The following topic was started in another thread titled Barth Data Tag Information - help wanted and is in response to that link.

Nick Cagle (below) has the entire question in quote that started this drift. It is a good discussion and deserves it's own thread.

Moved Reply:

quote:

Originally posted by JReilly:
but I was wondering about the other info..what does the following mean
GVWR 14500
GAWR Front 5000
Rear 9840 and is the 63 psi cold mean that is what the tire pressure should be cold???
thanks for clearing things up..
Hope my info helped you out

That is the Gross vehicle Weight the chassis and suspension is designed to carry. The total weight is not to exceed 14500 with a limit of 9840 on the rear axle and 5000 on the front axle. Note these are the limits fully loaded with fuel, water, everything you carry and the occupants. Some day when you are killing time fill the coach with fuel and water and take it to a public scale and have it weighed, then you will know how much good stuff you can carry on those trips.

That is the recommended tire pressure measured when the tires are cold.
Nick

Moved Reply:

quote:

Originally posted by Nick Cagle:
That is the recommended tire pressure measured when the tires are cold.
Nick

Yes, with the tires Barth put on.

Your tires are probably not the same. You should weigh each wheel fully loaded, then inflate to the corresponding pressure for your size and ply on the tire manufacturer's chart. If you can't find the manufacterer's chart, use the latest Tire Guide. Some people add 5 or 10 pounds.

Moved Reply:

"If you can't find the manufacterer's chart, use the latest Tire Guide."

Don't all modern tires have maximum (recommended) psi listed on the sidewall? e.g. "5000lbs single 9840 dual @ 63psi"
AAAAnd: some wheels, esp aluminum, have max WHEEL inflation pressure stamped in each one.

Moved Reply:

quote:

Originally posted by Gunner:
"If you can't find the manufacturer's chart, use the latest Tire Guide."

Don't all modern tires have maximum (recommended) psi listed on the sidewall? e.g. "5000lbs single 9840 dual @ 63psi"

Yes, but only the maximum. The recommended pressure for my tire loading is quite a bit less than the max on the sidewall, and would give a rough ride, as well as stressing the tire, wheel and suspension.

quote:

AAAAnd: some wheels, esp aluminum, have max WHEEL inflation pressure stamped in each one.

Yeah, most (maybe all) wheels are marked. My steel ones are marked on the inside. Good excuse to scrub the wheels.

On my Barth, the tire max is way above the wheel max.

Moved Reply:

quote:

AAAAnd: some wheels, esp aluminum, have max WHEEL inflation pressure stamped in each one.

Until now, I had never heard of a maximum wheel inflation pressure, thanks!

quote:

Yeah, most (maybe all) wheels are marked. My steel ones are marked on the inside. Good excuse to scrub the wheels.

On my Barth, the tire max is way above the wheel max.

Please verify the tire max is way above the wheel maximum inflation pressure. That sounds as if the wheel will come apart before the tire if over-inflated.

Moved Reply:

quote:

Originally posted by towerguy:

quote:

Originally posted by bill h:
On my Barth, the tire max is way above the wheel max.

Please verify the tire max is way above the wheel maximum inflation pressure.

The Michelin 8R19.5 XZA® LRF, the Goodyear G159LT and the Bridgestone M724F in that size are rated at a max of 110 psi.

GM motor home 19.5 wheels max wheel pressure is 80 psi for code ZT, and 95 psi for code ZY.

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Moved Reply:

The Alcoa wheels on my Breakaway are rated at 110 PSI at max load. I have tried all kinds of pressure combinations to get rid of or reduce the "tail wag" and found that it doesn't matter much.

I run the tires, 8R19.5 Michelin, at 105 PSI because I have found that anything less I get much faster wear on the outside edges of the tires (rear), a clear indication of under inflation. I am near the max axle weight on both the front and rear.

Moved Reply:

If you weigh your coach, & inflate the tires according to the tire mfrs. specs for that weight, you shouldn't encounter excessive wear on the shoulders of the tread. If you have to run near the rated maximum inflation pressure regardless of load, it suggests your Alcoa rims may be wider than those designed for the 8R19.5 tire. I don't have the book in front of me, but as I recall 8R19.5s are designed for a 6" rim. If your rims are wider than that, they will generate excessive pressure on the shoulders of the tread at any inflation pressure.

It might be worth your while to check the actual width of your rims. If they are wider than 6", they may be the source of your excessive wear. In any event you should have better luck with a P-metric tire. Size-for-size they have a wider, flatter footprint than the 8R tire, but a slightly lower profile.

Moved Reply:

My rims are 6" and that IS the size rim recommended for 8R19.5.

I don't want to go to the metric tires 225R19.5 because they are about 1' smaller in diameter and I would give up about 50-75 RPM at cruise. I do run metric on the front. (225R19.5)

I have been looking for 6.75" or 7" so I could run 245R19.5, they are the same overall diameter as the 8R19.5 BUT no one makes that wide a wheel for the 19,5 in a 6 bolt Budd style.

Moved Reply:

quote:

Originally posted by MWrench:
My rims are 6" and that IS the size rim recommended for 8R19.5.

I have been looking for 6.75" or 7" so I could run 245R19.5, they are the same overall diameter as the 8R19.5 BUT no one makes that wide a wheel for the 19,5 in a 6 bolt Budd style.

Have you run across wider ones in 10 bolters?

I know some people who run the 245 19.5 on 6 inchers, and report no problem on P30s in front.

