I've constructed a short tome with an eye toward consolidating most if not all of the information necessary to get a P-Chassis motorhome back into a position where the handling is something you no longer have to fight. Primarily, using the original factory equipment as opposed to any add-ons that cost $.

The booklet is available at

http://users.sisna.com/cebula/P-Chassis-AlignmentProcess.pdf

but be forewarned that it is 2.5 meg in size and will take a while to download. Version 0.5 dated July 12, 2005 is no longer current.
Version 1.2 dated Jul 29, 2006 is the most current and most likely will be the final version and has grown to approx 4.7Meg in size..

It no longer a DRAFT but I'm looking for any and all feedback information that can be added to improve its accuracy and helpfulness.

Mike

[This message has been edited by Relative (edited September 15, 2005).]

[This message has been edited by Relative (edited February 03, 2006).]

Mike: Excellent info.. Printed a copy for reference, to old to do this kind of work myself but nice to know what I'm paying for.
Thanx loads....carl

"THE TOY" 88 33' Regal SE Coach #3448

Just posted Version 0.6 to my site. Updated it with info on determining rear axle ratio.

Also, still looking for any feedback/corrections/suggestions to the writeup.

Mike


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Dear Relative:
I find your "P Chassis Alignment Draft" very helpful. Thanks for writing this for us all! I am the original owner of 22' 1996 Regency Style Barth, with just 14,000 miles. Using your draft, and as suggested by "bill h" and others, I have measured front Ride Heights to be equal at 4 1/2". However, my coach rides quite high in the rear. It has air bags front and rear. Back air bags at 40#, front at 70#. Tires are properly inflated for the loads (I weighed the coach) at 65# rear, 70# front.
Questions:
A. My rear Ride Height appears to be very large: 7 1/2" right; 8" left. What should it be? What criteria do I use to determine if this is too high a ride height in the rear? B. How does one interpret the Rear Load Height Chart (your Appendix B)? What does it mean that my ride height is off the chart to the left with a total Load of less than 2,000#?
C. Is this a dangerous situation? (The coach does drive reasonably well.)
D. History: when I picked up the coach at Barth, I commented on the high rear ride and they said, "Well, we could take a leaf out of the rear springs." I said, "No, leave it as is."
Is the removal of a leaf a way to decrease the rear ride height; and would it be safe to do?
Allan Pacela, from Solvang, CA

Wow! Sounds like you have a lot more chassis than your coach requires! Pretty unusual - but then I'm not a Barth owner and don't know how common this is for this manufacturer.

That rear ride height sounds unusual. Sure you checked in the correct places?

1/2" variation right to left is of very little consequence - as long as it's not because something is broken. Maybe a slight shift in your loose load would bring it even closer.

Can you tell me what the GAWR is for each axle per the manufacturer's label and what your actual weights were when you weighed it?

Also, it sounds like yours came with rear air bags - I've never had a straight answer as to whether these were add-ons by Barth, or by Chevrolet, or spec'd by the original buyer. Since you are the original owner of this coach, can you answer that? Also, how did you determine that 65# was correct for the rear bags and 70# correct for the front bags? My ideal would be to set the front air bags per spec and use the rear ones to get the coach as level as possible - this is in line with the way I think 'bill h' would advise. This means the rear springs are carrying the load as they should be and the rear bags are minor supplements for leveling.

Barth's comment about taking a leaf out of the rear springs makes me wonder if they had a practice of adding leafs beyond the original chassis equipment and may have added one too many to yours. Do you have anything giving you the original model number - "P31832" would be an example of what I'm looking for. Even the VIN number would be helpful. Maybe someone else can comment on Barth's practice with the rear leafs.

I, and others, might be able to provide more of an answer with that info.

Mike


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One other item to add. I was in N. Dakota 3 days ago and had to make a mad dash to PA because of a family emergency. May not get back to this forum for a few days.

Mike

Thank you for the extraordinary effort you have gone to for the benefit of the "many" P chassis owners out there.

I am may be totally wrong about this but I think that the only time somebody would reduct the number of springs in the rear would be because when adding additional (adjustable) helper spring it would allow you to retain the same U-bolts. Even Helwig advises going with the shortest ones possible.

