My df velomobile was ordered with tubeless tires on the front, Schwalbe Pro Ones 28-406. It was my first experience with the tubeless world, having spent decades happily using buytl tubes (and latex tubes, less happily) in the road bike world. I figured, since I'm switching machine types, I might as well also learn the new world of tubeless.
It was an eye-opening experience. I can understand why people give up on them as there's a steep learning curve to be overcome. I made a whole bunch of mistakes of course, fully documented below, but I'm now happily running tubeless tires and currently have no intention of switching back.
Inner tubes are much easier to deal with, but if you live in a puncture-prone environment, as I do, and you still want to run high-end tires, tubeless is the way to go. Some punctures will be self-healing and you may not notice you've punctured until your ride is done. If you're riding an event, that's a big time advantage. If you're riding in 40°C+ heat with no shade, as I often do, it's also important to get going again as soon as possible (before you become roadkill).
Although the liquid sealant must contribute some resistance, tubeless has the advantage of less rolling resistance these days than over the same tire/tube setup. (Even in the conservative world of UCI ProTour cycle racing, time trialists are using tubeless these days for a rolling resistance advantage.)
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Tires improve every generation. There's clear empirical evidence of that. On the front, I've been using Schwalbe Pro Ones 28-406 since my velomobile was delivered at the beginning of 2019. As my stock of Pro Ones became exhausted, I started using the Pro One TLE Addix Race. It obviously depends on the rim used, but my tire measures around 29.6mm wide when mounted on a high-end Fratelli FX18XCR rim. Such a wheel weighs about 808g without a tire. Total weight with tubeless is just over the 1kg mark. (I carry a spare front wheel inside the df shell behind my seat to the left. I believe a 1kg weight penalty is reasonable against a very fast wheel change should an unsealable puncture or blow out occur.)
There's about a 2W difference (at nearly 30 kph) between this tire and the best general-purpose tire, the Continental GP 5000 TL, see table below. However, the GP 5000 is not available in 406 size (as of 2020). (I use a 28-584 GP 5000 on the rear wheel.)
However, manufacturers need to balance puncture resistance against rolling resistance and so do you. We are also limited by velomobile wheel sizes and also sizing constraints from the velomobile shell wheel well. The turning circle, not a strong point of many velomobiles, can be adversely affected. If you use wheelpants, another consideration is sidewall durability. My tires tend to scrape the teflon tape off the wheelpants. And the result of that can be seen on the sidewall of the tire on the left below.
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Here is a snapshot of the fastest tires currently available, independently tested by https://www.bicyclerollingresistance.com (note: not every tire has been tested):
This website has some very good advice backed up by up-to-date empirical testing.
Some examples:
How much wattage are you losing to rolling resistance generally at velomobile cruising speeds?
I'm not aware of any definite measurements for a velomobile, but assuming the front wheels are properly aligned, the typical values reported for road bikes should be a good guide (ignore the aero contribution obviously). Notice rolling resistance generally scales with weight. Velomobiles are heavy. (My df has a 20 kg weight penalty over my road bike. The lightest custom velomobiles have maybe a 10 kg weight penalty.)
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Some tire levers are not strong enough to budge the tubeless bead. I never had problems with regular road bike tires, so this was quite a shock to me. Example below on the far left is a Zefal tire lever from a tube patch kit. It's a useless noodle when it comes to tubeless beads. In the middle is a busted VAR tire lever set that had served me well in road bike days. Yes, I broke both of them trying to get a tire off. On the right are basic yellow tire levers, available from a variety of sources. They really bend. Notice I also brought out the screwdriver on that occasion. On the far right are the strongest plastic ones I've used so far, they're from Doug Davis at Bicycle Evolution. I don't know what they're called.
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The 3D-looking Pedros tire levers available in several colors are borderline workable. (I have 6 of those.) I also own the Park plastic-wrapped steel core levers (TL-6.2), too bulky, and no-name metal levers. You want to have super-thin edges to get under the bead and levers that are as stiff as possible, but you don't want to scratch or dent your rims, so bare metal levers or a screwdriver should be a last resort.
