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Old 01-04-2010, 10:07 AM   #1
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Overslung vs Underslung axles

I'm considering switching from an overslung axle to an underslung axle to gain a few inches of clearance.

I was wondering if any of you that have done this have noticed any change in handling.



Thank you
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Old 01-04-2010, 10:41 AM   #2
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Without a doubt "flipping the axles" is the best mod we've done to the Tweety. Not only do we not drag going around switchbacks and coming out of the driveway, but it seems to feel even more stable towing. The underside is now more level with the underside of the truck, where before it was noticably lower than the truck. And I swear I even feel it less when a semi passes us. (although Steve doesn't notice that difference)
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Old 01-04-2010, 02:01 PM   #3
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The idea that the bottom of the tow vehicle and the trailer line up is interesting. Thank you for your insight.
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Old 01-07-2010, 05:41 PM   #4
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Underslung

Norm,
I believe you are using the terms "overslung and underslung" backwards.
There once was a car brand called "American Underslung", and I seem to remember they bragged about how easy exit and entry was because the vehicle was so low, - and yes, the axles were placed on top of the semi elliptic leaf springs. It was the springs that were slung under the axles.
Working from memory here, and that is always risky in my case.
Roar
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Old 06-26-2010, 01:52 PM   #5
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I looked at flipping the axles but went a different route. I got a Dexter K71-448-00 Heavy Duty Suspension Kit. It has a 4" equalizer (vs 2") and greesable shackles and pins with bronze bushings. This will raise the trailer 1" which will get me out of 99% of my problems. I also added 4" skid wheels in place of the skid bars. This will take care of the last 1%. Lots of ways to fix this problem, this one worked for me.
Steve

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Old 06-27-2010, 09:43 PM   #6
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Quote:
Originally Posted by Honda03842 View Post
I'm considering switching from an overslung axle to an underslung axle to gain a few inches of clearance.

I was wondering if any of you that have done this have noticed any change in handling.


Thank you
Norm

Are you still going to be using the Honda CRV as the TV?

4" more wind drag up top on a TV of that size is a larger % of power loss felt inside then on larger TV's.

We have had many here on SOC that did the flip and had good results. But their TV may have been a bit larger then yours. The science says the extra height will create an effect. How much you can feel depends on the TV you are starting with. Some cannot find it while others may. Do you have any idea how much extra power you had extra when pulling the original Sunline? You will be taping into that reserve what ever it was and the extra weight of your upgrades plays some in there too. But the wind drag can be worse then the added weight.

Ideal world is the bottom of the TT is at the same height as the bottom of the TV and the top of the TT is at the top of the TV with no open truck bed in the middle. That ideal most times never happnes. Closest would be a PU, a Hi Lo or a Trail Mannor.

John
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Old 06-28-2010, 05:17 AM   #7
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John,

I agree that increasing the frontal area of the trailer is a negative for towing. The new trailer has a frontal area about 12% larger than our original trailer. Your are correct, this is a concern and is probably more important than weight. This probably requires 25% more horsepower then the original Sunline for the same speed.

Due to the extra length we have increased the road clearence by 2 inches and may add another inch by moving up one tire size.

Do you have any thoughts about the effect of increased length? Our overall length has increased from 32 feet to 40 feet.

We initially plan to use the same tow vehicle. However, the Honda is now 6 years old and is approaching 150,000 miles, not a lot for a Honda but certainly a new tow vehicle is on our mind. We'd like to get one of the CRV diesels for improved mileage and towing capacity.

Equally we could drop our speed from 55 mph to 50 mph and reduce the frontal area effect.

Just another thing to keep me awake on this project, the fun of it all.
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Old 06-28-2010, 06:04 AM   #8
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John,

In doing my calculations I neglected to add in the things I added to the roof of our Sunline that will not be on our new roof. To get extra head room in our Sunline's shower I added a plastic bubble to the roof; as well I added two solar panels. As a result it appears that the New trailer will have 8% larger frontal area, still a concern but not as severe.
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Old 06-28-2010, 08:35 AM   #9
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I wonder what good a deflector on the TV would do?... Like the ones you see on Tractor Trailer rigs...
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Old 07-09-2010, 06:30 AM   #10
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I also consider the flipping of my units axels to be among the best of our modifications. The additional clearance has been very welcome when exiting service stations and in rougher parks. We may have seen a fraction of a mile lost in mileage but not sure because conditions are always different.

We recently changed TVs from a hemi Durango to a Ram 2500 Diesel 2wd. The undercarriage clearance is very similar. The cap we have makes the transition from TV to the unit very gradual and it hits the slopped portion of the frontal area.
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