I have contacted a tubular tire company about making the world’s first tubular 36" uni tire. Meaning a sew-up, where the tire & tube are one unit, and mounted with glue to a hookless rim.
Tubular tires offer much lighter weight and less rolling resistance, although some don’t like the fact that you have to carry a spare and some glue in the event of a flat.
Anyway, this company is willing to make the casing with tube inside. But they do not actually make the rubber tread. Their standard practice is for te customer to strip a tread off another (cheaper heavier) tire, and they attach the tread to their casing.
Since the only 36" tires we have are clinchers, I don’t know if it is possible to strip off a tread that they could attach to the new tubular casing.
It seems the tread would be a loop of rubber about 4cm wide, 4mm thick, and 36" around (the same circumference as current tires). It would be ideal to have a fine cross-pattern for the tread.
Thus: does anyone have any suggestions for finding a 36" loop of rubber with such a tread pattern already on it?
I feel that this is a project worth pursuing, as tubulars rule the bike world for performance applications, and don’t go flat any more than clinchers.
PS: please, no comments on how modern bike clinchers are just as good as tublars…that is NOT our situation with the current crop of heavy 36" tires!
If it requires cannibalizing a brand new 36" tire, how much are these things likely to cost? Or could you use the tread from two “regular” tires? That could be a lot cheaper, and also give you way more choices. But still it sounds pretty expensive…
Let me clarify. The tire company makes cotton and silk casings. All I need to do is supply a continuous loop of rubber tread that they will vulcanize to the casing to complete the prototype. If it goes into production, they will be more interested in sourcing the treads themselves.
So the tread has to be a continuous loop of rubber. I wasn’t suggesting that it absolutely had to be from a new 36" tire, although that would seem to make it easier and guarantee the right size. But it cannot be 2 pieces fused together. Then you would have a sound and possibly a bump twice per revolution.
R&D always costs money. You have to do it in order to reach a point at which you can predict what the production version would cost. I have R&D’d many parts. Only a few are economical enough to produce. But if all one ever looks at is the cost, nothing would get done and we’d be stuck with these ridiculously heavy tires.
As long as the two joins are made neatly and accurately, I don’t think that you would notice any kind of bump when riding. And, as been mentioned already, the choice of 26" tyre treads is extensive (and cheap). The fact that it’s a prototype should be enough of a reason to choose a good tread design firstly and worry about the slight joint mis-match less.
Sounds like a great idea, Pete. It seems to me that you’d have to develop an overall system (i.e., wheel) with specific applications in mind before spending any money. Here are some thoughts off the top of my head that may help you work your way through this.
The first thing to think about is your application. Are you going for a road-only application?
The second consideration is: what ultimate tire profile are you after? It might be worth copying something like the thinner Big Apple for a prototype. That way you are dealing with at least some known tracking and turning characteristics, although of course those qualities will change with a different tire composition. Another possibility is the standard Coker tire profile since it provides stable straight tracking and is easy to turn on pavement. A related question is: what ultimate tire pressure are you trying to run at?
Once you know what profile you are after, what rim would you use? A modified Airfoil? An unmodified Airfoil? The rim is a essential aspect of forming your ultimate tire profile. The rim’s materials and cross sectional design will also determine the maximum spoke tension the wheel will support (given a specific brace angle), so a related question will be: how stiff does the wheel need to be? The wheel stiffness will determine whether the wheel can be used with brakes and how efficient it is during acceleration/climbing. The typical thing that people think about, wider rims, is less relevant if your application is road-only. So the rim should be designed with tire profile in mind. Also, with higher pressures, the tire itself will be the predominant factor in shaping the tire’s cross-sectional profile, and an important role of the rim is to act as a cradle for the tire.
Finally we can get to what outer rubber sources you can use. Your tread choice will be determined by a) your application, and b) your available raw sources and c) your ability to “edit” the tread. Here it might be best, for a prototype, to use a thicker source than you might ultimately desire. The additional thickness will make it easier for you or the casing manufacturer to tailor the rubber and prepare it for vulcanization. In addition, the casing manufacturer may have preferred rubber types for the vulcanization process. I’m sure the three 36" tires available have very different rubber types. Another consideration: if you are removing the fabric from the tire to be cannibalized, then ply is a minor consideration. Lastly, you might analyze your rubber source for tread post-editability. For a prototype, though, tread pattern is insignificant. There are so many other variables that just getting through the process with a tire that works for a few miles will be a huge step forward.
Once you can build prototypes fairly reliably, then it would be good to investigate other ways to develop your own outer rubber, which is where you will be able to fine-tune tread pattern and overall tire weight, as well as feed back your results into the casing characteristics for better handling and lighter weight.
Yes, strictly road use. A fine cross-file tread like bicycle road tubulars is the idea.
The casing will be round, like all tubulars. The tread is just the rubber strip on top of the casing. It doesn’t have to be thick, and would not work well if it was as thick as the TA or Nightrider. The problem with “stripping” a tread off of a clincher is that the casing is built into a clincher tire. That’s why the more I think about this, the more a plain rubber loop looks like the solution.
