I installed Air-Lift air bags and rear Bilstein HD shocks and now I have poropising of the 5er when riding over expansion joints and dips between the highway and bridges and some road expansion joints as well. I removed the Timbrens because I didnt like the unloaded ride but I never experienced porpoising with the Timbrens. I need to know what my next step is, do I go for something like a RoadMaster or Helwig springs? I saw something that dampens the existing spring at the shackles, will this work? I am trying to control the unloaded ride as well as the loaded ride without porpoising.

Thanks,

Have you considered a different pin box for the 5th wheel? They aren't cheap (unless you find one used) but can make all the difference in the world.

A porpoise is usually an overweight tongue or pin cause the springs don't have the backbone they need.

I would go the way of SuperSprings, Hellwigs, etc but they still have a pre-load so you will be stiffer un-loaded. That I'm afraid is a fact of life.

Follow me on this. Most Cedar Creeks are over 2K pins and that is the magic number on a 3/4 ton. Near or certainly beyond 2K the rear droops too much. Airbags could help but they are not really meant for lifting weight beyond what the stock springs can do. Many do it with satisfactory results but it isn't really the correct way to solve the problem. Airbags are meant to support or level a load not lift it.

The Pin boxes might do porpoising but they are really for chucking and yes the price is up there.

I'm wondering if you have too much air in your bags. My 5ers have had certain types of joints and bumps they porpoise on, and not others. I don't have any bags or special pinboxes (although it would be interesting at times to have a specialty pinbox.).

Cedar Creeks tend to be pretty heavy on the pin unless you load to the rear more.

You mentioned something interesting, and I'm wondering if this might be the factor - you said you didn't like the ride of the Timbrens unloaded. If I remember correctly, you shouldn't even really engage your Timbrens unless you have pretty good load. If you hitting them unloaded, you really must be highly inflated. Again, if this is not correct, I apologize.

I'm wondering if you have too much air in your bags. My 5ers have had certain types of joints and bumps they porpoise on, and not others. I don't have any bags or special pinboxes (although it would be interesting at times to have a specialty pinbox.).

Cedar Creeks tend to be pretty heavy on the pin unless you load to the rear more.

You mentioned something interesting, and I'm wondering if this might be the factor - you said you didn't like the ride of the Timbrens unloaded. If I remember correctly, you shouldn't even really engage your Timbrens unless you have pretty good load. If you hitting them unloaded, you really must be highly inflated. Again, if this is not correct, I apologize.

I usually run the air bags at 45 psi when towing, I lowered it down to 25 psi and the porpoising diminished slightly. My Timbrens would normally sit approximately 1/2 inch off of the axle tube but when I would cross a speed bump or railroad track it would produce a violent snap back as the Timbren came in contact with the axle tube.

I run my bags at 30 lbs when towing. I found that when I ran 45 lbs in mine I would get porpoising. I would try and play around with the amount of air in the bags and see if you can find the sweet spot. Took me 4 trips to get mine where I like them.

All you need to do is adjust the air pressure in the air bags.

If I had to guess I would say you don't have enough air in the bags and are hitting the overload springs as the truck goes over the expansion joints (not enough air in the bags with a lot of pin weight) and then doing it again when the trailer goes over the joints-

Pump those bags up to 90 pounds and start working backwards in 10 pound increments until you start porpoising again at which point you know you went too low on air bag pressure.

I also feel it might be air in the bags related. Here are some simple steps to get to a very common base of starting and then fine tune the PSI.

- With no air in the bags and no extra load, take a measurement of your rear fender.

- Then add the air psi you use all the time and add the trailer/load. Take the rear fender measurement again.

What you are after is lets say your unloaded fender height is 45", you want to make sure you are not over 45" with air added in the bags and the trailer/load added to the truck. You want to have your suspension dropped into the springs about 1/2" +/-. Why? Because if you are over 45" then you are unloading the rear leaf springs and now using the bags more than assisting the leaf springs and you can see a bad ride reflection as in porpoising or the rear end tracking funny.

If you are sunk into the suspension alot with the air bags you can also feel porpoising but the rear will not feel as loose.

I would start by looking at the PSI and making sure you are within a good starting spot and after that depending on what you find I can suggest a couple more things to check.

Also I might add the reason you didn't feel this with the Timbrens was they are just a large bump stop and if the suspension can't move ...well there can not be porpoising.

Also, are you on stock size tires and not cranked up on the fron end? No rear added lift? Don't think you are but just making sure we are not over looking anything.

Keep us posted on what you find...

