Tires aren't pretty. Part 2 on Friday

Size Definition – Reading a Tire

Motor Home Tires

11R22.5

11= Cross Section (Inches)

R= Radial

22.5= Rim Dia. (Inches)

Towables

ST225/75R15

ST= Special Tires for Trailers

225= Cross Section in (MM)

* 75= Aspect Ratio

R= Radial

15 Rim Dia. (Inches)

Light Truck

LT235/85R16

LT= Light Truck

235= Cross Section (MM)

* 85= Aspect Ratio

R= Radial

16= Rim Dia. (Inches)

• Aspect Ratio = Section Height divided by Section Width. Lower number= Shorter Sidewalll & Wider Tread.
  Understanding Tire D.O.T. Numbers
  MC3TPXAW1204
  MC = Mfgr. Plant Code
  3T = Government Size & Ply Code
  PXAW = Manufacturer Construction Code
  1204 = Tire Build Date (12^th. Week of 2004)

Terms

• GVWR – Gross Vehicle Weight Rating

The Maximum Weight Rating Established by the Chassis Manufacturer

• GAWR – Gross Axle Weight Rating

The Maximum Weight Rating That Each Axle Can Support

• Tire Load Limits

The Maximum Load Rating for One Tire at a Specific Pressure As

Shown on the Load & Inflation Table. The Maximum Load and

Inflation Pressure is Shown on the Sidewall.

Tire Load Limits

• It is important to remember that exceeding the GVWR can cause premature wear and tear on the RV's components. The RV may have failures or need repairs due to excessive weight, although the weight factor may not be clearly evident. In the worst case, an overweight situation creates hazards.
• It is possible to be within your Gross Vehicle Weight Rating (GVWR) and your Gross Axle Weight Rating (GAWR), and still be overloaded on an individual wheel position.
• Unless you know the load being carried by each wheel position, you have no way to know the proper inflation of your tires. Improper inflation leads to improper wear, reduced life of the tire, and greater potential for rapid tire failure.

Negative Effects of Tire Overload/Underinflation

• Loss of Fuel Economy

Higher Expense

More Fuel Stops

• Possible Tire Failures Due

Tire Overheating

Fast or Irregular Wear

• Down Time
• Reduced Braking Performance
• Reduced Handling Capability
• Reduced Casing Durability

Conclusions

• Wear Rate is Optimal When The Tire Operates at the Correct Inflation Pressure
• Underinflation is Worse Than Overinflation, since not only does the Tire Wear Unevenly, But it Also Generates More Heat from Overinflation.
• Correct Inflation Pressure is Key to Satisfactory Tire Performance.
• Underinflation Results in Decreased Fuel Economy.