I just got done building the wheel for my 29’er. Mavic CXP21 rim, 14-15-14 double butted spokes, and a 36 hole Suzue hub. I won’t have my Nanoraptor untill Wednesday, so I put on a 700c x 25mm tire for now. I’m also using it in my Coker frame for now. The cranks are 125mm Bicycle Euros. I rode it across the basement a couple times and was able to idle on it too. I’ll have to find some dry roads to try it out on in the morning.
Mojoe
I should also note that the Suzue hub came from unicycle.com and was packaged very nicely. I have been sort of hard on them lately for some of the mistakes they have made with my orders.
here’s a pic of the clearance with the Coker frame and such a little tire.
Mojoe
And a close up of the rim. Mavic CXP21. 20mm wide.
Mojoe
Mojo-
The wheel looks great, though a little petite in the Coker frame.
I was just wondering if the difference between a 29 inch and a 24 inch is as great as a 24 inch and a 20 inch. Currently I have a 24 and a 20 and there is a sizable difference. Mainly I want to know about the difference in terms of speed and effort on hills.
Also, will having a larger diameter wheel affect the over all durability? Will a larger wheel be weaker?
What type of riding is your uni going to be for?
Daniel
Daino149 asked:
<<I was just wondering if the difference between a 29 inch and a 24 inch is as great as a 24 inch and a 20 inch. Currently I have a 24 and a 20 and there is a sizable difference. Mainly I want to know about the difference in terms of speed and effort on hills. >>
It’s a simple calculation. Take the size of the ‘new’ wheel and divide it by the size of the ‘old’ wheel. Then multiply the answer by 100.
So, 24 divided by 20 = 1.2
1.2 x 100 = 120.
The 24 is 120% as big as (20% bigger than) the 20.
29 divided by 24 = 1.208
1.208 x 100 = 121 (approx.)
The 29 is about 20% bigger than the 24.
So the step up from 24 to 29 is more or less the same as the step up from 20 to 24.
BUT there are other variables! The 20% bigger wheel will go 20% faster at exactly the same rpm. However, the rpm will vary depending on your skill, experience, confidence and choice of cranks.
On the whole, you will feel more confident about revving to the max on a small wheel - there’s less distance to fall.
Given identical cranks, the bigger wheel will be 20% harder to start and 20% harder to stop, so you lose out a bit there.
If you put on 20% bigger cranks to compensate, then you lose rpm and end up almost back to sqaure one! Seriously, on my 24 with 102mm cranks, I could hit the same top speed as on my Coker!
But a 28/29 is a pleasure to ride. Big enough to have some ‘cruise control’, small enough to mount easily, light enough to idle. My 28 is more like a big 24 than a small Coker, if you see what I mean. A 28 is the nearest a unicycle gets to ‘practical transport’.
A bigger wheel will be weaker, but I’m not expecting any problems with this one. I’ve taco’d my Coker wheel twice, but it has a very narrow hub and cheap-o steal wheel.
I’m going to use this as my commuter/easy trail uni. The 2.1 tire will be here next week. I rode a couple of 29’ers last week at MONDO and just had to have one. I love my Coker, but it dosen’t handle well in snow for me. Plus, I need to get a wide hub and a good rim for the Coker.
I just got back from a ride in the snow with it. The 25mm tire cuts right through snow but offers little traction on ice. I can’t wait to put the 2.1 inch tire on it.
Mojoe
What if you had the same size cranks but the same mass for each wheel? Would this still happen? Just curious,
Andrew
Don’t forget the tyre diameter- you really need a roll out distance (ie the circumference) with the tyre on to be accurate. The 3’ tyre on my KH24 makes it alot bigger than it really is. I’ll do some roll out measurements soon- I don’t think 24’X3’ is nearly as big as my 26’X2.6 wheel though.
Just for you Mike- I tried out my new YUni 29’er yesterday with short 150mm cranks- it rode surprisingly well- very fast and I was able to climb and descend almost as well as my 26’ x 170mm cranks. I must have gotten fitter since I last tried a 29’er a year ago- I remember then that I was struggling to ride up even moderate hills (but I was using my friends 29er with 140mm cranks). It’s so light that it seems to fly up those hills! And it wasn’t too bad off-road either, just needed to pick my lines a bit better than when hammering through on a Gazz. OK, I may even downsize the cranks on my 26’ 
Ken
Ken wrote:
<<Just for you Mike- I tried out my new YUni 29’er yesterday with short 150mm cranks- … I may even downsize the cranks on my 26’ >>
It’s always good to experiment. There’s a trade off between short cranks allowing you to ‘rush’ hills and obstacles, and long cranks allowing you to ‘plod’ up after you’ve lost that intial momentum.
<<Don’t forget the tyre diameter>>
When I’m writing about ratios etc., I normally assume for simplicity that a 24 inch wheel is 24 inches in diameter including the tyre, a 28 is 28 inches including the tyre, etc. I know this is often not true when there is a big fat tyre. Those who are interested can adjust the calculation accordingly. It doesn’t matter whether you work with actual diameter or with rollout. They are both linear measurements, so they will remain in proportion. The rollout will always simply be 3.142 (Pi) times the actual diameter.
Andrew asked:
<<What if you had the same size cranks but the same mass for each wheel? Would this still happen?>>
Like a lapsed Catholic, I ignored mass. The extra effort required to accelerate/decelerate is solely a result of the different ratio between the length of the cranks and the diameter (or radius or circumference!) of the wheel (including the tyre!).
