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Tire Impressions

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What are tire impressions or tracks? Tire Impressions are the tread design and dimensions of a tire. ... Sipe: small grooves. Slots: across a tire ... – PowerPoint PPT presentation

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Title: Tire Impressions


1
Tire Impressions
2
Tire Impression Evidence
  • What is tire impression evidence?
  • How is it involved in crime scenes?
  • How is it collected?
  • How is it analyzed?

3
Tire Impressions
  • 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.

4
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

5
Tire Impressions
  • Design Elements

Grooves around a tire
Slots across a tire
Sipe small grooves
Tread Wear Indicator raised bar under design
shows after wear
6
Tire Impressions
  • Noise Treatment
  • If tire design was exactly repeated around the
    tire, noise would result.
  • Design repeated at different pitch lengths

7
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.
8
Tire Impressions
  • Tire Track Evidence

Wheelbase measured from front center to back
center
9
Tire Impressions
  • Tire Track Evidence

Turning Diameter Diameter of a circle made when
the wheels are fully turned.
10
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

11
Tire Impressions
  • Recovery of Tire Evidence
  • Cast can be made of 3-D impressions
  • Long sections (3 feet) should be cast.
  • Use dental stone

12
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.
Class Characteristics
  • Size
  • Tread design
  • Some wear marks

13
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.
Known tires collected. Inked or 3D impressions
can be made for comparison.
14
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.
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