I know this will very greatly depending on the size of the unicycle and the terrain/distance. Average speed per mile on a level course.
Mike Adams
Total ride distance is also a factor. I can pelt it for a couple of miles / high cadence for a short ride. For a twenty mile plus ride I start off with a slower cadence so I don’t burn out.
I do an 8 mile ride my KH36 with 110 cranks on a bike path in the morning. I average around 12 mph without trying too hard. Any faster than that requires concentrating hard on really getting the RPMs up. I have patches where I am going more like 13.5 mph, but always end up averaging around 12 mph plus or minus .5 mph. I have averaged around 12 mph for longer rides too (20 miles). I hope to improve my speed with a Schlumpf when it arrives. Right now I seem to be more limited by cadence than cardio on flat rides.
Just cruising around I seem to average around 16-18 km/h with a 36. A bit slower with a smaller wheel. Race pace I would try to average around 20-22 km/h.
29’er
tested the other day on fire road (reasonably flat, some rocks) with a wrist mount GPS:
29" wheel with a 2.5" tire and 145mm cranks
slow spin: 4mph
sprinting: 7-8mph
moderate downhill: 10.5 mph, still holding back as I’m trying not to wreck my knee again. 
10-12 mph/16-20 kmh is about what I do on the flats with my 36 guni when I’m cruising. Bump it up a notch for races.
Why do you have a guni? As a 36" uni rider I average 10-12 mph. I would assume guni riders would be up in the 15-20 mph range. 
Scott
I’m pretty sure naturequack is faster than you are. 12MPH in total elapsed time for a non-trival ride is pretty dang fast on a unicycle. Ride The Lobster was won at less than 14MPH in total elapsed time, and that was a relay and in race conditions.
Hi Tom,
Yeah I would bet on naturequack in a race. I was surprised that the pace he mentioned was not a little bit higher, however. Yesterday morning I went on an 11 mile ride over a moderately hilly course with stop lights and other hazards and my cycling computer (which does not average in stops but does average in all the slow bits) reported an 11.4 mph average. I guess I thought a guni would kick up the pace a few mph.
Scott
my best so far on 4 mile loop, about 1 mile of that moderately hilly, the rest easy doubletrack:
8 mi/hr or ~13km/hr.
on a cheap 29er with 2.1 nano-raptor, 150mm cranks, relative newbie.
A couple weeks ago a buddy and I averaged about 7mph+ on a 20+ mile ride, both on 29ers.
The numbers are certainly not proportional to the fun.
Today a on my 36er a 16km loop (10miles) In 1:08 average about 14km (9mph)on bike paths mostly with a few stops for intersections and a few kiddies to dodge.
john
It seems that a 36 in is much faster than a 29er. I quess it would be about the same as a 24 in to a 29er… The reason I ask this is because I would like to be able to keep up with my wife while she is on her bicycle. I might need to get a 36 in.
Mike A
Today I rode to work on my 36" with 125 cranks. It’s 5.5 miles and I did it in 28 mins which makes 11.7mph. I had to stop at some traffic lights and walk for a bit after that but apart from that it was a clear ride.
It’s a comfortable speed without having to think to much and I passed a few ‘slow’ cyclists. Keeping up with a bike is possible it just depends how slow the bike is going.
Scott,
OOO! Dems fighten werds! 
But seriously,(Did I just say “seriously”?? Who am I kidding?) I ride a guni for the same reason that I ride a unicycle instead of a bike. Because it’s fun! Because I like to go fast, because it’s neato super coolio. Because I can tell people that my unicycle has two speeds. How cool is that? Because life is grand and I want to enjoy it. Gizmos add to my enjoyment. Because riding in high gear is another unicycle skill to master. Because one day in January 2008, I saw a big green unicycle for sale on Unicyclist.com and I knew deep down in my heart that I just HAD to have it. I’ve squandered plenty of money on useless crap over the decades. The Florian Green was a wise investment in comparison.
But because we’re talking about average speeds in this thread here are some numbers for you:
Reach The Beach Century ride, May 15th, 2010. 104 miles in a total elapsed time of 9 hours 20 minutes. That’s 11.14 miles per hour for the whole trip. I’m sure I took well over an hour’s worth of breaks in that time. There were several major hills on that route and some significant head winds as we neared the coast. No UPDs. So my average cruising speed on the flats that day was probably up around 14 miles an hour.
UGames/NAUCC 2010 Marathon. 26.2 miles, 1:48:32. No shortage of big hills, some rough roads, a couple of UPDs and one major crash. (With that crash, I realized that I was starting to get good at tucking and rolling. Up until that point, acquiring this skill had not been a high priority. I also learned that a strategically placed banana will further soften the blows involved with this roll.) Average speed: 14.48 mph.
