Tire Pressure (Eagle) & Monitors

[LegalEagle82]

Hate to bring up a subject that already exists in the archives but I just have to ask,

What is the average tire pressure everyone is running front to back.   Now before I get lectured, I found the "right" answer back in December by  Jack Conrad  what stated:

"Best bet is to have your coach weighed in "road ready" trim. (full fuel and water tanks, pantry and closets stocked, all passengers on board, etc.). Have it weighed on a ceretified scale such as a CAT scale at a truck stop. Their scale will weigh each axle separately. This will cost about 5-8 dollars. Take each axle weight and go to your tire manufacturers website. They should have a chart showing the correct air pressure to carry in your tires based on the weight the tires are supporting."

Now this comes up, because today I was in an 83 charter bus (Eagle) and the VIN tag on the front of the bus stated to run the front timres at 105 and the back tires at 90.  I have an 82 Eagle, and as soon as it warms up, I'm going go measure my pressure and see that its sitting at.   I appreciate Jack's answer, and I'll get to the method soon enough,  but I was really looking to see what was the average range everyone is working with.

And for those of you who have bought the tire pressure monitors, would do you it agian.  I was leaning this way.

Thanks

Evan

[TomC]

Evan- On my transit I have 11R-24.5 16 ply tires (like most Eagles).  My traveling weight with both my wife and I inside is 10,500lb front and 20,500lb rear.  I run 90psi all around. Blindly running 110 in front and 100 in the rear just makes the bus ride like a fork lift and excessive tire wear in the middle of the tire.
At 120psi I can carry over 14,000lb on the front tires.  The front axle is rated at 13,000lb.  On the rear at 110psi, I can carry 26,400lb on the tires with a 23,000lb axle.  So even with my weight now of 31,000lb, I'm still 5,000lb from my gross weight rating.  Compare that to a fully loaded sticks and staples that usually has only a few hundred pounds of lee way.  One of the many reasons I converted a bus.  Good Luck, TomC

[Eagle]

Evan on my 85 Eagle fully loaded the front weighs 10160 and the rears weigh 24960.  I have 95 Lbs in front and 90 Lbs in rears.  You can not go by the VIN plate on anything as to the air pressure you should use.  As Jack said get it weighed.  As for the air pressure monitors if you have the money to spend fine but look at all of the tour bus companies and greyhound and see how many have monitors.

[lostagain]

My Courier 96 weighs 23000 lbs. I run 70 psi all around. This after looking it up on the tire web site. They don't run any hotter and it is a smoother ride than 100 psi that I used to run. Also it is a lot easier to top up from air hose at home, from gas station or from bus air.

[rv_safetyman]

Based on having my Eagle (85 model 10) weighed, I run 105-110 in the front and 90 on the rear axles.  The tire temperatures would suggest that that pressure is in the correct range.

Someone posted that Michelin says that adding 10 PSI permits driving at higher speeds.  I only drive at 68, but when passing I find that I get up to 80 on occasions.

The other issue is wind loads.  I have encountered high side-winds that load the down wind side of the bus significantly more than static loading.

Based on all this, I make sure that I am on the high side of the pressure range for the axle loading.

Now, for the shameless plug, you can go to my website to read about the monitors we sell.

[Nick Badame Refrig/ACC]

Evan,

I have weighed my coach and determined that I should run 100psi. Now that I have the Preasure Pro from Jim Shephard,

I can now monitor all the tires including the Yukon. It sure suprised me to see the bus tires rise 10 to 15 psi  while traveling

at 70 to 75 mph.... The Yukon only rises up 5 to 6 psi.  After my toad disaster last june, I feel more worry-free with the system

installed. I think it's well worth the money!

