Rear suspension help

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zell66

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Feb 12, 2018
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We took a family trip to Door County this past weekend, And at almost every bridge we had the dreaded 5th hop.  I Am now thinking of installing airbags in the rear end to help with this.  I drive a 2008 Ford F350 SRW and pull a 2012 Sandpieper 365SAQ.
 

Gary RV_Wizard

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The first step is to determine whether the trailer balance is right or not. The hitch pin should be carrying 20-25% of the loaded trailer weight to insure best towing manners.  Next question is whether the pin weight, plus passengers and gear, equals or exceeds the truck's payload. If the truck is at max load or overloaded, poor ride is just one inevitable result.

Some people find that an air-cushion pin box, e.g. the Trail Air, helps.
http://www.adventurerv.net/ultra-fab-trailair-air-ride-5th-wheel-king-pin-box-fabex-730-rbw-7019-p-14227.html
 

Broke Boater

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No experience to your question, but I can tell you that I added airbags to my Ram 1 ton Dually. With the camper on, the ride is way nicer with some air in the bags getting some the load off the overloads. Your situation sounds different, but the airbags are awesome in case you have them in mind anyways,,,gregg
 

grashley

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As Gary suggested, get the loaded rig weighed and see where you are at.  Weight adjustments (moving the load around in the FW) may be all you need.  Also, crawl under the truck and give the rear springs a visual inspection.  Any cracked or bent springs?
 

steveblonde

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the hitch weight on that trailer is over 2000lbs now add hitch 200lbs and you and family? my guess is you are at your limits of the truck. adding bags will  help level out your truck but will also make the ride a lot stiffer and more bumpy
 
S

sightseers

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airbags are a wonderful,  they are the preferred suspension of large trucks.

Airbags are a load adjustable suspension unlike a spring suspension, so they actually ride a lot better...(the reason Lincoln, Mercedes and other limousines have air suspension)

When I air up my motorhome airbags it does not ride stiffer or harder...... and it sways a lot less.

IMO, Good airbags and good shocks are well worth the money.
 

steveblonde

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sightseers said:
airbags are a wonderful,  they are the preferred suspension of large trucks.

Airbags are a load adjustable suspension unlike a spring suspension, so they actually ride a lot better...(the reason Lincoln, Mercedes and other limousines have air suspension)

When I air up my motorhome airbags it does not ride stiffer or harder...... and it sways a lot less.

IMO, Good airbags and good shocks are well worth the money.

An air ride system as in a large truck ,ie semi. And air bags used on a pickup truck with leaf springs are a completly different setup and you cant compare the two . Bags used on a pickup are secondary ASSIST not the primary suspension. I sell thousands of air bags a year for pickups and semis on my pickup and all 6 pickups before the airbags stiffen up the ride as if you added another leaf
 

zell66

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ok weighted truck today

Truck with 2 people and full tank  8,996#  (2008 F-350 SRW Crew Cab 4x4)
trailer weight #14,020  (sandpiper 365SAQ)
Pin Weight 2,760#

According to ford Pin weight range is 15 to 25% of trailer weight =  2,370 to 3,950# which I am well within.

With no trailer it is a stiff ride so would airbags help with the 5th wheel bounce?

 

grashley

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I assume the weights are calculated correctly, and the weights are for the loaded truck without the FW attached.  Trailer wt includes pin wt.

If so, the loaded truck with the FW is 9,000# + 2760# = 11,760#, or just over GVWR of 11,400 (reg bed) or 11,500 (long bed).

Your GCWR is 9,000# + 14,000# = 23,000#.  If you have a diesel or the 6.8L with the 4.30 rear end, you are fine.

The pin wt is 19.7% of FW weight.

https://www.ford-trucks.com/specs/2008-2/2008-ford-f-series-super-duty-specifications/

Your load is well balanced, with a pin wt right at 20%.  You are slightly over GVWR, but 300 - 400 lbs should not be a big issue.  Assuming you have the diesel or 6.8L gasser,  your GCWR is acceptable as well.

