does 1 or 2 xtra lbs. in a trials uni make a noticeable difference? See scenario...

Let’s say one guy has a 15lb trials, and he weighs 140lbs.

The other guy has a 13lb trials, but weighs 142lbs.

Question: Assuming both riders have have the same skill level, and each are equally adept at hopping, will the guy with the lighter uni have a hop-height advantage, even though his total weight including his uni is identical to the lighter rider with the heavier uni? This hypothetical also assumes BOTH guys have the same strength level overall.

Point? Does an extra pound or so on a uni make an “appreciable” or measurable difference in trials riding and/or hopping potential since there is such a variety of weight variations in riders? :slight_smile:

you know what, i was gonna post the exact same thread.

So…deos and extra 2-5 pounds make THAT big of a difference for trials riding?

And in muni, I typically load up my camelback with 100 oz of water…that’s more than SIX extra lbs, plus pump, spare tire, all my 661 gear, helmet, etc! But even with ALL that extra weight, the total weight (including myself) is still more than TEN pounds LESS than it was about 2-3 months ago, when I weighed 162lbs!

In trials I wear all the protective gear, but I’ve improved my hopping quite a bit in the last 2 months or so…so I wonder if there’s any correlation between the fact that I’ve lost nearly 22 POUNDS (down to almost 140lbs.) since I started riding (mostly muni) four months ago, and the hop-height improvement? There MUST be! All that extra weight (fat!) is GONE, so there’s 22 pounds LESS to lift!

No, not at all. it’s all psychological, and any attempt at applying physical science to this is a waste of time. This topic has been beaten to death in previous threads, and the general conclusion is that weight is a minor factor in performance.

Give me a 15lb trials uni, and I’ll still jump however high it is that I jump on my own 12lb trials uni. I only jump 2" less high on my muni than my trials. I blame this on the larger muni wheel hitting me in the ass as I tuck (which it does). The 2" disparity supports this theory, as that is the difference in radii between the two wheels. This disparity has remained the same for as long as I’ve been tucking my sidehops to maximum effect. My hop height actually increased from 32" to ~34" when I added a brake to my muni. Go figure.

Until you begin to tuck your hops to their fullest (meaning SEAT OUT), weight is virtually irrelevant, as the uni is weightless in midair. Even when you do, weight is essentially meaningless.

Ever notice the strange hand positions of trials riders in full tuck during a SIF hop? There’s no way they could lift a unicycle with their hand in that position. Luckily they don’t need to, as the unicycle is essentially weightless during the hop.

I maintain that unicycle weight is simply an excuse riders use to justify statistics that are not entirely to their liking. I used to do the same thing, and understand, but now I think there are better things to do, like not measure one’s hops at all.

Let me close this with a question: Does a 2" diameter superball bounce higher than another 2" diameter superball with a small lead weight in the middle? I think not.

Looking at this from a physics perspective:

Lets say a person of M(mass) can exert X joules this will bring them to a height of

mgh = x
H = x/(mg)

so lets say some one weighs 60 kg and can normally jump 30cm(1 foot)

the energy the exert is 60(10)(.30) 180 joules

when an extra kilogram(~2.2 pounds) is added

H = 180/(10 x 61)

the new height is 29.5 cm. Therfore adding 2.2 pounds only reduces the height by .5 of a centimeter, practically nothing

Thanks, but I don’t think physical analysis of hopping is meaningful. Human bodies cannot be reduced to statics, especially since a significant portion of a SIF hop is tuck.

You also did not factor in the additional force applieded by the unicycle during its bounce, which would help to balance out its additional mass.

For a rolling hop (done by someone who is good) is there still a bounce to help cancel the extra weight?

Now compare the original scenario with the following:

Both riders are twins; exactly the same weight, height, abilites, etc.

