On a push skate it stops at the bottom of the hill.
On a Esk8 it just takes a charge break.
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Lowering you center of gravity on a skateboard will make it more YOU more stable. Watch any skate comp or this classic https://youtu.be/4YYTNkAdDD8
you will see what I mean. Land sketchy and you squat to hold on. For speed wobbles I am not sure, but if a wobble causes you to lean, it will help keep you centered over your board and have a chance to stay on your board.
The other side of center on gravity I am interested in is feet above the ground. If I have a shorter board and I want TB 110s instead of abec 90s, am I more prone to speed wobbles?
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read a lot about this.
Iāve considered myself rather lucky with speed wobbles since starting to esk8 at the beginning of the summer. My bone stock ownboard wobbled on me like crazy. After some research on the forums, I made some routine changes to parts and was able to end it. Since building into a new board, still havenāt had speed wobbles and Iām running a setup most would consider susceptible to it.
33in sector nine shoots deck, wheelbase of 25 inches. Itās re-enforced to stiff but didnāt flex much when new. Caliber 2s, 50/44 with Orangatang Nipples purple barrels, normal tension, riptide pivot cups 95A I think.
This thing has never wobbled on me all the way to 30mph. Above 27, Iām noticing how small it is at that speed, but havenāt had a wobble. However, at 30 Iām feeling close to it. These changes are just tried and true things I learned from other users to prevent/reduce wobble. This is pretty fast on a fairly short board (I mall-carry this without it dragging at 5ā9ā). So if any user gets to here searching for help fixing wobble and they havenāt done simple things, they should turn around.
Okay but lets talk about speed wobble. Speed wobble is the state in which the oscillation of the steering geometry becomes unstable and enters a sustained deterioration of that stability. This occurs in all drive geometries with a single steering pivot (scooters, motorcycles etc). Every time you ride down the road, there is a natural oscillation that occurs from the contact of the wheels through to the steering input. This occurs at all times and is unnoticeable when the frequency and magnitude of those oscillations are low ā at slow speeds. You can see this for yourself by riding a bicycle in a straight line while releasing the handle bars. They will oscillate back and forth even on a smooth road. I know youāre thinking, I see more oscillation in the bars if Iām going too slow? You need some momentum to give you some potential energy moving forward to allow things to stay in harmony. A nice cruising speed is perfect, donāt try this at walking speed.
This occurs because the tires are interacting with the road (which isnāt perfectly smooth) and your center of gravity is constantly moving (making intentional or not input to the steering geometry). As these changes occur, they change the contact pressures and alter the degree of friction in that area of the tire (this is basically how turning works in general, the geometry moves the wheels into a position that creates more friction opposite of the way you want to go) Things go bad when those little road imperfections and weight adjustments cause those steering inputs to occur at a speed where they begin to overtravel and destabilize the direction of momentum. This happens when one of those things creates a momentary directional input- that then deflects the steering geometry and tire from its initial direction of travel. However, since the rider has momentum in the original direction of travel, coupled with a wheelbase length on the vehicle (longer wheelbase makes changing direction more difficult) the wheel is influenced to return to the original direction of travel. At the same time, friction against the contact patch is higher than normal because the tire is not moving in the original direction of motion. These forces combine to send the steering geometry back in the direction they initially came from rapidly. The state of speed wobble occurs when that deflection of the steering geometry back to the original direction of travel overshoots the starting location so much that it creates another deflection state, back to the last direction and overshooting the center again. These forces build and multiply on each other as the wheels essentially begin whipping back and forth. Now there are massive states of high drag happening at each wheel or on each side (or on a motorcycle, on each edge of the contact patch), which are competing against the original vector of momentum, straight. When the forces overtake the direction of momentum, the vehicle will lose control. Much sooner though, those thrashing left to right oscillating forces will
I think the biggest thing everyone should take a second to consider is this:
Speed wobble occurs when the forces exerted on the vehicle and rider exceed those which the steering geometry, suspension and rider can accommodate. These forces can become exponentially more significant as speed increases. If youāre getting speed wobbles, either you or your equipment is not suitable for the speeds at which you are traveling.
