All about speed wobbles

1

I got speed wobbles for the first time about 35 years ago. My first skateboard, I was bombing a hill sitting on the board wearing my short-shorts and tank top. My board swerved left, then right and then left right out from under me. I bounced on my ass and took a lot of skin off.
Up until this last year, I had two approaches to preventing speed wobbles: tightening the trucks and using harder bushings. Of course the tradeoff is it gets harder to turn. I rode mostly indy 169’s and these were the only knobs I knew about.
This year I built my first esk8 and was surprised to see that caliber trucks had different kingpin angles. This just made me think of a lot of questions and realize that even after 35 years I knew little about the wobbles that have inflicted so much pain and caused many “soiled underware” moments. So, I thought I would start a thread to get the experts to provide some answers. Here is my list, but I am sure there are more:
What are speed wobbles?
How does equipment setup make this better/worse and what are the tradeoffs:
-truck width
-kingpin angle
-angled risers (and is this the same effect as angled kingpin?)
-Wheel base
-bushings
-Center of gravity
How much influence does the rider have? I know weight is a factor, but when riding halfpipes, I used to have my trucks a lot tighter than most of the people I rode with. Any looser and I would wobble on the flat and body slam into the other transition.

Thanks in advance for the enlightenment.

10 Likes
2

I’ve had speed wobbles but that was usually due to locking out my knees instead in loosening up. Now at high speeds, I just make sure I don’t lock out and keep my lower half flexible and “flowy”. In a pinch if I feel I can’t control the wobble, I crouch for a lower CoG and that usually helps.

Something else that I discovered helps too is making sure that the majority of my weight is on my front foot. Stomping down on the back causes the oscillations to get worse and out of control.

Also wobbles are scary but I do believe that for a large majority of riders, they’re made worse by the mind panicking and trying to adjust in the wrong way. Just stay calm, and crouch. If you’re gonna wipe, you’re gonna wipe so try your best to pull off what feels like “shady” recoveries :P. The bonus is you come out looking somewhat badass haha

I’ve ridden mostly randals 50 degrees for my analog/downhill boards but now with eskates, I’m on caliber II 50 degrees and gullwing double kingpins. My upper speed range is around 30-35mph and I tend to ride with loose trucks. Precision trucks are next on my list.

  • Truck Width - feels more stable the wider it is. Not sure there is a con here

  • Kingpin Angle - the higher the more carvy and the lower the more stable. This can be broken down into keeping the front at a higher angle than the rear. The rear becomes more stable but you can still turn with the front

  • Angled Risers - same idea as changing kingpin angle as it’s the kingpin relative to the ground instead of relative to rider.

  • Wheelbase - longer is more stable but larger turning radius

  • Bushings - harder is more stable but harder to turn

  • Center of Gravity - lower is more stable. Not sure there really is a benefit to high CoG.

Weight is not a factor imo. My fat ass is over the place with weight. At my heaviest, I was 225. At my leanest, I was 150. I’ve experienced speed wobbles with both ends of the spectrum and what corrected it was just learning to stay calm and loosen up.

On second thought, I can see weight being an issue only downhill. Ie you speed up faster but idk if that really counts.

6 Likes
3

What are speed wobbles:

Oscillations of the board that gets worse with an increase in speed and/or user inputs from attempts to stop oscillation.

Imo, usually of the rear truck but I’ve seen the front trucks also oscillate too.

image

2 Likes
4

Something to keep in mind is that you are never going perfectly straight. The carve never stops.

9 Likes
5

My worst speed wobbles experience was a while before I got my first longboard.
Took my skateboard with far too loose trucks down one of the steeper but short hills with my friends.
Got speed wobbles like halfway down, wobbled so hard I hit one of the plastic yellow lane reflectors. Went down, ripped a hole in my underwear bruised but ok.

2 Likes
6

does the width of the board need two be considered also?
a 10" wide board will have more leverage on the trucks than an 8" one (in my head it does)

3 Likes
7

Is had been a discussion of this somewhere we could link to. Wider≠stable

2 Likes
8

Good replies to this thread. I reccomend reading this: Split truck angles, wtf are they? and why should I care? and other stuff about trucks

they are magic is what they are.

