Recording Tire Test Impressions

A few general methods and their variations are available to the Technician to record tire test impressions. The technician will eventually select a method based upon which materials are available and the ease by which the tire's impression can be recorded.

The goal of any effort to record a tire test impression to is to accurately capture the tread pattern, design, individual characteristics and wear characteristics. Accurate recording and complete recording of the tire's details is essential in order to allow the expert examiner to fully compare the test impressions to an unknown tire track.

Descibed below are methods which can be employed to record tire test impressions:

General Considerations for Tire Test Impressions

Record the series of letters and numbers that follow the P or LT marking on the tire. This information refers to the tire classification, tire dimensions, and wheel diameter for the tire.

Record the series of letters and numbers that follow the DOT marking on the tire. This informaiton refers to the source and date of manufacture of the tire.

Lightly brush any grit or granular material from the tread. Do not remove any foreign material such as stones or other debris which is imbedded in the tread or grooves of the tire.

Push the vehicle across the length of the paper or poster board rather than driving the vehicle across. Pushing allows for more control and less slippage during the recording process.

Ink on Butcher Paper

Use Black printer's ink, not fingerprint ink, and plenty of it. The amount to be used far exceeds the amount normally required for inked fingerprinting.

Be certain to completely ink the tire from shoulder to shoulder (across the width of the tread). This is a common problem utilizing this method, in that the edges of the tread haven't been fully inked. Thus, these regions of the tire are sometimes not ever recorded.

Take care to assure that the paper dosen't buckle or fold during the recording process. By slowly pushing the vehicle across the paper, this distortion can be reduced.

You must use padding underneath the paper, or else, any texture or grit from the road surface will act to create "voids" in the inked tire impression. Cardboard, a short pile of newspaper, or an office carpet protector can suffice for this means.

Ink on White Chartboard

Be certain to use a quality poster board for this purpose. A stock of poster board that is too thin will defeat the purpose of using the board as opposed to the butcher paper. Try to obtain a poster board that has a thickness of at least 1 / 8 inch, preferably 1 / 4 inch thick.

Be certain to completely ink the tire from shoulder to shoulder (across the width of the tread). This is a common problem utilizing this method, in that the edges of the tread haven't been fully inked. Thus, these regions of the tire are sometimes not ever recorded.

Be sure to prevent tire squirming when pushing the vehicle/tire across the poster board. Use a lesser amount of ink than used in the butcher paper method.

Grease - Magnetic Wand on Poster Board

Be certain to use a quality poster board for this purpose. A stock of poster board that is too thin will defeat the purpose of using the board as opposed to the butcher paper. Try to obtain a poster board that has a thickness of at least 1 / 8 inch , preferably 1 / 4 inch thick.

A number of substances can suffice for the "greasy" substance. Margarine, WD-40, vasoline have all worked well. To apply, you can wear surgical gloves, apply the grease to your hands, and then run your hands across the tread. Do not over-grease the tread. Over-greasing will cause unacceptable build-up of the grease on the poster board.

Use a Magnetic Fingerprint Wand and Black Magnetic Fingerprint powder to develop the greased tire impression on the poster board. A "light dusting" using the magnetic wand will normally produce a test impression of good detail, with little "filling - in" of the tire's grooves and slots.

Notations on Tire Test Impressions

The following notations should be recorded on each finished Tire Test Impression:

• The Axle/Location on which the tire is placed (ex:  "Left Front Tire").
• The Outside of the tire in relation to the outside of the vehicle.
• The Inside of the tire in relation to the inside of the vehicle.
• The Beginning of the roll of the tire across the test medium.
• The End of the roll of the tire across the test medium.
• The Manufacturer & Model Name of the tire.
• Tire classification  P or LT markings on the sidewall.
• DOT markings from the sidewall of the tire.
• Case Number, Technician's initials, and Date of Recording.

Published Articles for Tire Test Impressions

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