Okay so Esk8 specific.
Everyone seriously, most of us are doing 30+ mph across pot hole laced, uneven paved, pedestrian covered pavement on boards that were never designed to hold 20lbs of components and 7500w powertrains. Most of these components were designed for sub 80mm wheels that slide, beautiful flowing roadways and are meant to be ultralight. Letās not also forget that you likely put 500-1000x the mileage on an esk8 that you would if you were pushing the same board around in the same amount of time.
We are all penny pinchers who want the cheapest shit, we want it to last forever, and we donāt do general maintenance often enough (go back to that last paragraph, think about how often you change wheel bearings and think about what their actual mileage might be for example). This is the area that I think most users could benefit. I just replaced a set of pivot cups that were 3 months old and looked like they shouldāve been replaced a month ago. We can literally throw everything in this thread out the window if youāre not already checking your current components. The wear rate is super fast on components for esk8.
Long story short, if youāre experiencing speed wobble, make sure you have well suited bushings that are in good condition. Also make sure your hardware is torqued appropriately and check frequently for part failures. Especially drop through decks, decks high performance motors and large diameter wheels and monitor your mileage.
Im very aware that if I push it in the 30+mph range, Iām going to get speed wobble and go down. Its at the limits of the current configuration of components. If I wanted to improve my high-speed stability, Iād do the following: lengthen the wheelbase, reduce the rake angle of the trucks, fine tune the bushings. Wider hangers have the potential to help, but the wider the hangers are and the more mass on the end of them, the more force that will generate when it goes haywire. Typically, we see large diameter wheels and high speeds on longer wheelbases.
I think that if riders wanted equipment designed and engineered for esk8 specifically that totally rethought things, we would wind up pretty far from where we are now. Even just the mounting for trucks has such a narrow footprint on the deck, especially for drop through, its at a huge engineering disadvantage. Regardless, engineering something that will stand up to the abuse of east coast roadways is technically very challenging and very expensive.
However, I have a feeling that too many people want everything and expect no drawbacks. Thereās an old saying: cheap, reliable, performance. You can pick two. Cheap and reliable components arenāt high performance. Cheap performance parts arenāt reliable. Reliable performance parts arenāt cheap. The same goes for all things including this. Speed, stability, maneuverability. You can have speed and stability at the cost of maneuverability (low angle trucks and long wheelbase). You can have a maneuverable board thatās fast but isnāt stable, and you can have a maneuverable board thatās stable ā well it could be fast, but its definitely heavy and not cheap. This is where you get into EMTB trucks and things that havenāt been invented yet. Whatever, you get the point.
I think if you are routinely riding your board and putting miles on it, you should invest in high quality components. Just because they are expensive doesnāt mean they are quality, always do your research. Think hard about the abuse your esk8 is put through compared to what it was designed for and go from there. This is why iām switching to precision trucks - even considered 10mm axles. I re-enforced my board with FG and my neck deck is a drop down and drop through. Drop down and drop through decks are some of the worst decks for longevity in esk8 - they have forces in places where most decks donāt see as much wear. Some of the best of these decks are handbuilt and extra thick. Especially in the drop down area. The bustin Iām building has a small drop down and is drop through. I intend to re-enforce all of these areas to stand up to the abuse of philly roads, large diameter wheels
Understanding how speed wobble occurs is the first step to fixing it. Based on physics principles, I would get low. Just bending your knee will loosen tension in your legs if you were locking your knee straight. This lowers your COG and while it may be challenging for balance, you should practice it. If youāve ever had to mash your brakes at 20mph for a car that pulled out, youre already used to this. Keeping your weight more on the front foot is good, but donāt dive it there or you could introduce it on the front truck. Its hard to remember to remain calm when it happens, but its also good practice not to brake. You need to ease off the throttle quickly. Dumping it to neutral may toss you from the sudden speed change and unstable state. Get low and try to ride it out. If you can maintain that forward momentum and stay above it, it will correct.
