No more flat tyres? Three puncture preventers tested

Three of the latest foam tyre inserts put to the test

The familiarity of flat tyres has to be one of the chief embarrassments of modern bike design.  Riders want relatively lightweight, fast-rolling and supple tyres; they also want to ride over rocks without flatting. These desires are not easily compatible. Even when using DH-casing tyres weighing well over a kilo, punctures are still a fact of life for many.


Schwalbe’s Procore system promised a solution. Essentially a tyre within a tyre, it was claimed to protect the tyre and rim from pinching together under an impact. It worked pretty well. But it was expensive, fiddly to fit, wasn’t recommended with certain rims (due to the high pressures inside the system), and it didn’t exactly take off.

Recently though, a slew of new solutions have stepped into the ring.

Huck Norris, Flat Tyre Defender and CushCore promise to protect your rims and tyres from large impacts, while providing a little extra damping to soak up and absorb bump forces. But do they work?

How we tested: CushCore vs. Huck Norris vs. Flat Tire Defender Enduro Kit

We’ve been hard at work testing these three systems on a range of terrain, front and rear, over the last six months.

At the end of this period, I did two days of solid back-to-back testing on the rough, rocky trails that make up Bike Park Wales.

For this, I fitted each system in the same wheel (DT Swiss EX471); I used identical tyres (Specialized Slaughter GRID 29×2.3”) and used 60ml of Orange Seal sealant in each. For simplicity, I only fitted the systems in the rear for this back-to-back test.

I tested at exactly 23psi in the rear, did two runs, then dropped to 21.5psi and rode two more. I then swapped systems, inflated to the same pressures, and hit the same lines at a similar pace to see how they compare on the trail.

I then found a 6-inch high square-edged rock to smash into. Starting at the same point, and without braking or pedalling to assure the same speed, I hit the rock in the same way with each system, starting at 23psi, and then going down to 21.5psi.

As a control, I then repeated these tests with no system installed. Check out this little video for an insight into the test.

These were our findings.


The CushCore system is a bit of a pain to fit but we found it to offer the best low-pressure protection of the three systems on test
Oliver Woodman / Immediate Media

4.0 out of 5 star rating
  • Pair, inc. valves: $149 US (£112 approx.)
  • Dry weight: 265g
  • Wet weight (with sealant):  271g

CushCore is hailed as by its makers as an “Inner-Tire Suspension System”. I wouldn’t quite describe it that way, but it has by far the biggest effect on the ride quality of any system here.

It uses lower density foam than the other systems, and takes up almost half of the tyre’s cross-sectional area, along with the rim bed. It acts as a cushion against impacts, while absorbing some of their energy (a bit like a damper, in theory).

CushCore’s larger volume results in a noticeably quieter, more controlled feel over rocky terrain compared to the other systems. I wouldn’t go so far as to liken it to suspension though — the effect is more subtle than I expected based on the marketing, but it is noticeable when testing back-to back against the other systems.

Unlike the other systems here, it actually pushes against the sidewalls of the tyre; this offers extra sidewall stability, as well as puncture protection
Oliver Woodman / Immediate Media

When using the same pressures, I did feel the CushCore added a little more feedback — like adding a few clicks of compression damping to your shock. But the whole appeal of the system is that it allows the use of lower tyre pressures.

This is partly due to the puncture protection, and partly to do with sidewall stability. When cornering hard at low pressures (23psi or 21.5psi) I noticed the tyres squirming less than with the other systems at identical pressures on the same corners. So I could go even lower on pressures without excessive squirm.

The other key to low-pressure running is impact cushioning. In my square-edged rock test, which punctured my control tyre (with no insert) first time at 23psi, I was unable to puncture the tyre or visibly damage the rim even at 21.5psi.

After several attempts, I gave up. Despite extensive testing, I’ve yet to puncture a tyre with CushCore inside. This is not to say that the system is foolproof — there have been some fairly public punctures involving CushCore at the top level — but my testing suggests this system provides superior puncture protection to the others here.   

It is a pain to fit, especially with thick-casing tyres or narrow rims. It took me about 10 minutes to fit a 2.5” Maxxis EXO tyre to a 30mm internal rim, and closer to 20 minutes with a 25mm rim. But the levels of tyre protection, bump-absorption and sidewall stability on offer makes CushCore worth the wait in my opinion.

Verdict: Pricey and fiddly to install, but simply the best performing low-pressure protection on test.

Huck Norris (DH edition)

We tested the tougher and more expensive downhill version of the Huck Norris anti-puncture insert
Oliver Woodman / Immediate Media

4.0 out of 5 star rating
  • £80 (2 x £40 per set, valves not included)
  • Dry weight: 106g
  • Wet weight (with sealant): 115g

Huck Norris is the simplest, lightest and cheapest, and easiest to install option here.

There is a regular version, which is a little lighter (85g) and cheaper (£55 for two), but we think this DH edition is worth the extra heft and price, as its higher density foam offers improved puncture protection and damping.

Installing Huck Norris is really no harder than fitting a regular tubeless tyre. Like the other systems, it makes inflation a bit easier too as it pushes the sidewalls onto the rim.

