can you run a 16" wheel with a 15" wheel on the same axle.

[80Ram]

I have a 25' AS twin axles. I put 16" wheels on, but haven't yet changed the spare out to a 16". I read where you can run on three wheels if needed. My question is, can you run a 16" wheel and a 15" wheel on the same axle without damaging it?

[Bgibbs]

You should be fine. Go easy at first to make sure there are no surprises.

[BayouBiker]

At a reduced speed in an emergency you can get away with what you describe but not without some perhaps unnoticeable stress and damage due to misalignment of the suspension geometry. Most or all of the damage would be to the tires. You can easily mitigate this with a larger aspect ratio and wider tread tire on the spare so that the diameters better align. If you are asking if I would stay with what you have? I would get a spare that matches at least the diameter and has sufficient load rating.

[dznf0g]

It's fine for an emergency spare. I used my 15 inch spare 3 times after I got my 16s put on. After they aged out, I got a steel 16 and kept the best old tire.
I only used the 15 spare to get to the nearest shop each time. It's less stress than running on 3, which is perfectly acceptable.

[brick1]

Why not buy the correct size spare?

[21Airstream]

Are the outside diameters of the tires close? I would think that would be the only possible issue. (I’m not an engineer though.)

[r carl]

It would be like running 1 wheel 10psi less than the others.

[turk123]

Originally Posted by brick1

Why not buy the correct size spare?

and a 16" steel rim to save money!

[dhroberts]

Originally Posted by 80Ram

I have a 25' AS twin axles. I put 16" wheels on, but haven't yet changed the spare out to a 16". I read where you can run on three wheels if needed. My question is, can you run a 16" wheel and a 15" wheel on the same axle without damaging it?

Interesting question. Unless the cost of a 16" wheel and tire is a serious limitation, why take the chance???

[dznf0g]

Originally Posted by dhroberts

Interesting question. Unless the cost of a 16" wheel and tire is a serious limitation, why take the chance???

What chance????? We have independent suspension, so there is NO change in camber. The 16" on the side with the 15"er will be carrying more load than if both were 16" wheels, but less load than running on 3 wheels, which is perfectly acceptable.
If one wants to rotate 5 wheels, or use the spare for extended driving, then I would agree. But if the mission is to get to the nearest shop, it isn't a problem. I'm all for doing thins right, but why waste money?

[dhroberts]

On a recent trip, my rig experienced two flat tires simultaneously. One flat was due to a large metal stud piercing the tire; the second flat was due to the rubber inflation stem being split open apparently from a piece of flying debris associated with flat #1. Fortunately I was close to a Discount Tire location - purchased a new tire and had the inflation stem replaced on tire #2.

The lesson learned: travel with two spares and make certain that all inflation stems are metal (not rubber). Was originally going to get a low-priced steel wheel. I found a reasonably priced 16" wheel that matches my OEM wheels. Vendor: High Sky RV Parts.

[dhroberts]

Originally Posted by dznf0g

What chance????? We have independent suspension, so there is NO change in camber. The 16" on the side with the 15"er will be carrying more load than if both were 16" wheels, but less load than running on 3 wheels, which is perfectly acceptable.
If one wants to rotate 5 wheels, or use the spare for extended driving, then I would agree. But if the mission is to get to the nearest shop, it isn't a problem. I'm all for doing thins right, but why waste money?

Thanks for your comment. The 'chance' I referred to is associated to the risk clearly implied in the original post - if the writer wasn't thinking of risk (or chance), he wouldn't have posted the question? As you and others have pointed out, there are methods to use a 15" spare with the other wheels being 16". That said, I don't believe any of writers of the posts are suggesting that there is zero risk of using one 15" wheel with three 16" wheels. One consideration given the very rural / remote areas in which many of us travel - how many miles will one need to drive on that 15" spare? There in-lies chance.

[rwnash]

Ram,

I would not worry about it. However if you are still concerned, you might want to determine the outside diameters - either with a tape measure or check the manufacturer's information. (It has been a few years, but I think the tire makers used to specify a revolutions/mile figure.) I would not be concerned about towing with a difference of up to 10% for a few thousand miles - let alone a hundred or two to get a repair.