11 Likes
9

Width of the board does give you more leverage but I think it would have minimal impact on speed wobble. It’s not the width that gives you speed wobble however an attempt to correct speed wobble could exacerbate the wobble due to having more leverage

Anecdotally, a wider board feels more stable so I wonder if this feeds into wider equaling more stable

2 Likes
10

makes sense, feel more relaxed on a wider board but the implications of a wrong move are greater, I feel I can go faster on a thinner board and trucks (again that’s “feel” no science here!)

2 Likes
11

I think the short short explanation is, speed wobbles is when the board can turn faster than you can react. When the board oscillates for whatever reason, it’s up to the rider to stabilize the board by giving opposite feedback.

To break it down into story mode:

A few things contribute to it, weight distribution being the most important. Keeping more than 50% of your weight over the front keeps the front end “steering” and the rear end “trailing”. If the rear end can turn more than the front, or if more weight is on the rear, the board will want to whip side to side, making it impossible to control. The same phenomenon can be seen in badly loaded auto trailers that are rear heavy, or driving a car in reverse where the “rear” end is steering. The actual physics behind this is complicated and can be explored further in trailer loading.

To assist in this, the rear trucks can have a lower steering degree - by lowering kingpin angle, or simply keeping the rear trucks tighter or fitted with firmer bushings will drastically help (but not a substitution for weight distribution. It is still critical to keep your weight forward.)

As speed increases, small steering inputs will cause more drastic movements, 2 things needs to happen now:

FIrst, finer control by the rider, aka learning the board and simply gaining experience. Nothing to do with the board here other than just riding, logging hours and slowly pushing to higher speeds until the rider gains better muscle memory.

Second, decreasing sensitivity via hardware. Extending wheelbase will increase the turning circle, which will slow down the rate of oscillation, making it easier to get under control at the same speed on a shorter board. Decreasing kingpin angle via various methods allows the rider to have more “leverage” over the truck hangers, both assisting in keeping them pointed straight, and also decreasing the sensitivity of input for the rider, allowing more margin for error before the board goes out of control.

In my opinion, increasing bushing hardness is not a permanent solution to removing speed wobbles. Bushings should be matched to the weight of the rider, allowing full cornering of the board without excessive pressure while giving proper feedback. Not enough and the board will tilt too easily, making it hard to feel for a center, too much and the board is sluggish, hard to turn and could possibly contribute to high speed wobbles.

Things that I believe has minimal effect on high speed wobbles:

Truck width (to an extent), longer is a bit more stable, short is more responsive, but it is more of a feel on how the board corners vs an actual factor to speed wobbles.

Board width, wider will give more leverage onto the kingpins, which should not make a difference with proper bushing hardness, but simply going wider may cause the board to have a wallowy feel simply because it is easier to leverage the kingpins without shifting weight as much.

Center of gravity, disagreeing with @annihil8ted, higher is more stable for skating. Lower is better for cars that does not involve balancing. Standing up with knees slightly bent is much easier than fully crouched on the board, think of trying to balance a pencil by keeping just one end on the tip of your finger. weight on top of the pencil makes it easy to do, a short and stubby pencil makes it much harder.

Weight of the board, usually irrelevant but a heavier board will be marginally more stable than an ultra light one, all other factors the same.

10 Likes
12

Interesting! Personally, I’ve always heard the opposite. The way I’ve had it rationalize is higher CoG give you more leverage relative to the pivot point and allows for over corrections. It’s why a drop deck is supposedly more stable vs a top mount. Plus being taller feels less stable than being closer to the ground.

The following is just me thinking aloud:

The pencil analog doesn’t fully apply here does it? To me, the pencil analogy shows us how a long moment arm allows for more control and therefore stability if the wobble can be correctly. However with a long moment arm also results in more distance travelled for stability.

