Does It Really Prevent Pinch Flats? We Ride the Flat Tire Defender

I posted a Vital MTB forum thread in May of 2014 asking "Why are flat tires something we still see these days?" The first two World Cup DH races had the typical race-robbing issues of pinch flats. "We have $10,000 bikes but we can't keep air in the tires if they're hit just right?" I was frustrated and I'm not even a racer getting hosed or a team sponsor spending tens of thousands of dollars on a single race effort.

Low and behold, industry-leading tire designer and tester, Frank Stacy, was already on the case. Frank is the lead man behind some of the most successful tire designs of modern mountain biking. He was working with Trek World Racing DH and Enduro athletes on what would finally be known as the Flat Tire Defender, a foam insert that prevents impact-driven flat tires in tubeless set-ups.

The idea is pretty simple; prior to tire inflation, a circular foam ring is inserted snugly around the rim. The valve stem passes through, the tire is in stalled, sealant is added, the tire is inflated and there ya go, you have an added layer of pinch flat protection. The execution, however? Not as simple as you might think.

Frank Stacy researched and tested a variety of different foam types to strike a balance between durability and protection while not increasing weight significantly. The material, EPDM (ethylene propylene diene monomer) was ultimately selected as the material of choice. Its properties allowed shaping (the cross-section of the Flat Tire Defender is not a perfect circle for a reason) and EPDM is available in a variety of durometers (densities). Frank, along with the help of team riders conducted extensive testing and landed on what they thought was the perfect combination of weight, durability and equally importantly, damping qualities. Tracy Moseley won the EWS series on the inserts in 2015, Laurie Greenland won Jr. World Champs DH on them in 2015 and in 2016, Aaron Gwin used the foam inserts to clinch the World Cup overall. Frank and the riders kept these things a secret, right under our noses.

Frank and Aaron worked together exclusively in 2016. Frank had obviously proven the idea of the product with other riders the year earlier, but Aaron freely admits that if he were to be involved with the product, he didn't want any other riders to have the advantage last year. Now that the FTD is publicly available, that exclusivity goes away.

So you may see the World Champs wheel pic and want to smugly comment that "the insert didn't help", but Aaron explains that the FTD performed as it should. Aaron struck a big rock, early in his run, damaging his rim. Despite the damage, he still rode hard, with tire pressure for a significant remainder of the track before striking the rim in the same place again, destroying the wheel. It's racing (World Champs no less) and things happen. Gwin believes without the insert, his run would have been over after the first rock strike.

That's Flat Tire Defender in a nutshell. During our time with Frank and Aaron at their product presentation, we were pretty excited about the testing history and the simplicity of the product itself, not to mention the installation (it's not difficult if you're already handling tubeless duties yourself). Fred Robinson, our resident product smasher and experienced mechanic mounted up the FTD into both front and rear tires on his DH bike without hassle.

We were supposed to experience some on-trail pinch flat defense that day but weather was not on our side and muddy trails shut us down. Upon learning about this product, my memory instantly went back to the early 2000's and the T.H.E. Eliminator rim. It was an aluminum rim that used this idea of preventing the sidewalls from ever being pinched sharply thanks to a rounded, raised structure down the middle of the rim. The Eliminator was built up with additional aluminum creating bulge down the center with a thin rubber liner over the bulge. So imagine the photo below, but instead of the foam you see, the "filler" area is immovable, permanent and made out of aluminum with just enough material out of the way for the tire beads.

T.H.E.'s marketing was video of a rider going full pace into a parking block, "KAPING, KAPING" and rolling on without a care in the world. No pinch flat, no problems. (I tried to find it online, but couldn't) Well, in the day of 4-ply Intense DH tires and extra thick tubes, it took 15 of the strongest humans on the planet, each with two tire levers to mount/remove a single tire and lacing them wasn't exactly something any wheel builder wished to tackle. Exaggeration? A little, but you get the idea and T.H.E.'s Eliminator eventually disappeared.

If T.H.E. could smash the curb and live, the Flat Tire Defender should be able to, right? I told Fred about the old video and asked if he was ready to sprint into cement for science? Game on.

