After suspension, wheels are some of the most expensive real estate on your mountain bike. Keeping them round and dent-free is paramount if you want to maintain the ability to run a tubeless setup. Getting some decent rim protection is, in our opinion, always a great idea, especially on the rear wheel which tends to take the most abuse. Over the last month or so, we’ve been testing the RockStop mountain bike tire insert, designed, engineered and manufactured in the Lake District, UK.
Review: RockStop MTB Tire Insert
RockStop MTB tire inserts are designed to protect your rim during tire bottom-out events and prevent pinch flat punctures. They do this by sitting directly in between the rim and the tire, forming a snug interface with the rim, overlapping it slightly. The amount of overlap depends on the external width of your rim. The polyurethane material is quite firm to the touch and immediately rebounds to its original shape after deformation.
Unlike other tire inserts on the market, RockStop isn’t one continuous loop. It has a two-piece design, connected via four cable ties.
| Width | Depth at Thickest Point | Depth at Rim Edge | Weight |
| 43.5mm | 19mm | 8mm | 254g (27.5″) |
We tested the 27.5″ version of RockStop on an aluminium WTB Proterra Tough i30 rim (though a DT SWISS rim is shown here for illustrative purposes) with an outer rim width of 34mm, leaving a good 5mm of overlap at the rim. Onto that, I fitted a Michelin Wild Enduro Rear tire.
So, how easy is it to install a RockStop insert?
Very! The RockStop instructions tell you to mount the insert to the rim first. This was super easy as the insert doesn’t have a very tight fit with the rim. Thereafter, the process of fitting the tire is the same as if you were fitting a tire without an insert – you just need to make sure you push the tire bead underneath the insert. It really is straightforward and effortless, much easier than fitting Nukeproof ARD, CushCore Pro, or Rimpact Pro.
RockStop is made of polyurethane which doesn’t absorb tire sealant. So, you don’t need to use anymore than you normally would. I don’t know exactly how much Slicy Banana Smoothy sealant I used, but it was well below the 130ml recommended by Slicy. You also don’t need to use tire insert specific tubeless valves. You just need to make sure you position the insert such that one of the holes sits underneath the valve to allow air and sealant to flow through it.
On the Trail
Riding with the RockStop tire insert, we very quickly became aware of its presence. Why? It rattles. While the loose fit means it is super easy to fit, it also means I could hear it rebound between the rim and the inside of the tire on bigger hits. It’s no biggie, really. Because of its two-piece design, you could quite easily cut up to 3-4cm off the overall length and cinch up the zip-ties to give it a tighter fit.
Aside from the rattle, how did RockStop perform?
Really well, actually. I rode the insert for several weeks on my local enduro trails, and two days of shuttling at the rough, hard-pack downhill tracks of Innerleithen. I ran a range of tire pressures from as low as 17 PSI up to around 22 PSI, way below the tire manufacturer’s recommendations. Satisfied I’d given the insert a good beating, I removed it (with ease) to inspect it for damage.
I found three points of damage; two cuts sat around 4mm inboard of the edge, and another that extended from there to the outer edge. RockStop does claim their MTB tire insert prevents tire burp. I was a little skeptical about this due to the relatively loose fit and because of how easy it was to push the tire bead underneath the insert during fitting. However, I found no evidence to contest the brand’s claim. After eight flat out runs of the DH tracks, the rear tire held 21 PSI, having lost no measurable quantity of air throughout the day.
The RockStop insert had successfully protected my aluminium rim, and prevented at least three possible pinch flat punctures over the test period. Thus, we’re happy to recommend RockStop.
Pros
- Protects Rim
- Prevents Pinch-Flats
- Doesn’t require special valves
- Extremely easy to fit and remove
- Doesn’t absorb sealant
Cons
- Heavier than most competitors
- Requires shortening to prevent movement and rattle
Pricing & Availability
RockStop MTB tire inserts are available in 27.5″ and 29” versions, with a 27.5″ Wide version for plus-sized (35-45mm) rims and tires. All retail at £65 each.
