6K axles to 7K axles

[BB_TX]

Been sitting here thinking. DW says I should not do that without proper supervision, but she is not here right now. This not something I have any intention of doing. Just curious.

Have read here (not lately) and other RV sites about someone wanting to replace their 5,200 lb axles with 6K or 7K axles. Or replacing 6K axles with 7K axles. But is that really a good idea? On the surface the immediate thought is the heavier duty the better. But trailer axles are made with a built in camber (bend or bow) that makes the center higher and the ends slanted slightly downward when installed. That makes the tires tilt slightly outward at the top until the trailer weight is lowered onto the axles. Then the axles would flex enough that, in theory, the tires would then be vertical spreading the weight across the full width of the thread.

But if the new axles were rated for much higher weight than the OEM axles, would those new axles flex enough to get the tires back to vertical? Or would they still be slightly tilted putting more weight on the outer edges of the tires and result in more/faster wear along that outer edge?

OK, that has made my little brain tired. Now I will dump it on you.

[JABURKHOLDER]

Too many variables. Camber, castor, frame capacity, axle flex, tires, etc. Made my brain hurt just reading about this.

[prndl]

Don't get mad and I know its your money but....
You have been on 6K axles since 2007. Have you bent them? Is the arch now flat from overloading your trailer?
If you have put several hundred thousand miles on the trailer then the current axles have done their job. If you don't pull many miles then why bother.
The actual "camber" or arch in the axle is not to allow deflection and flatten out from weight, it is to help the trailer track when being towed.

[BB_TX]

As far as the flex, I was assuming this information was correct.

http://blog.easternmarine.com/traile...its-all-about/

https://www.etrailer.com/question-154877.html

https://itstillruns.com/trailer-axle...s-7256328.html

And as I mentioned, I have no plans to change the axles. I have relatively low miles and don't load heavy.

[prndl]

All your links are correct.
However, if you were to put 6000# to each axle and if that weight would cause the axles to deflect to a 0Deg camber that would put your GVW at 15000# which is about 1000# over your rated weight per the factory brochure.
My Montana (almost identical weight capacity as yours) is sitting in my RV pad at the house with all the weight it will carry when we take to the road including full fresh water and the axles are still bent upward in the middle. It would take a lot of extra baggage to deflect our axles to a flat or 0Deg camber.
I have overloaded my HF 1500# folding utility trailer and bent the axle to a positive camber.

[cw3jason]

your GVWR is based the weakest link on your suspension to include tire ratings. If you increase your suspension, you can effectively increase your GVWR, although I do not know why you would want to unless you were continuously overloaded. Also I doubt you could get anyone to change the sticker on your trailer to show the new GVWR so it would be like adding springs or airbags to a 3/4 ton truck and calling it a 1 ton. in theory you would be correct, but getting it certified is another matter. As far as alignment, you can get the alignment fixed at a repair shop to fix the toe and camber.

[BB_TX]

All good information. But still the basic question. By installing an axle rated for a heavier weight than the OEM axle, wouldn’t the higher weight rated axle be too stiff to flex enough to get to the correct camber for the tires to sit correctly on the pavement for even wear? Particularly since most people probably do not load up to the full GVWR anyway? 3000-4000+ lb CCC (depending on model) is a lot of stuff. Full fresh water tank would only be about 600 lbs.

I am guessing the heavier units already come with 7K axles.

[cw3jason]

Yes, the heavier Montanas come with 7000lbs axles. My answer to your original question is you can have an axle shop align the new axle properly by bending it.

[Dave W]

You get into more then just changing axles if your 5er has 5200/6000 pound axles. To do the switch and to do it correctly, you have to look at everything below the frame rails - starting with hangers, equalizers, bolts, springs, shackles, 8 lug brake drum assemblies and 8 lug wheels and possibly tires. Not exactly cost effective on a 11-12 year old 5er

Instead of going with 7K axles, a new set of 6K springs with maybe an extra leaf if you feel that you need more capacity. If your 5er has 5.2K suspension, install the 6K outer hub bearings.

Of course, if you really feel the need to break the wallet open, a full independent suspension would be the best bet.

[Theunz]

As much as we who work on own stuff badmouth engineers, they do serve a purpose

[Texan]

Just because you install a heavier axle does not change the gvwr of the trailer. When i had sob i had 6,000# axles and an 10'' frame. The Montanas have 7,000# axles and 12'' frames.The DRV Mobile Suites have 8,000# axles and 15'' frames. Sure your axles would be stronger moving up the scale but there is more than just axles that help carry the weight. It's easy to get a false sense of safety going to heavier axles. The old adage 'If it ain't broke, Don't fix it might apply here.

[WeBeFulltime]

Sorry, but I've got to agree with your DW. You've got ENTIRELY too much free time on your hands!

[mtheo]

I hate to jump into this but I did bend the axle/axles on my 2007 3000RK when I hit a big bump in the highway. Mine had 5200# axles which keystone had change on the same model made months after mine to 6000#. After talking to a Dexter rep. I went to 7000#axles. Brakes were already same as those with the 7000# axles. Didn't change spring because trailer was leave and was not over loaded. I still had same load rating, just now got rid of a weak link. Put a lot of mile in the coming year with no tire wear problems. Cost $138 per axle and 4 hours labor ($00.).

[Dave W]

Originally Posted by mtheo

I hate to jump into this but I did bend the axle/axles on my 2007 3000RK when I hit a big bump in the highway. Mine had 5200# axles which keystone had change on the same model made months after mine to 6000#. After talking to a Dexter rep. I went to 7000#axles. Brakes were already same as those with the 7000# axles. Didn't change spring because trailer was leave and was not over loaded. I still had same load rating, just now got rid of a weak link. Put a lot of mile in the coming year with no tire wear problems. Cost $138 per axle and 4 hours labor ($00.).

I agree that the 12x2 brakes are the same, 5.2K - 7K but the hub/bearings are different/bigger plus 6 lug vs 8 lug.

[BB_TX]

Originally Posted by WeBeFulltime

Sorry, but I've got to agree with your DW. You've got ENTIRELY too much free time on your hands!

Yeah, that happens when she leaves me unattended.

[uhftx]

If the axles are only supported by the springs and attached to the frame. They are only supported nearest the end of the centerline. I doubt if the center arch or straight axle would make much difference.
The whole support system for the axle is only 10 inches from the end point and only some opposing force should be deflected to the center of axle, so long as the the circumference of the metal and integerity remains intact. Springs , hangers and hardware will weaken prior to axle failure. Unless there is a defect in the metal.

[mtheo]

Originally Posted by Dave W

I agree that the 12x2 brakes are the same, 5.2K - 7K but the hub/bearings are different/bigger plus 6 lug vs 8 lug.

No, on the 2007 everything is the same as the larger rigs, same rims and and same brakes. 8 lug rims, but in those days they still had 80# rims.