One is hopping with a 12 lb trials, the other twin is hopping with a 15 lb trials. I would say that in THIS case, the lighter uni WOULD yield higher hops; although the difference might be marginal, the rider would likely notice the difference in weight when comparing both unis.The lighter uni might also be easier to maneuver, and be less of a demand on evergy levels. In competitive MTB-ing, every pound or even OUNCES less bike weight can make a difference! Same thing with Jockeys; if they weigh even a pound more than usual, it can be enough to lose a race!:smiley:

you might jump a touch higher with a lighter uni. not much. other tricks(unispins, etc) should be easier with a lighter unicycle though. i think a stiffer uni will help more than light weight, also one that fits well. try doing tricks on a friend’s uni who’s a different size, feels really weird and difficult.

Yes, in the form of additional inertia from the moving unicycle. Even better if the extra weight is in the wheel.

Terry, which are you asking? Hop height or trials performance? Of course a lighter uni is more maneuverable, but that’s a completely different issue. I don’t prefer my muni for trials because it’s hard on my back and hard to maneuver, plus I use a low tire pressure. None of those are related to hopping height, though.

I don’t see any meaning in your hypothetical situations. Make it the same rider, then we can test it sometime. Next time I’m in socal, I’ll spend a couple of hours on someone’s heavier trials uni with you, okay? We’ll see if it makes a difference.

First of all dont write it off as mearly “statistics”. Everything is based off math and science and the only way to find an accurate solution to the question is through scientfic reasoning.

I assumed that the “tuck” would be the same regardless if the weight of the unicycle.

As for the

I assume you mean the additional force the unicycle exerts on the ground. Since I did an energy equation the forces are totally irrelavent and therefore my physics reasoning stands.

Just remember we’re trying to find out if a heavier uni makes a noticeable difference in jump height.
Of course a heavier uni is harder to jump with.
But a kilo or two may only change a few centimetres.
But when you’re doing hops every inch counts i guess
I don’t really know because i don’t do trials ((YET)

In conclusion, “heavy” Summit unis RULE!

Anyone wanna buy one?

Of course the ball without the lead weight bounces higher. Think of it this way; a 2" diameter superball obviously bounces higher than a 2" diameter lead ball. Make it a 1.5" diameter lead ball with .5" of superball material on the outside, and the 2" superball will still bounce higher. Simlarly for 1" of lead and 1" of superball; the more you shrink the lead, the higher the ball will bounce, until you get rid of the lead altogether, at which point the superball will bounce its highest.

The rider makes a much bigger difference than the equipment, but to claim that the equipment makes no difference is foolish. All else being equal, a given rider will jump higher and have more control on a lighter unicycle than a heavier one.

You misread Gerble’s post. He said “statics,” as opposed to dynamics. Your first-order-estimate of the rider - unicycle system was done with static equations, while the problem at hand involves dynamics.

Your statement about “everything” being solvable with scientific reasoning is only accurate in cases when every variable about the problem is either controlled or measurable. In the case of a uni rider doing a hop, there are other first- and second- order variables that you do not take into account in your analysis.

Your reasoning only stands to demonstrate that you do not have a full grasp of the problem at hand. The energy calculation you’ve made assumes that the motion of the unicyclist is completely reversible, ignoring the second law of thermodynamics. Energy is lost due to friction, drag, compression, etc.

Actually, to claim that equipment makes a difference based on an arguement of handwaving, generalization and pontification is foolish. What kind of difference are you looking for? What is this “more control” you’re talking about? Maybe, what, a 1% difference in dynamics? That’s not “more”… I claim any of the “mores” you’re barking about are washed out by statistical fluctuations in the rider’s performance and I dare you to prove otherwise. (Edit: there is no such thing as “all else being equal” in this problem)

If I could pedal grab onto a planter box with a 12 lb. unicycle and also with a 15 lb. unicycle, what’s the difference? If Gerble could rolling hop onto a loading dock with the same two unicycles, what’s the difference? If Joe Schmoe enters a unicycle high-jump contest and clears the bar by 1" on a 12 lb. unicycle but only clears it by 3/4" on a 15 lb. unicycle, what’s the difference? Insignificant… just like everyone’s scientific arguements.

You can argue physics until you’re blue in the face, but the proof is in the rider… the unicycle ain’t going to hop itself.

P.S. If you’re still hell-bent on being a “weight weenie” then read this thread and let us know how your new ultra-light unicycle helped you hop 1/4" higher.