Around 50 sounds good. I know the Nightrider is rated to 65psi, but what do folks think about that? I have only briefly inflated a coker tire to that pressure, and it is too hard for my liking. The idea of a tubular tire would make for less rolling resistance at 30-50psi. Thus maintaining some semblance of tire suspension effect.
Agreed. The prototype will simply be an airfoil with the hooks ground away.
Plenty of surface for gluing, and the width is in good tolerance for a 2" section.
I’m still thinking a plain loop of rubber, in the dimensions as previously posted. To try to strip the casing out of a 36" tire would take too long, and probably result in a tread much heavier than necessary.
To give you a better idea, go to any good bike shop and examine how thin the treads are on a road (not pista) tubular. That’s what I’m after.
I still have to have a conversation with the company about the final source of treads. Because they specialize in customers sending them treads to make into fine handmade tires, they don’t have all the materials at their disposal.
hence maybe I just get a 4mm thick piece of rubber and cut a loop to shape.
I’m not worried about the durability of the compound right now. I’m more interested in riding the handmade casing.
Since the big goal here is to make a light tire, the best combination would be a very thin tread layer and very high pressure. If the Coker tire you briefly inflated to 65 psi felt too hard it's probably because the tread is very thick. I would imagine it's around 5 or 6 mm. It would feel like you're riding a truck tire. I like to keep my tire pumped up to at least 80 psi. When it gets down to 60 or 70 it starts to feel soft, a little slow to turn and vulnerable to bumps.
If you thin out the tread to 2 mm and add that to the casing which is probably less than 1 mm then the tire becomes suitably light. It also is much more pliable than a thicker tire. Not only will this very thin tire need high pressure to maintain its support but it will feel great precisely because it is so pliable.
I just took my callipers and measured a new Continental Contact tire 28 X 1 1/4 X 1 3/4. (It's my preferred tire right now.) Its total thickness came in under 3 mm. So if you were to glue a 4 mm tread to a casing that would put the tire thickness up at about 5 mm which would translate to a needlessly heavy tire.
The tires on that link you gave us can be inflated up above 100 psi. Now those are fast and light tires! I'll bet they're less than 2 mm thick.
What are they using in their casing? Given the option, I'd recommend getting a layer of kevlar in there. I wore my last two tires down to the threads without getting any flats.
A light tire is so much more responsive in accellerating and turning. I always find riding one of those fat tires to be really sluggish and cumbersome. Yes, they're perfect for Muni and Trials but if you want to cover some distance then we'll need to keep developing skinnier tires.
Even though sew ups give me the heebie jeebies, they are apealing if the alternative is a 1900 gram lunk run at 50 psi.
Thanks for putting in the work on product development. This is how great ideas become standard production models.
Greatly appreciate the input, you guys are on the right path here. I agree the harshness of a higher pressure would be offset with the suppleness of a thinner tread. So maybe I shoot for 2mm thick tread?
Problem is still finding a continuous loop with a 113" circumference. Further thoughts?
Why not use a rubber rim strip? Or are they too soft…
The biggest problem I see with a flat piece of rubber is that without all that little detailing, which I guess is tread, that you see on bmx/road tires, turning will suck. But having a working prototype would be enough, I agree.
sew up 36 tires sound cool. Especially so if having to carry a spare meant only as much as a 29er tube weighs now anyways. I tend to ride my coker at 60psi or so when doing long distance, I hate the mushy feel when I’m riding up hills, so I could see myself having 80+ on a ‘pure road’ unicycle, especially with thin tread.
2 mm sounds perfect to me. About the only source that I can think of is cutting apart an innertube. You’d gett a nice thin rubber strip that is already curved to fit the casing.
Of course it’s too soft and would wear out in about 5 miles, but this is a prototype after all.
I still can’t see why you cant just use a flat strip of rubber which could just be butted up to itself in the vulcanizing process.
I am sure that these tires would be expensive if they ever become a production item. Could you repeatedly get your tire re-treaded when they wear out? Or would they be done once the tread is worn through?
Wouldnt it be a 34" tubular? if the tire is going to be the width of the rim (approx 1") would the diameter not decrease by 2". if your doing that there is going to be at least one seam, and if your having one seam why not make it 2?
Might want to re-read this thread. No one suggested the tire would be the width of the rim. The tire section will be at least 2", but I don’t think it necessarily needs to be the current standard of 2 1/4". The section plus the tread = the total diameter.
Plus, tubulars are more supple than clinchers, so we may not need the full section width to get a suspension effect with the tire.
I never said there was going to be a seam (referring to the tread). The ideal tread is a continuous loop of rubber, which is adhered to the casing. Think a large rim strip!
And yes, tubulars can be re-treaded! As long as the casing stays in good order.
I’m going to ejukate you guys on tire technology whether you want it or not!