Duro vs Gazz questions of road rideability etc.

So, I have a qu-ax with oem Duro Wildlife 24x3 tire on it.

This is the only uni, apart from the LX that I learned on. that I’ve ever ridden.

I have experienced NO side effects that I can discern from the duro tire.

I’ve heards tons of people say both that Gazz’s are better off-road, and seperately that Gazz’s suck on the road as they are too square.

I’m just curious, cuz I like to know where I stand and whatnot, have any of you that think that Gazz’s are better off-road tried Duro’s?

And have any of you that say that Gazz’s on road capabilities are lacking tried Duros?

Having never ridden another µニ (mu ni) I don’t know if Gazz’s really are better off-road, but as I said, I can’t tell any way that a Gazz would be better than my Duro. And I also just don’t get this Gazz’s are terrible on the road thing, but again, I have no way of knowing if Duro’s are just no where near as bad as Gazz’s on the road…

So, anyone care to shead some light on a total Gazz vs Duro idealogy?

If you keep low tire pressure in your gazz, more of it will contact the surface of the road (or trail) and it will be more difficult to turn and will wear faster. If you have more pressure in your gazz when you’re riding on pavement, it will be significantly easier to ride and will wear your tire much less.

I have ridden muni on both a gazz and a duro, and each one is better in its own way. The duro is definitely more maneuverable because of its more rounded profile, whereas, like you said, the gazz is more of a square profile. I think my gazz sticks to roots and rock better than the duro because it’s knobbier than the duro and has more tire-to-ground contact. Physics tells us that this causes more friction due to greater surface to surface contact, hence the added stickiness.

I will also say that the gazz is more tiring because it is larger and takes more energy to spin (again, physics). That having been said, I would really like to buy another gazz. I have a nearly new duro in my closet, but I love riding my gazz. The extra volume of air in the gazz cushions drops a slight bit more, and also is a little springier for hopping (This is just what I’ve concluded…)

Physics also tells us that the reaction force will be divided over a greater area, so the friction force will be the same, hence F=(mew)R - no area term involved. Larger tyres do genreally have more frictional grip, but that isn’t why.

Also physics tells us that a heavier tyre will take more energy input to reach a given speed, but for contant speed cruising the mass is irelevant.

But to avoid the threadjack, I’ve ridden a 24" duro on a KH rim (alot) and a 26" gazz on a LM rim (a little), the gazz is noticably less manouverable on hard surfaces.

The gazz is better on better offroad, the duro is better onroad.

If youre riding on the road for a decent proportion of your time, stick with the duro. The gazz turns bad on the road and will make you feel like your constantly falling one way if the road has any camber.

In a muddy forest I like the gazz a lot more, you notice the difference and everything feels easier. If youre only in the forest, choose the gazz.

However, it is more annoying on the road than it is better in the forest.

never need to apologize for jacking one of my threads…that’s how I think this whole forum should be.

And just fyi, mew is alt-0181 (µ) if you ever feel the need to use the symbol again.

And thanx for some answers to the original question…just a point of quandry, however, are you sure it’s noticably less manuverable? And not possibly just because you were less used to it and/or because of the added size of the tire?

also, just cuz i’ve seen you say it a couple times now, and it seems to clash with what I thought was the case. It’s been almost 10 years since I’ve taken physics, and I may just be a little rusty. But doesn’t it take more force to keep a greater mass spinning at a constant speed than a lesser mass in the real world? Taking into account real life frictions?

If either you wouldn’t have used such terrible grammar, you wouldn’t have doubled your words, or you would have stuck to what I actually asked and not answered a made up question that I more or less answered in my actual question, I wouldn’t have said anything.

I don’t like people that are spelling nazi’s or even people that correct someone’s error that they obviously did on accident, however, since it says that you live in London, and I’m therefore assuming that English is your first language. You should really be more careful about how you post things, as there is really no reason especially at 28 to be making postings like a 13 year old with English as their second language.

I don’t actually (though I know nobody will believe me) mean this to be negative or rude. Just that it’s annoying to read, and you should make some effort to proof what you write and correct errors.

And just as a point of contention, I often get answers to my quesitons that have nothing to do with my question, so I guess I am a little over sensitive that that happening.

