Air Bags

[AATA]

I was reading a Mack Truck Forum about putting air bags on dual rear axle suspensions and most, if not all the members over there said the trucks they owned or have owned with air bags were horrible off-road. This was in regards to traction and getting struck, rather than ride quality. These were all dump trucks, waste haulers, etc.

Their reason is when the tire hits a bump and compresses the airbags, it takes longer for each air bag to release, thus putting more pressure on the other axle/tire and digging in. I thought it was an interesting perspective, so I wondered if anyone here has experience this before. They did say the walking beam style air bag suspension solves this issue. Like this....http://www.hendrickson-intl.com/products/product_detail/ar2.asp

They also mentioned it limits the travel, so it doesn't sound like air bags are great for off-road? Any input would be appreciated?

Thank you!

 

[Wyowanderer]

I have a set on my '84 Ford F-150. I use them for leveling, and they work great for that. I can't imagine they'd be much use as a lift, and I wouldn't use them to raise the working load of the rear axle, since the brakes. axles, and wheel bearings need to match the load as well.
They're a hell of a lot easier to install than helper springs, and I've had mine on for over ten years with only the cheap air brake fittings and hoses that come with the kit to complain about. I'd say they're the best mod I've ever made to the truck.
I haven't experienced anything negative as far as being stuck, but I try REALLY hard not to get stuck in the first place, so I may not be the best person to ask.
For me, the bottom line is that they're great when they're used for their intended purpose; leveling. Stick to that, and you'll be fine.

 

[bob91yj]

Comparing a tandem axle air bag suspension to a pick up trucks air bags is apples/oranges.

Take a look at military vehicles, see what the run.

Just saw this thread, I'll bet he has some answers for you.

http://www.expeditionportal.com/forum/showthread.php?t=57506

 

[Jim K in PA]

Check out the Air-rock from ORO - it is an extremely competent setup, although a bit too complicated for my tastes. Air springs can make for a very competent off-road and on-road suspension system.

If we are talking about replacing the coil (or leaf + adding control arms) with an air spring, then there is no reason it should not perform just the same as a steel spring. I have read about some systems where the air springs were tied together via an air line. BAD IDEA! For off road run a seperate line/channel to each spring, and monitor the pressures.

My Jeep LJ will have a pair of Goodyear air springs in the rear. They will be shielded to avoid contact with rocks and such. The air springs will allow me to compensate for the substantial swing in rear axle load between fully loaded trips and general daily driving loads.

 

[bluejeep]

Adjusting for varying loads = great
adjusting for leveling side to side if camping = great

I remember reading somewhere (but have slept since then, so where it was is gone) that their spring rate is not 'progressive', so ride quality can be less than desired.

I use them on my trailer (haul my TJ with it) and love it cause I air down when empty, air up when loaded - smooth as silk either way.

Good point on the plumbing - keep side to side isolated either with separate lines or a 1/4 turn valve. Lessens the lean around corners.

 

[Deleted member 9101]

Take a look at military vehicles, see what the run.

The military runs springs because they are more reliable and cheaper than air bags and require no maintenance.

 

[Jim K in PA]

I remember reading somewhere (but have slept since then, so where it was is gone) that their spring rate is not 'progressive', so ride quality can be less than desired.

If you choose the right spring and use it within it's designed load range both in terms of height and weight, it is quite progressive and will not cause the ride to deteriorate with increased load and pressure. Using the largest bag you can for the application and the lowest pressure (within the spec) you can to support the load will achieve the desired result.

 

[bob91yj]

You guys are missing the fact that he is running a TANDEM rear axle (two rear axles) ORO/pick up truck air bags need not apply. Click on the link the OP posted.

 

[AATA]

You guys are missing the fact that he is running a TANDEM rear axle (two rear axles) ORO/pick up truck air bags need not apply. Click on the link the OP posted.

Thank you for clearing that up for me Bob. Congrats on your Baja wins too! We ride down to Bay of San Francisquito each year and camp at a friends compound. I'm sure we saw you go by.

I've done a lot more research on some of the heavy truck forums and Steel Soldiers and here's what I found.

From what I've read, air bags aren't as stable on the heavier trucks and have a tendency to lean more. This may not be an issue with a lighter expedition vehicle (lighter than say a dump truck loaded). I guess dump truck drivers dump the bags before unloading to prevent roll overs, which doesn't sound very stable. Some say you get used to the body roll, but I can see how it would be unsettling in such a large vehicle. With the 3 and 4 point mounting systems, the cabins seem to roll a lot already. It might be exagerated with air bags, but I don't have any experience to back this up. There is also the maintenance issue with the air bags, but a point was made that it's a lot easier to replace an airbag than a spring. I also feel the loads I'm talking about would be well under the capacity of air bags. One of the most important aspect of tandem suspension is to have a walking beam. This evenly distributes the load between axles rather than putting uneven pressure on each axle.

With that said, here's the 3 I've narrowed it down to.

The Frieghtliner Tuff Trac http://www.freightlinertrucks.com/trucks/featured-components/axles-suspension.aspx Has a rubber bushing for vibration and a spring. The spring can be customized to the load of the vehicle. Not a walking beam, but the spring is on a pivot that acts like a walking beam. from the pictures I found, the Oshkosh HEMTT vehicles have a similar looking system, but without the rubber bushing.

Chalmers http://www.chalmerssuspensions.ca/products/800-50.htm Seems to have a lot of moving parts, but also has a lot of advantages. No leaf springs or air bags to replace (has rubber springs that they say are indestructible) Minimum maintenance - no grease or oil needed and full freedom of articulation - both parallel and diagonal

This one seems very simple and gets good reviews. Has high articulation, minimal parts and very heavy duty. http://www.hendrickson-intl.com/products/product_detail/hn_fr.asp

It has air bags, but I also like this one. http://www.raydanmfg.com/?page=products&ProductId=32 I guess these are used by the Canadian military


Anyone have any experience with these? Maybe some military experience with the HEMTT?

Thank you!

 

[AATA]

I just found this so I decided to add it. Looks expensive, but the only independent system I found other than the Tak-4 used on military vehicles. http://www.timoneygroup.com/offroad/off_road.htm#