Define Tyre Contact Point

This discussion has an associated proposal. View Proposal Details here.

Comments about this discussion:


In several Track rules, reference is made to the tyre 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 tyre 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 tyre 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.

I suggest that we continue to use "tyre contact point" in the rules, but add a definition in 1D.1. This could be like:

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

BTW: I tend to write British English spelling (that's the way I learned, being European). If the majority of people here prefer Tire over Tyre, that's fine with me.


I was the one that proposed using the center of the axle in the track committee, but I now agree with Klaas that this is not realistic to judge and I think the definition he provides is clear. 

I am in favor of "Tire" because that is the spelling that is used in the rest of the rulebook.


I agree with all of the above. Contact point is the geographic center of the contact patch, which should be more than sufficient for all current uses I'm aware of.

On spelling, I don't have a strong opinion, so I think it should use the form of English that's used by the greater number of native English speakers. And I'm not sure who that is, these days. The UK, Canada, New Zealand and Sinatpore, to my knowledge, all use British English. I'm aware that Scott Wilton and I both originate from the American Midwest, but I agree with him that locating all the words that might need updating could be a bit of work.  :-)


Spelling: I agree to John's notion about the greater number of native English speakers, but I would factor in the prevalence of unicycling among those speakers. With that, I think the balance will tip in favour (I'm stubborn) of US English. Besides, I would agree that there are better ways to spend our energy.

In the absence of any negative comments about my text suggestion, I plan to create a proposal soon.


The proposal looks good; clean and simple.

- I'm not sure if we need to include "usually judged by eye" as this is inherently obvious in the situations where we use it, and adds an element of impreciseness (that may be a made-up word). Olympic Track & Field, to my knowledge judges long jump and similar events by eye.

- As this will be in the "dictionary" section of the Rulebook, its important that we standardize the use of "tire contact point" throughout the rulebook to make sure it is consistent. In other words, if some locations just say "contact point" we should edit those to say "tire contact point".


The inclusion of "Usually judged by eye" indicates that judging by eye is good enough, and prevents organisers from thinking that you would need to set up a camera or laser beam system in order to be in compliance.

I agree with the second dash (it's not a bullet). However:
* On page 20, there is a "contact point" that should stay that way (IMHO).
* On page 29, there is a "tire contact point". So that is OK, but the remainder of that paragraph should be changed, since it contradicts both itself and our new definition.
* On page 46 under Timing, there are three occurrences of "bottom of the (unicycle) wheel". I think they should all be changed into "tire contact point". Besides, also this section is somewhat jumbled, and not fully consistent internally and with our new definition.
* I didn't find any other contact point or similar.


Klaas, thanks for finding those references. I agree that we should be consistent with our language.

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