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Dear "relative"
As a result of the discussion on this forum, I am starting to understand my coach! I am the original owner; when I purchased it at Barth, they told me that they would use a "heavier than usual chassis, so that we could register the coach in California, because larger GVWR vehicles could be smog/registered more easily." Apparently, their other raw coach frames in stock at the time were only Federally smogged, not California. I accepted that.
The Coach tag says: GVWR 14,800; Front: 5,500# GAWR; Rear: 10,000# GAWR, tires are large 225/70R19.5, rims 19./5x6.0. I weighed the coach to be: Total 12,890# Front 5,050#; Rear 7,810#.
The rear springs have just four leaves, with two spacers at the bottom the same thickness as the springs. They hang high at the ends and down in the middle. The air bags were installed either at Barth, or there is a tag up front which says, "Intermediate Mfg.: M&M Fabricators, 7/10/96," ... maybe they did the frame work for Barth?
Yes, I rechecked and confirm the rear ride height as 7.5" There are large air bags between the rear axle sleeve and brackets to the frame. Looks solid to me.
So, I conclude that the rear ride height is unusually high because of a low weight load on a very heavy frame.
The frame angle is about 2.5 degrees (high towards the rear), which does not seem that unusual.
To help minimize frame angle, I had lowered the rear bags to 40#, and raised the front to 70#. Lowering the rear bags all the way to zero only gets one extra inch drop of the rear bumper, and they need a minimum of 10# to "not chafe" so I think I will stay with 40# in rear.
FYI: The VIN is 1GBKP37NXT33310171. I assume this to be a P31132-52 ... just information from your Draft, based on the 137" wheelbase, but I cannot find that number anywhere on the vehicle.
Conclusion: Unless I hear differently from you or bill h, or others here, I plan to leave the rear at 40#, front at 70#, and accept the high-in-the-rear frame angle of about 2.5 degrees, and add that to the caster, per your manual.
Any further ideas? Any safety concerns?
with best regards and appreciation,
Allan Pacela from Solvang, CA

I'm just starting to get into the ride height thing with my '85 28' Regal. First, we weighed the Barth. Front axle was 5040#. The front axle weight rating is 5000#. I hardly have anything in the Barth except two full fuel tanks. Do I have something to worry about? I have both front and rear air bags and an extra leaf in the rear. Sorry, I haven't counted the leaves yet. And the thing drives like a dream, even on old Michelin 225 70 19.5's.

Allen, I saw the other thread "How to Improve Ride & Suspension of 22' Barth" you have going and looks like quite a few folks chipped in with advice and you reached some pretty good conclusions. About the only other thing I might suggest is to remove the two spacers in the rear and change the U-bolts accordingly, but that's not really necessary.
That M&M Fabricators item is interesting and I'm going to try to track it down. Your chassis is definitely not "standard" and it looks like some other folks also have mods to theirs.

http://www.mandmfabricators.com/ is the web site for M&M and it sure looks like their business fits the bill for doing the type of modifications you probably have on your coach.

Mike

[This message has been edited by Relative (edited September 07, 2005).]

Jim, It's obvious you are slightly over the rating for the front axle - may be even worse if it's unbalanced side to side for that weight. If you pay real good attention to lube on the front wheel bearings you will probably be ok. Think age. I know my knees are getting creaky and wish there was a way to replace the bushings and lube them up a bit.

Where are the gas tanks located on the unit? Also, is that weight you recorded with or without front seats occupied?

The real test is to get a 4-point weight with everything the way you normally travel.

Do you have something to worry about? Probably not. Careful is the term I would use.

Mike

Mike, thanks for the info. We weighed at a CAT scale and Tere and I were seated in the front seats. We have a 40 gallon fuel tank in the rear and a 30 gallon just in front of the mid-entry curbside door. There's a fold out couch behind the driver's seat, and two swivel chairs behind the passengers seat. I was very surprised that we were over the gawr for the front axle. The batteries are on the curbside behind the right front tire and the main storage compartment is behind the left front tire. Do you think we should move some stuff around?

Correction to who was in/not in coach. I was inside the truck stop paying as Jim was weighing. That means our two dogs Nicky 58lbs & Rosie 25lbs. were in the coach but I was not. I weigh over 150 but less than 170. That means..... When we drive to St. Augustine in two weeks with the new Gear Vendor Over & Under thingy what will the weight look like???? Add Tere-around 160ish, subtract Nicky & Rosie-83ish & now take away what has to be removed to put the new over & under in, add the over & under & what do you have??? When we travel there is nothing but dogs &/or people in the front of the coach. We'll heed the greasing advise but there does not seem to be ANY wiggle room for any weight in the front. Is this normal for this coach?

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If you have a big object that is heavy enough to make the difference, move it to the back. Otherwise, you are in no worse shape than most folks with this chassis. Just keep it maintained, safe tires, etc. and should be fine. My opinion - for what it's worth. (Wife says I owe.)

Mike

The front end on my 33' Regal SE is close to the max with a normal load and 2 people in front. I would hope that, as wth most manufactured items where product liability is a concern, there's a little extra margin of safety in the factory GW rating.

I'll bet most motorhomes on "P" chassis are heavy in front., & I would not be unduly concerned at 1 or 2% over. More critical, IMHO, is keeping the right load range tires at the right pressures for the actual weight, with a little extra capacity to spare.

The factory "orange book" advises different front air bag pressures for different actual weights for different GW rated "P" front ends, but I don't have it in front of me.