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Blind test of a mass Vs. Rimpact Tuned Mass Damper:
Bought a Countershox/countersycle unit. I haven't ridden it yet so I can't comment on the ride quality, but I have already taken it apart. It appears to have a Brass(?) mass inside which is super tight in the outer tube. I guess this is some sort of friction damping, as the springs are really soft. The marks on the Brass are from when I took it out of the housing. No oil or lubricant inside the unit apart from grease on the springs. Will put it back together and take it for a ride.
Was there any preload on the spring when you took it apart? I am already riding one for a month and until now didn‘t dare to open it.
There is some preload but the springs are very soft so it's not a problem opening it up.
That's actually really smart, because I've been wondering how these things don't just feel like a bouncing lead weight, bouncing over and over again ad infinitum. A super tight fit with a malleable metal like brass creates simple mechanical damping for the low speed range. I was picturing really heavy spring rates and no damping.
Thats cool!, Are there any holes or grooves machined in the piston or chamber wall? A tight fit on the wall might also mean the internal air volume creates a progressive spring rate as well
Great points, as an undamped mass suspended with spring rates for 30-50hz would continue to vibrate the frame after rest.
So that begs the question - why does damping happen on the "compression" part of the event?
Shouldnt it be more beneficial for it to only happen on the "rebound" ? I know I'm inventing a poor fork/shock here.
how Ironic we go to great lengths to have stictionless suspension and yet the countershox relies on stiction for damping.
The big 2 suspension companies were in the wrong game all along it seems.
Stiction in suspension breakaway force is much different. I have heard from supercross suspension tuners that they have good results from fork fluid that has more friction than other fluids that are more slick. It gave them a feel they couldn't replicate with shims, pistons or springs
Dude what did you use to open that thing up? You animal.
Used his teeth like every other red-blooded American.
It looked like it had red loctite holding together, so left it front of a space heater for a while then cracked 'er open with a vice, didn't take much persuasion.
Want to hear from the Rimpact Founder about Tuned Mass Dampers?
Forum regular Jesse Melamed is out at round one of the EDR with what looks a lot like a Rimpact TMD fitted to his race bike, guess he thinks it's good enough to race on, probably some others lurking on bikes that I haven't spotted also. Good luck for the weekend Jesse!
The Scott DH team are running them also.
I have had one on my bike for a couple of months now. Initially it felt good, then I felt it was a bit 'chattery' so have gone up to the hard spring to see what difference that makes. It may have also been the TMD hitting the inside of the steerer so I will check that also
Thanks for the insight, be good to hear how you get on with the different springs.
I have been riding the same tracks to keep the tests consisten. The chatter I encountered was on one part of the track which was a steep fast chute, the other parts of the track I did not have the same feeling. Riding on Sunday so will see what the increase to the spring rate does.
I have Rimpact and countershox. With the Rimpact I do find some more noise, but I do like that it’s in the steering tube. Overall the countershox is working better for me on vibration damping and feel to my hands.
Ronan Dunne running the TMD at the rear wheel in his vlog from May 8th. Interesting to see, for sure!
Still struggling to get along with my Rimpact TMD. Swapped to the harder springs but still find it really 'chattery' Going to back to back on the same trail to rule out headset or forks issue.
Noticed in this video https://youtu.be/nYpi-M6LMp8?feature=shared that it looks like Troy is running one.
With my riding and bike set up, I thought the lightest spring worked the best. From most people I’ve spoke to. They are on the lighter spring as well.
I think another thing to remember is that the aren’t a cure all for chatter. They will work in certain areas, on certain trails reducing, certain frequencies.
Thanks for the advice, I will try the light spring next. Its one section of trail that the chatter is really noticable
an the TMD in france, did a few back to back runs on Pleney, which is notoriously rough at the end of the season.
With the TMD installed, the bike tracked through the rough corners better, less deflection from the front wheel. Added a chunk of weight (900g) to the underside of the downtube and the bike responded in the same way, also making the bike feel less choppy under brakes.
The racket the TMD makes is quite astonishing, certainly a lot of noise on the big hits. Anyone found the same?
Are you running the rimpact? Could make sense for the noise, it’s either not perfectly lined up in steering tube and hitting the side or bottoming out. Could try a stiffer spring but then it’s going to change the frequency. The countershox is self contained and doesn’t bottom out.
As far as I can tell Jackson Goldstone is no longer using a MD on his bike.
Looks like CounterShox to me from World Champs
Did check the alignment, and there are no marks on it or inside of the steerer. It only happens on the big square edged hits or repeated braking bumps (morzine). What it wants is a bottom out bumper, winter project...
I experienced loads of chatter, but no real noise (not at Morzine but in the UK)
Ronan still on the Seatpost damper
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