A handful of high-speed smashes into an every-day curb, the wheels were in one piece and the tires were at the same pressure. Frank and Gwin looked on slack-jawed after the first hit when Fred went back for more. This was not what they were expecting when we came to test the FTD. If there was ever a fairly legitimate parking lot test, this was it and the product passed. Initial impressions are one thing and we wanted to spend some time on real downhill trails with the Flat Tire Defender. Fred's on-trail experience with the inserts can be read below. -spomer

Flat Tire Defender Features

• Foam rubber polymer construction
• Closed cell foam to prevent sealant absorption
• High impact // high-density material
• 100% airless insert
• Kit includes foam insert, tubeless valve, installation Zip Ties, and FTD stickers
• Weight: 290g (tested)
• 28-34mm inner rim width (DH 27.5 kit)
• Recommended tire pressure: 24-32PSI
• Recommended tire size: 27.5x2.30/2.50”
• Enduro and Trail 26 // 27.5 // 29”, Downhill 26”, Plus and E-Bike kits also available
• MSRP: $121.50 USD (Downhill 27.5 Kit)

Flat Tire Defender on the Trails

Review by Fred Robinson

Initial Impressions

The FTD insert looks pretty basic at first glance. It’s a black, tubular foam donut, not much to it, right? Despite the R&D story we heard at the product launch, we were wondering if we could we just run down to Home Depot and grab some foam insulation or a pool noodle to make a similar product. It's doubtful, but stay tuned for our up-coming Tire Insert Face Off where we might just try.

The FTD kit includes two tire inserts, two tubeless valves, multiple valve gaskets to fit various rim shapes, as well as two heavy-duty Zip Ties and some stickers. Installation was surprisingly straightforward. With one side of the tire bead on the rim and the valve stem installed, the FTD insert can be stretched around the rim (with the seam opposite of the valve) quite easily. A quick run of your fingers under the insert helps ensure it’s seated in the rim bed properly before getting the other bead on the rim. We were able to do it without the need for the Zip Ties or tire levers. Sealant, which is still recommended, can be added two different ways: either remove the valve core and inject the sealant or add it before the second bead is completely mounted. We used the recommended 1.5-scoops of sealant to the system. Here’s Aaron Gwin’s mechanic, John Hall, demonstrating how to install the FTD system:

Flat Tire Defender recommends starting at your normal pressures, which is what we did. Airing our tires up to 32 PSI rear and 29 PSI front with a floor pump had the beads popping into place no problem. A quick tip if you’re struggling at this point is to go around the tire with your hands and squeezing the sidewalls to get the bead “under” the insert, which should help everything seat. Once everything’s seated and ready to go, it was time to see if these inserts would allow for maximum smashability on the big bike.

On The Trail // First Ride Impressions

As you may have seen from our Instagram feed, we held no reservations when it came to seeing how much we could really throw at these tire inserts. From full-on curb smashes to charging rock gardens with little regard for line choice, we were impressed with the performance of the Flat Tire Defender (FTD) system. We primarily rode the FTD inserts at our normal tubeless pressure, 29 PSI front // 32 PSI rear. At these pressures, we noticed no difference in overall traction from our typical setup. At 290g (0.64 LBS // tested) per insert, the FTD system is no welterweight and weighs roughly what a Maxxis Freeride tube does. With the addition of tire sealant (we used a scoop and a half), any weight savings by running a tubeless setup is negated. That said, we only noticed the difference in weight, which is roughly 1.30-pounds (580g), while pedaling up to speed from a dead stop. Where we did feel the FDT system was when things got rough. On our maiden lap aboard the FTD system, we botched a line off a jump which had a large rock protruding from the right side of the lip. We felt the impact as we took off, which almost sent us over the bars…and we hit that rock hard. Thankfully, and likely due to the FDT inserts, our carbon rims suffered no damage and our tires held air perfectly on the type of hit you’d expect some kind of failure.