Thank you for all of your great advice. The truck and tires are bone stock with no cranking of the front end. I am starting to see that the problem is really coming from the excess air pressure. I did notice an improvement when I went from 45 psi to 25 psi. I will measure the static height and adjust from there. When I originally aired up the bags in excess of 45 psi, the trailer started to tail dive and the clearance between the bed rails and the RV was way too close for comfort. It sounds like I have some work to do but I will get it right with your help.

Has anyone had any luck with the Roadmaster Active Suspension product? It looks very interesting.

Thanks for all of your help

You might want to check your tire pressure too. When we got our trailer, I assumed I should run the rear tires at 80 p.s.i., but doing so wore the center of the tires out. Turns out that even with the trailer pin weight, I am 850 pounds under the axle maximum and over 1,000 pounds under the tire ratings.

You might want to check your tire pressure too. When we got our trailer, I assumed I should run the rear tires at 80 p.s.i., but doing so wore the center of the tires out. Turns out that even with the trailer pin weight, I am 850 pounds under the axle maximum and over 1,000 pounds under the tire ratings.

I do run my tire pressures between 75 to 80 lbs in the rear. I know that I am close to or slightly over my weight ratings on the rear wheels. I dont feel safe running lower air pressure. I also have a TPMS on the trailer and truck tires just to avoid any low pressure or high heat situations.

http://s219.photobucket.com/albums/cc64/racechaser1/air%20bags/?
I have posted pictures of the air bag installation if anyone can spot any irregularities. The pictures are taken with 10 psi in the bags and nothing in the bed except the super glide hitch which weighs around 200 lbs. I installed a tee in the air lines so both bags are equal pressures.
Thanks again

I am still playing with my air bags. So far I have come up with this. I have 6000 lbs on the rear axle and I run 35 psi in the bags. This gives me about 1/4 inch off the overloads. I still get a bit of porpoising, but I do hit a nasty section of road there too. I am going to try to bump the psi up another 5 on the next trip. I run level with 35psi in the bags and have cranked up the T-bars.

I usually run 80 to 110 psi in my bags with a 4000 lb pin weight an the ride is pretty smooth. a cushioned pin box or fith wheel hitch will make alot of difference if you think you are loaded heavy.

I run 90 pounds when I have toys in my trailer (less pin weight) and 100 pounds without toys (more pin weight) in my air bags but then my trailer is probably heavier than most- I get no porpoising and a great ride.

It is my belief (and I could certainly be wrong) that most porpoising is caused by the truck bouncing on and off the overload springs-

In a situation where your rear suspension loads enough to engage the overload springs you want to control the rebound with good shocks and have enough air in the bags to keep the suspension from cycling through another loading and un-loading of an event that is now 200 or more feet behind you.

Now I am no truck suspension guru but I know a little about adjusting suspension on motorcycles- If you pump your bags up enough you are in effect increasing your pre-load and your rebound. This will do two things- It will keep the back of your truck out of the overload springs more often but also when you do engage them the stroke won't be as deep and the truck will return to rest (normal position) sooner.

The great thing about the bags is you can play around with them until you get things just right- but I would start with more and not less air.

http://s219.photobucket.com/albums/cc64/racechaser1/air%20bags/?
I have posted pictures of the air bag installation if anyone can spot any irregularities. The pictures are taken with 10 psi in the bags and nothing in the bed except the super glide hitch which weighs around 200 lbs. I installed a tee in the air lines so both bags are equal pressures.
Thanks again

I think the jury may still be out on the "T" idea. Hitting a bump with one side would cause it to compress and send the pressure to the other side. Running two lines would make the pressure effect only the side hitting the bump, which is how the bag is supposed to operate - I think!? :confused:

I think the jury may still be out on the "T" idea. Hitting a bump with one side would cause it to compress and send the pressure to the other side. Running two lines would make the pressure effect only the side hitting the bump, which is how the bag is supposed to operate - I think!? :confused:


correct. worse case scenario is guys that run a t fitting and haul a camper.........

go around a corner too fast, and wow, the driver gets suprised.

My 2002 has the two-stage rear springs. First stage is the multiple pack, and the second stage is the single thick spring.
I tow a 12K 5ver with pin weight of 2-2.5k lbs.
If I air up >25 PSI, the first stage starts to disengage with second stage and I notice a little sway.
I usually run 18-20 PSI in bags which levels truck, keeps all springs engaged, and rides very well. Rear tires at 80 PSI when towing.

I'd take that T out of the line and run two separate lines. That should help stop any side to side rocking.