Whit Nash

[azflycaster]

My trailer (used) came with 16" wheels and a 15" spare. I bought a new wheel and tire to have a closer match. The 16" wheel and tire did not initially fit in the tire carrier under the trailer. With a little bit of adjustment with a big hammer, it now fits very nicely.

[Silver.Sanctuary]

Originally Posted by 80Ram

I have a 25' AS twin axles. I put 16" wheels on, but haven't yet changed the spare out to a 16". I read where you can run on three wheels if needed. My question is, can you run a 16" wheel and a 15" wheel on the same axle without damaging it?

If the bolt pattern fits and the rollilng radius is the same.

[MSL]

Originally Posted by 80Ram

I have a 25' AS twin axles. I put 16" wheels on, but haven't yet changed the spare out to a 16". I read where you can run on three wheels if needed. My question is, can you run a 16" wheel and a 15" wheel on the same axle without damaging it?

I would think the biggest concern, if there is one, would be when breaking; if similar breaking is applied, which you would think it would, the tires would be fighting each other a bit ... maybe cause some tire wear. When not breaking, doesn't seem like it would be a big deal; it's not like two wheels on a car where they're connected by a transmission or differential.

[dznf0g]

Originally Posted by MSL

I would think the biggest concern, if there is one, would be when breaking; if similar breaking is applied, which you would think it would, the tires would be fighting each other a bit ... maybe cause some tire wear. When not breaking, doesn't seem like it would be a big deal; it's not like two wheels on a car where they're connected by a transmission or differential.

This could be true, about the braking. I never drive normal speeds while on a spare, for several reasons. And brake lightly and early. But again, if one is only getting to a repair establishment, tire wear , if any, would be negligible. They're not fighting each other. The smaller one could conceivably lock up earlier, due to less footprint pressure with the pavement. But it's a spare, an old spare, so I dont care. Never had it happen anyway.

[Trowbridge]

It's not like a car or truck where wheels turning as slightly different RPMs put stress onto a common differential. But if the OD of the tires are significantly different your Airstream is going to be effectively resting on one axle mount on the affected side during part of the up-and-down movement on the road. Should be fine but is not a good long term solution. If you do long-distance expeditions with your Airstream where tows would be for extended lengths, it would be wiser just to fork over the small amount. For my OCD, having one different sized wheel/tire seems unnecessary.

[switz]

Tire size comparison
16" Michelin LT225/75R16/E LTX M/S2 tire is rated 2,680 pounds @ 80 psi and 29.2" diameter

15" Michelin LTX (P) 235/75R15 XL tire is rated 2,183 pounds @ 50 psi - derated to 1,985 pounds and 28.9" diameter

15" GYM ST225/75R15D tire is rated 2,540 pounds @ 65 psi and 28.3” diameter

15" GYE ST225/75R15 tire is rated 2,830 pounds @ 80 psi and 28.3" diameter

14" GYM ST215/75R14C tire is rated 1,870 pounds @ 50 psi and 26.7" diameter

So the difference in diameter of the 16" Michelin and the stock 15" GYM or GYE is 0.9 inch or just under a half inch in radius. Used a 16" crescent wrench handle to "adjust" the spare tire carrier arms outwards enough for the 16" tire and wheel to fit. The biggest challenge was that the 16" tire cross section was slightly wider than the GYM cross section, but it still worked.

When we shifted our 2015 23D from the stock 14" GYM to 15" Michelins, the change in diameter was 2.2" which is significant. We built a custom spare tire bracket for a steel wheel and 15" Michelin tire.

I replace all five tires when the tires age out as milage is never the issue. What good is a rotten by age spare?

[dznf0g]

"I replace all five tires when the tires age out as milage is never the issue. What good is a rotten by age spare?"

Not much for a permanent replacement. Again, I advocate only for a run to the first convenient repair establishment. Even at the end of the old spare's life, it is 10 years old, may have seen zero to 100 miles in it's last 5 years and hasn't seen sunlight for 5 years. I have noted ZERO nasty looking issues with the spare, which is now 7 or 8 years old. Yes, I know about the inside of the carcass, but come on!

If one is rotating 5 tires out, or doesn't want to replace the flat back on the trailer, by all means, spend the money for a matching wheel and 5 new tires each time it is time,. but not me. Spending in excess of $350 - $400 now and another $240 or so (considering Michelin) every 5 years is unnecessary. I like spending money on the AS as much as the next guy, but I'll spend when it is necessary.