Proper Tire Inflation SUMMER SEASON TIRE CARE

[TechTalk]

Proper Tire Inflation SUMMER SEASON TIRE CARE

The simple rule: proper inflation for Michelin 315/80 R 22.5 front tires on a Newell motor coach is 130 p.s.i. cold for 65 M.P.H. speed rating and 140 p.s.i. cold for 75 M.P.H. rating. Running at lower pressure decreases the load carrying capacity and speed rating of the tire and can result in a blowout. This is particularly critical running freeway speed in the heat of summer.

The majority of the weight supported by a tire is actually being carried by the air contained within the tire body rather than the rubber tire carcass. A tires sidewalls are designed to contain air, not to support the weight of the vehicle. However, decreasing air pressure reduces the weight that the air can support, and causes the tire sidewalls to flex as the vehicle is driven. Excessive sidewall stress causes heat buildup, especially running in the heat of the summer.

When heat buildup reaches a critical stage, the rubber actually begins to liquefy, the bond between the tire casing and tread will begin to degrade, particularly with higher centrifugal forces at high speed, and the tread can suddenly delaminate from the casing. This typically happens at freeway speeds without warning.

Running at 130 or 140 p.s.i., versus lower inflation pressures, reduces sidewall flex and heat buildup, contributing to reliable, safe tire performance.

TechTalk

[ken thwaits]

Proper Tire Inflation?

Our coach is 1995 model with the taller front tires. What is the proper inflation for all the tires on this coach?

[TechTalk]

Your 1995 Newell was equipped new with 11R24.5 Load Range H tires all around. Make sure that the tires currently on the coach are Load Range H, as Load Range G tires do not have the load capacity required. In the front, these tires should normally be run at 120 psi. For an extra measure safety if you are running at interstate speeds in hot weather, tire engineers have advised that you should increase the inflation to 130 psi. The drive axle tires should be inflated at 105 psi minimum, and tag axle tires 90 psi minimum. These inflation specs are for cold tires. The inflation pressures will read higher warm or hot tires. Air should never be bled out of a warm tire to reduce the pressure to the cold specification.

TechTalk

[Charlie Kokesh]

My coach is a 1996 with Bridgestone tires. When I picked the coach up two weeks ago I was told that the correct inflation was 105 to 110 for the rears and 110 to 115 for the front tires.

Is the difference between what I was told and the 130 psi to 140 psi mentioned above a function of the Bridgestones vs. Michelin?

Is there a difference in the basic size of the tire that would also make a difference?

Charlie

[TechTalk]

Charlie, the inflation recommendation for the front tires depends on the size. The first message in this thread covers 315/80 R 22.5, with Michelin Load Range L being the only recommended brand and ply rating. The third message in the thread is our inflation recommendation for 11R24.5 Load Range H of any brand. We will remind the service staff of our inflation recommendations.

TechTalk

[TechTalk]

Wayne: Your 1994 Newell requires the load range H version of the 11R24.5 tire. Load range G does not have adequate weight capacity for the steering axle, although it can be used on the drive and tag axles. The proper cold inflation for load range H is 120 psi, increased to 130 psi for operation in high ambiant heat conditions. We will be in touch "off the board" to work out arrangements to change your coach to load range H tires on the steer axle.

TechTalk

[DICK MILLER]

ALL LOAD RANGES ARE PRINTED ON THE SIDEWALL OF YOUR TIRE; I THINK NEWELL WOULD SUGGEST YOU USE THE TOP RANGE FOR SUMMER USAGE. DIFFERENT TIRE MANUFACTURERS USE DIFFERENT PRESSURES BUT MOST WILL BE WITHIN 10 LBS OF ONEANOTHER. ONE THING TO ALWAYS REMEMBER IS THAT A TIRE RUNNING ON A SEMI WILL NORALLY BE READY FOR RETREADING WITHIN A YEAR AND A HALF AND THE RECAPPED TIRE CORE WILL BE OFF THE ROAD IN THREE YEARS MAX. I SAY THIS BECAUSE YOU MAY THINK YOUR TIRE LOOKS GOOD AT 4 YEARS SINCE YOU HAVE LOTS OF TREAD. DO NOT LET THIS FOOL YOU. I AM SURE YOU WILL NOT RUN THE MILES THAT A SEMI TRUCK DRIVER WILL, IE. 100,000 MILES ANUALLY. A TIRE CORE MUST BE REPLACED ON OR BEFORE IT'S FIFTH BIRTHDAY NO MATTER WHAT KIND OF TREAD IS LEFT. LOOK FOR DOT DATE ON SIDE OF TIRE. MANY TRUCKERS WILL TELL YOU FOUR YEARS MAX. I HAD TWO BLOW OUTS THIS SUMMER BECAUSE A TIRE DEALER TOLD ME THE TIRES LOOKED FINE. THE TIRES WERE ON THEIR 5TH YEAR AND BLEW LIKE A BOMB. CLOSER INSPECTION REVEALED TIRE CHECKING.