air bag driving height 8.5 inches

Topic: air bag driving height 8.5 inches (Read 922 times) previous topic - next topic

air bag driving height 8.5 inches

July 22, 2020, 12:10:42 pm

Called FT tech dept. and Ronnie says the traveling height is 8.5 inches. I'm a bit under that so will adjust up. Does anyone know how much you move the rod per inch of raising?
Thanks

Re: air bag driving height 8.5 inches

Reply #1 – July 22, 2020, 12:25:07 pm

Yes, ride height is 8.5" from top of top plate to bottom of bottom plate.

Adjustment is pretty simple. Park on dead level surface, air pressure up.

To raise ride height, make rod longer. In most cases it can be done with the rod lower attachment point bolt.

Re: air bag driving height 8.5 inches

Reply #2 – July 22, 2020, 12:37:30 pm

Quote from: dans96u295ft – July 22, 2020, 12:10:42 pm

Does anyone know how much you move the rod per inch of raising?

Adjustment is done by the time honored method called "Trial & Error".

Re: air bag driving height 8.5 inches

Reply #3 – July 22, 2020, 01:02:05 pm

I like trial but not errors!!! Any reason I can't go to 9 inches? with the lousy roads in Colorado I might save some damage being a bit over

Re: air bag driving height 8.5 inches

Reply #4 – July 22, 2020, 01:13:52 pm

Quote from: dans96u295ft – July 22, 2020, 01:02:05 pm

I like trial but not errors!!! Any reason I can't go to 9 inches? with the lousy roads in Colorado I might save some damage being a bit over

Two things come to mind. High ride height means a much stiffer ride which will transfer any hits right into the coach. And with the microscopically short driveshaft on pushers. It doesn't take long to put your drive line angle out of tolerance. This really puts a lot of stress on the u-joints and trans output shaft bearings.

Have you looked closely at your shock absorbers? If you have any oil on them. They are likely dead. This was the case on our coach. Four of the eight shocks were toast. Every bump felt like a foot deep pot hole and sounded like the coach was coming apart. After new shocks. Much better ride and the bumps and such are not sounding like the suspension is bottoming out.

Re: air bag driving height 8.5 inches

Reply #5 – July 22, 2020, 02:22:02 pm

New Konis! so those are good!

Re: air bag driving height 8.5 inches

Reply #6 – July 22, 2020, 02:41:18 pm

Koni FSD's are the best. Koni adjustables probably second best (assuming they have been adjusted).

The PN is stamped on them-- easy to look up what you have on Koni-NA's website.

Re: air bag driving height 8.5 inches

Reply #7 – July 22, 2020, 02:42:35 pm

With air bags the actual spring rate does not change with ride height. Taller bus drives less accurate than a lower bus. CG to ground etc. The ride height is very critical to the U joint angles. Changing it 1/4 in up or down every year or 20k may help the u joints last. May not.

Re: air bag driving height 8.5 inches

Reply #8 – July 22, 2020, 04:21:42 pm

Quote from: Protech Racing – July 22, 2020, 02:42:35 pm

With air bags the actual spring rate does not change with ride height. Taller bus drives less accurate than a lower bus. CG to ground etc. The ride height is very critical to the U joint angles. Changing it 1/4 in up or down every year or 20k may help the u joints last. May not.

Are you sure about that? Seems the only way to change ride height without changing spring rate (due to higher air pressure) is with an adjustable airbag mounting location. But even then. There is the driveline issue that has us locked into a rather narrow ride height zone.

Found this in a FAQ area at an air ride company.
Q: Can I adjust the Spring Rate of my air springs along with the height?
A: Yes, but the Spring Rate will be directly connected with spring height. As you raise the air spring's height, you will also be increasing the air pressure inside, thus increasing its Spring Rate.

Re: air bag driving height 8.5 inches

Reply #9 – July 22, 2020, 05:06:34 pm

Think your trying to describe something by calling it something it's not,if you increase air to the air bag in trying to increase
"spring rate" the coach will rise,spring rate is about springs not air bags as far as I can tell.Best thing you can do on the bumps is
SLOW DOWN,if you think Colorado has bumps wait till you hit the Alaskan highway and have miles of them.

