Tire Pressure for Rexhall Aerbus 1997XL2900

diplomatdon wrote:
Jeff, I would suggest you weigh the front axle, then go by the inflation recommendations on the side of the tire. You are better to run at the max rather then min as the tires will run cooler, as heat build up due to a lot of flexing is not a good thing. Remember the Ford Explorer/Firestone problems of 10+ years ago was from Ford telling the owners to run them lower to get a smoother ride. Don't believe the coach manufacturer, trust the tire manufacturer. Don

If you have weighed , why then go by the inflation recomended at the side of the tire ?? If you have weighed best is to look that weight up in list given by tire maker .

If you go by the pressure given on sidewal ( here 80 psi ) then weighing is double work.

Once you determined the weights on seperate tires by weighing , you can even add some reserve to give extra savety margin.
If you make lightest side on the axle 85% of the weight you look up the pressure for , you still wont get terrible bumping and gripp is still acceptable.
Then often heavyest side on that axle is about 95% of the loadcapacity for the pressure, and this gives some reserve for , pressure loss in time, misreadings of pressure and weight scales, etc.

This percentage can be calculated next way, Example.
Asume R side on the axle 850 KG/lbs or whatever, and left side 950 .
Then make R 85% ( 0,85) of the weight you determine the pressure for this way. 850/0,85=1000 , Left 950 then is 950/1000=0,95=95%.

Can be that the outcome then is higher then maximum load of tire ( or if dual 2 tires Dual maxload) so it would lead to higher then 80 psi AT-pressure. But this At pressure , thoug its called maxpressure mostly, is not the maximum allowed cold pressure of the tire.
Once concluded myself of an document of Semperit( Continental) that maximum cold pressure is 1.4 times the AT-pressure/maxloadpressure/reference-pressure.

Continental has Vanco Camper tires in Europe and they give on sidewall " maximum load xxxx kg/lbs AT 69 psi" and "maximum allowed cold pressure 80 psi. This is midway the 1.4 times, to be exact 80/69= 1.15 is 15 % higher.
Its also about 10 psi extra, wich for instance Goodyear allowew for ST if you want to drive 75m/h max speed ( but for 65m/h you then also are allowed to use 10 psi extra above the AT-pressure.
Its a 8PR tire wich can be compared to D-load, but European system alllows exeptions like here 69 psi instead of the standard 65 psi belonging to D-load/8 plyrated .

Michelin Agillis XC ( C for camper as we call a motorhome in Europe) has a similar idea but only gives maximum pressure apart from the notation of maximum load and dont give that 69/70 psi AT pressure on sidewall of those tires, even calls it AT 80 psi on the newer tires , wich makes the confusion only bigger.

Wrote Michelin about it because in Pressure/loadcapacity list I got from them , the XC is given the same list as the Agillis 81 , and they wrote me that its a D-load tire but the 80 psi is to cover peakloads , and I translated that to expected overload on tire for the Motorhomes that are used in Europe mostly .
Those are most GVWR 3500kg/7700lbs because normal driverslicence in Europe is for max GVWR of 3500 kg .

Don,

Totally true of the Ford/Firestone fiasco.

But, the GVWR plate in an RV gives the correct PSI for the OE size/load range tire WHEN EACH AXLE IS LOADED TO GAWR.

Also, agree that weighing and using the tire manufacturer's inflation table to determine the MINIMUM PSI is the correct way to do it.

You can get axle weights at most truck stops. Far better is individual wheel position weights, then use the heavier wheel position on each axle to determine correct minimum PSI for all tires on that axle.

Jeff, I would suggest you weigh the front axle, then go by the inflation recommendations on the side of the tire. You are better to run at the max rather then min as the tires will run cooler, as heat build up due to a lot of flexing is not a good thing. Remember the Ford Explorer/Firestone problems of 10+ years ago was from Ford telling the owners to run them lower to get a smoother ride. Don't believe the coach manufacturer, trust the tire manufacturer. Don

I haven't weighed my rv, but the paperwork I have states that the weight listed
for the RV (brochure) is 17K, the distribution on the placque shows 6K front, 11K rear. Even if the placque is max, subtracting to make it empty would seem to always put me in the 80lb category always as the 80lb is for only 3K in the front, and 5.5K in the rear (dual). jeff

enblethen wrote:
35 pounds is not enough. Weigh your rig and go by tire manufacturers specs
Tire pressure chart

Followed the link and its not a list that gives save pressures in the lower loads, or the other way around gives to high loadcapacity's for the pressure .

If you would use a list from Michelin from the European market it would give already lower loadcapacity's .

Will see if I can find one , alredy searched for it for another topic.

In that list look at the 235/85 R 16 and below that the 245/70R16 also E load with same maximum load
Strange is that in KG the list is the same but in LBS there is a difference. To my opinion an administrative error.

But this is added to the wrong old American calculation wich leads to to much deflection in the lower pressure/loadcapacity range.
If your pressure is close to maxloadpressure of 80 psi no problemm.

35 pounds is not enough. Weigh your rig and go by tire manufacturers specs
Tire pressure chart

By law, you should have a GVWR plaque-- generally near the driver's area.

It will give OE tire size and recommended PSI if each axle is loaded to GAWR (Gross Axle Weight Rating). Until you weigh it, that is a reasonable place to start IF you have the OE size/load range tires. If not, it will give you a GAWR to go to the charts for your new size tires.