How much difference is ok on rear R/L rear tire diameters?

[PalmSprings]

Please,only feedback from those that have actually done this and have real life experience with it.
How many of you have run different ,1/2 inch or less, tire diameters on one side vs the other on the rear without any known damage ?

Im guessing that 1/2 inch is probably okay,but mine will be less
Any actual experience out there?
How many miles was run thar way?
Mine RV is a Rexhal ford chassis/drivetrain

[doc]

Are you speaking of duals side by side?

[PalmSprings]

oh yea, duals

[Alan_Hepburn]

Originally Posted by PalmSprings

oh yea, duals

Again - are you trying to run different size duals on the right vs. the left side of the vehicle, or trying to run different size tires on the duals on one side of the vehicle?

If you're putting different size tires on a single set of duals then the larger tire will carry the majority of the weight, possibly to the point of being overloaded. While 1/2" diameter may not be a lot I would try to match the duals as closely as possible to prevent any loading issues.

[Norm4015]

Originally Posted by PalmSprings

Please,only feedback from those that have actually done this and have real life experience with it.
How many of you have run different ,1/2 inch or less, tire diameters on one side vs the other on the rear without any known damage ?

I can't answer because I have never done it and I don't know anyone who has. Sorry.

[Tha_Rooster]

If both tires are smaller on one side that means it's spinning faster than the other side no good. If one tire is smaller on the same side no good, bigger one will carry more weight and try to roll at different speeds. In other words I see no good either way.

[Rick Long]

If your talking about different size tires on each side.... Yes I did it back when I was in the service and couldn't afford a new tire... little did I know.. the rear end I tore up ended up costing a whole lot more than the tire I should have replaced.

[doc]

When we had trucks back years ago, we tried to match the by side tires as close as possible. I have seen new re-caps we ran on the trailer be different heights when they came back from the shop. Mixing a new and old tire was a pretty much surefire recipe for a blowout with the loads we hauled. Add 90 - 100 degree temps here in South and get ready to have problems. Match the side by side tires as close as possible. A half inch is a big difference running maximum loads ( and many times over if the scales were closed)

[Craig_R]

My experience with truck tires has always been that two tires set up as a dual wheel rotating on the same spindle should always be very close to the same diameter for the same reasons that Alan pointed out above. If one tire is 40" in diameter and the one next to it is 41" in diameter, even though they may look close, the 41" tire is going to carry all of the weight. It will almost be as though the 40" tire isn't even there. Eventually the 41" tire will overheat and blow out possibly destroying some key parts of your RV in the process. Duals should always be as closely matched as possible.

[rvjimmy]

If one tire is bigger than the other it will make the smaller one to wear out because they don't spin at the same speed. We see this all the time on the trucks when a tire goes bad on the road and they don't match the tires. Keep them as close as you can I mean real close if you want them to last.

[PalmSprings]

Im not doing this on my RV,I was just curious.

Ive mixed tires before with 1/4 inch difference and no pb. Well then maYBE i never put enough miles on them either.
Yes I can see the points mentioned already,neverthe less i was curious from those with experiwence of the larger tire diameter differences .

[Gary RVRoamer]

The circumference of the tire changes as the diameter increases - the formula is C = 3.14*D, so a 0.5" increase in the diameter equals a 1.57" increase in the circumference of the tires on one side. That means one end of the axle has to continually turn faster than the other, which puts huge continuous stresses on the rear differential.

The tire industry recommends no more than 1/4" diameter variation in tires used as duals. That applies to two tires paired on one end of the axle, or the sets of tires on either end of the axle. Here is one reference on the subject:
http://www.retread.org/?page=DualWheelPositions

[JimM68]

What Gary said. but the diff might be able to take it.

That same difference on 2 tires on the same side of the axle, tires locked together that must rotate at the same speed?

1000 revolutions of a 40 inch tire covers 10,466.66 feet.
1000 revolutions of a 41 inch tire covers 10,728.33 feet, 261 feet less.

So you're basically DRAGGING one of the tires two hundred sixty one feet every 2 miles you drive.

Not sure which one is going to win, I think the bigger one.

I replaced a blown outer dual (26k miles on it) with an identical spare that had never been on the road before.
The inner dual lasted a day, about 300 miles, before suffering a violent tread separation

[Mr_D]

Originally Posted by JimM68

What Gary said. but the diff might be able to take it.

That same difference on 2 tires on the same side of the axle, tires locked together that must rotate at the same speed?

1000 revolutions of a 40 inch tire covers 10,466.66 feet.
1000 revolutions of a 41 inch tire covers 10,728.33 feet, 261 feet less.

So you're basically DRAGGING one of the tires two hundred sixty one feet every 2 miles you drive.

Not sure which one is going to win, I think the bigger one.

I replaced a blown outer dual (26k miles on it) with an identical spare that had never been on the road before.
The inner dual lasted a day, about 300 miles, before suffering a violent tread separation

Yep, bigger one will "win". It's carrying most of the load and dragging the smaller one along. Larger tire will probably blow out due to the overloading condition, if not then ther smaller tire will wear faster,