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Old 08-30-2019, 10:11 AM   #1
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BO SwayPro Tuning and Ride Hgt

Hi, I'm new to the Airstream life. Could use some advise on my towing setup. There are two issues: "porpoising" and dragging sway bars on pavement. Here are the details. TV is a 2015 Ford F150 FX super crew 5.5' 3.5L, BO Sway Pro with 750# spring bars, and 9 hole drop receiver (using holes 6 and 8). RV is 2017 19' Airstream FC. I closely followed the BO instructions. The AS trailer measures 18-1/2" level at coupler height. The F150 measures 19-1/2" to top of hitch ball. The sway bar chains are set at the 9th chain length. I followed advise on this forum, and mfg instructions, about setting sway bar chains on/off with trailer jack extended. It's very difficult to get that 9th link engaged. Connected vehicles are level. The drop receiver and sway bars are typically 6-3/4" clearance from pavement.
Assuming I have the correct setup, I think that further tuning and possibly adding Bilstein 4600 shocks could resolve the porpoising. Not sure I can do anything to improve ground clearance on dragging sway bars. Any advise would be much appreciated.
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Old 08-30-2019, 06:50 PM   #2
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Porposing is a factor of the BOSP flexible connection between the TV and the coach. It's not a bad thing. Stiffer dampening on the tow vehicle helps. The common suggestion is to increase the spring bar preload or gvo to a higher rate bar, but there is a limit to the value of that solution.

The ninth link from the loose end is tight and certainly a good starting point for tuning.

Other considerations -

What is your loaded for travel tongue weight? More weight on the tongue is more weight for the spring bars to control. An accurate tongue weight gives you a base line for a reference.

How is the trailer and TV gear loaded? If you can move heavy items over or slightly in front of the trailer axle and only load light bulky in the ends, you will reduce the tendency of the coach to pitch up and down over bumps. It also helps to run with the tanks located behind the axle empty. A single axle trailer is a great teeter totter. Anything you can do to reduce that tendency helps.

Dragging the spring bars is one of the short falls with the BO. Ground clearance is somewhat limited by the design. It you crank in a bit more preload, that raises the bar. But, it's only a good idea if you need the associated weight distribution.

The hitch shank clearance can be increased by using a shank that hangs no lower than necessary. Helps also to use a shank that minimizes the distance the ball is located behind the bumper. A closer pin hole is often required. If your hitch shank hangs too low, you can replace it with one that does not or remove part of the excess if the structure allows.

Just checked ours and we have a bit more clearance with the 9th link from the loose end engaged. You might try one more link, but a trip to the CAT scale to get your axle load weights is advised first, so you can determine the impact of small adjustments as you make them. Part of hitch tuning is hard numbers, but there is also an element of subjective personal analysis required to judge how the rig rides and handles.

The other factor is the Tow Vehicle hitch receiver. It should be stiff, but if it flexes, it's part of the problem.

Understand your frustration, but tuning your hitch lashup can help. A tow rig is a combination of many elements, including your driving style. We had a section of road in the Sacramento Delta that undulated so muchs so much it could not be traveled at much above 25-30 mph. Sometimes you just have to slow down. Pat
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Old 08-30-2019, 06:58 PM   #3
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Iíll let others speak to the tuning but with my BO hitch with 1000# bars and the same F150 as yours the porpoising did indeed reduce to a very great degree with Bilstein shocks. I think youíll want to do that no matter what.

A CAT scale is really what it took for me to get the BO adjustment right.
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Old 08-30-2019, 07:33 PM   #4
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Thanks much for the advice. I'll replace the shocks with Bilsteins and find a CAT scale to help with load balance. Also, will do measurements to verify TV (fender well to ground) and RV are indeed level.
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Old 08-30-2019, 07:37 PM   #5
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Porpoising is a problem with F150’s. I put a roadmaster suspension kit on my F150 and the ride is much more stable. If you are handy they are easy to install.

https://activesuspension.com/suspension-kits/
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Old 08-30-2019, 07:39 PM   #6
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Welcome aboard...👍

Do you have wheelhouse measurements, and or CAT tickets? Tongue weight?

Photo's would also help.
Shocks may very well lessen the problem, but 3 yr old shocks are not likely the cause.
The road construction and hitch set-up are the most common causes.

Bob
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Old 08-30-2019, 11:31 PM   #7
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I have a BOSP on a 2014 F250 pulling a 28', so not the same combo, but this is what I did to greatly improve clearance issues and improve towing:

Added Dexter Axle Lift Kit to raise trailer ride height 3". Obviously this also gives 3" of additional spring bar clearance.