Flat tire defense aside, what we were most impressed with regarding the FTD system was in their performance in rough rock gardens. Aaron Gwin spent a lot of time discussing how the system helps to dampen vibrations from the trail that make their way to your hands and feet. And, we have to agree, this is by far the biggest advantage we found with the FTD system, as it tends to take the sting off those sharp impacts. For reference, we rode the FTD system on a carbon bike, with carbon bars, carbon rims, and even carbon cranks, all of which should help damp the feedback from rough sections. Even with all that plastic, we felt a big difference when it came to plowing through those rough sections with the FTD insert equipped, and true to form the inserts took a lot of the feedback out of those consecutive square-edge hits. For those of you who suffer from hand and foot fatigue, this product could be a game changer.

We did experiment a bit with dropping the pressure lower than our normal setup. Typically, anything lower than our normal pressure results in a fair amount of tire roll when cornering hard. The folks at Flat Tire Defender let us know that their inserts help stabilize the sidewall of tires, and we could get away with dropping pressures a bit and maintain a solid feeling tire. We tested their claim by dropping the tire pressure in 2PSI increments and seasoning the same two sections of trail, a berm section with six consecutive turns and a rock section with two separate rock gardens (one you plow through and the other you can gap). Dropping from 32 PSI front and 29 PSI rear to 30//27 PSI and hitting both sections, we honestly didn’t really notice a huge difference; the tires didn’t roll in the corners nor did they ping any rocks. Dropper further to 28//27 PSI, we did notice a slight increase in rolling resistance and maybe a bit extra cornering traction, yet the tires still held their shape without any real negative side effects. Sub 26 PSI front and rear is when we started to feel our tires bottoming out in the rocks. We were purposely shorting the section we’d typically jump over and landing directly into the rocks, and despite feeling the tires bottom out, no rim damage was a result. Even so, at this point (for the sake of our rims) we reserved any lower pressure testing to cornering only. Pushing the envelope, we were able to drop all the down to 19 PSI rear and 17 PSI front. While these pressures were far too low to actually ride in a typical scenario, for the sake of testing whether or not the inserts would hold the bead, we gave it a shot. And, despite some mega sketchy tire roll, the system didn’t burp an ounce of fluid.

That said, even though you can get away with far lower pressures than you’d typically run, we found the system to be most beneficial running our normal pressures or within 2-3PSI of it.

When it came time to dismount the FTD inserts there was a bit of a learning curve. The first tire took us a good 30 minutes of struggling and cursing to remove. But, after we calmed down and collected ourselves, and actually thought about how to remove the next tire effectively, here's what we came up with: Deflate the tire like normal and unscrew the valve's retaining ring. This allows you to push the valve into the rim, which lifts the FTD insert out of the rim bed. With the valve pushing the insert up, break the tire bead at that point first. Once you get the bead unseated at that point the rest of the job is pretty standard practice, and we were able to pop the second tire off in less than a minute.

Things That Could Be Improved

While we love being able to ride with less regard to damaging critical components on our bike, there’s always going to be a penalty of some sort. In the case of the Flat Tire Defender system, that penalty is added rotational weight. At 290g (0.64 LBS) each, you’re adding over a pound of weight in one of the most critical areas of your bike. On a DH bike, this is somewhat less of a concern being that the advantages outweigh (pardon the pun) the penalty of the FTD system. But, for those of you interested in running this product on your trail bikes, it’s worth considering.

What’s The Bottom Line?

To sum up our time on the Flat Tire Defender system, we’ll simply say it'll be staying on our downhill bike, for sure. The difference in handling rough sections alone was enough for us. After all, that’s what downhill bikes are designed for - charging the roughest terrain out there, as fast as possible. And, if that’s your main goal the FTD system definitely aids in that practice; not to mention the benefit of additional flat protection and sidewall reinforcement. Is the system without flaw? No. It does add rotational weight and it does have its limits which we all saw during Aaron Gwin’s 2016 World Champs run. That said, while the system may not be 100% bombproof, it is an improvement over a standard tubeless setup in terms of how much abuse you can throw at it, and the improvement in vibration damping can’t be ignored and we’d recommend this system to anyone who suffers from hand and foot fatigue, as well as gravity racers up against the clock.

For more information, visit www.flattiredefender.com