Freightliner Airbag replaced. Now not level

fairway2002 wrote:
So, how is left/right ride height in back?
Back is perfect.

Now you’ve gotten my attention. The area of the new bag is smaller than the original...they did not replace with the correct air bag.

Ivylog wrote:

fairway2002 wrote:
So, how is left/right ride height in back?
Back is perfect.

Now you’ve gotten my attention. The area of the new bag is smaller than the original...they did not replace with the correct air bag.

That’s what I was guessing too. Rear valves put the correct amount of air in, bag is taller.

Replacing other bag will probably result in the front being too high or rear being too low.

Big Katuna wrote:

Ivylog wrote:

fairway2002 wrote:
So, how is left/right ride height in back?
Back is perfect.

Now you’ve gotten my attention. The area of the new bag is smaller than the original...they did not replace with the correct air bag.

That’s what I was guessing too. Rear valves put the correct amount of air in, bag is taller.

Replacing other bag will probably result in the front being too high or rear being too low.

They would be me. It was the same bag. Same numbers same manufacture (Firestone).
Im thinking they stretch over time. Thinking rear has nothing to do with it. Rear was level before and after.

Yup. Diameters don't match. Either replace the other side, or switch to a 2-channel valve setup, so each side will be leveled independent. Independent control will reduce body roll as well, since air won't transfer when weight transfers in turns.

No question if you supply bags of different sizes with the same air pressure, do not assume they will be the same height.

Absolutely, all air bags on an axle must match.

carringb wrote:
Yup. Diameters don't match. Either replace the other side, or switch to a 2-channel valve setup, so each side will be leveled independent. Independent control will reduce body roll as well, since air won't transfer when weight transfers in turns.

This is interesting. Explain a little more. If I have 100lbs (this is just a value for conversation) in each bag with a single valve. How does a 100lbs in each bag with two valves help role? I trouble shoot electronics so I see things different
Thanks

Each bag will have different pressure from the different ride height valves.

fairway2002 wrote:

carringb wrote:
Yup. Diameters don't match. Either replace the other side, or switch to a 2-channel valve setup, so each side will be leveled independent. Independent control will reduce body roll as well, since air won't transfer when weight transfers in turns.

This is interesting. Explain a little more. If I have 100lbs (this is just a value for conversation) in each bag with a single valve. How does a 100lbs in each bag with two valves help role? I trouble shoot electronics so I see things different
Thanks

When you have a single valve, both bags maintain 100 psi all the time, however the volume changes. Say you are taking a right-hand curve.... The weight transfer of the motorhome will apply more load to the left side bag. Since it still has 100 psi overall, if will compress the same amount that the opposite airbags extends.

With independent airbags controls, the left airbag won't compress as much, because the air pressure in the airbag will go up proportionally to the added load, making it behave like a progressive spring. Fast acting valves can even add and release air continuously, further helping the coach maintain a level ride around corners.

The downside to independent controls, is the same increase in roll stiffness, will also creating a stiffer ride over surfaces with lateral unevenness, such as a diagonal speed bump, or turning into a sharp driveway. But if the rear suspension already has high roll stiffness, then you may not ever notice. Also, if the coach cannot resist torsional forces well, the added front roll stiffness may cause the coach to twist more.