.....It is my belief (and I could certainly be wrong) that most porpoising is caused by the truck bouncing on and off the overload springs-

In a situation where your rear suspension loads enough to engage the overload springs you want to control the rebound with good shocks and have enough air in the bags to keep the suspension from cycling through another loading and un-loading of an event that is now 200 or more feet behind you.

Now I am no truck suspension guru but I know a little about adjusting suspension on motorcycles- If you pump your bags up enough you are in effect increasing your pre-load and your rebound. This will do two things- It will keep the back of your truck out of the overload springs more often but also when you do engage them the stroke won't be as deep and the truck will return to rest (normal position) sooner.

The great thing about the bags is you can play around with them until you get things just right- but I would start with more and not less air.
x2. I would also get rid of the T-fitting. If your worried about drilling a second hole, I put my airline valves on the same plate the 7 way connector is hanging in. Put some black caps on them and no one will even notice them.

I also feel it might be air in the bags related. Here are some simple steps to get to a very common base of starting and then fine tune the PSI.

- With no air in the bags and no extra load, take a measurement of your rear fender.

- Then add the air psi you use all the time and add the trailer/load. Take the rear fender measurement again.

What you are after is lets say your unloaded fender height is 45", you want to make sure you are not over 45" with air added in the bags and the trailer/load added to the truck. You want to have your suspension dropped into the springs about 1/2" +/-. Why? Because if you are over 45" then you are unloading the rear leaf springs and now using the bags more than assisting the leaf springs and you can see a bad ride reflection as in porpoising or the rear end tracking funny.

If you are sunk into the suspension alot with the air bags you can also feel porpoising but the rear will not feel as loose.

I would start by looking at the PSI and making sure you are within a good starting spot and after that depending on what you find I can suggest a couple more things to check.

Also I might add the reason you didn't feel this with the Timbrens was they are just a large bump stop and if the suspension can't move ...well there can not be porpoising.

Also, are you on stock size tires and not cranked up on the fron end? No rear added lift? Don't think you are but just making sure we are not over looking anything.

Keep us posted on what you find...

Nick,

Thank you for all of the good advice, I have taken some measurements and posted them in an excel file below. I think that you are on the right track with excess air in the bags. I took particular note of the distance between the spring pack and the overload spring. With excess air in the bags, it appears that I am supporting the load off of the overload springs and when I hit a bump, I am assuming that the overload spring kicks in hard. It took 75 psi in the bags to get any clearance on the rear overload spring pad To me, it seems that 10 psi (minimum recommended pressure) towing is what I want to try next, any comments will be appreciated.

Nick,

Thank you for all of the good advice, I have taken some measurements and posted them in an excel file below. I think that you are on the right track with excess air in the bags. I took particular note of the distance between the spring pack and the overload spring. With excess air in the bags, it appears that I am supporting the load off of the overload springs and when I hit a bump, I am assuming that the overload spring kicks in hard. It took 75 psi in the bags to get any clearance on the rear overload spring pad To me, it seems that 10 psi (minimum recommended pressure) towing is what I want to try next, any comments will be appreciated.


After looking at your spec's it looks like 40-50psi should have you in a good starting spot to do the final tweaks. Have you drove the truck with any different psi from before to see if any ride changed?

I looked back at your earlier post and it said you had been running 45psi. How is the trailers stance front to rear when hooked and that much psi? Front to rear level or noise high?

I looked back at your earlier post and it said you had been running 45psi. How is the trailers stance front to rear when hooked and that much psi? Front to rear level or noise high?

Also, when you add air bags and height, make sure you drop your pin box on your trailer 1 notch to get the weight distribution back onto your truck. I had similar issues when first using air bags back in '92 and that cured the problems you describe. Don't lower the hitch height if you can, but drop the pin box.

WoW!! I just purchased the Air Lift 5000s today and I had no idea what I was getting myself into!

Thanks for all of the information you guys are sharing with us newbies!!

The system will be installed next week in time for a 2000 mile trip the following week!! Hopefully by the time I get back I will have all of the bugs worked out. BUT at least now I have a place to start on how to adjust these things. Thank goodness I'm ordering the AirLeft Remote system so I can make all of these adjustments on the fly and from the driver's seat!! Also glad to have the presets as I sometimes tow with and without toys which should make a huge difference in pressures!!

Keep up the conversation so we can all keep learning!!

Thanks,

Nicholas Traub

I looked back at your earlier post and it said you had been running 45psi. How is the trailers stance front to rear when hooked and that much psi? Front to rear level or noise high?