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ehhh, im pretty sure it would be a bell curve. Theres definitely a sweet spot for stability. Im sure there is some correlation between wheel/tire width and overall width. But going too wide has issues because of the suspension geometry. Honestly once youre outside ~14 inches you should have independent suspension
The components would be costly, but id love to see it for esk8 in a smaller form factor for urethane wheels
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You know, I might add that minor differences in motor torque and/or kV may contribute to wobble. This is just a random thing I found through personal experience, Iāve noticed that on boards with 2 or more motors, nearing the top RPM of the motors, the board sometimes will feelā¦ washy and squirrely, not necessarily wobble, but feels like it could induce one.
For example, if I gear a board so that max throttle is 30mph, then pushing near 30 starts to make the board feel uneasy, where simply changing the gearing to higher, lets say, 40mph, but still cruise at 30, it feels solid and tracks well. Iāve noticed this on various motors and VESCs, not traction control related. I donāt know if Iām the only one who noticed it, but thought Iād put it here.
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On my limited experience with speed wobbles - i dont get speed wobbles on acceleration, only on easing off the throttle and deceleration - why is that so?
Also to refute the theory about wheel base and wide trucks - i recently went down a fairly steep but smooth slope at speed on a penny board - no issues with speed wobbles for its sizeā¦ getting confused now
Really guys, just get good bushings and good truck angles and learn how to ride your board. Not super complicated
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Yes. Good bushings and control. Thatās what I do and Iām on Dkpās and still able to do 35.
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I just relax my self and go full throttle ā¦with a big smileā¦
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Smooth is good for the surface. But thatās interesting. Iām not sure I agree it debunks it. I think your mass, the speed and the significant amount over forward momentum compared to what those little trucks can generate in off direction forces if they were to wobble.
Strap on caliber 2s and 90 wheels and try that. 
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Maybe itās bumping up against an ERPM limit or some sort of limit? Ie itās pretty easy to hold anything under a hundred but at a hundred percent, trying not to overshoot or undershoot becomes harder when thereās not much to overshoot with?
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Now that he mentions this I have to admit itās a perfect description of how mine feels at the top. But 10s 190kv shouldnāt be there
Could be a software limit maybe? That said Iām not exactly sure why at the open end it would be hard to control
Alternatively, anything below full throttle is susceptible to small variations in speed (not keeping throttle as constant as we think) whereas full throttle maxes out on speed. Maybe the small changes in speed feels more stable versus the absolute of top end
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Thanks for this wonderful link. Split truck angles, wtf are they? and why should I care? and other stuff about trucks
It should be a must read for all.
If I am reading right, the front of the board should tilt higher than the back. If this is the case and you donāt have the luxury of lower back trucks and higher front trucks - can a larger diameter wheel in front work?
Basically, after doing a search, I havenāt come across anyone who has tried placing different sized wheels in front from the back.
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If you are just wedging/dewedging with angled risers, the difference in height will be very minimal.
For one of my boards that has an adjustable baseplate, which has the front tilted to 60, and the back tilted to 30, i had a riser at the back to compensate for the height, in this case it was a tunnel riser to route my wires into the enclosure.
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Now that I think about it, thatās true. I guess that means people should take extra care in having their boards level w.r.t. the ground / the front a bit higher on setups with near equal angled trucks. Otherwise the back will steer more than the front, which isnāt that good.
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Angle is relative to the board isnāt it? Also wouldnāt you need significantly bigger wheels to change the degree relative to the ground
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Very good question. I donāt actually know 
But you could change the angle with a lot of risers on one side as well, donāt need differently sized wheels necessarily
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Angle of the trucks is relative to the road, not the deck. (actually I may be wrongā¦)
I used to ride with the back slightly higher than the front and didnāt notice anything at all about that really.
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I almost always had the front of my board lower than the rear when I was doing downhill.
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