Rimpact TMD V2 tuned mass damper

The Rimpact TMD V2 (tuned mass damper) uses a sprung weight inside the bike’s steerer tube to counter vibrations at specific frequencies. It can make the handlebar feel calmer, taking the sting out of sharp bumps from roots and rocks and potentially reducing hand fatigue. However, fitting takes a little patience; the springs may need greasing to prevent creaking, and the benefits are incremental rather than a replacement for a good tyre, fork and cockpit setup.

Rimpact TMD V2 – Technical Details

Rimpact has designed its tuned mass damper to fit inside the fork steerer of a mountain bike. At its centre is a spring-mounted 250g weight that can move in response to vibrations coming up from the front wheel. The idea is to take some of the sting out of rough ground before it reaches your hands. Rimpact claims that it makes the bike feel calmer and helps reduce rider fatigue.

For version two, Rimpact forgoes the user tunability, using one pair of springs in place of the original’s interchangeable options. These new springs have more travel, which is said to allow the weight to react quickly to smaller inputs while retaining control on bigger hits. A pair of elastomer bumpers provides extra control at the ends of that travel.

With the 250g moving mass, Rimpact claims a 330g weight for the complete unit. It’s designed for a metallic 1 1/8” in steerer that’s at least 180mm long, although it may work with shorter steerers with spacers installed above the stem. The TMD comes with extensions to adjust the overall length of the unit, allowing it to fit a wider range of steerer lengths.

Rimpact TMD V2 – Performance

Fitting the TMD V2 takes a little patience, but it is a relatively simple affair. If you have a traditional top-cap bolt in your steerer, the first job is to remove the star nut by knocking it through. With a clear steerer tube, the TMD’s length can be adjusted by adding or removing the thread extensions. Once the right length has been achieved, simply tighten it up, almost like you would a regular headset, and you’re good to go.

Initial impressions on the first ride were two-fold. Part annoyance as the TMD introduced a “creaky spring” type noise to the bike, but also part intrigue as the feeling through the handlebar was noticeably different. The “creaky spring” annoyance was easily solved with a little grease in between the mass and springs, which helps them slide more quietly.

It’s taken several rides and some back-to-back testing to really understand where the TMD excels. For me, I struggle with hand fatigue when riding longer, rougher trails, and this comes primarily from small bump chatter such as roots and rocks. I think the TMD may go some way to helping with this. Let me explain.

The tuned mass damper is designed to move in the opposite direction to the input forces, which in turn tries to cancel out the peak forces. The “tuned” part of the equation refers to the frequencies at which the damper is designed to work. Rimpact doesn’t specifically talk about which frequencies this damper is designed to deal with, however, I can confirm that the damper targets some appropriate ones.

With back-to-back testing, there is a noticeable change in the feel through the handlebar which, as Rimpact says, can only be described as a calmer feeling. It’s similar to riding an e-bike where the extra weight calms things down.

Larger impacts are less noticeable, however, the small but harsh inputs from thicker roots and square-edged rocks are where the TMD starts to make sense. I can liken the feeling offered by the TMD to that of running a compliant handlebar – it takes the sting out of the harsh frequencies which would usually cause hand fatigue.

I see the Rimpact TMD as another tool in the arsenal of finding the perfect set-up, but it is by no means the singular answer. In terms of the front end, tyre casing, tyre pressure, fork set-up, bar stiffness and grips all play a part in the optimal set-up, and if you’ve got that lot nailed, the Rimpact TMD is worth considering if you’re looking for another small incremental improvement.

Rimpact TMD V2 – Verdict

There is no easy way to say this; the retail price is £200. On the plus side, the TMD is a fit-and-forget item which won’t need servicing or repairing throughout its life.

Tuned mass dampers are not new anymore, and there are of course other options to choose from. The CounterSycle Tuned Mass Damper is another take on a similar concept, using its own container for the mass damper and connecting externally to the steerer tube. At $275 plus shipping and a bulkier fitment, it’s a hard one to justify but worth investigating nonetheless.

If you want to leave no stone unturned in reaching set-up perfection, the TMD V2 is worth a look, however, it should only be considered alongside good suspension set-up, bar compliance and appropriate tyre pressures.