Tire pressure check

[richard5933]

We are running Firestone FS400 (315/80R22.5) on our 4108. They came on the bus and since they're in great shape we are running them for now. I know that they are more tire than we need.

Weighed the coach this weekend with full tanks all around and a typical load of stuff. Only thing missing was the two of use in our seats, and together we done make 350 pounds.

Steer axle: 11120 (approx. 5560 each front wheel)
Drive axle: 18460 (approx. 4615 each rear wheel)
TOTAL: 29580

Chart from Firestone shows the following:

Dual: 5575/80psi     5840/85psi     6070/90psi     6395/95psi
Sing: 6175/80psi     6415/85psi     6670/90psi     6940/95psi

I have been running 95psi all around, but it appears my math was off. Thinking of dropping to 90psi in front and 85psi in rear to bring things closer to the chart but still allow for a good safety buffer above the minimum. My thought is that this will give a softer ride.

Any thoughts? Is the difference going to be noticeable enough to be worth the effort?

[kyle4501]

Changing the air pressure from 90 to 105 didn't make any difference  in ride. However, changing the shocks out to what was supposed to be there made a very noticeable improvement !

I like having my tires at the max sidewall pressure. That way, when there is a leak, I'll have more time to catch it before it drops low enough to cause damage.

I also use CrossFires on the duals to ensure both tires are carrying the load equally.

Added on edit -
BTW, I've experienced tire failures while driving - My choice is to do as much as I can to prevent that ever happening again.
If ride quality is so bad that you need to lower the tire pressure to minimum levels, you might want to consider a good tire pressure monitoring system. . . .

[TomC]

Heck I would drop to 80psi all around. You're still above at the psi.

[eagle19952]

 

but, 92 psi is not enough...it has been said   

[luvrbus]

LOL if ride is what you after buy a Eagle 

[chessie4905]

Too many issues with rust falling off and causing leaks in rear tires from running over it.

[eagle19952]

Too many issues with rust falling off and causing leaks in rear tires from running over it.

so, be happy in a Bouncy Bellowed Betty

[chessie4905]

Bouncy? Have you ever ridden or driven a GMC? The older models would rock side to side some.

[eagle19952]

Bouncy? Have you ever ridden or driven a GMC? The older models would rock side to side some.

did you mean roll u out of bed ?

[chessie4905]

I couldn't reach steering wheel and pedals from the bed, so I wouldn't know.  My 4905 doesn't rock and neither did out 4104. Both had rear sway bars. Neither rusted, or broke belts or had drop boxes or had tags.☺

[luvrbus]

All buses rust even GM's

[dtcerrato]

We ran close to max rated pressure in our tires, when we got to our destination over 5000 miles away, we reduced the pressure to what the tire chart showed for the actual load (similar to Richards #s) the difference in comfort was quite impressive - wished we knew better from the beginning.
Now we're in the market to replace the shocks - these observations weren't focused on until running nasty far north roads (frost heaves, loose gravel, pot holes, etc.)
Our 1953 GM bus has no rust :-)...

[luvrbus]

LOL oh yea it will have rust on the roof brows just dig around

[opus]

Its more about tire wear than comfort.  Full pressure and no weight leads to poor wearing tires, plus a hard ride, let alone road "sticking" power.  You need to ride on the full foot print of the tread, not just the high centers of your tires.  Why do you think they have charts with the proper pressures?

[chessie4905]

Last I checked, aluminum roof brows don't have a tendency to rust much. At least  in a GM, most rust can be seen, not hidden in the walls. I would not buy an MCI or Eagle unless it was a later model with stainless wall ribs. Well, to be honest, the only one I would buy would be a later Prevost.