Need help with '99 Patriot weight, tires, pressure

[JimCasazze]

We've had our PT for a bit over a year, and I hate to admit it, but never weighed the coach.  The dealer said to keep the tires inflated according to the placard by the drivers door which says 100 front/90 rear.

We are considering replacing all the tires as the are just over the 5 year mark and we're planning a pretty long trip starting next month.  

So today I decided to weight the coach and figure out what the axle weights were, so could start to look at the right size, load, etc tires.  What I found out is somewhat bothersome, unless I am not understanding the Axle, GVWR, etc ratings.

We filled the fuel tank and water tank.  The grey/black tanks are empty.  We have very little in the way of clothes, etc and NO food on board.  I have maybe 200lbs of tools, but that is it.

I brought the coach to our local CAT scale, drove onto it and recieved the following weights:
Steer Alxe 11,320
Drive Axle 20,560
Gross Wt 31,880

No persons on board, we are 880 lbs over the posted 31,000 GVWR.  Does this sound correct?  If so, I will have to dump 1/2 the fuel and run the coach by remote control as I drive behind it.

I'm not sure I understand the GVWR.  Is this the summation of GAWR front and rear (at the listed pressures?)  If so, can the GAWR be increased by higher load range tires (and pressures) or is the limit actually the physical limits of the axle, brakes or something else?

I have driven the coach a few thousand miles now hanging a 1000 lbs of HD motorcyle off the back, with no problems at all.  In fact, I talked with a few other Beaver owners that have done the same without incident.

[Bill Sprague]

RVs and weight are a touchy subject.  It involves safety, engineering, a little legal and lots of opinion.  You can't increase any of the specifications assigned at the point of manufacture.  Nobody, including me, will tell you it is OK to be overweight.  

We bought our motorhome new.  It was several months before I learned that I would never be able to operate it within the Beaver assigned limits.  I spent 18 months being very angry at Monaco and finally had to accept there was nothing I could do about it.  

There is little you can do about being overweight, except doing the best you can at not hauling around unnecessary equipment.  In eight years of paying attention to weights and motorhomes, I've not seen or heard of any suspension failures.  

Tires and tire pressures are something you can and should pay attention to.  You can use tires that have the capacity to carry any extra weight and inflate them appropriately.  

I've decided that 8 years is my limit on tire age.  I've weighed my motorhome and know the axle weights.  I round the weights up a little and then use the pressure charts provided by the tire manufacturer.  The Goodyears I had required 90 psi on the drive axle and 100 on the front.  My current Michelins need 5 more psi.  I use a tire pressure monitor system to (hopefully) predict any tire failure.  

Some will say you need to weigh each wheel separately because, not only can a motorhome be overweight, but it will be heavier on one side or the other.  

Did your listed weights include the motorcycle?  If not, you might want to weigh it again so you can at least get your tire pressures right for the actual load.  

[Joel Weiss]

Axle weight ratings are just that, they are the "weak link" ratings which could be the axle, the tires, the suspension, or all of them.  It's quite common for the tires to have load ratings that add up to more than the axle weight rating.  Tires should be inflated to carry their actual load (or slightly more); you can't do anything to change the axle rating without rebuilding the coach.

Our 2000 PT has a GVWR of 32,700; us on board and with a full load of fuel but only ~35 gal of water but all our possessions we run within 200 pounds of that weight.  However, our rear axle has a load of ~21,300 against a rating of 19,500.  We are running Load Range J tires so we have many more pounds of tire capacity than we need both front and rear.  

When we had new tires mounted last summer our tire dealer said that our old tires did not indicate any significant "flexing" of the rear axle which is what he normally sees with serious overloading.  He felt we were Ok since there typically is a 10% margin built into axle ratings and since we weren't in any danger relative to tire load. We subsequently did weigh all 4 wheels and, to the surprise of our weighers, the coach is nearly perfectly balanced side-to-side.  With the measured weights the calculated correct pressure on our 275/70-22.5 LRJ Michelin's is 108 front and 98 rear.  These are right out of the Michelin online data sheets.

There is no way we could possibly get the rear weight within spec even if we unloaded all of our possessions.  I think when Beaver created the PT it didn't change the coach significantly to accommodate the much larger engine.  I figure that as long as my tires are not overloaded I can live with the axle load issues, particularly since there is no evidence of handling problems, etc.  At least we do not have front axle load issues; I know a number of people with tag axle coaches who have overloaded steer axles and steer tires which, to me, seems to be a more serious issue.

I agree with Bill that you should re-weigh with the motorcycle on and with a normal load so you can get correct pressures on all 6 tires.  You and I have talked previously about the effect of the cycle; it will reduce the steer axle weight slightly as well as adding the weight of the bike.  Since I don't know what tires you have I don't know whether this load will put you near the limit of your rear tires.  

[JimCasazze]

Bill/Joel,

Thanks for the reply.  I will re-weigh with the bike (probably another 850 on the rear) and also do a right/left weight measurement as well while I'm there.  Should have read about how to weigh, before I headed to the scales... oh well.

I've learned a bit more since my post and actually found another posting on BAC regarding this that my search missed 1st time around.  As always, good information on this site.  I've stopped sweating at this point - but was blown away when the scales reported my weight was over the spec'd limits.

I've decided to move to Michelin load range J tires, because they are available now (not sure if they made them in '99) and will satisfy my "tire" capacity issue.  As for the axle "limits", there really isn't much I can do about them like others have already mentioned, excpet keep a watchful eye on the bearings and lubrication.
J

[Gil_Johnson]

Weighing each side of the axle is more important than you might think.  Other boards report coaches with as much as 2,000 pounds difference between what the right and left side of the same axle weighed!  The heaviest weight (left or right on a given axle) determines the tire pressure for that axle.