Community Forums

Beowulf2 · 01-20-2013, 08:50 PM

This may be a dumb question but,

Last summer we were traveling in a 40' diesel pusher on a two lane paved road in the Utah desert which had wide shoulders.
I decided to pull off the road and stop. When I pulled off the road and onto the shoulder the motorhome really leaned to the side. The shoulder did not look that steep but it gave me something to think about.

We have had class A gas motorhomes which have never gave me the same feeling that I had in the diesel unit that day.

The class A gas motor home was taller than the diesel motorhome but the inside floor is higher than the gas unit. Does the center of gravity change and could the diesel more susceptible to tipping?

Any thoughts

bluepill · 01-20-2013, 09:02 PM

If the shoulder is not well compacted soil, or is wet, the extra weight of a large rig may cause it to sink into the soil. That could lead to tipping or sliding.

KIX · 01-20-2013, 09:15 PM

Quote:

Originally Posted by bluepill

If the shoulder is not well compacted soil, or is wet, the extra weight of a large rig may cause it to sink into the soil. That could lead to tipping or sliding.

Could also lead to a tow truck too

Just For Fun · 01-20-2013, 10:48 PM

Quote:

Originally Posted by KIX

Could also lead to a tow truck too

YEP!!!!!!

Love at my Avatar. Been that, done there?

Larry & Rita · 01-20-2013, 11:08 PM

Top heavy is an issue with any class A--We saw one in Wyoming that pulled off the road and landed on it's side due to the soft sholder.
Spoiled his lunch break.

Alan_Hepburn · 01-21-2013, 08:29 PM

...and that's why I will never pull onto a shoulder unless it's an absolute last resort. I'll look for a paved area to pull into...

Wayne M · 01-21-2013, 08:32 PM

I never let the tires off the pavement. To risky.

SteveSkinner · 01-22-2013, 01:26 AM

This is not about top heavy at all

Class A motorhomes are not top heavy by any stretch. Certainly not my Monaco anyway.
Most of the weight is in the chassis - below floor.
I generally pack heavy items at flloor level and bulky items in the overhead cupboards.
Obviously pulling onto a soft shoulder as opposed to Tarmac is not a wise choice as the tires bite into the dirt and increase the lean.
Im sure the angle needs to be pretty high to lay one down. You shouldn't blame the coach.
I believe they are a very stable platform. Driven appropriately, a perfectly safe mode of transport.

bdpreece · 01-22-2013, 11:13 AM

Just a guess but by any chance was the coach on a Freightliner chassis? On my previous coach I had that exact problem. It was so bad that the washer/dryer would try to come out of the cabinet in the passenger side rear if I drove off the pavement. The problem is most noticeable on 4 air bag coaches where when the coach tips air is force out of the air bags on one side and into the other side causing a jerking motion. Henderson's Line Up carries Supersteer Motion Controls to fix this problem. SuperSteer Motion Control Unit 1/4.

JohnBoyToo · 01-22-2013, 11:26 AM

Yes, shoulders are not for heavies

but I would think it's more a factor of the suspension than the height...

Zoafan · 01-22-2013, 11:32 AM

Quote:

Originally Posted by bdpreece

Just a guess but by any chance was the coach on a Freightliner chassis? On my previous coach I had that exact problem. It was so bad that the washer/dryer would try to come out of the cabinet in the passenger side rear if I drove off the pavement. The problem is most noticeable on 4 air bag coaches where when the coach tips air is force out of the air bags on one side and into the other side causing a jerking motion. Henderson's Line Up carries Supersteer Motion Controls to fix this problem. SuperSteer Motion Control Unit 1/4.

Have you used those? Is it really as simple as they say to install? You just cut the line and insert the device?

Would like to hear from people who have used this.

bdpreece · 01-22-2013, 01:32 PM

Never got around to installing them as I sold the coach. Funny thing is we were in a mom & pop diesel repair shop in San Jacinto CA just before we traded in the coach and I was talking to the owner about this problem. He said he had been able to help the problem by reducing the size of the air line to each bag. I suspect the motion control units are doing something similar. He claimed to be able to do it for a couple of bucks per air bag for parts.

RickO · 01-22-2013, 02:04 PM

Quote:

Originally Posted by bdpreece

Just a guess but by any chance was the coach on a Freightliner chassis? On my previous coach I had that exact problem. It was so bad that the washer/dryer would try to come out of the cabinet in the passenger side rear if I drove off the pavement. The problem is most noticeable on 4 air bag coaches where when the coach tips air is force out of the air bags on one side and into the other side causing a jerking motion. Henderson's Line Up carries Supersteer Motion Controls to fix this problem. SuperSteer Motion Control Unit 1/4.

Doesn't air transfer from the low side bags to those on the high side on 8 bag systems too?

I have had Henderson's Motion Control Units on my rig for several years. They do minimize the "rocking" from side to side... as when I pull into and out of driveways... but I doubt they would have an effect on what the OP is seeing because all they really do is slow the transfer of air rather than completely control it.

Rick

Gary RVRoamer · 01-22-2013, 03:30 PM

In my opinion the number of air bags has nothing to do with tipping or leaning. The net upwards pressure on each side or corner of the chassis is the same in either case, i.e. the air pressure is in equilibrium with the weight on that corner or side. If it wasn't, the side or corner would rise or fall until it was. Likewise, spring suspensions push back in reaction to the weight applied on them from above and achieve equilibrium.

The control of the air flow in/out of the bags may be a different story. There is a ride height valving arrangement that attempts to maintain a constant distance between axles and frame (which is not the same as level). In nearly all air suspensions, one set of bags have individual height controls and the other set are tied together on one height control, so that only one set can respond to a side-to-side shift in weight.

I will readily agree that a DP with air suspension seems to respond more quickly, and perhaps more extremely, to the slightest tilt. Maybe the air system is that much more responsive than springs? The motion control valves mentioned above work basically by slowing down the air flow out of the bags.