Flats happen. But how to repair punctures in tubeless tires—and even if they should be repaired—is a tricky subject. It all depends on who you ask. The truth is riders fix flats all the time, but they could be plugging away indiscriminately with limited knowledge of the proper repair process or the risks associated with riding on a repaired tire. In this installment of MC Garage, we’ll explore the issue from several angles and discuss motorcycle tire repair kit options so you can make a more informed decision if you “pick up a nail” on the road.
One of the reasons a concise answer on plugging punctures is so elusive is because each tire manufacturer, which every tire-plug manufacturer will ultimately defer to if pressed on the subject, has its own take on the topic.
Continental, Michelin, Pirelli, and Shinko’s position on dealing with punctures is clear as day: Don’t even bother carrying a plug kit. “Call a tow truck,” is how one VP of marketing replied when asked what to do when you get a flat. These tire manufacturers assert that there are too many variables involved, from the puncture to the repair, and that there is simply too much at risk in terms of rider safety and liability to condone it, even in an emergency. Most dealerships and repair shops share this sentiment.
Fair enough. After all, your tires are the only part of your motorcycle that connects it to the road, and a rapid deflation resulting from an improper repair or unseen internal damage could cause a lot more parts of your motorcycle to make contact with the road. Even so, a canned “no” is not what riders want to hear when they just got a flat on a nearly new, $250 tire.
Other brands, specifically Avon, Bridgestone, Dunlop, and Metzeler, offer an opinion that’s more in line with what consumers would hope to hear: Yes, punctures can be plugged in an emergency situation, and a repair that both fills the wound (plug) and seals the damage (patch) that is installed by a professional can even be considered permanent if specific criteria are met.
While Avon, Bridgestone, Dunlop, Metzeler, and the RMA (the Rubber Manufacturer’s Association, the nation’s preeminent voice on the topic of tires) all agree that a combined plug/patch applied from the inside of the tire is the only acceptable permanent repair, each group has its own requirements and restrictions. Here are a few areas they all agree on.
Everyone who says that you can plug a tire (including tire-plug makers) agree that the repairable area is limited to the crown of the tire. “You cannot plug a sidewall because it doesn’t have the structure to hold the plug,” says TJ Tennent, Bridgestone’s engineering manager. Not even the entire treaded area is fair game, since “closer to the sides the carcass flexes too much and the seal won’t take,” Max Martin of Gryyp says. “The repair has to be within the belt package,” Tennent adds, which limits the repairable area to the center 50 percent of the tire. There must also be at least 1/32 inch (0.8mm) of tread remaining on the tire. Any less and the tire could flex too much to retain the repair.
The size and shape of the damage is another important factor. Tears or oblong punctures cannot be permanently repaired, and opinions on the size of round holes that can acceptably be repaired run the gamut from 3mm (Avon) to 6.8mm (Dunlop). Assuming the puncture isn’t too big (research suggests that 90 percent of all punctures are the size of a 16-penny nail [4.1mm] or smaller) and was made in the right area, the tire will still need to be dismounted for inspection and have the appropriate plug/patch installed.
Beyond those very basic guidelines, opinions begin to diverge. As an example, Avon prohibits tires with “wound on” belting or tires with a speed rating higher than V (up to 149 mph) from being repaired, while Bridgestone contends that any repaired tire forfeits its speed rating and is limited to 80 mph. Dunlop says that any tire that’s previously seen a liquid sealant is excluded from repair, while Metzeler simply defers to “your country’s regulations” to determine if repair is legal in the first place (in America it is). When it comes down to it, if you really want to know the specifics for your tires, your best bet is to contact the company embossed on the sidewall.
As stated, every manufacturer that permits permanent repairs says that an off-the-rim inspection is mandatory. Why? Since tubeless tires are unlikely to bleed all of their pressure at once when punctured, it’s possible for the rider to be unaware of a leak and cruise along on a deflating tire. This isn’t uncommon and leads to the possibility of internal tire damage, either from overheating or from the puncturing object gouging the tire’s inner surface after deflation has occurred.
Additionally, escaping air can creep between the plies of the tire, encouraging tread separation. This scenario is of particular concern on steel-belted tires (the majority of motorcycle tires on the road today are steel belted) since any ingress of moisture can cause the steel strands to rust and eventually fail.
Any damage to the structure of the tire could lead to a catastrophic failure, and a thorough inspection of both surfaces of the tire is the best way to nip a catastrophe in the bud—that, or just replace the tire, which is always the first recommendation, regardless of who you ask.
Great, but what if you can’t replace the tire or dismount it for inspection and repair because, say, you’re in the middle of nowhere with no cell service and a descending sun? “If you need to get off the side of the road, you do what you have to do to get to a safer location,” Bridgestone’s Tennent says.
That’s where the myriad aftermarket tire-plug kits come into play. Common options include the ubiquitous rubber-impregnated ropes, Stop & Go’s mushroom plugs, Dynaplugs’ brass-tipped ropes, Gryyps’ screw-in “cargols,” and liquid products from Slime and Ride On. Each product has its own purported benefits, whether it be ease of use or affordability, but the underlying idea is that they’re all emergency repairs. Out of all the options, mushroom-style plugs like those sold by Stop & Go are the only form of temporary repair endorsed by manufacturers, namely Avon and Metzeler. And don’t forget that once you plug the tire, you’ll still need to inflate it. See the “Airing Up” sidebar at right for your inflation options.
If you began reading this piece with a firm stance on tire repair and now feel like you’re standing on shaky ground, we apologize. Ignorance is bliss! As we said in the beginning of this piece, how you should go about dealing with a flat really depends on who you ask. And, ultimately, the only person left to ask is yourself. Hopefully after reading this you are better equipped to make your own decision.
Tubing It In A Tubeless Radial Motorcycle Tire
Is An Inner Tube An Acceptable Emergency Fix?
“It used to be a solid no,” says Sukoshi Fahey, sales and marketing manager at Avon. “But opinions have evolved.” The original cause for concern was tire flex, which could cause the tube to overheat and rupture. However, today’s tubeless radials are more rigid and unlikely to cause issues when used with an appropriate-size inner tube as an emergency repair, but other manufacturers, including Bridgestone and Metzeler, still prohibit it.
A tube may serve as an acceptable way to deal with a punctured tire, but if you are considering carrying a tube (and the tools needed to remove the wheel and tire), why not just carry the appropriate patch/plug and perform a more reliable, potentially permanent repair?
Because Sometimes You Want More Pressure In Your Life
There are numerous ways to plug a punctured tubeless tire and lots of methods to re-inflate it too. For side-of-the-road repairs, the three most common sources of pressure are CO2 cartridges, compact electric compressors, and old-fashioned hand pumps.
A compressor that runs off your bike’s battery offers unlimited air supply anytime you need it, but these devices can be bulky and expensive. Manual pumps like those used for bicycles (high-volume pumps designed for mountain-bike tires are the way to go here) also offer unlimited fill-ups, but they also require a tremendous amount of elbow grease!
CO2 cartridges are another popular option. They’re compact and easy to use, but it takes a lot of them to fill a tire (six 12-gram canisters will inflate a 180/55-17 tire to about 20 psi according to our tests), and you can only use them once. When discharging CO2, keep in mind that the gas exiting the canister is extremely cold (about -50 Fahrenheit), so protect your hands and remember that the tire pressure will rise quite a bit as the gas warms to ambient temperature; there’s no need to inflate to final pressure with the canisters.
Another option for airing up in an emergency is a parasitic hose with two clamp-on female ends. This device isn’t commercially available but should prove easy to assemble at home and will allow you to draw pressure from another vehicle’s tires in an emergency.