Moved Reply:

8 and 10 bolt Budds are available in 7 3/4 inch width. I have been considering replacing the hubs and rotors on the back with 10 bolt Budd style pattern then I could run 245R7019.5 with a G rating for a stiffer side wall. I have looked into have custom wheels made that would be a 6 bolt Budd with a 7 3/4 inch width but haven't found a good wheel maker.

On my Breakaway I am right at 30% weight distribution front to rear which is considered close to the the minimum for proper handling (tail wag!)

I have also been looking into moving the batteries up front to better the weight distribution but it isn't a lot of help for the effort. would need much more weight shift.

I have exhausted all other avenues to get tail wag to a minimum

Moved Reply:

Ed, Rusty has a 28' Breakaway with long rear overhang, & claims it rides like it's on rails. You might compare notes with him & see what differences/similarities you share as to chassis, suspension, etc.

Have you tried a Panhard rod to restrict lateral movement of your rear axle? I had a 24' S.O.B. with single tires on the rear. I had to bend it into a curve, & apply reverse lock like a dirt track racer to nudge it around the most ordinary kind of curve (not quite as severe as the usual dirt track car, but significant nonetheless). My local 4 x 4 shop welded up a Panhard rod (sometimes also called a "track bar"), & cured 90% of my problem.

"hendersonslineup.com" in Grants Pass, OR makes a bolt-on "SuperSteer" rear track bar for Chev chassis. Their website has a drawing of 2 different varieties. The one my 4 x 4 shop made was simpler, & required welding. I had some photos of it, but unfortunately I recently did some house cleaning on my hard drive, & they're no longer here. The Henderson website will at least give you a visual of what I'm talking about.

Moved Reply:

quote:

Originally posted by MWrench:
8 and 10 bolt Budds are available in 7 3/4 inch width. I have been considering replacing the hubs and rotors on the back with 10 bolt Budd style pattern then I could run 245R7019.5 with a G rating for a stiffer side wall. I have looked into have custom wheels made that would be a 6 bolt Budd with a 7 3/4 inch width but haven't found a good wheel maker.

On my Breakaway I am right at 30% weight distribution front to rear which is considered close to the the minimum for proper handling (tail wag!)

I have also been looking into moving the batteries up front to better the weight distribution but it isn't a lot of help for the effort. would need much more weight shift.

I have exhausted all other avenues to get tail wag to a minimum

Ed, I think you are on the right track with moving the batteries forward. I have had several vehicles, even station wagons, that responded favorably to movement of the heavy stuff. Even amount of liquid in various tanks made a big difference. I removed the genset from one MH, replacing it with a teeny weenie one, and found better mountain handling. Present Barth, even with a tag axle, responds differently with the rear mounted 75-gallon gas tank full.

The percentage weight figure is just one guideline, which addresses static forces mostly. The dynamic forces involved in tail wag are not reflected accurately in axle weight percentages. The moment arm of any weight affects dynamic forces more than static forces. Unfortunately, the effect of dynamic forces are most often measured with seat of the pants instrumentation.


I would agree with Roy on the Panhard rod, and raise the ante a little by suggesting a Watts linkage instead. The roll center of a Panhard rod changes with left or right roll, so the sway, while lessened, is now asymmetrical, which can be unsettling if you are analytical or on the edge of handling. The more serious the problem, the better you will like a Watts. The classic method of attachment is to mount the bellcrank on the axle. A less common approach is to mount the bellcrank to a crossmember conveniently located near the axle, and attach the outer end of each arm to the axle out at the spring perch, one high, one low. This made a previous P30 much better than the Panhard. I would say the Watts was two times better than the Panhard, but at least four times more work. Alas, it is always thus; the cost-benefit ratio is not a linear progression.

You will have to make the bellcrank yourself, I think, as the ones available seem not to be heavy enough for a MH. But all you need is a drill press and a welder. The bars, Panhard or Watts, can be top links from a farm supply store or you can make them up from bits from www.quartermax.com. They also have nifty brackets for attaching things like ladder bars to axle tubes.

Don't laugh, some motor homes need at least one ladder bar. (I found out)

Moved Reply:

Rusty's chassis and mine are very different. He has a Dana 80 diff and I have a Eaton 15040 which is much larger, He has a much lighter engine/trans combination and it sits further forward (GM V8 and 4L80 shorter assembly vs. B5.9 Cummins and Allison MD3060) and that is where most of the trouble comes from. From the center of the rear wheel to the back of the coach is 10'3 inches, the total outside length of the coach (not including the bumpers) is 30' 1". Can't find the axle weights right now but from memory it is very close to the maximum of 6000 front and 12000 rear. I have had lengthy discussions with Spartan about this.

Mine has a panhard rod that extends from the frame rail to the center of the diff and I have replaced with a new one, the old one was shot and had a lot of play in the end joints. I didn't like how the panhard was attached to the frame rail as it was not the stiffest point on the frame rail so that was beefed up.

All spring bushings and spring shackles have been replaced front and rear. All new Bilstein shocks. New steering box, new ball joint ends. Henderson does not make anything for the Spartan EC2000 front end steering, really no need because there are no pitman arms in this system. The steering box is mounted to the front axle (it is a solid axle not independent) with a drop link connection to the right wheel tie rod link, then a drag link to the drivers side. Virtually all of the suspension parts and pieces have been replaced.

Much, much better then when I first bought it but still not where I would like it.

Sorry for the thread drift but at least I got the actual length of the coach here!