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All about speed wobbles

Haven’t seen it mentioned, but has anyone considered the pendulum effect? CoG below pivot point is more stable than CoG above pivot point? Can also be harder to turn, but you see where I’m going?

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YIKES!
10char

I’ve been thinking along these lines also. The problem with a speed wobble is that the truck is perturbed by say a bump and the bushing is compressed, while doing so a turn is initiated and this takes kinetic energy from forward motion (i.e. Change of direction = change in velocity) also compressing the bushing. As the bushings are elastic, this potential energy is then released creating a restoring force that pushes the truck past its neutral position into a turn in the opposite direction adding yet more energy back into the system and amplifying the wobble.
So the way to combat a speed wobble is to remove some of this excess energy so the restoring force brings the truck back to a near neutral position, so damping essentially.

I remember that early mountain bike shocks (Rockshocks) used to market “nitrogen filled elastomers” as a damper material, but looking now it appears these were just normal elastomers that used stiction rings for damping, so crap essentially.
3do and the likes of g-form materials do sound interesting, but I’m not sure of the actual damping properties, like g-form just appears to get harder, thus spreading the load in a crash and not essentially dissapating energy. Etoxx/Trampa elastomers, certainly have some dissapating properties compared to springs, I’m not so sure that material is any better than the material we use in our conventional trucks currently. I’d love hear suggestions of other materials that could be used as a damper, as you suggest, in conjunction with normal bushing.
The other thing is as riptide pointed out, adding damping this way will likely negate the the stuff we like about our current set ups, i.e nice rebound for carving.

Really the best way to damp unwanted oscillations is to go with hydrolic damping, this is how it was solved on motorbikes, preferably something with both high and low speed adjustment, so steering inputs (low speed) can be tuned seperatly to speed wobbles (high speed), whilst still keeping the feel if the bushings we love. Nowind did experiment with this but was not terribly impressed, possibly due to the cheapo Chinese damper he was using, good ones for bikes cost in excess of £350.

Anyway this is all pie in the sky stuff, currently split angles, split duro quality bushings (riptide), and a boardside precision cup washer on the rear always seems to work wonders for me in banishing wobbles for me.

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That’s an extreme drop deck right? I think someone on here actually had a deck that could do that. Someone was running AT wheels on a board flat enough that they were able to ride the board inverted :laughing:

As for below the CoG, that would be without a rider. With a rider, the CoG is above the pivot point but your point still stands that it would offer more stability

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Ok, I’ve just returned from a super straight and super smooth tarmac speed test on larger 100dia wheels in the front and 90dia wheels on the rear - both truck angles are the same on a drop-thru drop-deck Bustin board, managed to hit 22mph / 35kmh this time, overcoming the anxiety by having a few runs back and forth.

However I did feel slight speed wobbles when I rolled over a painted graphic on the asphalt like I did on the 90dia throughout in the original setup. And I felt a little wobbly immediately cutting the throttle. I feel there’s just a very difference in having 100dia wheels in front - as in it feels a little more stable? These are stock Paris trucks, nothing reconfigured. I honestly hate that wobbly feeling, and really hope to gain something from the wealth of shared knowledge above in this thread.

If you have managed to get rid of the unwanted oscillations or speed wobbles altogether, do share your setup. So far I’ve gathered :-

  • split angles : 35° at the rear (hard to find a drop thru that does this, does a drop-thru compensate as a low angle like 35°?) and 44°-50° in front, maybe next will try top mounting the front?
  • split duro quality bushings - what is the meaning of split duro? different duro ratings?
  • precision cup washer (have attached screenshot - which one is it?)
  • potential added damping through even softer bushings.

Thanks, much more tinkering to do to get rid of the wobbles entirely.

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What bushings are you using on the trucks?
I found that changing the bushings greatly upgrades the overall feel of the board and prevents wobbles almost entirely. Majority here uses Riptide bushings. I have a set of 90A bushings that you can grab from me if you are around 70~80kg.

Also, there is this glorious thread where the founder of Riptide can help you recommend bushing settings for your ride

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Yes! I am around that weight, fantastic I’ll grab them off ya sometime soon, we’ll arrange. You folks are far advanced - maybe that’s how bioboards can reach those insane speeds! Incredible - Thanks Linny, you’re one in a million!

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You should try my Evo board sometime.
That deck is legendary in downhill. Something about the split angle on the deck paired with riptide pivot cups and bushings make it really stable. I have gone 50km on it before comfortably with zero wobble. But of course padding up is a must when at those speeds.

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You all have balls as big as coconuts - 50km is :skull_and_crossbones: for me with wobbles - maybe I’m just a beginner, but sure I wouldn’t mind trying (fully padded of course) - oh I forgot to mention, I’d have no clue on the bushings and duro of them, they’re just stock but real Paris trucks straight out of the pre-built box.

