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Old 07-22-2016, 07:47 PM   #1
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Infiniti QX 80 suspension

I am using a QX 80 to tow a FC 27FB with a Blue OX sway pro w/d hitch. The only issue i have is the TV seems to porpoise from front to back quite a bit. Has anyone else had this problem and resolved it? Thanks Gary
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Old 07-22-2016, 08:30 PM   #2
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Not sure if they make them for the Infiniti, but a set of firestone riderite airbags under the rear fixed the porpoising on my expedition
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Old 07-22-2016, 08:55 PM   #3
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We get a bit. I kind of expected the characteristic, because the BO is a design that uses a flexible spring to transfer weight and control sway. The TV to Coach connection is more like a hinge than a stiff bar, hence the bounce on some transitions. The TV does not slam the coach and the coach does not jar the TV, but your rear suspension should dampen it out quickly.

I have always considered this characteristic to be one of the advantages of the BO hitch design in that it was soft on the AS, as long as the movement is not excessive, which is of course a subjective analysis. Suggest you contact BO tech support and get their recommendations. Also suggest that you verify the TV receiver is rigid and does not flex. That would add to the motion.

And then the disclaimer - just because I think it is not a bad thing does not make it a good thing. Investigate and determine the reality for yourself. You may decide a force projection design is a better solution for your application.

Edit - there is some flexibility in tire side walls. It's another spring in the system. Low profile less. High profile more. Light Truck less. Run flat less. Standard passenger car tire more. May be a dead end, but a consideration.

Edit - if your hitch shank extends the ball behind the bumper, drilling a new hole to move the ball as close as possible reduces the lever on the TV and improves the suspension/sway control. If you have the H-beam shank, you will need to go to a solid shank to provide the material to drill an alt hole.


Travel safe. Pat
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Old 07-23-2016, 05:57 AM   #4
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Welcome Aboard....

Roads....seams in the pavement will sometimes cause it.

More common....too much or too little WD, tongue high or low. (TV & AS not level).

Bob
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Old 07-23-2016, 08:30 AM   #5
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Are the shock absorbers on the QX 80 worn.

Porpoising may be from not enough load transfer to the truck's front axle by the w.d. hitch. And there are limits what it can do. It's a half-ton vehicle; too much load behind the QX 80 rear axle, and/or too heavy hitch weight of the Airstream will put too much load on the truck's rear axle, more than the w.d. system can help.

Airstream warns 1,000 lbs hitch weight maximum in your Airstream Owners Manual, and your QX 80 will have a maximum load on the axles (GAWR) printed on a door sticker. Start by weighing the rig hitched up ready to go to see what you have on the truck's axles, if you haven't done so.

And as Bob says, some roads (segmented concrete) are lousy.
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Old 07-23-2016, 08:59 AM   #6
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I have the same suv. Sounds like you may not have enough weight distribution to re-load the front axel.

As a point of reference my front wheel well measures 36" unloaded, 37" with the hitch in ball but without weight distribution and I return it to 35 3/4 when weight distribution bars are applied.

I would notice a lot of "bouncing" and understeer otherwise (used to return the front axel to 36 1/2 but it wasn't enough weight transfer). Rides very well now. My tongue weight has been measured at 780lbs.
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Old 07-23-2016, 06:24 PM   #7
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Numbers

Payload of QX 80 is about 1650 lbs
Tow capacity 8500 lbs
Tongue weight about 825 lbs
AS 27FB rated at 7400 lbs fully loaded. I am running at about 6800 to 7000 lbs depending on water,gray and black tank levels
Both TV and TT are level. w/d hitch moved about 400lbs to the front.

Will try next travel day with less tension on the w/d bars
Thanks for the input, appreciate it. Gary
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Old 07-23-2016, 06:40 PM   #8
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Infiniti QX 80 suspension

You need more (not less) tension on the WD bars to transfer more weight to the front axel.

Make sure to check your measurements before / after applying weight distribution.

Also - read your driver door sticker for actual payload. Mine is less than 1,500lbs once fuel weight is taken into consideration.
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Old 07-23-2016, 06:49 PM   #9
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As long as you're out there, it would be good to just get one weighing at a CAT Scale and see what the truck's individual axles are actually carrying, as well the the trailer axles together. You may be able to move some load around in truck and trailer for better w.d. adjustment, and a much improved ride.

Does the QX 80 have auto leveling air bags?
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Old 07-23-2016, 08:04 PM   #10
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Infiniti QX 80 suspension

Yes the QX80 has rear air bags. When the tongue weight is loaded on the receiver they will recover about 1/2" - 3/4" of sag on the rear suspension. This recovery does not move any weight to the front. With the internal layout of the QX there isn't much you can do to distribute load other than to remove any non-driver related weight from behind the drivers seat.

That being said I often tow with driver + 6 passengers and dog without issue. The key for the QX to behave properly is proper weight distribution - especially with a tongue weight of 825lbs....

BTW golfer - how did you measure the fact that WD moved 400lbs to the front axel? That would likely be too much weight transfer on a dead tongue weight of 825.
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Old 07-24-2016, 05:44 AM   #11
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Question

Quote:
Originally Posted by wulfraat View Post
......
.....BTW golfer - how did you measure the fact that WD moved 400lbs to the front axel? That would likely be too much weight transfer on a dead tongue weight of 825.
^
X2
??

Being that some of that 825 is also moved the the trailer axle= not enough TW.

Bob
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