For the rest of this post, I am going to consider the pencil analogy where the top is the “trucks” and the part where it touches the finger to be the rider. Ie the pencil flipped outside down represent a rider.

Hitting the tip of the pencil, with a longer arm you’ll be able to correct more easily however you’ll have to travel a greater distance to correct. Translated to speed wobbles, that distance is the board whipping back and forth. With a longer pendulum, the oscillations are able to whip out more.

Now consider a shorter pencil, ie lower CoG. In a scenario where the wobble is out of control, ie hitting the tip, you’ll want a smaller “distance” so to reduce the wobbling. It will be harder to balance but the oscillations should be smaller and therefore the distance travelled should be less.

The pencil also isn’t a perfect analogy because at rest, a board is able to stand upright whereas a pencil can’t really. Instead, we should just look at the distance travelled due to changes in cog which is relative to pivot length

2 Likes
13

I think a drop deck being more stable than a top mount has more to do with the moment of leverage on trucks, the virtual rotation axle etc. It is not entirely because it is a couple inches lower to the ground.

The way to understand it is that, the majority of the mass of a rider/skateboard combo is in the torso of the rider. That is your center of gravity. Consider the board and rider as one unit, your pivot point is around your upper body, and the moving/balancing point, your feet. The closer you crouch to the board, the lower your CoG is.

For all intents and purpose, the board can move freely of the center of mass (the torso of the rider), therefore your idea that a lower CoG will cause a smaller oscillation amplitude does not apply here, the board will simply move out of the range of the rider’s control. To break it down, a given tilt angle of the board will give a certain turning angle, regardless of the height of the CoG. By giving a longer distance from the CoG to the point of balance, the rider has more “range” of control before the board moves out of that range (and goes bouncing down the street). Obviously standing up fully will lock your knees and severely decrease that range, but that’s another topic.

The proof is looking at professional DH longboarders. Crouching is their method to decrease air resistance and accelerate, but almost all of them will stand up to stop a wobble or add stability as a bailout.

Edit: To clarify my point, your idea is completely valid in the senario that the board is attached to your feet and your knees/ankles cannot bend. But they can, so the calculation is entirely different with those additional pivot points

3 Likes
14

Hmm maybe we should redefine what CoG means. When I talk about CoG, I’m talking about it relative to the pivot point, ie the trucks. If we’re talking about overall CoG, I think that’s a little harder to talk about as speed wobbles are relative to pivot distances, not overall distances. This implies rider height and weight distribution affects stability which my first take is those shouldn’t be factors.

Exactly, this is why a drop deck is more stable. Moment of leverage and virtual rotation axel are related to stability and CoG no?

Ahh see this is why I think we’re not exactly agreeing. I have my pivot point as the truck seeing that’s where the oscillations start. But let’s go with the torso idea.

I think oscillation is due to overcorrecting the wobble. A board on its own going down a hill is stable. As a result, a higher CoG gives more leverage which allows for easier overcorrection. Crouching down and bending knee limits the range of possible overcorrection. For me, crouching on a board also forces me to put the majority of my weight on one leg too so maybe this is why I feel crouching helps with stability

Yes standing up does give more range before loss of control but that means letting the speed wobbles get out of control right? If you start lower, you can help prevent the possible overcorrection. I can see if you’re able to effectively correct how standing up will give you better control of the board.

I thought standing up is more for air braking and slowing down into the range of stability?

I would say by crouching or staying low (not necessarily crouching), you’re simulating the effect of having lower angle trucks, ie limiting the amount of overcorrection.

In this articles, it explains how staying low helps with the speed wobble.

1 Like
15

. I have my pivot point as the truck seeing that’s where the oscillations start.

I think that is where our disagreement lies, I visualize the point of oscillation at the hip of the rider. Watching a video of someone suffering from speed wobbles, their upper body stays in a straight line as the board goes side to side.

The neat part about oscillation is that it requires a lot of factors to play perfectly. Change 1 thing and the oscillation stops. Crouching is a shift in weight and upsets 1 of the criteria causing the wobble.