Anywho…sorry for the rant.

solid vs. tire phisics

It you make a wheel twice as wide each square inch of contact will have half the pressure as the original wheel. So traction is the same with a skinny or fat wheel. This is true of train wheels (steel on steel)
Traction is more complex with rubber wheels. Extra friction is created by the rubbers distortion, locking into surface imperfections.
So in rubber tires a wider tire will give better traction. Think dragsters, wider rubber helps.

Thank for the µ, funnily enough i saw you use it in another thread early today.

It could well be because I was less used to it, and because it was a heavier uni, but it felt like you coudn’t lean it over, you had to sit more upright and ride it round in a circle rather than leaning in to the turn like on the Duro. It might well become less noticeable with time, I’m sure like anything you get used to it. I’ve only had a choice of tyre once and i bouth another duro just because the extra price of the gazz didn’t seem like good value.

As for force and spinning wheels. When you are spinning a wheel at constant speed the energy in the wheel is 1/2 I w^2 (assuming the wheel is stationary, im ignoring the fact that the wheel is also moving along the ground here, it only complicates matters) I is a function of the the mass distribution in the wheel ( the mass of your hub, spokes, rim, tyre and how far each of them is from the centre) and w is the angular velocity, the speed the wheel rotates at. So, for fixed I the amount of energy in the wheel is only altered by how fast it spins. So if it spins at constant speed the amount of energy in it doesn’t change, i.e. the rider is putting no energy in to the wheel. it takes more energy to get a heavier wheel (i.e. one with greater I) up to a particular speed, but once there the rider puts no energy in to the wheel, its mass is irrelevant.

So where does your energy go? If you just pick your uni up and spin the wheel: in to the bearings, and air firciton of the tyre spokes etc. If you’re riding along there is also tyre friction on the ground (includng tyre deformation energy) wind resistance of the rider etc.

I hope that clears it up, heavier wheels are harder to get up to speed, harder to ride up hills but on the flat at constant speed make no difference.

I’ll just add that Gazz rideability is very much a factor of tire pressure. Higher pressure makes a huge difference for pavement riding, but the same high pressure makes it kind of sucky on the trail. Riding a Gazz on pavement is kind of a waste of the tire though, as it may wear faster there while not being appropriate for the job. Those things are made for dirt.

If you need to ride a constant mix of dirt and pavement, the Duro is probably the better choice, though I have little experience with those tires.

And it isn’t physics that tells us, but rolling at a constant speed, while possible on a Coker on flat road, is not something that happens in most other forms of unicycling, especially MUni. You are constantly making corrections in wheel velocity the whole time, which makes your cycle’s rotating mass, especially out at the rim & tire, very important. The Gazz is heavy, which means a constant higher workload to ride it on trails.

Yes, in a frictionless world. But, the wheel is constantly slowing down and you have to constantly speed it back up again to keep at a “constant” speed due to the frictions put on it. A lighter wheel takes less force to keep at a theoretical constant speed than does a heavier wheel, in the real world.

That’s how I see it. I may very well be wrong, but I don’t understand how I am, if that’s the case.

Ok, I just did some quick net research. Like I said, it’s been a while since I’ve used this stuff, so I don’t have the best grasp on it right now.

What I said before might be true or not. But that aside, I’m pretty sure you’re still wrong. :slight_smile:

I first found stuff about rotating weights and different questions and what not. The mass of the roating object is always a part of the question, but I still never found an equation to link them together.

Then I found this, and I’m fairly sure it’s talking about what we’re talking about:

[I]Is motion around a circle with constant speed (“uniform rotation”) an accelerated motion?

Yes, it is.

Why is it accelerated, if the speed does not change?

The speed doesn’t, but the direction of the motion does. By Newton’s laws, only if a body moves with constant speed along a straight path are no forces needed to maintain that motion.

So, for a body with mass m to move with constant speed V around a circle of radius R, a force is needed. What is that force called, what is its magnitude and what is its direction?

It is called the centripetal force
Its magnitude is m V2/R
Its direction is towards the center of the circle.[/I]

I’m FAIRLY sure that this means that as the mass of the rotating object increses, the force (centripetal force) required to keep it spinning at a constant speed also increses…

Again, I may be wrong, but again, I don’t see how.

Ok, so a chunk of tyre has a force towards the centre of the wheel, however the force does not move any distance (the tyre doesn’t get any closer to the centre) so the energy is zero, energy = force*distance. Consider an energy balance on the wheel, where does the energy you propose is being fed in to it go? Energy cannot be created or destroyed.

