So different tires.

Tires are used on the following vehicles: • cars / SUV / quad • motorhome / delivery van • truck / bus • trailers and caravans • bikes (bicycles, motorcycles, mopeds, scooters, eScooters) • agricultural vehicles (tractor, agricultural trailer) • earth moving machines (excavators, wheel loaders) • Industrial vehicles (forklifts) • transport equipment (hand truck, bicycle trailer, wheelbarrow) • toys (tricycle, balance bike, unicycle) ... and all these tires have a different structure, different dimensions and different profiles. Tires are the interface between the vehicle and the road. All driving, steering and braking forces are transmitted to the road through the contact surface of the tire. When choosing the right rubber compound and the tread pattern, a toothing effect can transmit forces that are higher than the weight of the vehicle. Usual car tires transmit all forces to the road surface over an area that is between the size of a postcard and DIN A5. In the case of a truck, the footprint per tire is approximately between DIN A5 and A4. Thanks to their rounded profile, motorcycle tires have an elongated contact area about the size of half a postcard. Forensics mainly deals with cars and delivery van tires. The world tire market has a lot of these tires available for sale every yea r. In Germany, the bicycle is a common means of transportation. Therefore, many perpetrators use the bike to get to the crime scene and e.g. to use as a climbing aid for the 1st floor of a house. For this reason, it is possible that bicycle tire marks can be found at the crime scene . In order to keep an overview, some federal states have tire model databases. Tires can be determined using these databases. Of course, based on the tread pattern and the width of the tires, there are already indications of the tire type (e.g. use of sipes for all-season and winter tires), but in most cases a manufacturer cannot be determined without a tire database.

Comparative investigation of tire tracks.

Tires have the same pattern when leaving the manufacturing plant within a tire model. They usually have no individual characteristics. The tread of the tire is only equipped with individual characteristics when it is used. For example, cuts in tread blocks, breakouts, buildups, indicators or stuck bodies. If these peculiarities become visible in a track, evidence can be provided that a specific tire caused a track at the crime scene. The difficulty of comparing tracks is, that creating a comparison track is not easy in some cases. If there are imprint traces, simple devices can be built. The effort is higher for impression marks. The following methods are used to generate a comparison track in Germany: • Applying soot powder on the tire and rolling the tire over laid paper • Applying black color paste on the tire and rolling the tire over laid paper • Applying Bio-Fluid oil on the tire and rolling the tire over lined paper, then contrast with magnetic powder • Apply soot powder to the tires and mask with transparent adhesive film • Roll over in MicroTrack mass, optional plastering the track • Rolling over in quartz sand, optional plastering the track A useful method for comparing traces in the presence of impression marks is the use of MicroTrack . The plasticine is pressed in with the tire and then poured off with plaster. The problem here is always to achieve the correct contact pressure. Driving over with the vehicle it‘s too much contact pressure, only rolling the tire with hand force over the mass the impression is too soft . However, depending on the length of the track from the crime scene, an equally long comparison track must also be made. With a Mercedes C-Coupe C205 and the associated 225/50 R17 tire, a complete track would e.g. 2.06 m. That would be a great comparison track. Since there are often only partial tracks, the comparison track only has to be the same length of the partial track. The comparison of two plaster casts is made in the comparison process. However, there is also the option of producing a transparent film for the overlap process on which the comparison track was printed.

Axle track information.

The axle track or wheel track at the front and rear axles is usually different. The driving behavior of the vehicle will be influenced constructively by different track gauges. With a larger track width at the front, the breaking out of the vehicle at the front (understeering) and with a larger track width at the rear, the breaking out at the rear (oversteering) can be improved . Based on the axle track can be concluded of one car or several vehicle models. Here is an example: • BMW 5 Series 525d (from 2010) axle track front 1558 mm, rear 1582 mm • Opel Corsa D (2014) axle track front 1485 mm, rear 1478 mm Since 2002 the State Office of Criminal Investigation of Bremen has a car axle database. With the help of this database, lane widths at the scene of the crime can be assigned to one or more cars in order to achieve helpful investigative approaches for criminal prosecution.

Do you know that ?

A tire has a lot of markings on the wall. An expert for tireprints must be able to interpret them correctly. Summer, all-season and winter tires Based on the lamellar structure in the tire treads, which are often visible on the track, it can be determined quickly whether it is a summer, all-season or winter tir e. Bicycle tires. Depending on the type of bicycle tire, a tire track is only approx. 2 cm to 5 cm wide. With a few exceptions, there is no change in the profile of bicycle tires as we know from car tires. Determining the exact location is therefore challenging. Hand truck At some German crime scenes, the burglars use hand trucks to transport safes. These tireprints can also be assigned to a specific hand truck when it is foun d. MikroTrack A reusable tire track impression mould. MikroTrack creates a perfect three-dimensional impression with accurate recording of all pertinent information in the evidence. The MikroTrack impression can be stored and will not dry. Bio-Fluid This bio-oil from Weicon is a resin-free and acid-free, medically pure white oil that was specially developed for lubrication and maintenance. It is non-toxic, water-white, solvent-free, odorless and tasteless, creepable and water-repellent. It is very suitable for creating comparative prints . AccuTrans AccuTrans casting silicone is a low- viscosity, thixotropic elastic impression compound for taking accurate impressions on smooth, textured or rough surfaces. AccuTrans is ideal for lifting impressions of toolmarks or other impression mark s. Since 2002, the experts for technical formtracks have been using the impression material from Coltene. A short time later, it was introduced all over Germany for securing evidence at the crime scene. The following picture was taken during the test phase at the State Criminal Police Office of Baden-Württemberg. . Speedex light body For several years German experts of toolmarks have been using Speedex light body and the associated Universal Activator for double impressions in order to create almost lossless impressions of tools for the identification of impression marks .