Re: air bag driving height 8.5 inches

Reply #10 – July 23, 2020, 11:57:40 am

Yes. I was going 25 , 10 under posted but looked in my mirrors because I was holding up traffic just at the point of the holes and missed seeing them in time to slow even further. No worries, I have a fix for it

Re: air bag driving height 8.5 inches

Reply #11 – July 23, 2020, 07:03:06 pm

Quote from: Protech Racing – July 22, 2020, 02:42:35 pm

With air bags the actual spring rate does not change with ride height.

Mike is right. The air bags on Foretravels are wrapped back on themselves, and unroll to expand with more air without any resistance. It doesn't take any more force (pressure) to support 20,000 lbs at 8 inches or 9 inches. It does require pressure above what's in the bag to add the additional air, which seems like you are adding pressure, but once filling stops, pressure is the same.

The cheaper non-rolling air springs that are often used on pickups that actually stretch to expand will need more pressure to get longer and will ride stiffer with more height.

Re: air bag driving height 8.5 inches

Reply #12 – July 23, 2020, 07:12:32 pm

Ah ha. Good to know Fleming. Thanks

Re: air bag driving height 8.5 inches

Reply #13 – July 24, 2020, 09:53:45 am

Just a thought,maybe look at your air valves,2 in back one in front,if for some reason they are worn and exhausting air faster then
normal it could be a factor,many articles on them here.

Re: air bag driving height 8.5 inches

Reply #14 – July 24, 2020, 10:32:56 am

Before you make the adjustment, check for ride height valve wear by:
1. dump the air and then go to ride height; measure.
2. raise well above ride height, then go to ride height; measure.
If the two are significantly different you might need a new height control valve.
I don't know of a tolerance for this, but I would think the two dimensions should be within 1/4"
Does anyone else know the tolerance?

Re: air bag driving height 8.5 inches

Reply #15 – July 24, 2020, 10:38:00 am

John,

Have never seen specs on this but agree there is (and should be) a small "dead spot" in the ride height valve.

Dead spot= place where valve is neither adding nor exhausting air.

Re: air bag driving height 8.5 inches

Reply #16 – July 24, 2020, 10:54:02 am

So if koni FSD are the best could better be attained? I don't have enough miles in seat to have that answer, but I do have a source to build off-road race shocks. These are rebuildable and completely tunable. I spoke with them about six months ago and they were willing to make up a set for me to beta test for them. They would cost more than the FSDs but not much more. Also we are using the same shocks front and rear and the loading is more than doubled in the rear. I would think they should be sized and valves appropriately. Our demands are much different than a race shock, but can be catered to precisely. This was not the time to bring this up, but kinda just curious? They also can incorporate progressive internal bump stops to control extreme operation requirements rarely encountered. Like big holes in the road.
Scott

Re: air bag driving height 8.5 inches

Reply #17 – July 24, 2020, 11:03:36 am

Scott,

Wouldn't suggest that one could not develop a better shock, but Koni has been in the business of designing them for specific applications on motorhomes for a long time.

Advantages of the FSD Konis:

Significantly more dampening on extension vs on compression (dampening on compression adds to effective spring rate= rougher ride). Dampening on extension does not add to effective spring rate, but dampens motion/improves handling.

Changes dampening characteristics (the FSD part) so far less dampening over those small sharp bumps and much more over the large ones. So, both smoother ride AND better handling over the big ones.

I was involved in the development of the FSD's-- our coach was the test bed and worked directly with the engineers (drove to their North American HQ in Hebron, KY). So, had the opportunity to drive many miles on the same coach with Bilsteins, Koni adjustables and then Koni FSD's. FSD's win hands down. More expensive, more sophisticated, but do what they are deigned to do.

Re: air bag driving height 8.5 inches

Reply #18 – July 24, 2020, 12:44:52 pm

On dsd's comment about the more weight in back,maybe that's why the rear has 2 height valves and the front one.

Re: air bag driving height 8.5 inches

Reply #19 – July 24, 2020, 01:41:35 pm

There are two ride height valves in the rear to keep the coach level (really parallel to the road surface) side to side, with one valve up front to keep the front level with the rear.

Affiliate Notice