Thanks again for all of the advice. I have been towing at 45 PSI and it was the worst porpoising experienced. At 25, it was better. The trailer definitely became nose high at 45 psi, At 25 psi it was slightly nose high but not too bad. I am afraid to lower my pin box height as the clearance between the bed rails and the 5er will become too tight. I am also afraid to raise my 5er axle height on the trailer because I am already 13 ft 3 inches on height and I just make it below some of the bridges in my area. The superglide hitch has no height adjustments so I am at a loss on how to lower the pin height. My thought was to lower the psi down to 10 in the bags which will take out the possibility of lifting the suspension too much and also lower my nose height on the 5er. Other than cranking the torsion bars on the truck to possibly lower the rear or adding Roadmaster Active Suspension, I am at a loss.

Thanks again for all of the advice. I have been towing at 45 PSI and it was the worst porpoising experienced. At 25, it was better. The trailer definitely became nose high at 45 psi, At 25 psi it was slightly nose high but not too bad. I am afraid to lower my pin box height as the clearance between the bed rails and the 5er will become too tight. I am also afraid to raise my 5er axle height on the trailer because I am already 13 ft 3 inches on height and I just make it below some of the bridges in my area. The superglide hitch has no height adjustments so I am at a loss on how to lower the pin height. My thought was to lower the psi down to 10 in the bags which will take out the possibility of lifting the suspension too much and also lower my nose height on the 5er. Other than cranking the torsion bars on the truck to possibly lower the rear or adding Roadmaster Active Suspension, I am at a loss.


I feel you are seeing a reflection of ride from the trailer not being level. The weight is not across the axles proper. You might need to lower the rear of the truck. I say this because your spec's on the truck make sense but the trailer is noise high and if it was not you should be looking pretty dialed for ride, maybe +/- alittle psi.

Whats the spec's on the trailer?
How long and how many axles, also when you say noise high what is the front to rear spec when you have 45psi in the bags?
Whats the space look like between your bed and the 5er?




Here is a side shoot of my set up and I run about 70psi in the bags depending on whats loaded in the toy hauler, and the trucks sits 3/4" lower than unloaded height when all hooked up. On the trailer I site about 1-2 higher in the front noise that the rear. The 5er is 40" so 1-2" between the front and rear is not bad and still ride great. After I had lifted the truck from the leveling kit I was all over the road and had to spend a weekend of about 4 hours changing positions on the pin box and what not to get her dialed in and now it's way better. I think it was about 5" high when I started and that was with out changing any major psi in the bags from what I started with back when the truck was just leveled on smaller tires.
http://www.norcaltruck.com/01_misc_pic/nicks_3500hd/truck_5er_side.JPG

I feel you are seeing a reflection of ride from the trailer not being level. The weight is not across the axles proper. You might need to lower the rear of the truck. I say this because your spec's on the truck make sense but the trailer is noise high and if it was not you should be looking pretty dialed for ride, maybe +/- alittle psi.

Whats the spec's on the trailer?
How long and how many axles, also when you say noise high what is the front to rear spec when you have 45psi in the bags?
Whats the space look like between your bed and the 5er?




Here is a side shoot of my set up and I run about 70psi in the bags depending on whats loaded in the toy hauler, and the trucks sits 3/4" lower than unloaded height when all hooked up. On the trailer I site about 1-2 higher in the front noise that the rear. The 5er is 40" so 1-2" between the front and rear is not bad and still ride great. After I had lifted the truck from the leveling kit I was all over the road and had to spend a weekend of about 4 hours changing positions on the pin box and what not to get her dialed in and now it's way better. I think it was about 5" high when I started and that was with out changing any major psi in the bags from what I started with back when the truck was just leveled on smaller tires.
http://www.norcaltruck.com/01_misc_pic/nicks_3500hd/truck_5er_side.JPG


Nick,

The trailer is 37.5 feet long with 2 axles. The clearance between the bed and the 5er is about 5 inches. At 45 psi in the bags, the nose was probably about 5 inches higher than the tail. The setup tows and handles great with no sway or tracking issues. The only problem that has developed is the porpoising since I changed from Timbrens to bags. Even towing nose high, I dont have any stability problems just the transfer of weight on the rear of the truck over road bumps and dips seems to overwhelm the suspension. I keep looking at stiffening up the rear springs as a cure... It would seem to me that even if I was level, the weight on the pin would still overwhelm the suspension. Am I correct or should I look to lower the rear of the truck? Next question is how to best accomplish that.