The amount of energy you have to input to change the momentum of the unicycle is a direct function of its mass. That’s true whether you’re jumping, turning, starting or stopping; a 15-pound uni will require 50% more energy input than a 10-pound uni to alter its momentum.

That energy is only one portion of the total energy input into the system; the energy required to move your body is larger, and is more or less identical in the two scenarios. But consider that a 15-pound unicycle is about 10% of the weight in the system, and the unicycle is doing more movement than most of the heavy portions of the system (like your torso). So the impact of the weight of the unicycle on the amount of energy required to move the entire system from one place to another is greater than 10%. A 25% change in the weight of the unicycle will make a difference greater than 2.5%, perhaps as large as 5%, in the amount of energy required to move the system.

5% is not negligible. It will not make a huge difference in how high an obstacle you can get up onto, or what kinds of moves you can do, but it will make a difference over the course of a day, and it will allow you to be a bit more accurate when gapping or twisting.

I’m not a weight weenie. I’ve never purchased a unicycle or a unicycle component because I thought it weighed less. I think there are other factors which have a greater impact. But to say that weight has no impact or negligible impact is simply ignorant. When I take off my CamelBak, I can hop higher and more accurately; are you seriously claiming that isn’t true?

I’m calling you out on this one. Give me the function. Don’t forget to include the unicycle’s response to the compression / rebound of the tire against the ground. I’ll make it easy on you and say you can assume the ground is incompressible.

I’m not going to start throwing around meaningless percentages but I’d like to remind everyone that the rebound of the tire makes a difference on the height one can achieve with their hop. A heavier unicycle will have more inertia, changing the impulse transmitted to the tire. This isn’t a first-order function, so don’t go believing an x% increase in weight correlates to an x% decrease in hop height. That’s a crude approximation at best.

Again, I say it’s insignificant; the variance of a given rider’s performance over time is about that much, if not greater.

We’re talking about the weight of the unicycle. Don’t confuse the issue here.

I agree that weight and hop height aren’t directly related, but weight and energy required to change momentum are. The amount of energy put into the tire is exactly the amount of energy the rider puts into it, minus friction and heat losses. You might argue that there’s something about a heavier frame which makes it easier to put more energy into the tire, and therefore the weight doesn’t affect hop height; I don’t think that’s very plausible, but in any case, it’s still only a function of the energy input, so the point that a heavier frame takes more energy to move the same amount stands.

That doesn’t make it insignificant. To take a statistical view, a given basketball player may shoot 75% of his free throws on average, but some days shoot 80% and some days shoot 70%. If his average goes up to 80%, that is not an insignificant increase, because the entire range of his variance has risen.

Jason and Tom, thanks for weighing in on this one. I was hoping someone who had done more than dinky highschool physics could weigh in.

Might I point out that the idea that physics and science could predict all aspects of life was abandoned nearly a century ago? I dig physics and don’t mind using it to solve problems, but I do my best to avoid deluding myself into thinking I’ve solved problems orders of magnitude beyond my ability and knowledge. A rider hopping on a unicycle is one of those.

Tom, I don’t think any difference will be made so long as the lead in the superball does not alter the nature of the ball’s bounce. Maybe I should modify my question: A pair of metal cored superballs is dropped. One contains a 1cm ball of aluminum in the center, the other contains a 1cm ball of Pb. Does one bounce higher?

Tom, this isn’t an arguement over rider weight or unicycle performance beyond hop height. Of course a lighter uni is less tiring, but noone’s debating that.


Tom, a heavier frame DOES make it easier to input energy to the tire. The limiting factor is NOT the strength of the rider, owing to the use of prehops and rollups. In rolling hops, the limiting factor is how fast the rider can spin approaching the obstacle, not how much he or she can accelerate the unicycle. Similarly, in sidehops, the limiting factor is the shape of the prehop, not the strength of the rider. By prehopping, the rider is making the unicycle weightless with the use of the bounce. A 17lb unicycle will bounce in the same way a 12lb one will.

So help me Allah, the next time a thread like this comes up I am going to throw my computer out the window. I can’t tell if the Internet helps spread knowledge or stupidity.