Tire question for Bus Warrior

[dtcerrato]

Radius rod bushings should always be replaced with good ole' soft rubber not hart plastic or nylon.

[DennisDenison]

OK guys, I'm new here and going to be a new 4106 owner in a few weeks.  I am getting 6 new tires installed when I pick it up in CA.  Where can I find a chart to see how much pressure to run in the tires?  I will get it full of fuel, water and weigh it before heading out home.  Would like to start out with close to the right pressure.

[richard5933]

Congrats on the new-to-you bus.

The inflation chart should be available from the tire manufacturer. Probably can find one on their website.

[Ed Hackenbruch]

If you run them in the 80-90 lb. range you should be just fine. 

[richard5933]

If you run them in the 80-90 lb. range you should be just fine.

Not saying you're wrong, but what are you basing that on without knowing the tires or the weight of the bus?

[Ed Hackenbruch]

 90,000 miles on 2 different brands of tires and i am pretty sure my MCI 5A weighed more than a 4106 does.  

[dtcerrato]

It's best to run pressures from the specific chart to your specific tires. A simple google search of your specific tire should reveal a load chart for that tire from it's manufacturer. That's only half the equation. Then you need to know the axle weights of your bus when traveling. The weight of the axle will bring you to the proper area of psi on the tire load chart. Don't forget to differentiate for dual or single tires on the axle - it will show dual or single tire psi on the load chart.  Of coarse if a steer axle is 12,000 lbs. each tire is loaded with 6,000 lbs so you'll look on the chart for the closest psi for 6,000 lb single. On a dual tire axle that's weighing in at 16,000 lbs. you'll look on the chart for the closest psi for 8,000 lb dual. Always run the next higher psi # so you're not running any softer than the chart dictates. A little harder (more psi) will keep it safer & run a bit cooler. All this coupled with good shocks will make your bus ride as comfortable as it was designed for.

[richard5933]

...On a dual tire axle that's weighing in at 16,000 lbs. you'll look on the chart for the closest psi for 8,000 lb dual...

Be careful with the dual wheels on the charts!!

What Dan mentions sounds like the RV tire charts for Michelin which list the dual tires by AXLE END and not by each individual wheel. On other charts, you would take that 16,000 lbs and and divide by 4 to get the weight per wheel to use on the chart.

Read the charts carefully!

One other twist to make the math more difficult...

A tire industry guy on another forum recommends that unless individual corner weights are known, it's best to assume that each end of an axle carries 53% of the total axle weight. This is done to account for the fact that most coaches are out of balance side-to-side, and one side is likely carrying more than half the total weight. So with Dan's example, the weight per wheel would be calculated like this:

Front:     12,000 x 0.53 = 6,360 lbs per wheel
Rear:      16,000 x 0.53 = 8,480 lbs per axle end OR 16,000 x 0.53/2 = 4,240 lbs per wheel

Not a huge difference from Dan's math, but enough that it may put you in the next column in the manufacturer's chart.

90,000 miles on 2 different brands of tires and i am pretty sure my MCI 5A weighed more than a 4106 does.  

Really hard to know what another coach weighs. Take ours for example... A 4108 converted by Custom Coach that weighs in at 30,000 +/- a few hundred lbs. I would guess that we are heavier than most DIY 4108 conversions by a long shot. CC was fond of making their cabinetry of 3/4" plywood, and their interior walls are made of double layer 3/4". Makes for a heavy coach with how much cabinetry they put inside. We also carry large tanks and an old-school heavy generator. You never know by looking at the model or at the outside of the bus how things are configured.

Changing just the size of water & waste tanks can vary weight by up to 1,000 pounds, and generator choice can also vary weight 500 pounds or so.

Again, I don't know that you're wrong or right. But I know that since he's getting his coach weighed it's easy enough to check the charts. Odds are he'll end up within 5 psi of your recommendations, but depending on tire size it could be much more.

[dtcerrato]

Richard's examples are point on & I covered that in a different way by stating to go to the next higher not lower psi cell. We personally run 3 to 5 psi higher than what the load chart calls for for a safety margin. At any rate running closer to chart ratings is a world better than running max tire psi. Easier on the bus AND its occupants. 

[luvrbus]

Truckers would have a hard time going by the charts all truckers I know run with in 10 or 15 psi of the max for 150,000 miles then buy new tires

[richard5933]

Truckers would have a hard time going by the charts all truckers I know run with in 10 or 15 psi of the max for 150,000 miles then buy new tires

Apples and oranges...

Truck owners are trying to get the max number of miles from their tires. Ours will age out long before we get near the max miles.

Truck owners have to set pressure based on the max load they will carry. We know what we weigh and can set for a much more specific load.

Truck owners don't care how comfortable their load is. If we bounce our occupants around on hard tires we may be driving alone.

[DoubleEagle]

Speaking for one truck driver, I am concerned about my load because things can shake apart if the ride is too hard. In some cases, the load can wiggle around and shake the truck. When I drove a tanker hauling hot acid, the company required that all tires be inflated at 90 lbs. on every position, and checked and reported daily. The gross load was always 75,000 to 80,000 lbs, which divided by 18 wheels was 4444.44 lbs per wheel, average maximum. Considering that it was an open chamber tank with no baffles, the load could move around a lot with wave action, loading some tires up quite a lot. That pressure worked because it provided decent traction whether loaded or empty, and the tires wore evenly. Greyhound puts 130 lbs. in their steer tires currently, and I assume that it is for fuel mileage primarily. A conversion on eight wheels puts about the same weight on each tire as the tanker.

[buswarrior]

Greyhound puts max pressure in their steers, same as every other modern bus company, because the steers are going to see max LOADING.

Front axle weights of +14k lbs is not uncommon for the 45' coaches. Neither is 14k lbs on the tags. 

These ain't your father's Oldsmobile...

That's why they have the big 315 tires... in revenue service, they need 'em.

Weigh your coach, buy and set tires according to the manufacturer ratings.

Save money if you need to, don't put heavy rated tires on a coach that doesn't need them.

Happy coaching!
Buswarrior

[luvrbus]

About all the 45 ft buses run the max on the front axle with the 315/80 some even use the 365/80 on the front,like BW said it is not your fathers Oldsmobile the suspension system and air bag location on the newer buses they really don't care what pressure you run it doesn't affect the ride one way or the other

[neoneddy]

My thoughts on PSI is simple, too low and you can have a catastrophic failure, too high and it's a bumpy ride.

When at the tire load rating you don't have much safety margin. If you have a TPMS I suppose you'd know of a leak sooner and it's less of a risk. I check every fuel stop / extended stop.