Thanks,
John

If the noise is up that high you are not putting the weight over each axle even. I also had my duallys back end porpoising when it was noise high. I think you have to at least know that the trailer vs. truck stance is correct before you can pin point the exact problem because it all add's up for the best results. You might be able to hide a problem with a mod but not sure myself how to get it to act better with out strutting out the rear end to be stiff and that's not the answer, if it was we would all have to be doing that. I feel the trailer noise needs to come down, going off what I found on my trailer and what I changed. Everything else is about the same of how we are set up.

if you could post a pic of your tow rig hooked to your 5er it may help get you a more definite answer. i dont know how much clearance you need between your trailer and the rails on your truck but i have 4 inches between mine and i have never got close to hitting them.

92181

92182

Here are some pics of the setup with the Timbrens installed. I was always a little nose high but the Timbrens produced no porpoising. I will be pretty close to this height when I lower the air bag psi. I have hit the bed rails with the 5er slightly on several occasions when going out of driveways etc. so I am afraid to get closer to my bed rails by lowering the pin box.

off topic, but lovely looking rig and trailer combo....

-Rob

looks like you have your ride height just about right. id try what norcal nick suggests an see how that works

Ok...so here is a really simple question!!

With all of the pressure recommendations, are those pressure suggestions with load or without load. I'm assuming that will make a difference?!?! A little clarification would be great before I start this same process next week!!

Thanks!!

air pressure should be checked LOADED.

I am certainly no expert on this issue, though I have towed 5th wheel rigs for a long time (always with a long box and DRW). That's a very nice looking rig — but it appears to be a short box. For me, that raises the question as to where the pin sits in relation to the rear axle. Directly above or behind. Whatever the case, the more truck that sits ahead of the pin (as with a long box), the less leverage the pin weight has to lift the front of the truck. If the pin sits behind the axle, it has leverage and a fulcrum to lift the front of the truck — especially if it gathers downward momentum due to insufficiently stiff springs. So, while the pin weight is a critical issue, where it sits is equally important. A weight within the GVWR of the truck that is placed incorrectly can have the effect of a much larger weight due to the leverage.

I am certainly no expert on this issue, though I have towed 5th wheel rigs for a long time (always with a long box and DRW). That's a very nice looking rig — but it appears to be a short box. For me, that raises the question as to where the pin sits in relation to the rear axle. Directly above or behind. Whatever the case, the more truck that sits ahead of the pin (as with a long box), the less leverage the pin weight has to lift the front of the truck. If the pin sits behind the axle, it has leverage and a fulcrum to lift the front of the truck — especially if it gathers downward momentum due to insufficiently stiff springs. So, while the pin weight is a critical issue, where it sits is equally important. A weight within the GVWR of the truck that is placed incorrectly can have the effect of a much larger weight due to the leverage.

yes it is a short box and the SuperGlide hitch sits direcltly over the rear axle per the installation instructions

If you listed I missed it- What is the pin weight of your trailer? Get is weighed if you haven't. Don't go by what the mfg. lists as that generally does not include options like an on board generator if you have one.

With a slide up front, only two axles and the length of your unit it would not be hard to have 3000 pounds of pin weight- especially if your generator is located in the front of your trailer. Also need to consider the location of the tanks and how full they are- They can certainly effect pin weight.

If you listed I missed it- What is the pin weight of your trailer? Get is weighed if you haven't. Don't go by what the mfg. lists as that generally does not include options like an on board generator if you have one.

With a slide up front, only two axles and the length of your unit it would not be hard to have 3000 pounds of pin weight- especially if your generator is located in the front of your trailer. Also need to consider the location of the tanks and how full they are- They can certainly effect pin weight.

The last time I weighed it I think I was about 2300 lbs on the pin. my generators are portable so it really isn't a major factor. I usually tow with empty tanks but have experienced the porpoising with both empty tanks all around and filled fresh water tanks as well.

With that kind of pin weight you are right about at the max for a 3/4 ton. Try what most of the gang says- less air in the bags. Then try really pumping the bags up and see what happens.

Report back to us and let us know what you learn.

Take that T out of the line and install some Frederico sway bars.

IMHO, you are towing a lot of 5er with a good amount of pin weight for a short box SRW truck. While I may be wrong, I believe that you don't have enough truck — though I don't know whether there is a suspension solution. It would be interesting to hear from anyone else who is towing this much pin weight on a 3/4 short box. BTW, the balance of the 5er also affects the equation. While you have 2K on the pin, it would be interesting to see what your 5er counter balances that with weight (how far) behind the rear axle of he 5er. Enough weight far out back can reduce the pin weight but act to set up an harmonic motion that acts to lift the rear of your truck like a see-saw. I have heard of trailers that had a severe design problem in this regard. Does your 5er have shocks?

