Avoid tubeless disasters

There is high demand among mountain bikers for tubeless tires on their bikes, and for good reason! Anyone who has ever ridden a bicycle has experienced a mid-ride flat tire. Since these are relatively rare on pavement with a good quality tire and proper installation, I will leave road tubeless alone for now. I want to focus today on tubeless tire for off-road applications where riders are concerned with thorns punctures and pinch flats.

The beauty of a tubeless system on a mountain bike is that the latex-based sealants available will seal up most punctures caused by the local vegetation, and eliminating the tube means there is no tube to pinch in a hard impact. This means riders can ride worry-free through over-grown trails and run much lower pressures to increase traction on the trail. Many who are used to pumping their tires to 35-40 psi to avoid pinch flats can enjoy a grippier, softer ride at pressures below 25. The feeling is liberating and many bike shop customers will ask their local shop if a) the new bike they are eyeing is "tubeless ready" or b) if the shop can convert their existing wheels and tires to tubeless.

As I have seen, many bicycle mechanics are all to eager to please and are willing to "convert" a rim and tire combination to a tubeless kludge. Consider the results of a badly done tubeless conversion: your customer happily starts riding after you return the freshly converted bike. He or she drops the tire pressure to 24 PSI and decides to test the system on the local trails. As the rider gains some confidence and rails a tight turn, the tire slips off the rim. If the rider (and the mechanic responsible) is lucky, the tire merely "burps" some air and the rider has to top off the pressure at the next stop. Otherwise, the rider could crash, causing bodily harm and damage to the bike. The shop that did the work could get negative reviews or face a lawsuit. This is a lose-lose for mechanics and customers.

The other reason to refuse to do questionable conversions is productivity. Anyone who as attempted more than a few conversions knows that some take longer than others. A conversion should take no longer than the time it takes to wrap the rim in tape, install a valve, mount a tire, squirt some sealant, and inflate the tire. You should not have to struggle to get a tire to inflate and seal. Inflating the tire should take no more than one minute- if it takes longer, the tire and rim combination is somehow sub-optimal and will likely not stay sealed and inflated.

Basically, inflating a tubeless tire needs to result in a tight fit on the "shelf" of the rim. If the rim is not designed to form a tight enough seal or the rim is fitted with a strip that sufficiently seals it, the movement that results tire failure what could be catastrophic. Stan's has an excellent article on the topic here.

To minimize the chances of a tire failure, let's first lay out what NOT to use in a tubeless conversion:

• "Cheap" tires- in a professional setting, I would not attempt a tubeless conversion on any tire that has a wire bead, or any tire that is not somehow identified by the manufacturer as "sealant compatible" or "tubeless ready," or at least otherwise known to be a good quality tire with strong casing. Some tires are known to break down chemically with some sealants, which is why Kenda identifies some of their tires at SCT.
• Rims that are not designated as "tubeless ready" by the manufacturer, unless used with an appropriately chosen and installed tubeless rims strip, such as Stan's strips.
• Tire/ rim combinations that are known to be problematic. You will need to do some research on this, but if the mounted tire is impossibly tight or incredibly loose, the end result will be bad.

Manufacturers have developed several options and "standards" for tubeless tires and rims, and not all of them are compatible with one another. I will not go into very disputed merits of each system, as I am primarily concerned with compatibility. The most common tubeless interfaces you will find are:

• UST- Universal System for Tubeless. This system requires rims and tire casing and bead to be manufactured with narrow specifications to be considered UST.
• BST is Stan's NoTubes design is intended to allow riders to use "regular" tires in a tubeless system. It is found on their ZTR rims, and on a few licensed products, notably Sun-Ringle (click "Features"). Stan's rim strips can also create a BST-type interface when done correctly.
• "Tubeless ready" is a bit murkier. Most "tubeless ready" tires have a bead similar to UST specifications but without the airtight casing and therefore require sealant to work. Wilderness Trail Bikes' TCS and Bontrager TLR designs might fit under this category.
• "Ghetto tubeless" is a DIY kludge involving the use of a split inner tube, various tapes, home-brewed latex sealant, and other methods. Some of these methods work wonderfully for riders, but should never be done in a bicycle shop.

The final but equally important issue to consider is how well any particular tubeless-specific tire will fit and seal on any particular tubeless-specific or converted rim. I have found that BST rims and Stan's rim strip conversions do not play well with UST, TCS, or several other "tubeless ready" bead tires. I witnessed the anguish of a friend trying to fit some WTB TCS tires on his Stan's rims recently, breaking several tire levers and very nearly breaking some fingers in the process. The bead on most rims with a bead based on the UST design is simply too tight to fit reasonably on BST rims (Stan's agrees with me here), so I don't recommend trying those.

If you are ever uncertain about what kind of materials are needed to successfully convert a rim to tubeless, ask the manufacturer directly. If it causes your customer to wait an extra day to get wheels back, it will be worth it to both parties to do it right rather tan compromising in the name of expediency. For example, I just noticed that Alex manufactures several rims (MD21, for example) with their Tubeless Ready System or TRS, which they describe as "Tubeless Ready System = Universal Valve + Rim Tape + Sealant," but they fail to specify what tape and valves are to be used. That kind of specificity may seem absurdly fastidious to some, but a good bicycle mechanic makes or breaks a career on that fastidiousness. [I will follow up with Alex on this topic.]

Whatever you do, make certain that you understand how tubeless systems work, what combinations and techniques work the best. Set standards for your shop so that everyone on staff is on-board with using the same techniques so there is continuity from the sales floor to the service writer to the mechanic and back to the customer. Your shop and your customers will be happy.

addendum 5 July, 2018: I recently had my Schwalbe mountain bike tires leaking a lot of air in spite of a proper tubeless rim, tape, valves, and sealant. I sprayed soapy water on the tire and rim to locate the leaks and noticed fine bubbles all around the sidewalls of the tires. I pulled the tires off the rim and discovered that the Truckerco sealant I have been using had not reached the inside of the tires' sidewall at all, but had concentrated on the middle of the tire tread.

Suffice it to say that the "tubeless dance" you're supposed to do it important! when installing new tires, turn the wheel sideways in your hand so the rim is parallel to the ground. Roll, swish, shake, dance a little gig to slosh the sealant all over the inside of the tire. Schwalbe sidewalls are notoriously thin, so really coating the inside of tires like this is especially important. I have not tried "painting" the inside of the tire with sealant, but I might try that with an actual paintbrush in the future.

The other bit of advice is to avoid tires with very thin sidewalls. As nice as lightweight tires feel, tires that hold air consistently are preferable.