The ride in a F350 IS stiff, but better with a load, like the FW.  Unfortunately, I have no experience with the air bags.  I find my ride stiff, but acceptable. (F350 Diesel)
 
S

sightseers

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steveblonde said:
An air ride system as in a large truck ,ie semi. And air bags used on a pickup truck with leaf springs are a completly different setup and you cant compare the two . Bags used on a pickup are secondary ASSIST not the primary suspension. I sell thousands of air bags a year for pickups and semis on my pickup and all 6 pickups before the airbags stiffen up the ride as if you added another leaf

yes, you likely sell overload air springs like the Firestone ones.

a true 4 link airbag only suspension is a really smooth ride and it allows you to raise or lower the vehicle,  I did one on my 72 Chevy C10 shortbed.

many high end cars, Lincoln town cars and Mercedes 500 series are air bag only, no spring suspensions with auto level. many higher end motorhomes are air ride and auto level.  As you probably know it's much nicer ride than a spring suspension.

on my motorhome I run about 75 psi in my Firestone bags it does not change the ride or height of the rig but if I let the air all the way out it sways a lot more.
 

steveblonde

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sightseers said:
yes, you likely sell overload air springs like the Firestone ones.

a true 4 link airbag only suspension is a really smooth ride and it allows you to raise or lower the vehicle,  I did one on my 72 Chevy C10 shortbed.

many high end cars, Lincoln town cars and Mercedes 500 series are air bag only, no spring suspensions with auto level. many higher end motorhomes are air ride and auto level.  As you probably know it's much nicer ride than a spring suspension.

on my motorhome I run about 75 psi in my Firestone bags it does not change the ride or height of the rig but if I let the air all the way out it sways a lot more.

This is correct ( i work for International truck Hd Parts ) in this case adding bags will stiffen up the ride more than what he has like Grid says its already stiff - adding bags is cheap even with the on board compessor and controls its under $1000 and is a huge plus to any person towing of the last 7 trucks ive owned ive had them on 6 the only one i havent is my current dually, and that will probably change one day when im bored.

In this case though i say yes put them in you will not regret it just run them at 45-55 lbs when towing ang 5-8 when not - remember to always make sure you have a min 5 lbs in tge bags at all times or they will rip
 

zell66

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grashley said:
I assume the weights are calculated correctly, and the weights are for the loaded truck without the FW attached.  Trailer wt includes pin wt.

If so, the loaded truck with the FW is 9,000# + 2760# = 11,760#, or just over GVWR of 11,400 (reg bed) or 11,500 (long bed).

Your GCWR is 9,000# + 14,000# = 23,000#.  If you have a diesel or the 6.8L with the 4.30 rear end, you are fine.

The pin wt is 19.7% of FW weight.

https://www.ford-trucks.com/specs/2008-2/2008-ford-f-series-super-duty-specifications/

Your load is well balanced, with a pin wt right at 20%.  You are slightly over GVWR, but 300 - 400 lbs should not be a big issue.  Assuming you have the diesel or 6.8L gasser,  your GCWR is acceptable as well.

The ride in a F350 IS stiff, but better with a load, like the FW.  Unfortunately, I have no experience with the air bags.  I find my ride stiff, but acceptable. (F350 Diesel)



I have the 6.4L diesel
 

zell66

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Feb 12, 2018
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SeilerBird said:
I think your tire pressure is not correct. Too much air. Probably inflated to the maximum stated on the sidewall.

Tire pressure is set correctly.
 

SpencerPJ

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Many of the smart ones have chimed in,  ;) 
So here's one from the dumb one.  How fast you driving?  :eek:
 

edjunior

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YES, the air bags will help with the 5th wheel hop.  It may not rid it entirely, especially on concrete highways (think Houston).  But it will help.  When I take off for a trip and go through any part of Houston, I air mine up to around 60 - 75 psi.  It greatly reduces the bouncing and hop from the 5th wheel.  When I get clear of the concrete roads, I back the psi down to usually around 35 - 45 psi. 

Air bags do help this.  I put them on my previous truck, and on this one.  I highly recommend the wireless remote compressor for on-the-fly adjustment without wires and tubes and stuff run through your cab.

Also make sure your shocks are in good shape.  This helps also.  But the airbags will make a huge difference.
 

zell66

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Feb 12, 2018
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spencerpj said:
Many of the smart ones have chimed in,  ;) 
So here's one from the dumb one.  How fast you driving?  :eek:

65mph on interstate and 55 to 60 on hwys.
 
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