So if the wheel is, say, 20% bigger, and the cranks are the same, you have less leverage, so the wheel takes more starting and stopping. (It takes the same amount of energy, just it’s harder to apply the force using the shorter lever.)
If the two wheels being compared had identical mass, the larger wheel would be that little bit harder to start/stop because the mass is that little bit further from the centre (the mass being concentrated mainly in the rim and tyre) so in fact my simplistic calculation overlooks an important effect. This is most notcieable in a Coker which has a very heavy rim (steel) and tyre, and a big radius, and there is a flywheel effect which makes the Coker much harder to start/stop than a simple crank:wheel calculation would suggest.
A 36 inch wheel with 6 inch (150mm) cranks has the same ‘ratio’ as a 28 inch wheel with 4.66 inch cranks (119 mm) but in practice, it is easy to idle a 28 with 110s, and difficult to idle a Coker with 150s.
Re: I got 29’er envy
In article <Mikefule.iwx7b@timelimit.unicyclist.com>,
Mikefule <Mikefule.iwx7b@timelimit.unicyclist.com> wrote:
)
)When I’m writing about ratios etc., I normally assume for simplicity
)that a 24 inch wheel is 24 inches in diameter including the tyre, a 28
)is 28 inches including the tyre, etc. I know this is often not true
)when there is a big fat tyre. Those who are interested can adjust the
)calculation accordingly. It doesn’t matter whether you work with actual
)diameter or with rollout. They are both linear measurements, so they
)will remain in proportion. The rollout will always simply be 3.142 (Pi)
)times the actual diameter.
It will be Pi times the diameter of the rolling wheel–that is, after you
put your weight on the tire and it deforms. You can’t just measure the
unloaded diameter, if you want to be accurate.
-Tom
i think that you guys are getting way to into this ration stuff. the way i see it is if you can mount it and ride it then buy it. correct me if im wrong but when did ratios become so important with unicycling?
it’s all the same to me
Daino,
I can’t answer this from experience, but I just had my 28er finished and it will be here on Wednesday. But I worked with the person who built it, (U- Turn) and stated my needs. The wheel was built around those needs. He assures me that the wheel will hold up very very well to the requirements I wanted to ride with. Namely, to drop off curbs, ride up them, and side hop them up and down, as well as take light off road. You can build a large wheel to take a lot of abuse if that’s what you want. So, just because the wheel is larger, doesn’t necessarily mean it is weaker. It all depends on what it’s compared to and how strong it is built, I guess.
I am the benefactor of the 700C drag brake uni that came up on yesterdays board with pix!!!
I can’t wait to ride it!!
I rode out to the beach yesterday (my first YUni ride). A 15km ride each way with several K’s of off-road and a couple of hills. When I’m riding my 26’x170mm the fastest I’ve done this is 1:08. I went out on my 29’ x150mm at a relatively easy pace and did it in 55:30. I reckon if I went out hard I may get it down to 45min. There will be less advantage on a more technical course but still what surprised me was how well the 29’er handled the off-road section- I think the bigger diameter wheel helps roll over obstacles and it was so light! And I didn’t realise how much drag DH tyres have till I tried the Nanoraptors 
The cheap steel rims that came on my 28" Sun were bent within 2 days after I got the uni, so the wheel has a horrible wobble when I ride. I didn’t do anything unusual on the unicycle. I rode it down curbs, hopped, and fell off it so the uni went bouncing down the road. On a 20’’ wheel, none of these things would have caused a problem, but the 28" wheel is more delicate. I have put the steel wheel on my Torker 20" through a lot more abuse and never had a problem. My advice is to not buy a cheap steel wheel for your 28/29" uni.
I agree with the sentiment, but not the whole comment. You can jump in a Land Rover, a Ford or a Lotus and drive it. Which would you choose if you wanted to tow a trailer, race round a track, or take the family to the cinema? They all have different gearing, different engine characteristics, and so on.
On a Uni, you have 4 main variables:
Wheel diameter
Crank length
Tyre section
Quality of components, including weight
The first two make a fundamental difference to how the uni performs, even on smooth tarmac.
So if you want extreme speed, you go for one combination of wheel and crank; if you want extreme hill climbing/descending, you go for another; and so on. Comparing ratios is a useful guide to how two unicycles will perform, but it does not give the whole story.
If you want to do general purpose riding, without extreme hills or extreme speed, then I agree, you don’t need to worry too much about ratios. However, if you ever get the opportunity, try a 24 with 150s, and then with 102s and see the difference.
It’s a game, and you can play it lots of ways.
i am Muni at heart and ive ridden two different types of cycles, one is a 20" tire and the other is a 24". The way i see it is you can get involved in all that mathematics and crap, but when you come down to it the cycles are just two different types of riding. one would be concentrating on lines and moves and trying to get certain jumps. Its way more meticulous(i think thats how you spell it). When i jump on my 24" i just go crazy on downhills. when you get to the bottom at the end of a run then you look back at what moves you could have done and do them next time.
You can sit here and talk about crank shafts all day or get out there and ride!
And if you take this advice, you’ll start thinking about ordering custom length Profiles: abandon pocket-book, all ye who enter here. Thanx Mike!
-Christopher
Some people like to think about what they are doing. Some people like to just do it. Both types frequently make great strides forward. Both types frequently fall on their faces. Each type benefits from the exploits of the other. The bickering about which is better is great stuff when done in fun. Otherwise it is just petty jealousy.
i tend to fall on my face more than anything, but it’s fun nonetheless to just ride and not think. did that make sense?
can anyone tell me where to get a dyno fireball tire?
E-bay
