Flat tires suck, plain and simple, especially if they happen during a race run. That 'pssst' of air escaping, followed by the feeling of your rim hitting the ground is gut-wrenching, and something that still happens far too often, even to the best racers in the world. Just ask Aaron Gwin, Greg Minnaar, Jared Graves, or Richie Rude how they felt when they got flat tires this season.
• Closed cell foam
• 27.5 and 29" options
• Fits tire widths 2.1 - 2.5"
• Fits rims with internal width 22 - 35mm
• Weight: 290 grams (29" version)
• Price: $149 USD (pair), $76 (single)
Schwalbe's ProCore system kicked off the tire insert party nearly three years ago with their tire-within-a-tire design, but more recently we've seen a number of foam inserts hit the market that are designed to help prevent pinch flats and damaged tires. Huck Norris, Flat Tire Defender, and CushCore have each released their own spins on flat prevention, but they're all designed around the premise that a section of foam placed in between the tire and rim will help keep the tire's sidewall from getting pinched and potentially sliced against the rim during an impact.
CushCore is made from closed cell foam that's been molded into sort of a T-shape, with the narrower portion sitting in the rim bed, and the upper part extending over the sidewall. CushCore doesn't just bill their system as something to protect against flats – they call it an 'Inner Tire Suspension System', claiming that the insert acts as a damper, with the air in the tire above the insert acting as the spring. That's supposed to lead to better traction, cornering, as well as a smoother ride in rough terrain. Does it work? That's what I wanted to find out.
The kit, which includes two inserts and two valve stems, retails for $149 USD, or a single insert and valve can be purchased for $76. CushCore is currently only available for 27.5 and 29” wheels, but 26” and 27.5+ kits are on the way. Even though it's “just” foam, the inserts aren't super light – our 29” version weighed in a 290 grams per insert. However, the protection that the insert provides may allow some riders to run a lighter weight casing than usual, which would help counteract a portion of that weight penalty.
The CushCore insert is designed to work with rims from 22 - 35mm, and tire widths from 2.1 - 2.5".Installation
There's no getting around it – installing a CushCore system can be a royal pain in the ass. A lot of that has to do with the tire / rim combination, and familiarity with the process. Once you've done one install, the next one is easier – at the very least you'll know what to expect.
Before going near any tools, I'd recommend putting on some soothing music, doing some meditation and deep breathing, and possibly consuming an adult beverage or three in order to ensure that you don't end up snapping tire levers and throwing your wheel across the room in a fit of rage. Once you're all Zenned out it's time to grab everything and get to work.
CushCore recommends stretching the insert over the rim first, and then installing the tire, working your way around one side of the tire at a time. Don't do that. I found that getting one side of the tire seated on to the rim, and then sticking in the CushCore insert was much easier. That way, once you get the insert into place all that's left to do is dump in a couple scoops of sealant and get the other side of the tire seated. Of course, that's easier said than done.
The hardest part of the installation will be getting the final eight inches or so of the tire beat to pop over the rim's sidewall and into place. Be patient, and work your way around the rest of the tire, tucking the bead into the center of the rim as much as possible. This should help create enough room to pop that bead into place, although it probably won't be easy. A spray bottle of soapy water and strong tire levers are going to be very helpful at this stage. Performance
I don't usually get a ton of flats (knock on wood), but with the Whistler stop of the Enduro World Series looming on my calendar, I decided to install a CushCore insert in my rear wheel for a little extra peace of mind. I typically run 23 psi in my rear tire, but after some experimenting settled on 20 psi with the CushCore insert. Running a CushCore insert is similar to installing volume spacers in a fork – it allows you to run a little less pressure without worrying about bottoming out. And believe me, I smashed that wheel into all sorts of things – curbs, rocks, roots – and the rim survived without any damage at all.
The insert also adds sidewall support, which helps keep the tire from folding over in hard turns. Even at silly low pressures it feels like it's only the top 1/3 of the tires that's really moving around – the rest stays the same shape thanks to the insert, and no matter how hard I tried I couldn't get the tire to burp or peel off. There's a more muted feeling when you hit something hard, similar to the way a dead blow hammer behaves, or a medicine ball. In rough sections of trail it felt like my rear wheel wasn't getting bounced around as much, giving the bike a more planted feeling - it's genuinely impressive how much of a difference such a simple product can make.
After weeks of running the CushCore insert without any issues, I did still manage to get a small puncture on race day – even with a Maxxis DoubleDown tire a sharp rock was able to jab through the center of the tread. Luckily, the slit was small enough that the sealant helped slow down the amount of air leakage, and I was able to add more air and finish the last stage of the day. Punctures or slices are scenarios that CushCore can't completely prevent, but I think it does help – it limits just how far a sharp object can penetrate, which could reduce the amount of damage that occurs. Pinkbike's Take: