CushCore is a foam tire insert that promises to protect rims from impacts. In doing so, it claims myriad other benefits, including enhanced shock absorption and traction, flat resistance and, if you do flat, the ability to keep rolling. For two wheels, that comes at a cost of $150 and 520 grams. With a carbon rear rim to protect, I set out to determine whether or not there's something to this glorified pool noodle. But first, I had to install it.
The Infamously Awful Installation
"This doesn't look that hard," I thought, as I viewed CushCore's tranquil installation instructional. I should have known better after watching a handful of YouTubers make cow-birthing faces as they tried to get their tires on over the foam inserts.
Start with a taped tubeless rim. Install CushCore's valve. At this point, you may be able to pull the insert onto the rim with little trouble. If not, get a few inches of CushCore onto the rim and stand the wheel on that section of installed insert. Take a hammer, or wrench, or really anything with a rubberized handle, and place the handle on top of the section of rim you just put the CushCore on. Step on the other end of the tool to hold the rim and CushCore in place while you pull the rest onto the rim.
This next part is where the bovine birthing commenced. With the insert seated in the rim, I started trying to push the tire on and into the space between the rim and the insert, which, to be clear, was not a space that existed in plentiful quantities. But I eventually got most of the tire on. Unfortunately, the last 8-or-so inches were nowhere close, and completely taut because the rest of the tire was seated firmly into the bead, with the CushCore holding it in place as intended.
This is where I started doing the same wrong thing over and over and expecting it to eventually work. Shockingly, it never did. CushCore's installation video clearly demonstrates the technique that ultimately worked, but first I spent an hour trying various means of tearing my fingers off, such as attempting to tuck the tire in below the CushCore, zip tying the ends of the unseated section to keep them from coming off as I tried to force the rest of the tire on with levers, and spraying copious amounts of soapy water everywhere. And then I finally made a good choice and went to bed.
The next day, I re-watched the video and realized that I’d been trying to tuck the tire in below the CushCore by pushing the bead down in the direction of the hub. I had the right idea, but the wrong technique. As shown in the video, I needed to orient the rim sideways—parallel to the ground—and push the tire bead straight down, toward the opposite rim wall in order to unseat it and create enough slack to get the rest of the tire on. I had both sides of the tire seated moments later. Uninstallation requires the same process, and is only slightly easier.
CushCore does what it claims in terms of rim protection. I typically run 22- to 24-PSI in the Maxxis DHR 2.4 I used for testing, and I was able to drop those pressures way, way down without ever bottoming out on the rim. Invoking science, I went as low as 6 PSI for several laps on a rough section of trail. I wasn't riding close to full speed, to be sure, but I was riding. I never felt rim—even when I purposefully pushed the rear of the bike down into nasty jumbles of rocks and roots. Had I ridden that trail at 6 PSI without CushCore, I would have had to tiptoe through to avoid rim damage.
Without CushCore, adjusting tire pressure is mostly a balancing act between traction and rim protection. With CushCore, choosing a pressure is reduced to the question of how much vertical tire deformation you want.
I say “vertical” because CushCore all but eliminates lateral tire squirm. You’ll still feel the casing compress vertically when ripping into a corner, which is slightly unnerving at first and might cause you to think your tire is going to roll, but it won’t. That means you enjoy the traction boost of the larger contact patch created when your tire compresses into the dirt, without that nauseating, unpredictable-feeling tire squirm.
Vertical deformation comes with its own set of consequences. Like too-soft suspension, the tire will also start to feel like it just took a few Ambien. Lower pressures mean more contact with the trail and more rolling resistance, of course, but also a less-lively feel.
I settled on 19 PSI in my rear tire with the CushCore (I didn't test it up front, since I can't remember the last time I had a front pinch flat). At that pressure, I felt an appreciable increase in traction in all situations, without the sluggishness that accompanied even lower PSIs. You can think of CushCore like a volume spacer for your tires, which, if you think about it, are air springs. By decreasing the air volume inside, it increases the spring’s progressiveness, which allows you to run a lower pressure and enjoy more suppleness with less risk of bottoming out. But, unlike the volume spacers that go in your fork or shock, CushCore also provides a pillowy cushion when you do get to the end of your travel.
Despite having five fewer pounds of pressure in my rear tire, I’m able to push the back of the bike much harder than before, since I can rely on the CushCore to shield the rim from really hard hits.
True innovation in tire technology has proven difficult to achieve. Sure, tires probably get a little better every year, but they still subject riders to the same choice between flat resistance and rim protection or traction and cushion. CushCore isn’t without it’s own trade offs—namely weight, cost and pain-in-the-ass, and it doesn’t completely eliminate flats. But it does make them a lot less common, and serves up some significant performance gains on the side.
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