When compared to riding with no system installed, DH Huck Norris makes the ride feel a little quieter and less jarring when slamming into rocks. But it’s not quite as ‘cushioned’ as the Flat tyre Defender, and much less so than CushCore.

Huck Norris is the simplest, lightest, cheapest, and easiest to install option
Oliver Woodman / Immediate Media

Unlike CushCore, it makes very little difference (as far as I can tell) to sidewall stability and squirm when cornering.

Although we did manage to dent rims and puncture with regular Huck Norris, the DH version seems to offer noticeably more protection. In my square-edged rock test, which punctured my control tyre (with no insert) first time at 23psi, I was unable to puncture with this installed at that pressure.

At 21.5psi, I did pick up a small hole in the tyre by the bead after a few runs — the kind of puncture you could finish a race run with, but the tyre would need to be fixed or replaced for continued tubeless use.

Huck Norris seems to have similar (perhaps slightly higher) levels of puncture protection to the Flat Tire Defender, and a similar effect on ride feel, despite weighing just over a third as much when dry.

It doesn’t offer the same level of protection, cushioning or sidewall stability as CushCore, but it’s far cheaper and easier to fit. The fact that it can be bought individually for £40 makes the entry price far more palatable for those who only need rear-wheel protection.

Verdict: Not as effective as CushCore, but offers useful protection while remaining relatively inexpensive, lightweight and easy to fit.

Flat Tire Defender Enduro Kit

The Flat Tire Defender Enduro Kit is essentially a round tube of high-density foam which stretches onto the rim and sits in the rim bed
Oliver Woodman / Immediate Media

2.5 out of 5 star rating
  • Pair, inc. valves: £110
  • Dry weight: 293g
  • Wet weight (with sealant): 297g

Developed for top level downhill and enduro racing, this system is essentially a round tube of high-density foam, which stretches onto the rim and sits in the rim bed. There is a downhill version, but I’ve tested the enduro version as it’s more similar in weight to its competitors. 

Installation is mid pack. Though not quite as easy to fit as Huck Norris, the insert doesn’t fit the rim as tightly as I expected when running 25 to 30mm internal rims, and so it’s easy enough to push the tyre onto the rim bed underneath.

When hitting rocks at speed, the extra padding was noticeable, taking the sting and bang out of the impact when compared to nothing at all. In this regard, it feels similar to Huck Norris, if a little more forgiving, but it’s not as damped as CushCore.

It doesn’t offer any real benefit in sidewall stability.  I’m not convinced it prevents burping either as it sits too loosely between the tyre’s beads, especially on wider rims.

The results of our testing mean it’s hard to recommend the Flat Tire Defender Enduro Kit over its competition
Oliver Woodman / Immediate Media

I was unable to puncture at 23psi in the square-edged rock test (suggesting it offers at least some protection), but as with Huck Norris, it did puncture at 21.5psi.

Outside of this back-to-back testing, I dented a rim (DT Swiss XM481) during a rock strike with the system installed in the rear, and punctured a Schwalbe Snakeskin tyre with it installed up front. That’s not to say that it doesn’t prevent punctures, but it certainly doesn’t work all the time.

Ultimately, I reckon it’s just a bit too skinny, and so can’t offer much protection to the tyre or rim bead under a really hard impact. The DH version (650b only) would likely perform better, but even this enduro version is the heaviest on test. And given that it appears to offer no better protection than the much lighter Huck Norris, this makes it hard to recommend over the competition.

Verdict: Relatively easy to install and reduces clatter from trail chatter, but seemingly not as effective as its lighter rivals.

Which is best?

If you’ve got the cash, and don’t mind a slightly fingernail-busting installation, CushCore is the best performer by far.

If you want a lighter and easier alternative, Huck Norris still offers useful protection, especially if you only need one-wheel protection.

But should you buy any of these systems?

I’ve seen these inserts described by other publications as “band aids” for inadequate tyres and poorly designed rims, but as it stands, the only company to rethink rim design with the intention of mitigating punctures is ENVE, and it’s charging upwards of £1,050 per rim. Hardly a practical solution then. At least, not yet.

So what if you’re fed up of flats, but don’t have £1,050 to spend on a new rim?

Well, the first thing to do is keep an eye on your tyre pressures. Buy yourself a proper pressure gauge, and use it. That’s not to say crank your tyre pressures too high — lower pressures will give you more grip, better comfort; and in rough terrain, less rolling resistance. The key is to find the pressures that work for your tyre setup and riding style, then stick to them.

The next thing to look at is your suspension setup. Suspension that’s too firm, or bottoms out too easily, or rebound damping set too slow or too fast, will increase the chances of puncturing. Check out this guide to setting your suspension up properly.

Finally, you could just fit heavier tyres. Yes, that will increase wheel weight; but to some extent, so will any of the above systems.

Tougher tyres have other drawbacks, though. Thicker casings are less supple, so you’ll get more feedback through the bars and rolling speed will suffer too.

So a lighter tyre with an in-tyre system is probably a better, if more expensive, solution, especially for racing.


Also, if you’re the type of rider who already runs full DH tyres and still suffers flats, these could be your best chance of eliminating those pesky punctures.