Nick-

[TomC]

I have the PressurePro wireless tire monitors on the bus and car.  They have a small transmitter that screws into the tire stem.  The problem is that the transmitters are not calibrated well.  I first went through and got the tires all to the same pressure.  Then installed the transmitters and programmed the unit.  It works properly, but it reads differently for each tire-like from 89-92psi.  Also if you do use the car transmitters and have a 40ft'r or more, I would suggest using the additional antenna possibly mounted under the bus.  The car will frequently loose the radio signal and then the unit beeps.  Personally- just luke warm to its' usefullness.  I usually stop about once an hour and the best (like I used on big trucks) is to walk around and feel the temp on the tires.  Warm runners will be lower in pressure.  Good Luck, TomC

[Nick Badame Refrig/ACC]

Hi Tom,

Jim sold me the system with the new Repeater for picking up my toad. It looks like the dash unit without the display and I mounted it

in the bedroom. At the house, the bus is 75 yards away from where the yukon is parked  and it has no problem recieving

the yukon senders.. [Sure supprized me]

Nick-

[rv_safetyman]

A couple more thoughts on tire monitors.  As TomC points out, there is some variation in the calibration of the sensors.  I suspect you will see that much variation in tire pressure gauges.  I have posted some of the technical details of the Doran/Pressure Pro system at:

http://www.rvsafetysystems.com/doran.htm

You will note that the advertised accuracy is plus/minus 5%.  That seems like a reasonable value to me.

What is important is that each sensor sets its own baseline and then the monitor sounds an alarm at 12.5% pressure loss from that baseline for the first warning and 25% for the major alarm. 

One thing I have run into, is false alarms at very cold temperatures.  As noted, the tire pressure changes significantly with temperature.  Most of us air up our tires in "normal" temperatures.  Several of us have experience temperature around zero.  At that temperature, the pressure can drop below the first alarm threshold – especially if the tire has lost a little bit of air over a long period of time.  As soon as you put a few miles on, the alarm goes away.

I have thought about how to address the issue.  I could re-baseline the sensors by removing them for about a minute (that resets the baseline).  However, that would drop the point of the alarm trigger points.  I have decided that the cold temperature alarms are really a situation that confirms the system is working.  The first level of alarm is not really obnoxious and once you acknowledge the alarm it only gives you a short alarm sound at reasonable intervals.

[Nick Badame Refrig/ACC]

Jim,

If anything, this teaches us a little about tire preasures and hot and cold vairiations..

Thanks
Nick-

[Chariotdriver]

  I'm wondering out loud.
If you plugged in the outside temp, either automatically or manually, could you adjust for the pressure drop due to temp?
  Phil

[NJT 5573]

Evan, I've got 2 Eagles and seperate manuals for each coach. Both the 1979 (TW19797) and the 89 (NJT5573) have a factory recommendation for tire pressure. It is the same as the coach you referenced in both Eagle Manuals, 105 steer, 90 tag and drive. Lets keep it simple!

[TomC]

NJT 5573- "keeping it simple" when it comes to tire pressure is fine if you want a rougher ride, irregular tire wear, and the tire not having the maximum foot print on the pavement (traction).  But I think most hear would want to get the most out of their tires (even though most won't put on those kind of miles-like my tires they wore out from drying out), get the best traction and to have the best ride.  That is why the tire manufacturers have extensive tire inflation charts for each tires size-sometimes for each tire model.  It is always the best to weigh the bus in traveling form and look up your specific tire in the chart and run THAT pressure.  Those tire pressures suggested by Eagle is for a full bus of people. I highly doubt you have that much weight in your bus.  Good Luck, TomC

[D+C4106]

RE  tire monitors,  We  added that feature last fall,  it sure kept us busy,  we hope to get the bugs worked out so that it does what it is designed to do.   35' bus and toad  IS too long for the regular antenna,  Possibly will work with the auxillary antenna but not sure YET.     But it gives us something to watch while driving!   Denis

[pete81eaglefanasty]

 We got the Pressure Pro on our bus a 40 footer and with our Jeep in tow we have no problem with the antenna that came with it. its mounted on the Monitor. We have ours stuck to the windshield.

         Pete & Jean
          Fantasy