Proposal 29: Add definition of Tire Contact Point in 1D.1 [ Revision 1 ]

Committee: Main Committee
Submitted on 2019-04-30
Status: Passed on May 17, 2019


This is to add a definition of "Tire contact point", a term that is used in some rules in Track: Racing and Track: Other, to clear up what we mean by it.


(There is no old rule, c.q. old definition)

New rule, to be added in 1D.1 in the correct alphabetic location:

Tire Contact Point: The centre of the contact patch between the tire and the riding surface. Usually judged by eye.


In several Track rules, reference is made to the tire contact point. In a current discussion someone remarked that there is no such thing as a single contact point. There is a contact patch with finite dimensions. Hence, it is not clear if said "contact point" refers to the front of the contact patch, or maybe the centre or the rear of it. Also, the contact patch, while roughly being oval, is not a precisely defined shape. If you would look closely, you would see "islands" of contact outside a main contact area (and also "lakes" within the "mainland"), due to irregularities in the tire and the riding surface.

It was argued that the centre of the axle is more precisely defined. However, the centre of the axle is not necessarily located vertically above the tire contact point (e.g. if the unicycle is twisted sideways to any degree AND leaning sideways). This means that the two definitions are not always the same. Moreover, the centre of the axle crossing a line (for example the finish in Slow racing) is not easy to see because you have to imagine a vertical line. Therefore, in practice, judges will judge the passing of the contact point/patch anyway.

We can continue to use "tire contact point" anywhere in the rules, if we add a definition in 1D.1.



View Discussion

Votes on this proposal:

19 out of 23 voting members have voted.

Agree: 19, Disagree: 0, Abstain: 0.

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