An analogous example which avoids all this rotation stuff, the top speed of a car is entirely independent of its weight. The force provided by the engine in one direciton equals the force of wind drag and rolling friciton in the other direction, mass is irrelevant. All other things being equal the heavier car will of course take longer to get there as F=ma so acceleration will be decreased.

Of course john is right, you can’t ride a uni at constant speed, more massive wheels require more force to accelerate and decelerate, so heavier wheels are more work, particularly on the rough stuff.

That’s exactly what I was thinking. Not only that, but now kington99 is assuming that there’s no friction at all to keep a wheel spinning at constant speed. We know this is false, so again, not only due to the constant change in angular velocity of the wheel, but also due to added friction, it physically takes more energy to keep this wheel spinning on flat ground.

kington99- thanks for pointing out the friction thing with greater surface area, but I will stand that it will be harder to turn due to friction because there is more surface area contacting the ground. Also, the gazz seems to have softer rubber since it tends to wear faster (at least for me), increasing the coefficient of friction, making it yet even harder to turn.

Nope, of course there’s friction, else you wouldn’t require any effort to pedal. However if the friction is the same for big and small wheels, then the same energy is required to keep them spinning, the wheel size makes no difference.

Yep of course it’s harder to turn the gazz, i don’t refute there’s higher friction, if the gazz has a higher coefficient of friction the this will of course increase the frictional force, but there are other things in play besides basic friction.

Some of this stuff has already been stated.

A heavier tire will require more effort to maintain a constant speed because you are always correcting your ballance. Minute speeding up, slowing down and turning. So there are angular accelerations of the wheel as well as the rider.

With a heavier tire turning would be harder because of the increased gyroscopic effect, but lighter since friction at motion is less than when stationary. In my limited experience these two cancel each other when on dirt, but when on asphalt turning is easiest w/ a bit of speed (not too fast, not too slow).

The only Muni tire I’ve ridden is a 24X2.6 Kenda Kinnetics.

I have made this case in multiple other threads (mostly in regard to hops), however I’ll make it here as well. Physics and unicycling should not be mixed. They do not work well together. A unicycle and a rider are too complicated of a system for basic Newtonian mechanics as applied by joe schmoe to solve. Read the second most recent “Physics Today” magazine, and you will see a research paper on the physics of walking. These re post-docs doing that work, to boot. I’m an undergrad physics major and have a mechanics class under my belt. I still don’t tell myself I can solve problems this hard.

AscenXion, what you are referring to is a larger TORQUE required to accelerate a more massive wheel (remember, accelerate means both in speed and direction). We all remember our basic newtonian kinematics equations, right? Force=MassAcceleration. Well, the same goes for gyroscopes, except replace force with torque, mass with “moment of inertia” and acceleration “angular acceleration” (units: radians per second per second, aka inverse seconds squared). Moment of inertia has units of mass(distance squared).

Well, I said physics and unicycles shouldn’t be mixed, but here I go anyways. Bear with me, this does lead somewhere.

So, we can model a unicycle wheel as (approximately) an ideal ring with all of the mass concentrated at the rim (if it were a uniform disc it would be 1/2 of what it is. Really it’s somewhere in between). Thus, a wheel has a moment of inertia of M(R^2) where m=mass and r=radius.

Now, what is important is angular momentum (we will call it “L”), which is moment of inertia (commonly called “I”) times angular velocity (radians per second, which we will call “O”). Thus, L=I*O. Now, Torque (“T”) can also be described as the change in angular momentum, L. Thus, T=dL/Dt (t=time). This means that the instantaneous torque on a system=the change in angular momentum with respect to time (rather than position, for example). Thus, a greater L means a greater T must be applied in order to get the same change in angular momentum (dL/dt). Follow? Note: Angular momentum, unlike regular momentum, is a VECTOR which means it has a direction and a value associated with it. Thus, a gyroscope can spin at the same rate but have its axle rotated perpendicular to the direction of its spin, and the angular momentum will have changed.

So, ultimately, it takes more energy for a rider to change the direction of a heavier wheel (where the mass is at the rim) than a lighter one, as well as speed it up or slow it down. however, if we model a unicycle rider as riding in a straight line at a constant speed, all of this falls out, since the only issue is friction in the system, which remains constant. The problem is that we don’t ride in straight lines at constant speeds.

