How do you decide on tire pressure?

[TomC]

If you run 100psi all around, it isn't a bad thing. I only suggest you get your bus weighed to get the exact inflation needed. Then try running the suggested tire inflation-you'll find the ride improves tremendously! Good Luck, TomC

[dtcerrato]

"if you run 100 psi all around, it isn't a bad thing" - not for the tires but for the occupants, radius rod grommets, bulkhead grommets etc. A harder than has to be condition exists. We not so long ago finally upgraded from nylon bias belted @ 80 psi max to steel belted radials @ 120 psi max. We were running @ 110 psi. On our FL to AK 12000 mile road trip - after getting in to AK from FL @ 5000 mile later I went to the load chart for the new radials. According to the load chart the front dropped to 90 psi & the rear dropped to 75 psi. When we got back on the road after the pressure adjustment the ride was phenomally much smoother & more comfortable and the drivability (handling) was much better. Sorry it took us so long to make the change. FWIW.

[Oonrahnjay]

"if you run 100 psi all around, it isn't a bad thing" - not for the tires but for the occupants, radius rod grommets, bulkhead grommets etc. A harder than has to be condition exists. We not so long ago finally upgraded from nylon bias belted @ 80 psi max to steel belted radials @ 120 psi max. We were running @ 110 psi. On our FL to AK 12000 mile road trip - after getting in to AK from FL @ 5000 mile later I went to the load chart for the new radials. According to the load chart the front dropped to 90 psi & the rear dropped to 75 psi. When we got back on the road after the pressure adjustment the ride was phenomally much smoother & more comfortable and the drivability (handling) was much better. Sorry it took us so long to make the change. FWIW.   

     Thank you, Dan.  That's a very useful and complete discussion of your changes and experiences.  This makes a lot of sense to me (and the change between bias belt and radials makes the contrasts more understandable to me).

[eagle19952]

They're both round and if you flatten the bottom down, you change the amount of surface area in contact with the ground. I would never do this with the tires on my bus. They're way too expensive to be mucking around with. But then, I'm not familiar with peach baskets. Is there a reason you can't put bananas in a peach basket? 

yes, yes you can. but putting a bus in a place where flattening the tires to gain traction seems a flawed argument.
but you just said that...
logic and peach baskets seem more rational, to me.

[dtcerrato]

Got to admit that the AK road trip is the ultimate proving grounds for a lot of different systems, especially on a vehicle such as a bus. When you involuntarily have to do sometimes hundreds of miles of stuff like wash board hardpan, loose gravel, potholes, frost heaves & dips - the not so evident stuff that we take for granted on our nations super slabs comes right to the front burner & will sit on your shoulder and eat your ear & pound your head... Just to paint the picture. One of the hardest thing's to have dealt with was when those little warning signs like small red flags on the shoulder or red spray paint that the trail blazing road crews set out after thaw but prior to repair would be at the bottom of a 10% grade & the start of a 10% grade, curses! Ok, I'm done :-/...

[PP]

"if you run 100 psi all around, it isn't a bad thing" - not for the tires but for the occupants, radius rod grommets, bulkhead grommets etc. A harder than has to be condition exists. We not so long ago finally upgraded from nylon bias belted @ 80 psi max to steel belted radials @ 120 psi max. We were running @ 110 psi. On our FL to AK 12000 mile road trip - after getting in to AK from FL @ 5000 mile later I went to the load chart for the new radials. According to the load chart the front dropped to 90 psi & the rear dropped to 75 psi. When we got back on the road after the pressure adjustment the ride was phenomally much smoother & more comfortable and the drivability (handling) was much better. Sorry it took us so long to make the change. FWIW.

I agree, that's great first-hand information. I like the ride of my bus at 100PSI, so I'm going to leave them there. However, if a trip to AK on the AlCan ever comes up, I might reconsider 

[B_K]

but that isn't really how bus OTR tires are designed...you are comparing bananas to peach baskets....totally different species 

Umm glad you mentioned it!
I just went and took some bananas and peaches out of the fruit basket and put them in a bowl with fresh cream and peanut butter Capt'n Crunch cereal and OH BOY IS IT GOOD! (even if they are different species they sure taste good together!)
  BK 

[Jon]

Forgive my sarcasm, but it seems some owners appear to know more than the tire engineers. If the tire pressures on the charts were listed as minimum pressures for a given weight it might lend credibility to those who think nothing of ignoring the information and going with their more carefully calculated pressures well in excess of the charts.

Excess pressure DOES change the tire footprint and we were able to see and measure the difference. It has a serious impact on stopping distances and our coaches take a lot of real estate to stop anyway, so why would we make it worse?

This is directly out of a Michelin tire service manual as relates to inflation pressures:

"Unless otherwise recommended by tire manufacturer
for optimized tire performance, use the tire inflation
pressure shown in the application data books for the
particular axle load. Exceeding this pressure could result
in reduced traction and tread life. "

Note especially the last sentence, while we don't care about tread life most of the time, in a panic stop we surely will care about loss of traction.

[luvrbus]

It will not change the foot print between the min and max air pressure stated on the tire,I asked that question at the same place you attended and at Bridgestone in TN .I can see where excess pressure over the max pressure would make a tire change.
Me personally I don't take everything from Michelin as the gospel like the BS UV cracking is normal and won't change a tires life I lost one on the front of Sonja's Trek 2 years old the UV cracks blew out  .Michelin didn't become the largest tire manufacture in the world by not making tires to sell  JMO it's a love hate deal with all tire brands they make tires to sell