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.

Comment 16 May 01:47

The Kranium tire is a 24x2.10 one, with ETRTO 54-507.

Concerning world records, the impact should be rather small. Again, the limit increase is only by 0.3%, and the tires that would benefit from this small increase may not be the best ones for beating world records. In swimming, the non-textile swimming suits decreased all world records by a minimum of 1%, often more, and the swimming federation does not make separate world records. Anyway, if changing the wheel size limit would force to reset world records, I would be against the change.

I agree that it would be better to survey the different tires, including on 26" rims, but it seems a lot of work. If such a big study is necessary, I am not sure the proposed change is worth the effort.

Comment 16 May 05:23

The reason I want to get actual tire size measurements is to insure that we have picked an appropriate value. If the intended tires only sometimes fit in our new standard, then we have built new check fixtures without actually solving the problem. It's not an easy measurement to take accurately, which is why I am willing to take it, as i have access to 30 inch calipers. I just don't want to take ownership of a dozen tires I'll never use.

I'll give emailing Kenda tires a shot. I doubt it'll go anywhere but maybe they will work with me.

Comment 16 May 14:56

Suggestion for Tim, make your email sound fascinating, including the fact that unicyclists like that tire so much, we are considering changing a competition rule to fit them. Get them on your side, and interested in the process. But insist on a concrete number that they will stand by as the maximum diameter of the product, when inflated to the recommended tire pressure.

Because non-black 24" tires are so rare these days, I believe it's worth the effort. You could even suggest to Kenda that racers all over the world may end up buying that particular tire if we can confirm it will be legal for racing. You don't have to tell them it will only have a tiny effect on their sales.

For myself, I'll stick with the ~23.6" tire on my 44-year old Miyata because it's not going to change anything. :-)

Comment 30 May 11:56

Kenda was kind enough to get back to me. Their spec is an outside diameter that is nominally 622mm with +5mm tolerance on the Kranium 2.1 inch on a 20 or 25mm rim. So if we made a rule change to 620mm it would likely not solve this problem

Comment 30 May 16:25

Oh bummer. That makes Kenda's "official" measurement 617-627mm, which would be a big jump from 618. I've just been banging around the Internet looking for those tires; haven't found them in white but saw some with gray tread and black sidewalls, but all I was getting of those were the photos, not vendors selling them.

But the general idea of this thread is a worthy one; to make sure riders can find 24" tires that fit the spec without being too much smaller than 618. Many of my (80s-90s) Track records were set on the Miyata 24" tires of the day, which measure roughly 600-605mm. But those tires are hard, if not impossible to come by in the USA at present. They're still being made, but Unicycle.com USA is unable to get them through their current distributor.

If a commonly available tire comes along that's not too much bigger than 618, we should remain open to the idea of raising it, but only for a tire or tires that are very widely available easy to obtain in most of our Unicon-attending countries. being flexible, though at that time we might need to reconsider if we allow ourselves to become much bigger and still call it 24", which is 610mm (rounded up from 609.6).

Comment 03 Jun 10:01

This is indeed a very large range and I don't know if it would really make sense to adjust the wheel size to cover the entire tollerance range.
In addition, the vast majority of riders in track racing use other tires anyway - the most common are probably 26 x 1.0 (like the Schwalbe Right Run in 23-559) and these 23-559 tires fit pretty much perfectly within the current 618 mm limit. With a very large adjustment upwards, many riders might look for new tires to make better use of the permitted size, which could lead to new problems.

A few days ago, I also asked myself whether there are any problems with white tires in timekeeping? The finish line is also white and I could imagine that the contrast between the tires and the finish line is extremely poor with white tires, making timekeeping extremely difficult. Is there any experience of this in France? I have practically never seen a white tire on the track in Germany, so I have no experience of how timekeepers cope with it.

Comment 03 Jun 17:21

We have had many races with white tyres, without any trouble. The systems definition is high enough.

Comment 05 Jun 09:27

I was mainly concerned about the low contrast between the white tire and the white finish line, but if this has never been a problem in France, then there is obviously no reason to be concerned.

Is there a particular reason why non-black tires are so often required in France? I've never heard of any problems with black tires in Germany. Metal pedals are sometimes disliked, but even that is not really a problem (especially as athletics use spikes anyway). But at least I can somehow understand that someone is worried that metal pedals could damage the track, but black tires definitely don't do that.

Comment 05 Jun 09:30

Non marking tyres are required in gyms (and plastic pedals too), and usually, people have the same unicycle for basketball and track (basketball is BIG in France).

Comment 05 Jun 09:30

Non marking can be black, but are often white, or other colors.

