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Tire Impressions
Tire Impression Evidence
What is tire impression evidence? How is it involved in crime scenes? How is it collected? How is it analyzed?
What are tire impressions or tracks?
Tire Impressions are the tread design and dimensions of a tire.
Tire Tracks are the related dimensions of the 4+ wheels.
Tire Impressions
Different Types of Tires:
Original Equipment (OE) Tires sold on new cars thousands of cars have same brand and size
Replacement Tires: purchased to replace old, worn tires usually different than OE tires
Tire Impressions
Design Elements:
Grooves: around a tire
Sipe: small grooves
Slots: across a tire
Tread Wear Indicator: raised bar under design; shows after wear
Tire Impressions
Noise Treatment:
If tire design was exactly repeated around the tire, noise would result.
Design repeated at different pitch lengths
Tire Impressions
Tire Track Evidence:
Track width: measured from right center to left center
Track width of front tires and rear tires are not always the same.
Tire Impressions
Tire Track Evidence:
Wheelbase: measured from front center to back center
Tire Impressions
Tire Track Evidence:
Turning Diameter: Diameter of a circle made when the wheels are fully turned.
Tire Impressions
Recovery of Tire Evidence:
Photos taken along with log of location.
Since tire tracks are variable along length (pitch), entire track should be photographed (examination quality) with overlapping photos.
Ruler included
Tire Impressions
Recovery of Tire Evidence: Cast can be made of 3-D impressions Long sections (3 feet) should be cast. Use dental stone
Tire Impressions
Analysis of Tire Evidence:
Class Characteristics can be used to eliminate a suspected tire or suggest a tire could have made the track.
Size Tread design
Tire Impressions
Some wear marks
Class Characteristics:
Analysis of Tire Evidence:
Class Characteristics can be used to eliminate a suspected tire or suggest a tire could have made the track.
Known tires collected. Inked or 3D impressions can be made for comparison.
Tire Impressions
Analysis of Tire Evidence:
Similar to shoes, individual characteristics can be used to identify an exact tire.
Remember, individual characteristics change over time.
Tire Impressions