Your wheel may fall off

[Wrknrvr]

If you happen to see a tandem axle motor home it may have a single tire on the rear axle. Heck the wheel may just fall off.

I do RV service at a resort in Montana. I have counted up to 20 rigs sitting there at a time that have a single tire/wheel on the rear axle. With the wheel faced out just like the front rear axle.. So that means the brake drum is to the inside.

Provost coach bodies have the rear rear axle wheel faced like the front steer axle. With the axle wide enough to track in line with the front rear tire.

If you go to the Freightliner chassis web site you can see the rear wheels faced out with the drum on the inside.

 

Big 5 R You might stop one just to see for yourself. Tiffen, Monaco, Entega and maybe Foretravel run single outer wheels on some models.

I will take a better look this next week to see there are other makes with just one outer wheel.

 

I am pointing this out as some manufacturers do it every day. On a normal rear wheel assembly the bearings are probably 35 percent under the inner wheel with 65 percent of bearing support under the outer wheel.

The brake assembly has to be attached to the axle on the inside under the drum.

 

Now think about how much force is applied to the front wheel bearings. Max load all the time. Much smaller bearings . Now going down a steep grade and and do a hard turn.

 

That will take Peety3 or someone like him to figure out those forces.

 

Now if you are in a campground there maybe a Motorhome with a tandem axle the you could look at it in person

 

 

Yes I did have a flat and did have to stop and change the tire. That tire was less than 2 years old and about 8000 miles on it. So yes it can happen. I am near my tire weight rating capacity on both rear axles. Yes I have weighed the truck and al my stuff to ballence the load .

 

The rear of the bed is 15 ' from the back of the cab and still accommodates the jeep

If you have a flat on the steer axle you will need to stop and change that tire.

 

Now let's not drag this out to far..... If it gets to bad I will put inner tires and wheels on. Maybe even get another handle for this site.

 

Be nice, Vern

[Big5er]

Those MH's use axles made for 1 wheel for the additional axle, just like your front axle is made for one wheel. That axle is different than one designed for 2 wheels on each side. I see drop axles on dump trucks all day that are the same way....it's a different axle

By adding a 2nd axle, even one designed for only 1 wheel they increase the weight allowed from 20,000 lbs to 34,000lbs. A single rear axle can't carry enough weight for those heavy MI's.

[peety3]

Those MH's use axles made for 1 wheel for the additional axle, just like your front axle is made for one wheel. That axle is different than one designed for 2 wheels on each side. I see drop axles on dump trucks all day that are the same way....it's a different axle

By adding a 2nd axle, even one designed for only 1 wheel they increase the weight allowed from 20,000 lbs to 34,000lbs. A single rear axle can't carry enough weight for those heavy MI's.

I concur that those axles are made for 1 wheel use. On motorhomes, they're also set up to handle the load in excess of what the driven axle can handle...in other words, they're not loaded to 9,500 pounds.

 

Big5er, assuming a normal-width tire, isn't the tag axle limited to 10k if single tired? Still makes the tandem set good for either 27k (17k+10k) or 30k (20k axle rating + 10k tire-limited) though.

[rickeieio]

Time to stir the pot a little more....

 

So, if an axle is designed for duals, and you put on a super single, are you breaking the law in Texas?

 

Seriously, there are lots of tire sizes. Using what's commonly known as "floater" front tires on the rear would give you a foot print somewhere between duals and a regular single, plus have additional weight capacity. Of course that would also mean buying new rims, so not a cheap proposition.

 

There are solutions, and compromises, if you care to think outside the box.

 

As to the bearing loading, I seriously doubt you could exceed the design loads of your hub bearings without overloading your tires as well, even with the offset wheel position of a single tire.

[Big5er]

I concur that those axles are made for 1 wheel use. On motorhomes, they're also set up to handle the load in excess of what the driven axle can handle...in other words, they're not loaded to 9,500 pounds.

 

Big5er, assuming a normal-width tire, isn't the tag axle limited to 10k if single tired? Still makes the tandem set good for either 27k (17k+10k) or 30k (20k axle rating + 10k tire-limited) though.

Peety, the permissible weight table (used by the feds and "most" states) does not consider tires, only axles. You can do a web search and find it. A "tandem" is a 2 or 3 axle group under 8ft and it is allowed 34,000 lbs. Aftet 8ft you get into axle groups and "bridge" law. A single axle is allowed 20000 and a tandem 34000, so that means you could get 54000lbs, right? Not if your wheel base is 20ft or less. That's were the weight table comes is. It will show you the mathematical formula, and also shows you the allowable weights, already done for us stupid people who can't spell math.

 

Once you know the allowed Max weight, then you find the tire weight rating. The allowed weight is the one that is most restrictive.

[Big5er]

Rick a super single is not considered a single tire in my business. It replaces a tandem set of tires.

[Exile]

Rick a super single is not considered a single tire in my business. It replaces a tandem set of tires.

I understand that to be duals not tandems.

 

Henderson axles just say to check with them on axle rating, not that it is banned. So if the manufacturer says it is good, should hold up to scrutiny by any lawyer. Rated for use should be rated for use.

 

AXLE BEAM RATING — SINGLE OFFSET TIRES

The use of offset tires can affect the axle beam rating For applications where dual wheels are utilized or

an application that uses a zero offset single tire, the axle rating will not be affected However, the use of an outset or inset single tire does change the way in which the axle is loaded and therefore affects how the axle will be rated

Inset single tires move the point at which the axle is loaded inboard towards the center of the vehicle Using this type of wheel will not affect the axle beam rating, but can reduce bearing life

The use of a single outset tire configuration moves the load point out away from the center of the vehicle, which increases the bending load in the axle and also reduces bearing life

To determine the rating for an axle that uses inset or outset wheels, contact Hendrickson engineering for assistance

[Big5er]

I understand that to be duals not tandems.

Exile, thanks for correcting my "oops". I was replying from my cell which doesn't really like this forum so my concentration was elsewhere.