RockStop Tubeless Insert | Review

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Can’t Stop The Rock. We’ve been warned repeatedly. It’s been received wisdom for decades, but now, thanks to Rockstop, could Apollo 440 be wrong? There’s a chance. The rock might be stoppable.

Rockstop is made by a UK company, based in Cumbria and named Urofoam. They developed it in collaboration with Grizedale Mountain Bike Hire, and unlike most inserts, which are generally forms of EVA foam, it’s made of a polyeurethane elastomer. That gives it a smooth finish, which is good at shedding sealant.

Rockstop Tubeless Insert
Line up the holes with your valve

It’s available in three sizes: 29in, 27.5in, and a wide version of 27.5in for plus tyres. They sent us some 29in and 27.5in ones, and given the difference in material to other inserts, we were certainly curious.


Excited to see if The Jesus and Mary Chain were telling us the truth in 2016, I popped a tyre off my bike and whacked a Rockstop in. It weighs around 250g per wheel, and has plenty of gaps through and underneath it to allow free passage of sealant. The large holes mean all you have to be careful to do is line one up with the valve.

The install method I settled on was to mount the tyre, remove one bead, then put the Rockstop in. The overall fit on a rim is tight, but not absurdly so – just enough that it snugs down to the bed and isn’t able to flop back out. As you get to the last bit, it needs to be stretched slightly to go over the rim. The central recess between the two rows of underside nubs is really useful for this, allowing you to hook the insert halfway onto the rim, preventing one side from sliding back off as you work on the other.

Getting the second tyre bead back on, the insert has just enough solidity and shape that you can clearly feel it through something like a Maxxis Exo tyre. The slight elasticity of the polymer means it also springs away from the rim wall easily while you’re getting the tyre beads in, then pulls back in and centres itself well.

I tested it on a selection of rims, from 25 – 30mm internal widths. Even the narrower ones presented no problems with fitting, which in all, was painless. Rockstop is definitely one of the better insert designs in this respect.

The Ride:

Tyres stuffed with polymer, I set out to thoroughly test the 1991 claim of Christian metal band Stryper. Accordingly, I took it down everything rocky I could find in Calderdale, followed by a hundred kilometres or so of natural alpine descents. Despite rims occasionally doing audible jazz percussion on clumsy lines, they survived it all.

Rockstop Tubeless Insert
A small tear

Rockstop even survived my least favourite water bar in the world. From pinch flats to smashed wheels, that one’s given me no less than six ride stopping incidents over the years, even doing in a carbon wheel through another insert I’ve tested. Running Rockstop, I yet again messed up the timing on a high speed bunny hop, smacked the back wheel… and kept rolling.

Removing it later for a look, there was a small cut passing right through the Rockstop, but much smaller than the damage I’m used to seeing on other inserts. Apart from that, in months of use on several bikes, the inserts showed absolutely no other damage.

Of course, I’ve not been able to test Rockstop against every rock, but as it happens, I did bump into Dwayne “The Rock” Johnson at a mid-ride coffee stop. The precise details of what happened next are bound by a non-disclosure agreement, but I can confirm that not all Rocks can be stopped. Just most of them.

Extra Credit:

During this test, I noticed a rattle inside the tyre and found the insert had come undone at the joint. This hadn’t really affected much, as it was still in position covering the rim, so I just zip tied the ends back together and carried on.

I was going to email Rockstop the same day, but to their credit, they emailed me first. No excuses, they just outlined the problem they’d discovered, which was dust from mold flashing removal interfering with glue at the pinned joint. They showed their solution, showed a new testing machine they’d built, and sent new inserts too.

The usual from companies is to wait for contact from a bike journalist, claim “Oh yeah, we had a problem with a small number of preproduction prototypes”, then hope you believe them and don’t mention it in the review. Full credit to Rockstop for proactively owning and fixing this. Every Rockstop insert now has a zip ties backing up the joints, preventing separation.

Rockstop Tubeless Insert
The proper fix


Solid protection and easy fitting make Rockstop one of the best all rounders in the grouptest. It survived a big hit from my local nemesis, and just carried on rolling. The only minor hitch was the join coming unpinned, but that was easily fixed and Rockstop have revised their product to prevent it happening in future. Rockstop is easily one of the more confidence inspiring inserts out there.

Review Info

Brand: Rockstop
Product: Rockstop
Price: £65 per insert
Tested: by David Hayward for 3 months

David started mountain biking in the 90’s, by which he means “Ineptly jumping a Saracen Kili Racer off anything available in a nearby industrial estate”. After growing up and living in some extremely flat places, David moved to Yorkshire specifically for the mountain biking. This felt like a horrible mistake at first, because the hills are so steep, but you get used to them pretty quickly. Previously, David trifled with road and BMX, but mountain bikes always won. He’s most at peace battering down a rough trail, quietly fixing everything that does to a bike, or trying to figure out if that one click of compression damping has made things marginally better or worse. The inept jumping continues to this day.

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