Freightliner Airbag replaced. Now not level

[fairway2002]

I had a front airbag go bad. Started leaking and would not air up. Replaced (very easy) and now that side is 1.5 inches lower. There is only one leveling valve on front. Do I sim or replace other side? 6 days, 150 miles out of warranty. They are $300 a pop.

Thanks

[carringb]

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.

[Ivylog]

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

[fairway2002]

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

[wolfe10]

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]

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.

[fairway2002]

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.

[Big_Katuna]

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.

[Ivylog]

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.

[fairway2002]

wolfe10 wrote:

Ivylog wrote:
Side to side is controlled by the 2 rear ride height valves. Adjust the rear one on that side.

Correct. So, how is left/right ride height in back?

Back is perfect.

[wolfe10]

Ivylog wrote:
Side to side is controlled by the 2 rear ride height valves. Adjust the rear one on that side.

Correct. So, how is left/right ride height in back?

[Bill_Satellite]

MrWizard wrote:
i'm only guessing
but the New one maybe stiffer, the old may stretch more when inflated with the same pressure
i think i would replace the other old one with a new one, keep it for an emg spare

I just did exactly this. ^^^^^^^^^^ I blew a hole in a front air bag and I know they are at least 9-10 years old so I wanted them to be the same. I have the old one in a bay as an emergency spare.

[Ivylog]

Side to side is controlled by the 2 rear ride height valves. Adjust the rear one on that side.

[fcooper]

Since you have a Freightliner chassis, give the helpdesk a call. It's free. They will need the last 6 digits of your vin number.

1-800-FTL-HELP

They were very helpful to me on several problems.

Fred

[MrWizard]

i'm only guessing
but the New one maybe stiffer, the old may stretch more when inflated with the same pressure
i think i would replace the other old one with a new one, keep it for an emg spare