UGames/NAUCC 2010 Criterium. This was allegedly about two miles. Tom and Nathan might have a definitive distance. Eight laps around a San Francisco city block, 32 turns and one spectacular crash! A fun time was had by all. I’m glad my mother didn’t see me crash. The road rash that had been healing from the marathon two days earlier was reactivated in the exact same spots. Apparently my tuck and roll was both effective and consistent. Yea! My cycle computer also took a hit in the crash and was dangling by a wire. I ripped it from its mooring and hurled it, along with half a dozen expletives, off to the side. So I was unable to measure the distance of the race. Total time 6:57 for about two miles. That’s up around 17.25 mph, but without an exact distance I don’t have much confidence in the mph.
The top speed that my computer has registered is 35 kmh/21.75 mph. I did this twice a couple years ago. This was sprinting on the flats for a brief moment. I am confident that I could improve on this number a smidgen, but not by very much. 23 mph maybe? That was way scary!
To add some perspective to these numbers and to show that I’m not just blowing my own horn: On both the marathon and the crit I came in fourth place. Ouch that hurt. More than the road rash. 
Two out of the three people ahead of me in both races were racing on single speed hubs. The indignity of it all. Why can’t I buy my way on to the podium with a Schlumpf? It’s so not fair. As usual, the most important factor in the race is the rider.
The Schlumpf makes cruising at high speed easier (for me, anyway) and it does seem to increase the maximum speed that a unicycle can be ridden.
But it is not as huge of a factor as one might imagine. In the marathon, Corbin (on his Schlumpf) beat Scott (on a single speed) by 2 minutes 16 seconds. While the Schlumpf offers different gearing options to increase efficiency, there is a small percentage of efficiency loss just due to having gears rubbing against each other.
I would love to have a speed trap set up where we could accurately measure the maximum speed of top unicyclists over a short distance, say 10 meters. How fast can we really get going? Are we actually approaching 30 mph? What is humanly possible under ideal conditions? How good are we at tucking and rolling when we get launched from our gunis at 25 mph?
But, yeah, back to the original topic. I find that an easy long-distance cruising speed on gentle terrain is around 10-12 mph. It’s a Sunday morning ride. Enjoy it.
Geoff
So where do you place your banana?
The problem is, top unicycle speed is an elusive thing, particularly on a big wheel. You have to be perfectly placed ahead of your balance point, and your pedal and body movements have to be perfectly balanced. In a 10-meter speed trap, I expect you’d see speed differences for the same rider of 20% for different attempts. It would be interesting to run speed trap races, but it might just provide another set of data which looks weird.
Corbin and Beau were not riding at 100% speed for much of the 10km at UNICON XV; they thought they had dropped the field and were more concerned with each other’s speed than Scott Wilton’s, which is what allowed Scott on his ungeared 36" to catch them despite crashing twice, and nip them at the line.
Our closest thing to speed trap is the track races, but those are all on 24" and thus extremely lame.
if im silly i can get 15 mph out of my 29er but for not even 50m before i get the burn a bettter speed is more like 10-12mph
Geoff,
Thank you for the detailed stories. Yes the rides sound like a lot of fun, which is why I have ordered a Schlumpf and will have it set up as a 36" guni. I appreciate the comfortable Sunday morning cruise, but it is nice to hear that you can push that guni to higher speeds. After all, if I am going to plunk down that much money it should do something that my current KH 36" will not do: go too fast.
Scott
PS-Good luck in the criterium May 1!
Scott,
I have had my 36 guni put together about a month now. I was able to up & down shift the second time on it. I am still working on smoothing things out. I am having to shift with my ankles because of long feet. I would prefer using my heel. I have 137/165 cranks. I have only used the 165 hole. I have about 25 miles total guni riding so far. My fastest speed so far was 16.7 mph. My colleague was following me home last week on his bicycle. My average speed is around 12mph. That was my old average speed on my Nimbus Nightrider with 127 cranks. I am still geting used to the Schlumpf. Even if my average doesn’t improve I still enjoy riding a guni. With the 165 cranks in 1:1 I can climb steeper hills and maneuver through traffic & people better than a fixed uni with shorter cranks. I switched to the 165 hole one week before the Chilly Hilly ride in Feburary on my Nimbus Nightrider. My average speed with the 165 cranks was only 9.5 mph. The Schlumpf has made a big difference in my commute. I usually shift alot. I use 1:1 through the light rail platform & several bussy intersections I traverse on my commute. When I hit the back streets and bike paths I kick up in high gear. When I’m cruising in high gear I usually get triple takes from people. They are surprised that a uni can go that fast.
Back pocket of my jersey. It ended up being a nasty brown pile of mush and inedible. Yuck. I’ll blame my poor performance on the resulting lack of sustenance at a critical moment.
Weird data or not, a speed trap would give us an idea of what is possible. It’s a much more accurate way to measure top speed than cycle computers. We could spend a few hours, with each rider getting half a dozen tries. Pick the best attempt for each rider. Stick a gold star on the winner’s forehead, bandage up the road rash of the not so fortunate and head out for a celebratory dinner with fine wine and seafood.
Yeah, racing on a 24" is a completely different animal.
Go too fast. You’ll be glad you did. Living on the edge.
Thanks, you can expect a full write up. I’ll be sure to pack a ripe banana in my back pocket. Just in case.
Geoff