Also I think I understand your point now, the only part I disagree with is that staying low should not really affect over correction, because correction of the board is done entirely by pivoting your ankles, and I don’t see how your upper body’s position affects it. But I have been assuming crouching means a position where the rider is tucked on the board, i.e. able to put their hand on the ground, and standing means an upright position with bent knees and torso.

I think being lower than fully standing helps with balance because it lets the rider have the most range of motion in their legs, and I feel like that is the biggest contributing factor here, the ability to bring the board back from side to side.

2 Likes
16

Yeah there are a lot of factors that come into play when it comes wobbling and how one can go about correcting wobbles.

Yeah couching is definitely a shift in weight when it comes to front and back of the board (horizontal CoG) but I think it may also change the vertical CoG too. That said, it’s hard to say if the stability comes from the change in CoG horizontally or vertically.

I definitely get your point. It’s a slightly different circumstance than what I had in mind but it definitely makes sense to me and I agree. I would say, however, at high speeds, you’re not really trying to turn with your ankles but more so with lean and therefore the body (mostly lower body) overall. You want small corrections at high speed and I think for most people, that’s easier done with leaning instead of their ankles pivoting.

For me crouching is just getting lower to the board but I had envisioned a pre sliding position. A bent knee, somewhat hunched position is within what I would consider to be overall lower CoG. Standing up is with knees almost locked and back pretty much straight and that for me is a higher CoG. Standing up is also equal distribution of weight which you definitely don’t want.

Haha I think we’re probably referring to the same “positions” of stability but calling it differently because I too think that the most stable is a bent knee forward leaning position with fully crouch, pre-sliding position as the extreme of stability.

Long story short:

Standing up (locking out) - super bad. You have fully range however you’re also probably distributing even weight which can make the oscillations worse

Crouching (bent knee, forward lean) - the best. You have range to combat the range of oscillations and your weight will be forward

Crouching (knees slightly bench, upper body almost horizontal, think downhill position) - range restricted in a trade off for less air resistance. You have some range to combat the oscillations and your weight will be more forward.

Crouching (pre-slide, almost sitting, weight over one foot) - debatable. Your range is highly restricted (although maybe not needed?) however almost all of the weight is on forward truck.

2 Likes
17

It would be good to get Brad’s opinion on this. I call on him too often though so someone else can do it :joy:

3 Likes
18

Yeah I get your point now.

Crouching (bent knee, forward lean) - the best. You have range to combat the range of oscillations and your weight will be forward

This is what I was considered standing, full standing is exclusively reserved to cruising down the boardwalk at 5mph I think.

Crouching (pre-slide, almost sitting, weight over one foot) - debatable. Your range is highly restricted (although maybe not needed?) however almost all of the weight is on forward truck.

This was what I was considering crouching, i.e. taking a tight corner with your hand on the ground. I found this position not all that stable at high speed.

I think your point that at high speed, it is easy to visualize a lean into a turn, rather than carving of sorts, but I think when it comes down to it, your ankles will pivot regardless of leaning into a turn or not, even if you’re not intentionally turning with your ankles, it is the last part of your body that moves before it touches the board, and still ultimately responsible for balancing and stopping wobbles even if it’s subconsciously done.

2 Likes
19

My 2¢:

  • My friends still don’t believe me that it’s the back truck that needs to be dewedged. (The back always follows, they say) Now that I have an adjustable baseplate, I will have them try for themselves riding down a hill with 60 in the back and, let’s say, 20 in the front. lol
  • On my board (build thread in a few days), I actually found that if I put all my weight in the front, despite my rear truck being dewedged, it will start to wobble unless I put a little bit of pressure in the back too to control it. Might be shitty caliber bushings, or my angled riser doing it; dunno.
  • I find it hard to steer when kneeling down, but I think it’s just because of the leg muscles being positioned awkwardly. I don’t think standing up to control the board has to do with the center of mass being higher. You could test this by going fast with a setup that wobbles a bit, and just lifting your torso up and down.
4 Likes
20

Someone put that shit on a t-shirt. I’ll buy it right now!

7 Likes