Aaron Gwin credits his Flat Tire Defender inserts for carrying speed through the roughest sections of race courses, but it couldn't prevent the slashed tire that cost him the Lenzerheide World Cup victory.
Recently, a number of innovative souls entered the mountain bike market with tire inserts—Huck Norris, Cush Core, and Flat Tire Defender are the most notable entries of what appears to be a rising tide of foam rubber tire and rim savers. Laughter was the initial response, but the room quieted down after we learned who had been winning races using inserts. Aaron Gwin was one of them. He had been on the ground floor developing the Flat Tire Defender and was so impressed that he insisted on a one-year, exclusive-use clause in his contract. Gwin won the World Cup DH series that season.
Bolstered by favorable results in competition and equally glowing reviews in the media, I have no doubt that large bike brands with comprehensive component ranges will join the party, touting their own “better than X” wheel-saving inserts. And, it won’t stop there. If inserts can save downhill or enduro wheels and tires from destruction, predictably, smaller and lighter-weight versions will be produced to share the love with cross-country riders.
At 84 grams, the Huck Norris insert is presently the lightest alternative. The simple, full-width design wards off pinch flats.
The Flat Tire Defender insert's oval shape helps secure the beads and functions as the tire's bottom-out cushion.
Inserts could not have come at a better time. Mountain bikes and rider skills have jumped to new levels, while tire and rim technology has stagnated. Armed with some form of insert, future mountain bike riders may not have to suffer the disparaging sidewall slashes, pinch-punctures and damaged rims that many of today’s riders take for granted. Once again, grassroots inventors have stepped in to solve a persistent problem for their fellow mountain bikers and in doing so, also created an additional revenue stream for sagging retailers and bike brands searching for the new it. Everyone wins.
So, what’s wrong with this picture?The elephant in this room is that tire and rim makers could have addressed those issues long ago, but they didn’t. Without any recourse, their customers were left to figure out a solution. Tire and wheel manufacturers must have been aware of those deficiencies soon after the first wire-beaded pneumatic tires were mated with Thomas B. Jeffery’s clincher rim—which means they have had over a hundred years to figure it out. A century of gradual improvement that resulted in some darn good products, but failed to produce a spark bright enough to illuminate the insufficiencies of the existing system or ignite a fire underneath manufacturers that was hot enough to inspire action. Brush aside the silly science, peer behind the marketing terminology, and it becomes apparent that the only real innovations that cycling’s rim and tire makers have given us in that century have been the folding bead, and the tubular cross-section rim profile. (For the record, UST was a fail.) If any of you are tearing up over this abuse, grab a hanky and let me explain how the process actually works. There’s the design phase and then there’s the manufacturing phase, and it all boils down to this:
Thomas Jeffery patented the clincher rim in 1882, five years before John Dunlop invented the pneumatic tire.
Rim designers fuss about tenths of a millimeter here and there. They play video games with powerful Finite Element Analysis software to optimize materials and experiment with shapes to counter stress, both real and imagined. But, when the meetings are over and the profiles are finalized, the people with clean fingernails hand their files to the folks with dirty fingernails and the woman in charge of manufacturing, wearing blue overalls and black-rimmed magnifiers yells: “Listen up! It appears that (your name here’s) new lightweight, fragile rim design is thinner and their cutting-edge heavyweight, strong design is thicker! Imagine that?”
Stan's Arch rims exemplify the modern tubular cross-section clincher design.
Continental's graphic depicts the strategies used to bolster conventional tires.