IMHO, you are towing a lot of 5er with a good amount of pin weight for a short box SRW truck. While I may be wrong, I believe that you don't have enough truck — though I don't know whether there is a suspension solution. It would be interesting to hear from anyone else who is towing this much pin weight on a 3/4 short box. BTW, the balance of the 5er also affects the equation. While you have 2K on the pin, it would be interesting to see what your 5er counter balances that with weight (how far) behind the rear axle of he 5er. Enough weight far out back can reduce the pin weight but act to set up an harmonic motion that acts to lift the rear of your truck like a see-saw. I have heard of trailers that had a severe design problem in this regard. Does your 5er have shocks?
Yes, the Cedar Creek has shocks in the rear as well as equa flex on the spring equalizers and Mor Ryde on the pin box. I have no handling problems like sway, wandering or the tail wagging the dog, just the porpoising with the new air bags. I will tow this weekend with 10 psi and see what happens. If I really pump them up then I become nose high which isnt good either. I may wind up going back to the Timbrens as I had no porpoising with them.

Update: Towed over the weekend with 10psi in the bags, took out about 85% of the porpoising. It seems tolerable and worth the trade off for the comfortable ride while not towing as compared to the Timbrens.

I still might consider the Roadmaster Active Suspension, has anyone had any luck with this setup?

Update: Towed over the weekend with 10psi in the bags, took out about 85% of the porpoising. It seems tolerable and worth the trade off for the comfortable ride while not towing as compared to the Timbrens.

I still might consider the Roadmaster Active Suspension, has anyone had any luck with this setup?


I can't remember but what shocks are you running?

Bilstein HDs all around

You may need something with a slower rebound to control the bounce. The yellow shocks are very loose on rebound. Stiff on compression. Thats what we use on trucks when setting them up for the same use as you.

In regards to the "T" in the line, I put a needle valve in the line on one side of the tee. Once air is added I close the valve to stop the sway.
My .02

Gang...

Have a 2001 2500HD DMAX/Ali, 4x4 SBCC with the 22K SuperGlide. Stock Height. Tow a 36.8 ft Kountry Star (Newmar) 14,000lbs. I put Airlift's even before my first pull of the 5th as I was concerned at being to close to max touge/bed weight. Had a Nightmare on my 1st pull with Pourposing. Only had 10 lbs of air in the bags. I was level between truck and 5th (maybe up an inch on the nose of the 5th). Advertized nose weight of the 5th was 2600lbs plus the SuperGlide 350 lbs.

My Fix, Trashed the factory rear shocks and replaced with rancho 9000s adjustables, and removed the airbags. Turned the Rancho 9000s up to number 9. Replaced front shock with Bilsteins. No more pourposing.

After 100,000 miles, just replaced the Rancho 9000s with the new Rancho 9000 xls as the pourposing started again. Been fine ever since.

Added an additional 300lbs to the bed with a 21 gallon Natual Gas Fuel tank, and 180 lbs under the drivers seat (in the frame) for a Real Power 10k Generator that runs off the Alllison PTO gear.

Put the air Bags back in to support the extra weight and get off the Big Load spring. I have also replaced the Bilsteins on the front with the Ranch0 9000 xls and run the at #7.

In short, A SBCC Can pull a 14K 5th safey. Plenty of truck. Recommend the Rancho 9000 xls shock replacement before the air bags. Let the Truck ride on the Big Load Leaf when towning the 5th rather than trying to get off the big leaf (when loaded). GM made the load leaf to be used when loaded. You will also maintain the stability. They just use really poor shocks.

I install a lot of these air bags in my line of work. One tip when installing which will affect ride. Run two seperate lines to fill each bag seperately!
Do not run both bags to a t fitting then to one fill valve.
If your left rear tire hits a bump in the road it will compress the air bag and send that air pressure over to the other side of the truck causing that horrible rocking things the fith wheels do.

And if you guys are looking for crafty ways to hide your fill valves, Either behind your gas door, or remove your license plate, drill the holes out and use the valves and washers as license plate bolts. its virtually un-noticable.

racechaser1, what ever happened? Did you get it worked out?

I towed with minimal psi in the bags late last year and it was better. It seemed to quiet down if the overload springs remained in contact all of the time. I just installed Roadmaster active suspension and I am waiting to see how it tows this Spring. Thanks for the follow up, I will post again after towing.

Perfect, yes please do.

