Welcome to the two-part insert test. This is the second part, where we put the inserts through their paces in a controlled test. If you want to read about how the inserts felt on the trail then please see part one.
Every insert is accompanied by bold claims of life-changing performance. Each brand championing its product as the
one true insert that will give you more grip, more stability and better protection compared to either a standard tubeless system or indeed anything else on the market but how true are these claims? And is there any way that they can be tested in a controlled setting?
Hunt, a wheels manufacturer that is also behind such brands as Privateer, invited us to use their wheel testing jig to torture test all these inserts with whatever it took until we yielded the truth - which insert, in terms of ability to resist shear load, is the best insert on test?
Hunt originally built this machine to test and develop their own wheels. They’ve even not only benchmarked but also published their data
about competitor’s wheels too.The Test So Far
The first part
of the test was there to talk about the feel of the inserts. I did this part of the test first as I didn’t want any of my judgments to be influenced by previously gathered data.
During a month of back-to-back runs on a downhill track I was fairly confident in my assertions about feel. I concluded the article with the following.
But how would they all stack up against the jig and how did we test them?The Method
During the test we used Hunt Enduro Wide V2 rear wheels with a 31mm internal diameter and had 32 spokes and shod with 2.4” Magic Mary Super Trail tires which typically come in around 1150g. The tire on this rim, at its widest part, measured 58.6mm at 25PSI.
We wanted to test in two distinct ways. Firstly, a square hit that impacts both sides of the rim at the same time. We wanted this to be something like a maximum load test.
The second part was to move the wheel to a 5-degree angle and then see how the wheels cope with angled impacts. We wanted to see if the order of impact resistance would be replicated through both parts. I wondered if some of the narrower inserts might be vulnerable to being pushed across to the side of the rim under load.
All impacts were done between the two parallel spokes on the same part of the tread pattern. A caveat here, we never put the impact in line with the valve hole though for fear of compromising the findings. The spoke tension was checked between each run and sent off to one of Hunt's on-site wheel builders if it required adjustment. The tire pressures were checked with the same digital pressure gauge between each run.
We decided that our threshold for a failure would be any visual signs of stress to the rim as well as check for any discoloration of the potentially stressed metal. If we were ever in any doubt we removed the tire and measured the dimensions of the rim with some digital vernier calipers to see if the metal had in any way been distorted or bent.
During the course of the test there were two factors that made us readdress our methodology. Firstly, even with the machine maxed out during the square hit test no rim was taking any damage whatsoever. Chris Colenso, one of Hunt’s engineers, had already run tests to work out the rough parameters needed, albeit without inserts, and we were both very impressed with how the inserts, even the lighter ones, took the burden off the rim.
During both the angled and parallel test, we were dropping the22.4kg impactor 546mm. It was measured and realigned between in run.
So, what was happening then? How can a bit of foam make that much difference? Well, when inspecting the inserts you could see just how much damage they were taking. This threshold wasn’t breached during this initial test. That’s not to say the rim wasn’t undergoing stress, only that we couldn’t show that it did.
How many times you hit something exactly square is probably open for debate, and its subsequent implications to the real world should perhaps be taken with a grain of salt, but either way, all of the inserts passed this parallel strike test with flying colours.
It’s for that reason we had always intended for the second part to hopefully give us a more realistic scenario… but how much difference would 5 degrees really make? Well, as it happens, the gulf between the two is absolutely huge.The Results
From the parallel hit, where all the inserts resisted damage to the rim, to a small alteration of five degrees, how much difference does each insert make? You can see in this graph the point at which the rim took damage. We ran a control of no insert and the rim received damage at 32PSI.
From this, we can clearly see that two of the lighter inserts, which are both often recommended to be in the front, or for benefits other than impact resistance, immediately show that their light weight does come at a cost. That’s not to say that they don’t still carry some benefit - only that the supposed benefit was significantly less than some others on test.
Speaking of weight, how do these inserts compare pound for pound with one another?
Here, with the weight on the right side of the y-axis, we can see the trade-off between weight and resistance. Ideally, we want both of these bars to be as low as possible.
A few things are immediately apparent. Firstly, the Rimpact Pro seems to have the aggregate best score of resistance to weight. Not far behind is the Tannus. As somebody that has ridden them both, this is fascinating because they feel so different.
The Hamburger, the heaviest insert of the test, goes some way to justifying its weight by showing itself to be the most resistant to impact overall. It’s also very interesting to see the MegaNorris range’s weights and resistance work inversely to one another.
Both the Cushcore Pro, which offers comparable protection to the MegaNorris Hamburger, and the Hamburger itself, do offer the most protection but both come with a considerable weight penalty.
Another consideration that may well be a factor is cost. If you’re trying to save some cash and see inserts as an investment to protect your rims then what would the best bet be?
The price per set is on the right hand side of the y-axis and we can compare it against the impact resistance. Here, again the Rimpact Pro is the strongest, closely followed by the Tannus Tubeless Armour and the Vittoria Air-liner.The Limitations
The impact resistance of the inserts, and the parameters set out in this test, are important but only in relation to one another and within the context of the comparison. The pressures don’t necessarily reflect what you would ride in the real world.Conclusion
There are some important takeaways to take from this.
Firstly, this test only shows maximum load and not how these ride passively or indeed increase cornering stability. That’s largely what the first part of the test was for.
Something I learned through the previous back-to-back testing was that one of the main benefits of running inserts was how they dulled down and damped compressions before they got to your axle. This cannot be understated. Just because something doesn’t resist high-speed impacts it doesn’t mean that it won’t provide damping at lower speeds.
That’s not to diminish these results but rather to understand that there isn’t a one-size fits all approach to testing. It is useful though.