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Old 12-03-2012, 05:58 PM   #1
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Why two axles vs dual wheel axles?

I was kind of curious why with fifth wheel and travel trailers why they use two axles vs just one but we dual wheels. It seems like this could lesson more issues since you dont have to worry about the two axles in line.
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Old 12-03-2012, 06:21 PM   #2
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Quote:
Originally Posted by adehaan86 View Post
I was kind of curious why with fifth wheel and travel trailers why they use two axles vs just one but we dual wheels. It seems like this could lesson more issues since you dont have to worry about the two axles in line.
When Newmar was still building 5th wheels they used dual axles wth dual wheels on their larger/heavier rigs.
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Old 12-03-2012, 06:55 PM   #3
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Compare the frames on trailers with these configurations. The trailer is already (in most cases) as wide as law allows,so dual wheels require a narrower frame than single wheels. That narrower frame requires stronger axles because the spring locator is farther from the centerline of tire contact point. Not saying it is a bad design, just more expensive to make.
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Old 12-03-2012, 06:59 PM   #4
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Compare the frames on trailers with these configurations. The trailer is already (in most cases) as wide as law allows,so dual wheels require a narrower frame than single wheels. That narrower frame requires stronger axles because the spring locator is farther from the centerline of tire contact point. Not saying it is a bad design, just more expensive to make.
That's a good answer.
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Old 12-03-2012, 06:59 PM   #5
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Two axles = four brakes...........one axle with four tires = two brakes
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Old 12-03-2012, 07:20 PM   #6
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Just guessing here, but I think two axles distribute the weight over a larger area. I would think a heavy FW with a single axle would have to have an incredibly strong frame. As I recall, Newmar put duallies on the front axle, and singles on the rear axle, similar to what you see on a big diesel pusher that has a tag axle. Those Newmars were also very heavy in comparison to most other FWs then on the market. I suspect some engineer decided their six tire arrangement was better than having three axles with single wheels, especially during tight turns. On the other hand, I don't think there are any other mfgrs. that copies Newmar's arrangement. For example, two other biggies, NuWa and Mobile Suites, still use triple axles so that says something to me about their effectiveness.
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Old 12-04-2012, 08:51 AM   #7
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just guessing two
but could it be as simple as a better ride with two axles...
(That's what most bus/rv companies used to say about tag axles...)

I know the trucks rear bounces like HECK when going over speed bumps, but the trailer seems to just climb up and over with little jostling...
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Old 12-04-2012, 10:13 AM   #8
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Some good observations above. I will add one more observation. Odd as it may seem, backing up a single axle trailer is more difficult IMHO. The first TT I had was a 19' Nomad single axle. The tendency to turn is different. I found the double axle much easier and more stable to back into a site.
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Old 12-04-2012, 11:23 AM   #9
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When Newmar used the dual wheels, they still used dual axles. They used this configuration rather than triple axle single wheel setup. This was used on their Mountain Aire and Kountry Aire 5th Wheel model which were the heavier models.

Their theory was (don't shoot the messenger here) that there would be less strain and scrubbing on the tires when turning with the dual, dually setup than a triple axle with single wheel configuration.

At least that is what a Newmar Rep explained to me.
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Old 12-22-2012, 10:11 AM   #10
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Additionally, those dual axle Newmars only had a 3000 pound payload. Not great for full timers.
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Old 12-22-2012, 04:12 PM   #11
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the more axles better the ride. the more axles the worst the tire wear. more axles more braking.
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Old 12-22-2012, 07:01 PM   #12
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I was kind of curious why with fifth wheel and travel trailers why they use two axles vs just one but we dual wheels. It seems like this could lesson more issues since you dont have to worry about the two axles in line.
I suggest you look at the load tables. You will see that in dual application two tires do not carry the same load as two tires in single application.

Better solution is to demand larger tires (increased capacity) and maybe even US made (better quality?) LT type on any RV you purchase.
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Old 12-22-2012, 08:25 PM   #13
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Anyone consider what the axle size would have to be to equal 2x6000 axles? What about 2x7000, or 2x8000? And the balance on it would be a nightmare towing at 10 to 14000lbs.
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Old 12-22-2012, 08:53 PM   #14
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The more axles the more braking capacity/less hitch weight/greater towing stability/less pounding the tow vehicle/less pounding the trailer.

Just a lightweight 8k-9k trailer would have to have a 8k-9k axle. Axles that size and larger require 19.5" to 22.5" tires and wheels. That puts the trailers floor height and total height even higher.
Balancing a load for proper bumper or 5th wheel pin weight percentage would be nitemare for engineers and for the trailer owners to keep up with.

I think the RV industry has already thought the issue through.
Having pulled single axle implement trailers (12k) a few times on short local runs, I certainly wouldn't want a single axle RV..... unless its a 8'-12' shorty.
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