How far off was the PSI at the point you felt it better?

10 psi seemed to be the best

I am still playing with my fun bags.
:eek:

lol

WOW 10psi I would not of guessed that. Keep us posted.

WOW 10psi I would not of guessed that. Keep us posted.


It seems that when the bags would lift the truck off of the overload springs, I would get porpoising as the weight hit the springs and then rebounded until the load equalized. I am hopeful that the Roadmaster will tame that. Time will tell

It seems that when the bags would lift the truck off of the overload springs, I would get porpoising as the weight hit the springs and then rebounded until the load equalized. I am hopeful that the Roadmaster will tame that. Time will tell


Yea, I have seen this before many times. Keep us posted because info is great.

It seems that when the bags would lift the truck off of the overload springs, I would get porpoising as the weight hit the springs and then rebounded until the load equalized. I am hopeful that the Roadmaster will tame that. Time will tell

Got to keep the overload spring engaged to prevent stability problems and the porpoising action. Through trial and error I figured this out with my signature toy hauler. My PIN is probably a bit more than yours but set-ups are similar SB pullrite and such. It is a fine line between sag control/stability/porpoising when filling the air bags. Having a common fill on the bags will accent this action too.

Might consider looking at the Torklift Stableload product to engage the overload quicker.
http://www.torklift.com/p.php?w_page=stableload

We have the same camper for the most part. Minus any difference in options and personal effects. I have just a liitle porpoising depending on the road but not enough to caused a lot of concern. I have always blamed the tires for most of mine. See vehicle in signature. Our trucks are also not that different. I too am wondering if some of it is in the hitch height or pin box hight. I have a reese sliding hitch that is adjustable in height. I have been concidering air bags in mine just to smoth out the ride and keep it from bottoming out when hitting big bumps. Hope you get it worked out.

Hi Racechaser1,

I also have a Cedar Creek, and run airlifts. I had the porpoising problem too. I lowered my air pressure to 15-20 psi unloaded. The other thing I did was raise the trailer via the spring shackles, one hole. That gave me more box clearance, less pin weight, a much better ride, and it also allows the trailer shocks to work better because of a more vertical angle of the shocks .

I have Firestone airbags and I run 0 unloaded and 35 psi with my 5th wheel.

Racechaser1 & WellShooter,

Let me rephrase the comment I made in my last post about lowering my air pressure to 15-20 psi unloaded. What I meant to say was, I adjust it to 15-20 psi before I hitch up the trailer. When I'm not pulling the trailer I set at 5 psi as recommended by the manufacturer to keep from damaging the airbags.

Hi Racechaser1,

I also have a Cedar Creek, and run airlifts. I had the porpoising problem too. I lowered my air pressure to 15-20 psi unloaded. The other thing I did was raise the trailer via the spring shackles, one hole. That gave me more box clearance, less pin weight, a much better ride, and it also allows the trailer shocks to work better because of a more vertical angle of the shocks .


I would think it did get rid of the porposing but I also think it added pin weight. Be careful with your shocks. On some they have a range and often the range of travel is only 3" or so. If you have Monroe shocks they have specs on them and I think you can look up the specs at Monroe's website by going to the RV section.

I would think it did get rid of the porposing but I also think it added pin weight. Be careful with your shocks. On some they have a range and often the range of travel is only 3" or so. If you have Monroe shocks they have specs on them and I think you can look up the specs at Monroe's website by going to the RV section.

Coolbreeze,

I dropped the pinbox to compensate to for raising the trailer, which actually helped level the trailer. It now sits level on all tires when hitched.
I do have Monroe shocks but they were not the originals. It came with some Chinese's made junk that broke at the mounting stem because there wasn't enough movement in suspension vertically. I have new shock that have more travel now then the originals.

Hi Racechaser1,

I also have a Cedar Creek, and run airlifts. I had the porpoising problem too. I lowered my air pressure to 15-20 psi unloaded. The other thing I did was raise the trailer via the spring shackles, one hole. That gave me more box clearance, less pin weight, a much better ride, and it also allows the trailer shocks to work better because of a more vertical angle of the shocks .

Raven,
I was thinking that this would be my next move as the trailer is slightly nose high. Did you raise both the front and rear shackle position or just the rear up one notch? I wanted to try this but was afraid of increasing my overall height and hitting low bridges etc. I sit right now at 13 ft. 2 inches.

IMO the very first step to ride problems is to make sure the trailer is riding in a suspension neutral position. This means the trailer frame needs to be level or just a smidge front high (not able to eyeball this small of an amount) when hitched up and loaded for a normal trip.