Tire makers would love you to believe that they allocate twenty engineers and spend a gazillion dollars on rubber compounding for each and every bike brand who walks in with a tread design in hand, and even if that were true, after the manufacturer’s designers are done designing. After the know-it-alls at Big Bike Brand USA, or TrailBreaker International walk out of their secret meetings, the large, bearded man with black shoes and a sweaty brow who runs the production line yells; “TrailBreaker International Enduro Tire—more rubber and extra fabric!” And; “You guys, over there—Big Bike Brand XC Trail Tire—less rubber and less fabric!” Yes, I have toured wheel factories. Yes, I have toured tire-manufacturing facilities. Yes, I have participated in those design processes and, yes, I understand that most of those people are very passionate about their crafts. Excuse me for oversimplifying it, but the end result is the same: another clincher tire is born to pinch flat, suffer sidewall punctures and probably fall off the rim shortly after—and another clincher rim will be born to assist in that process. Embarrassing? You bet. Pathetic? Wait for it.“Pathetic” is that mountain bikers—paying customers—put up with that cycle of inertia for over 30 years and bought those products with hardly a whimper. “Pathetic,“ is when we finally wake up and realize that wheel and tire makers are never going to get off their asses, we buy eighty-dollar rubber snakes to stuff into thousand-gram tires, mount them to DH-weight wheels and then high-five each other for this cutting-edge solution. “Pathetic” is how many who read this will adamantly defend the status quo.
Cush Core's graphic echoes performance claims made by most insert makers. One Cush Core weighs about 250 grams.
Jared Graves flatted, but finished the stage using a Cush Core insert (laying on the ground) at the Madera EWS.
Follow the same path and you will always arrive at the same destination. The law of diminishing returns suggests that, regardless of the magnitude of their investments, tire and rim makers will fail to achieve any significant improvement in performance or durability by employing their present construction and fundamental design methods. You don’t have to search far to find proof.The best pioneer mountain bikes, with their rigid frames and forks, weighed 30 pounds. Today, a top 150-millimeter-travel dual-suspension trail bike weighs the same, and it is a magnitude more durable and reliable. We got there by exploring different paths—by abandoning construction methods and design standards that were weak and then adopting new ones that were lighter, stronger and more efficient. Imagine how pendulously heavy a mountain bike would be today if we simply added extra layers to every component that lacked sufficient strength or durability?
To their credit, Mavic co-developed the UST system, which introduced the tubeless concept, and a modest locking bead interface. Tire and rim makers, however, largely rejected the open-source system.
I don’t think it’s my place to tell all of you rim and tire makers how to run your businesses, but as part of your food chain, I think it’s fair to offer up some suggestions. So, while you are discussing your next products, please consider these starting points:
Casings that can’t be torn: Hate to break it to you, but rubber is not armor. Same goes for polyester and nylon. There are a number of fabrics available off the shelf that don’t abrade, and that can stop shattered glass, sharp knives, micro-meteorites, and bullets. Rubber is the heaviest component of a wheel. The only place it should be used is for the tread and to seal the tire. A tubeless tire should never suffer a sidewall tear.
Locking beads: A tire should never come unseated from the rim after a puncture, and a tubeless tire should never burp air. Give us a rim and bead interface that locks in place.
Design a cushion: Dump the sealing tape and give us an engineered plastic liner that has an O-ring for the valve stem, seals the rim, and incorporates some sort of cushion between the rim flanges and the tire. Bottoming the tire casing onto the rim is a fact of life. Design for it.
Safe failure mode: Optimize lower tire profiles for wide rims and then mold them so if a tire goes flat, the tread mushrooms over the rim to protect it, and also to maintain a degree of control. (A feature that could also prevent a lot of road riders from becoming human hamburger.) It would be great to roll out from a flat without inflicting fatal damage to the rims.
If any or all of those tips prove helpful, don’t thank me. Thank the folks who designed those tire inserts I mentioned earlier. They risked their own money to solve your problems and, to a large degree, they managed to address every item on that list. So, rather than steal their work by developing your own inserts, why don’t you folks invent a new tubeless tire and rim system that offers us a permanent solution. No need to rush. We’ve waited 30 years.In the meantime, I wholeheartedly recommend inserts for aggressive riders who suffer punctures and damage caused by the inadequacies of existing clincher rims and tires. Shelling out over 80 dollars for inserts and adding 200 grams or more to your wheels is a smart investment when you consider how miniscule the performance returns would be if you gave your 80 dollars and 200 grams to the tire and wheel guys to do the same job. In the end, however, inserts are not a real solution, they are a cry for help.