All else being equal, the rider with the heavier wheel should ride a straighter line, since the heavier wheel will be more resistant to the rider’s slight wobble. This indicates that the heavier wheel will take LESS energy to ride, since because it wobbles less, the rider will ultimately cover less distance and thus do less work (int he technical sense) to fight friction. Furthermore, the heavier wheel will be more stabler (the heavier the gyro, the more stable it is, and a spinning wheel is a gyro). At the same time, the rider with the lighter wheel will have to exert less force to make a turn. This will use less energy. He or she will also have to use less energy to get up to speed and slow down. Ultimately, these four effects balance out to some degree, and you should ride whatever you prefer. And once again, this is a VERY simplified model of a unicyclist, and has little if any bearing on reality.

AscenXion, please, lets not criticize people’s grammar. That would be like me, instead of taking the time to explain the nuances of why you’re wrong, just calling you a dumbass for not being able to infer what to me is intuitive basic physics (which it is).

Edit: Centripetal force has absolutely nothing to do with this problem. Centripetal force would be a problem if we wanted to figure out (to an ungodly precision) how much tension is in the spokes of the wheel at various speeds. Even then, my physics professor would slap me for using it instead of “centripetal acceleration”. Once again, if we assume the rider is going in a straight line at a constant speed, the ground will exert the same friction no matter what the mass of the wheel (don’t tell me you can tell the difference of the friction due to a few grams of extra mass) and thus the rider will have to exert the same force to keep the wheel spinning.

Honestly, I think AscenXion spends too much time posting about equipment choices based on minor details rather than just going out and riding to see what he prefers. I’ve ridden the gazz and duro, and I really see little, if any difference between the two. Neither takes more energy to ride (just from experience I say that), and whomever thinks that is projecting based on pre-determined conclusions.

I’m surprized that no-one has pointed out that there is very little difference in weight between the Duro and Gazzaloddi 24 x 3" tyres. In fact, according to the UDC UK’s tyre page, the Duro (aka Halo Contra) is actually 20g heavier!

Now, now, don’t get all tricky on me and answer my query with another much more sophisticated question…that’s not fair. :slight_smile: I don’t know the answer to your question (though I kinda suspect that it’s in part a trick question, but again, I may be wrong) but what I quoted was from a science website and I’m pretty sure it’s what we’re talking about. Rotating a mass around a fixed point at a fixed speed DOES take energy because it’s an accelerated motion.

Could you PRETTY PLEASE tell me why this isn’t the case without issuing another question to confuse me. :slight_smile:

Also, I’m FAIRLY sure that given the exact same car and engine, if one car has more weight in it, it will be unable to gain as high a top speed as the other car. And, no offense, but having just read that you are only 21, (and assuming that you were much older) I’m pretty sure that you are just learning this stuff, and applying it slightly wrongly. Again, I don’t mean offense to you, but I’m PRETTY DARN sure that you’re not right on a lot of this stuff, and I wish that someone smarter than myself would come along and let me know if I am indeed wrong, or what.

p.s. oh, btw, I had to say that it’s quite odd that John and I ALMOST agree with one another on this as having said almost the same thing, and I hadn’t read his reply when I made mine…I think that might mean that the world is comming to an end.

Actually, me asking someone to proof their post is a LOT like you telling me that I spend too much time posting about “shit” and not enough time riding.

Funny, though, I’m not asking about equipment choices…never was.

No sorry I don’t think i can, the simplest way of explaing it i can thinkof is to consider the conservation of energy. I’m sorry i can’t express my logic more clearly. My questions are not intended to confuse you, more for you to see flaws in your own logic. Incidentally I must have learnt this stuff about 6 years ago, and have done little else except study engineering, physics and maths ever since.

I didn’t think that you were trying to confuse me, it was a joke.

Ok, here’s another quote:

[I]Since a body moving in a circle (or circular arc) is accelerating, it follows that from Newton’s 2nd law that there must be a force acting on it to cause the acceleration. This force will also be directed toward the centre and is called the centripetal force. It causes the body to deviate from the straight line motion it would naturally follow.


I simply want to know why m is in that equation if it doesn’t matter…All you have to do is tell me why that equation isn’t applied to what we’re talking about, and I’ll walk away happily defeated.