Spicer Tire Matching Guidelines and Calculations - Manual

Spicer ®
Axles & Brakes
ABIB-0315
Information Bulletin
Bulletin Type: Service Information
Topic: Tire Matching Guidelines and Calculations
Affected Models: All Tandem Drive Axles
Tire Mismatch is the difference in the number of revolutions a tire in a tandem set will make, typically determined in
revolutions per mile. When mismatching occurs, excess heat builds up in the axle, thus increasing wear on internal axle
components.
Effects on Axles due to Tire Mismatch are as follows:
Side-To-Side Mismatch: (Single & Tandems)
ƒ Increases wear on wheel differential
ƒ Differential lock-out system
Front-To-Back Mismatch (Tandems)
ƒ Decreased life on inter-axle differential and power divider on the “D” (Forward Tandem) Head Assembly.
Dana recommends maintaining a tire mismatch no greater than 1.25% or less (see sample equation on page 2).
The best methods for measuring circumference are with a “Trammel” or “Flat Tape”. DO NOT measure from the top of
tire to ground; due to tire construction and inflation pressure this is an inaccurate method. When using a “flat Tape” for
measuring circumference, run the tape around the tire and figure the diameter. The diameter is figured by dividing the
circumference by 3.14.
NOTE: This is the only way to accurately measure the diameter.
This bulletin contains product information.
Dana Corporation is not committed or liable for canvassing existing product.