Cut 1.5" off of the bottom of drop shank.

Drilled additional pin hole in receiver shank to bring coupler closer to TV, still leaving room to open tailgate when hitched.

The 28RB is a fairly nose heavy model, so I have 1500# bars using the 8th link.
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Old 08-31-2019, 01:33 AM   #8
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Quote:
Originally Posted by ROBERT CROSS View Post
Do you have wheelhouse measurements, and or CAT tickets? Tongue weight?

Photo's would also help.
Shocks may very well lessen the problem, but 3 yr old shocks are not likely the cause.
The road construction and hitch set-up are the most common causes.

Bob
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All I know is I towed my FC25 with a 2016 F150 Supercrew cab with 1850 of payload and max tow package and I cured the porpoising with airbags. With my new 2019 F150 (again with 1850 payload) with stock shocks the porpoising was unacceptable. I didnít want to take on the expense and complexity of airbags again so I tried Bilsteins. That too care of the problem. Used a Blue Ox on both setups with 1000# bars.
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Old 08-31-2019, 10:44 AM   #9
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MY advice would be to get the hitch adjusted properly before you start spending money on different shocks, and air bags. If your trunnion bars are dragging, obviously, they are too low. Height of the shank and ball and the tilt of the ball, and how much tension is on the trunnion bars are the items that determine where the bars are positioned.

The bars, when adjusted properly should be parallel with the "A" frame of the trailer. Find out what the total weight of the trailer is, and use a Sherline scale to measure the tongue weight, that should be 10 to 15% of the trailer weight.

It takes some experimentation to "tweak" a new hitch installation. Even with a Ford F-150 as a TV, you really shouldn't need to mess around with air bags, and heavier shocks....

Good luck, and keep us posted as to progress...

Larry
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Old 08-31-2019, 02:57 PM   #10
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Quote:
Originally Posted by Daquenzer View Post
Porpoising is a problem with F150ís. I put a roadmaster suspension kit on my F150 and the ride is much more stable. If you are handy they are easy to install.

https://activesuspension.com/suspension-kits/
I second the Roadmaster improvement on a F-150.
I did install it along with Bilstein shocks and it was a 100 percent improvement in the suspension.
Matter of fact I experimented with Airbags previous to that which turned into a disaster. Couldn't remove them fast enough. Following that I went with the Roadmaster.
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Old 08-31-2019, 02:58 PM   #11
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I'm using the BO with 1000# bars, F150 super crew cab, 6.5' bed. 2005 Safari 25, 850# tongue weight (Cat scale). No porpoising to speak of, stock suspension with FX off-road and max tow packages.

Coincidentally, my setup is on the 9th link from the loose end too. On level ground, I raise the TV and hitched AS with the tongue jack until the top of the closed tailgate is about even with my shoulder height (I'm 6'0"). I have very little trouble setting and releasing the 9th link when raised to this level.

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Old 08-31-2019, 08:17 PM   #12
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Originally Posted by Airhead59 View Post
I'm using the BO with 1000# bars, F150 super crew cab, 6.5' bed. 2005 Safari 25, 850# tongue weight (Cat scale). No porpoising to speak of, stock suspension with FX off-road and max tow packages.

Coincidentally, my setup is on the 9th link from the loose end too. On level ground, I raise the TV and hitched AS with the tongue jack until the top of the closed tailgate is about even with my shoulder height (I'm 6'0"). I have very little trouble setting and releasing the 9th link when raised to this level.

Happy Streamin'.
Makes sense the FX4 package would damp the porpoising as well. Thatís basically upgraded shocks along with skid plates under the truck.
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Old 09-01-2019, 09:04 AM   #13
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Originally Posted by daleyocum View Post
Iíll let others speak to the tuning but with my BO hitch with 1000# bars and the same F150 as yours the porpoising did indeed reduce to a very great degree with Bilstein shocks. I think youíll want to do that no matter what.

A CAT scale is really what it took for me to get the BO adjustment right.
Yes, at the end of last year it seemed porpoising was happening more frequently at different speeds even. We have a 2016 F150 Lariat, Supercrew and 6.5' box towing our 2016 27' Serenity. And the Blue Ox. Reading posts like you are doing now trying to decide on what might be causing it (concrete roads/joints, BO setup, shocks, etc), I decided on the Bilstein's for the rear replacements to see if that is all I needed. It was, at least so far, and have no porpoising issues this year. No other mods needed or made to our setup. Does the truck tow or drive without the trailer ride different with the Bilsteins? Not sure I notice.
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