Tire Help

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CruisingTheCoast

New member
Joined
Aug 17, 2016
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Sorry to start another tire thread, but we're new to the RV world and are hoping for some insight.  I have a E350 V10 Ford 22ft Class C Gulfstream Cavalier dually and just had a rear outer wheel sidewall failure.  Tire rating is LT225/75R16 M/S on all the tires.  They also say "all terrain" and appear to have thicker tread than the spare did. I put the spare on, which had the same rating, but the vehicle has been wonking back and forth.  Almost like there is a training wheel on it. 

I need new tires in a pinch as we have our first full week off since buying the vehicle and took it to Wheel Works to replace the tires.  They put on a Firestone with the same rating and afterward, I drove down the road with the same problem.  It does not appear to be bearing the same weight as the inner tire.  I told the shop it weighs 10,000 pounds and I am pretty sure they didn't put on the right tire.

Questions:
Does the "all terrain" make a difference in the thickness of the tread or change the diameter of the tire?  Why is the same rated tire a different size?
Or is that I don't have the right load capacity for the new tire, but again why would the diameter be different than the other tires?
Does the number of ply have anything to do with this?

And where would I pick up the appropriate tire in a pinch, 1-2 day notice. We are in San Francisco and will be heading south on 101 or 5. 

Thank you!
 
Why is the same rated tire a different size?

What is the "different size" that you refer to?  You began by saying that "Tire rating is LT225/75R16 M/S on all the tires."

M/S = Mud & Snow. That plus All Terrain means a more aggressive tread. There may be a tiny difference in overall diameter due to the tread design, but your problem may be the difference in the tread pattern if the spare is not the same M/S design. "wonking back and forth" is not exactly a detailed technical analysis, though, so I'm guessing. It's possible that spare has a defect as well, e.g. tread separation that becomes noticeable as you speed up. Chances are a spare is an old tire, maybe so old that it is failing structurally inside. What is the tire date code on it (stamped on sidewall at the end of the DOT numbers).

LT 225/75R16 tires should be readily available - it's a common size.

Does the number of ply have anything to do with this?

No. The "ply rating" is not the actual number of plys in the tire and it is a load (weight capacity)  indicator, not size difference.

The ideal solution would be to move one of the front tires to the rear in place of the spare and buy two new and matching tires for the front. That way the rear axle tires all match, and so do the front axle tires. More expensive, though.
 

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