Precision washer cupped:


Split duro (different board) harder boardside:

Split angle, can be done with board, baseplates or risers:

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Bioboards bushing configuration is this: KranK Barrel / FatCone front and Barrel / Chubby rear

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Do you feel more of your weight is shifted back? I can see with bigger wheels up front, the board is angled up forcing a more natural weight placement in the back which isn’t good for countering speed wobbles.

What do you mean? I’m a little lost here :sweat_smile:

I think with a drop through setup, your options are definitely limited when it comes to angled risers as I don’t think I’ve really seen anyone use them in a drop through. Drop throughs don’t really compensate either, it’s just mounting the deck lower. You could try and find a drop through board with angled tips? I would just top mount and use angled risers to adjust. If you have money to burn, you could also get adjustable base plates

A lot of getting rid of wobbles just comes down to learning how to ride and being more confident in riding. Sure there are things that can help but the majority of which is remembering to ride loosely and not panicking when a wobble starts

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Wow, this is invaluable stuff! Thanks Brad - If I only knew what to order from you, but first I’ll check with Linny to understand specifics more - it takes awhile to absorb.
I’m reading your other thread, and from what I gather they seem to be harder - can I confirm if your duros are harder or softer for this speed stability result? Thank you!

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Rolled over a painted graphic like a bicycle symbol painted onto the surface of the asphalt. It threw the board off a little.

Not really, I can safely say that it’s not just about learning how to ride. I came from longboarding (not downhill, but intend to learn forced sliding and braking). Wobbles are wobbles, and in all honesty, you just don’t want to have something you can’t exactly control at speed. I’m a mad driver in my car, so I doubt it’s got much to do with confidence.

I rode with a damper on the rear truck for a while and loved it. it was adjustable, made the ride insanely stable but still manuverable. I could basically turn it off if I wanted to do low speed hard fast carving or turn it up for speed runs.

Changed boards, disappointed that my mount wasn’t universal to transfer to my next deck. I got wobbles at 50mph without it, and none for almost a year while using it.

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:exploding_head:

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OK @spade a couple of things about your setup from your recent post. Bustin boards have a tendency to hammock the setup in that the flex and rocker of the deck cause both the front and rear truck to be angles above their base pate angles. This can be great for commuting and pedestrian slalom but not so great for stability at speed. Not sure why you are running larger wheels in front than the back but that can lead to unknown issues. The Paris trucks I assume are 50 degree front and back with the added wedging influence of the Bustin, you are likely at 52 to 55 degrees symmetrical which is a handful to handle to be sure. It would take a lot of skill and experience to go fast on that setup. Let me know what you are willing or able to change and we can go from there

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Ahh it was probably the change in road that made the board feel less stable or maybe losing grip? (I doubt that in good dry conditions you would lose grip though)

I mean that’s fair, don’t get me wrong, I’m not saying go fight wobbles with an unstable or poorly setup board but a large amount of wobbles are just riding loose and mind over matter. That’s what it did for me as I too came from longboarding background (garage bombing and slides). You just got a new board right? The bustin one? It’s slightly flexible right? Flex doesn’t help with wobbles but I would definitely say as you become more confident in riding that board, the wobbles will disappear without you having to change it.

haha to be fair, crashing in a car or even speeding is way different than crashing from speed wobbles. One on hand you either have a roll cage or at least some sort of metal plating. On the other hand, it’s road rash or bruisings for days :sweat_smile:

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Good catch! I just came back from reading his post and realized this might have also contributed to wobbles

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Wow! thanks Brad for your much welcomed advice - I have no idea about the exacting degrees on the trucks, but here are some photos I just took to see if anything can be made out just by looking at them… this will be interesting. With regards to larger wheels in front, I have no idea really, of what I’m doing and have many assumptions like loading weight in front and raising the board higher in front because of the “higher angles” in the front theory - I assumed they are like one in the same?

I’m certain I am wrong after the test run. Most of all, the low clearance of deck off the ground (which convinced me to buy the board) didn’t really help much which again proved my assumptions falsely. The board itself has zero flex- one of the stiffest I have ever stood on. But yes I somewhat feel the hammocking effect.

My goal is simple, I just want to get rid of speed wobbles at top speed of the the board which isn’t really that high anyhow (27mph). I was experiencing it at 18mph onwards and anything you suggest to change is welcomed (I would dearly like to keep these beautiful Paris trucks though) and I don’t exactly have all the expert DIY tools to dissemble the motor mounts from the trucks etc etc… quite limited in terms of what I can do. But thank you!