Change of "618mm" into "620mm" for the 24 class to accomodate non-marking tires

Comments about this discussion:

Started 29 Apr 15:43

I, and the French Track race committee, would like the following rule to be considered. It mainly concerns Track, but probably also Road and thus the main committee.

Background

The non-marking (white) Kenda Kranium 24x2.1 tire on non-narrow rims with normal pressure does not fit the 24 Class requirements.

Proposal

Sections 2B.1.2 in particular but in fact in the whole document, change of "618mm" into "620mm" (the upper wheel size limit of the 24 Class). It would also be the occasion to uniformly choose between "620mm" and "620 mm" (not sure which one is correct).

Body

Some competition organizers add the requirement that the tire used for the Track event should be non-marking. This was for example the case for the last Unicycling French Cup (CFM). The thinnest and usually only non-black tire for sell is the (white) Kenda Kranium 24x2.1 tire. This is the case in France and this is the case in the few unicycle.com shops that I checked. The issue is that this tire, when on a not narrow rim with a pressure compatible with the weight of an adult gives a wheel which is slightly above 618mm. A non satisfactory solution is to sufficiently deflate the tire. A more satisfactory solution is this rule change proposal. Indeed, the increase of the limit is just 2mm, less than 0.33%, and should solve the problem (to be checked by several independent people?). Also, there is no need to separate the records for such a small change.

One could argue that some non-marking tires are black. This may be true but this is much more difficult to check. For basketball in France, everybody uses non-black tires, to avoid endless discussions on which black tires are marking and which are not.

As a summary, the idea is to slightly change the definition of the 24 Class to accommodate the Kenda Kranium 24x2.1 tire, the only non-black 24-inch tire available in most parts of the world. This would allow riders to use the same tire for basketball, hockey, track and race events. This would in particular allow France to comply with the IUF rules for their events without informal relaxations on site. For the last CFM (Unicycling French Cup), we had to be tolerant with the many people having a Kenda Kranium tire for the Track races (allowing being slightly oversized rather than forcing them to deflate).

Comment 30 Apr 06:32

In the against column: This standard has remained unchanged for how long? Since the 1980s, right? It would also require remaking or adjusting the various check fixtures we have already. And lastly there is a Duro tire in white in 24”x1.75 (with an unfavorable tread design) that i assume would be in spec. I agree that the market for appropriate tires has gotten much smaller over the years.

In the for column: 618mm has had its share of headaches in the past, most “track 24” unicycles of 559mm BSD do not fit unless specifically underinflated. These problem tires frequently share the same sidewall marking as compliant tires so it is very hard to know your tire will be compliant before measuring.

I would ask that we gather a little data. Something like 5 samples of this kenda tire at a recorded pressure (40psi?) and rim width (internal is better, but external will work as long as we have the same figure across the board. I want to insure that we don’t change a rule and find that only half of these tires will actually pass on race day.

I’d like to run the same on a handful of 559mm track unis as well if possible so we know what is likely to pass/fail in advance of a rule change. I would be willing to do the measurement if it were reasonable for people to mail me tire samples, but i don’t think it is unless someone in the US owns or wants to own a bunch of these tires.

Comment 30 Apr 10:47

I'm a bit surprised that some organizers actually require special tires for track races. I'm not familiar with that in Germany, and here you can always use any tire. So, I've never actually seen white tires in track races here. But I see the point that the number of white tires is obviously much smaller than that of black ones and that can certainly lead to difficulties.
Increasing the permissible wheel diameter would of course have quite a strong impact, for example on existing world records. I think we should really consider what makes sense and is necessary here. Collecting data is certainly a good idea.

Comment 30 Apr 14:36

Things to consider:

- If we choose to modify this rule to fit a specific brand/model of tire, we need to be really sure we set the right number. Tim's idea above is a good one, using examples of the product purchased in multiple countries if possible, and even contacting the manufacturer to see if they have a maximum number they expect that product to fit. Doing this should eliminate issues with underinflating for measuring, inconsistencies in manufacturing, etc.

- Do these white tires have a "diameter" listed on the side, and is it a number larger than 24"? This is mostly because I'm curious about the product. Our existing rule is based on the very non-metric 24.333" diameter, which was the arbitrary number we chose to work from back when we realized we needed a specific size limit for tires. At the time, I don't remember if we were allowing for the skinny (nominal 26x1") tires that were on the market. I think we were, but didn't do a survey of actual diameters so picked that arbitrary number.

- Because that number *is* arbitrary, I don't have a problem with changing it. But we should only do it for products that are internationally available so a wide range of countries can have access to it.