G, H etc. I suspect your probably calls for H or higher. If you run a lower rated G where you should have an H, you will have to run higher pressures for the weight, and the sidewall will flex more which downgrades handling and causes premature failure/blowout.
The pressure on the sidewall of a Michelin RV tire and many others is not the "Maximum" the tire should ever have (unlike car tires) it is the minimum to support the maximum rated carrying capacity of the tire.

From the Michelin RV Tire Guide:
Quote:
"If you look at the tire's sidewall, you'll see the maximum load capacity allowed for the size tire and load rating, and the minimum cold air inflation needed to carry the maximum load."
From page 6 of the GoodYear RV Tire and Care Guide:
Quote:
"How much air is enough?
The proper air inflation for your tires depends on how much your fully loaded RV or trailer weighs. Look at the sidewall of your RV tire and you’ll see the maximum load capacity for the tire size and load rating, as well as the minimum cold air inflation, needed to carry that maximum load."
From TOYO:
Quote:

Inflation Pressure Safety Margin
Toyo Tire does not recommend an “inflate-to-the-load” policy for RV tires. Tires that are inflated to accommodate the vehicle’s actual loads do not have any inflation safety margin. Consequently, even a minor loss of air pressure will cause the tires to be under-inflated and overloaded. Toyo Tire’s policy is to observe (as a minimum) the tire pressure established by the vehicle manufacturer as indicated on the tire information placard. There are multiple reasons why a safety margin
(by inflation) makes sense:
• All tires lose about 1-1.5 PSI per month due to natural permeation of the tire’s internal air pressure through the tire’s rubber membrane.
• In the event of slow air leaks from punctures, an inflation “reserve” may allow detection and repair of the leak prior to reaching a dangerously low inflation level.
• A safety margin is prudent for users who are apathetic regarding tire inflation maintenance.
But then they go ahead and publish a weight/pressure chart allowing lower pressure for RV's!!

From the August 2010 Motorhome Magazine "Tread Carefully" tire article:
Quote:
The maximum load capacity allowed for the size tire and load rating and the minimum cold air inflation needed to carry that maximum load are located on the tire’s sidewall.
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Old 06-12-2013, 12:42 PM   #11
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Tire pressure first. Then remember there is more flexible rubber between your wheels and the road than you had with the old tires.

I had the same event after putting new tires on my 3/4 ton Suburban years ago. After about 100 highway miles the problem was gone.
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Old 06-12-2013, 04:07 PM   #12
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If the problem goes away in 100 miles, it is more likely that the driver got used to a different "feel" than the tire actually changed in any way.
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Old 06-12-2013, 04:11 PM   #13
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I agree with the tire pressure, weigh your vehicle.
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