Comment 05 Jun 09:47

That's true about black non-marking tires; the classic Miyata tires never made marks on a gym floor anywhere, but were often hassled due to "prejudical" rules. I can't remember how many times I had to demonstrate to an official that they wouldn't make marks.

Comment 05 Jun 10:09

I can confirm that about the white tires being common in France. For the last CFM (French nationals) I also had a white tire as I used it for both basketball and track (as do quite a lot of riders in France as basketball is so popular). And if I remember correctly, the rule of the gym facility of the last CFM was *non-black* tires, I think as they wanted an immediate indication of tires that might mark. (Oh, I see that was already stated above in the intro concerning France).

For track and basketball I used the Impac Streetpac 24x1.75 that is white, which fulfills the current track wheel size requirement on my Nimbus E-Sport. I'm not sure, but I think many French riders had white tires for track.

Comment 05 Jun 10:23

So it's not really a problem with the tracks, but purely a problem for the gym? Only because many people in France also use the indoor unicycle for track racing it becomes a track problem? That explains it of course - as I said, otherwise the standard unicycle for track racing is more likely to be a 26 x 1.0, which probably is rarely used indoors.

Comment 05 Jun 13:51

For the record, the use of 26 x 1.0 tires was an unintended by-product from setting our rule of 24.333" as the limit for Track racing. That rule change was probably in the early 2000s. Before that, we were relying on what was printed on the sides of tires. But as wider tires became more common, especially for Muni (like the legendary 24 x 3" Gazzaloddi at ~26") we needed to be more specific. And then we had to make boxes because tires are so hard to measure! That number was chosen to allow some room for tire size variations, and was based on measurements of several common uni tires at the time. It was soon discovered that it allowed for skinny 26" tires, which is fine. It allows Track specialists to work with really light wheels.

The tire market will continue to change over time, possibly with new options coming from the growing flood of electric bikes on the market. Let us hope they also give us some more options that will work for our tracks. :-)

Comment 09 Jun 04:06

For me, the rule change is not intended to the champions/optimizers (who will indeed choose a light 26"-rim wheel) but to the "normal" people who use a limited equipment for all events.

To avoid endless discussions on whether a black tire is marking or not (cf. the tires of the American basketball team at UNICON 20), we tend in France to transform "non-marking" into "non-black" for basketball. For track, the rule of this year's CFM requires non-marking tires (I don't remember last year's wording). As François said, many people in France play basketball, and most would prefer to use their basketball tire for track (and possibly road) events as well.

Also, the question in France is not that the Kenda Kranium is the most optimized non-black tire for tracks, it is rather the only non-black tire at all for 24" rims.

Since the issue is mostly for non-champion riders, it is not that problematic to ask people to deflate their Kenda Kranium tire, but it is annoying nevertheless. That's why we submitted this rule change proposal.

Comment 10 Jun 02:16

> Since the issue is mostly for non-champion riders, it is not that problematic to ask people to deflate their Kenda Kranium tire, but it is annoying nevertheless. That's why we submitted this rule change proposal.

I totally understand that and if a change from 618 mm to 620 mm would have been sufficient to eliminate this problem, then I would certainly not oppose the proposed change. But if the tire can officially be up to 627 mm, this would mean an increase in diameter of almost 10 mm and thus the rule would certainly not only affect a few athletes who want to use their basketball unis for track racing, but for the broad mass of athletes who have so far made optimum use of the 618 mm with the 26 x 1.0 tires and now suddenly give away 10 mm radius. This would mean that some athletes would optimize their tires to make optimum use of the new limit and the broad mass of athletes would either feel disadvantaged or would also have to start using other tires in order to make optimum use of the new specification. I am therefore very critical of introducing such a major change for just a small group of athletes (and I am very sure that it only affects a very small group of athletes in relation to the total number of athletes who regularly race on the track).

Comment 10 Jun 05:52

I agree with you Jan.

Comment 10 Jun 10:45

It is good to learn the source of this request! Since 24" tires are not a large part of the cycle tire market, choices are limited for what works for us unicyclists. I want one of those tires, but I have not yet found a source I can order from that's not overseas (with big markup for shipping).

This discussion should probably end with us agreeing to keep an eye on the tire market and see what else is available in our respective countries. I do not want to race track on a little 1" wheel, not because it's bad for Track, but because I use that 24" for local transportation at Unicons. I used to have a purpose-built Track uni, but it was stolen at Unicon X in Beijing. :-(

I recommend that the participants in this discussion keep looking for 24" tires that they can purchase without big surcharges for shipping, and among us we may find one or more models that may be good in the future. We'll also need to get them measured, etc.