It actually really depends on the rim, so your mileage may very well vary. The standard rims supplied with the df are fairly wide and easy to deal with given stout levers. But when I took delivery of a specially-dished wheelset for use with wheelpants, things got a lot tougher with the narrow Fratelli FX18XCR rims. Hence the broken tire levers.
Mounting the tire is made easier by using the VAR wishbone lever to lift the last bit over the edge of the rim. I had bloody fingers a few times before I got the right tools for the job.
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I initially had no problems with removable-core valve stems. On the wide stock df rims, there is enough room in the center channel for the stem. It shipped with Schwalbe stems. But see the left picture below. On the narrow Fratelli rim, it squished the base in from the sides. The valve stem then became a source of slow leaks. This was a Milkit valve stem: compare with the original in the adjacent picture . (Too wide for the rim, otherwise it is a brilliant piece of kit because you can remove the valve core without losing air, see 3rd picture from the left.) The WTB and Schwalbe ones work fine, but lose air when the core is removed.
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On tubeless systems, the rim tape must not be the source of leaks. Well, actually tubeless is really a system: the rim tape, the valve and the bead all have to work perfectly in order not to leak air. In a perfect setup, the sealant wouldn't be needed until you puncture.
The rim tape should also be very thin indeed to allow maximum room for the tire bead to maneuver. My df came with Schwalbe rim tape installed (but no sealant), bottom left picture. (The seal was only good for a day's worth of air. But I didn't realize this until I took the tire off.) With wheel cover but no tires, these wheels weighed about 1037g each.
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The fancy lightweight wheelset (about 800g each) came with a double layer of rim tape (weighing 7.1g), see center picture. Leaks around the valve holes developed in conjunction with the squished Milkit stems. Eventually, I replaced both the tape (with single layer DT Swiss tape) and the stems, pictured bottom right. Seal was good after that.
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Sealant, when it's doing its job does this:
Sometimes when I get back from ride, the only clue that I had a puncture is that tell-tale sign of the sealant on the tire surface. However, in this particular case, the tire failed to hold air on the ride. (I swapped the wheel quickly and investigated once I got home.)
What happened? Well, the problem with sealants in dry climates is that they dry out quickly. If they dry out, they won't help seal punctures. Examples of dried-out tires below.
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But how do you know when your tires have dried out? You can't hear the sealant sloshing around. Maybe open up the tires every other month and hope you don't discover a mess like this? Or top up with 10ml occasionally?
Update: as someone told me, if you stir/shake it up properly, the Stan's will clog the Milkit syringe. There are just two many fibers around. That didn't happen for me until I'd used half the container because I wasn't shaking it enough. So I switched to Milkit's own sealant, which doesn't have big pieces that clog the syringe.
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It looks quite different from the Stan's, it's white and blue.
My first line of defense after the sealant is my spare wheel. If I get a second puncture, it's possible to make a very fast repair unique to tubeless sometimes. On the left picture below, it's obvious where the hole is. It's too large for the sealant to seal. The tool on the right makes it possible to insert a plug and re-inflate the tire quickly. (I've only done this once. Though I did decide to toss the tire shortly afterwards.)
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Simply jab it into the tire, release the CO2, and cut off the excess plug. No, you won't feel any thump, thump from the tire.
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I also carry two spare tubes and a patch kit. On a velomobile, we've easily got room for inner tubes, a regular repair kit, that repair kit with CO2, a portable pump, the tire tools I mentioned and a spare wheel. I should probably carry a spare front and rear tire too. Total, about 2kg?
I can't be that unlucky, right? Don't laugh. Back on June 11th 2007, it was day 2 of the Pactour Elite Southern Transcontinental. 188 miles. Didn't seem like a hard day on paper or at first. I was on my road bike. And I got 4 flats on the rear tire. It hit 104°F (40°C) and I only had two spare tubes and a patch kit. I remembered I wished I had carried 4 spare tubes that day.