Changing the spring eye position in the hanger will net about a ~2" height change. Move all spring eyes and equalizer to the same position or the suspension won't be in a neutral position. You may need to adjust PIN Box height after adjusting the hanger position. Pullrite makes a hitch spacer that is not widely known about that raises hitch 3"


http://i232.photobucket.com/albums/ee2/map_guy/Pullrite%20Superglide/4408_Lift_Install__9-30-081.jpg

My trailer originally had the wimpy Lippert Frame Spec'd chinese double stud shocks too. It rode too low for my signature truck with the spring eyes in the lowest (tallest) position. I did a spring over axle conversion -original wimpy shocks way to short so we retrofited Monroe RV shocks that are nearly as big as the shocks on our Dmaxs -trailer rides really nice without any type of cushioned PIN Box because the trailer is riding down the road using all the suspension unlike before the mods began. I travel on a lot of secondary, county and Forest roads to go dirt bike riding so a well riding trailer is mandatory due to conditions....My truck is not lifted or leveled either....

Really common for the NBS trucks to need the trailer raised/leveled in part due to the taller bed box wall height....

Raven,
I was thinking that this would be my next move as the trailer is slightly nose high. Did you raise both the front and rear shackle position or just the rear up one notch? I wanted to try this but was afraid of increasing my overall height and hitting low bridges etc. I sit right now at 13 ft. 2 inches.

Racechaser,

Actually you lower the spring eyes in the shackles. Both spring eyes, front and rear, and the equalizer. This effectively raises the trailer. It will raise the trailer height some what, but not more than 1 1/2". If your noise is high now you may want to hitch up first to see how level the trailer is before move the pinbox down. I would think moving the spring eyes and equalizer in your case maybe all you need. I also installed a wet bolt kit at the same time. Dropping the pinbox if necessary, is easier and cheaper then buying a riser from Pullrite.

Racechaser,

Actually you lower the spring eyes in the shackles. Both spring eyes, front and rear, and the equalizer. This effectively raises the trailer. It will raise the trailer height some what, but not more than 1 1/2". If your noise is high now you may want to hitch up first to see how level the trailer is before move the pinbox down. I would think moving the spring eyes and equalizer in your case maybe all you need. I also installed a wet bolt kit at the same time. Dropping the pinbox if necessary, is easier and cheaper then buying a riser from Pullrite.

Correct -lower the front/rear spring eyes and center equalizer to raise trailer. Measure the height difference between hanger holes -this is the exact change. Factory shocks will not work in the higher position -they will be too short. Depending on the length of the OEM shock Monroe might have a longer one available. If spring eyes/equalizer is already installed in the lowest hole -a spring over axle conversion maybe needed. If you are using the PIN box to lift nose for bed rail clearance -the suspension change may make very little difference in actual trailer height as nose is already up there...

It has been noted several times -but remember porposing will happen if the overload spring is not engaged fully. this allows a cycling of impact energy (porpoising). You trailer has many ride control features causing it to feel stable during towing but still allowing a minor towing stance set-up problem to accent an unwanted ride characteristic.

Anything you do before getting trailer level /suspension in neutral position is a band aid. Tandem axle trailers are less forgiving of the front to back leveling than a tri axle due to geometry. Having my PIN a full 1" higher than frame level makes my second axle suspension noticeably compressed limiting travel. 30' 14K Toyhauler. Trailer is not able to "float" on the suspension fully this way.....causing reactionary related towing quality problems. Yes it made towing on Idaho washboard gravel a real chore and why a spring over conversion and shock retro fit was done on my trailer to fix the issues related to towing a trailer that was not setup properly in a suspension neutral manner.

Good luck!

IMO the very first step to ride problems is to make sure the trailer is riding in a suspension neutral position. This means the trailer frame needs to be level or just a smidge front high (not able to eyeball this small of an amount) when hitched up and loaded for a normal trip.



I agree. If the trailer is not resting level and the suspension across both or all 3 axle included you will get some un-likable ride conditions.

I towed over the weekend to the Dover races and the Roadmaster Active Suspension had a tremendous impact on the overall driveability of the setup. The porpoising is all but gone except over the most extreme road bumps. The air bags are set loaded at 10 psi and the Roadmaster made the drive a pleasure again. Thanks for all of the help on the site.

Wow, what great information. I just bought a 2011 GMC SBCC this week. I will be pulling a 34' Heartland Elk Ridge and this is going to help me out a lot. I'm new to the diesel truck and to pulling a 5th wheel. God help anyone in my way :driver: