Was on tumblr.com and searched the keyword “unicycle”. This photo came up that I managed to cross reference and find on USA Today. Has to be the biggest wheel I’ve ever imagined. I would love to find out who this guy is if anybody knows him?!!
Wow, nice find.
What’s that, about a 60" wheel? 
I think I want one. 
why has john foss not commented here yet? anyway i think he has a pic of a 72" wheel. he can tell you
Okay, time for me to speak up:
from the link the o.p. posted, text from the caption…
Leo Waltl photos
Leo Waltl rides a unicycle he built past Lake Pillersee in St. Ulrich, Austria.
I’m aware of John Foss’s oversize wheel, and I’ve seen the references to other very large wheels with solid rubber tires.
Unfortunately, building such a beast is beyond my ability.
Which got me to thinking: where could I find someone who does make such items? . . . those wacky Penny-Farthing guys!
This company looks like they’d be pretty cooperative in making a custom large-wheel uni: http://www.hiwheel.com/antique_replicas/boneshaker_standard.htm
They make various size Penny-Farthings, as well as recumbents, tandems, pedicabs, etc., and advertise their abilty and willingness to do custom work. From the prices on the P-F’s, I’m guessing a custom 48" or 52" uni would run around $1000 - $1200. It will probably be a long while before I pursue this (if ever). But it’s nice to know the option does appear to be out there.
Edit: Upon reading more of that web page, I now see they already list the wheels as a stand-alone part for purchase. 54" for $700. http://www.hiwheel.com/parts/index.htm Looks like they use cottered cranks, so would probably want to have them do the build with a Nimbus super-wide hub, which they might charge for as a customization (and there’s the cost of the hub). The frame would be the easy part.
Well the biggest ive seen for sale was 43" and was priced at 600 dollars
Just looked around on the website you’re linking to and found a t-shirt was a picture of worlds tallest unicycle and it say’s that is was 113’ tall! anyone noes where i can find a video of some one rinding that?
Unishark listed the RBR website, but he did not show a link to their standard line of unicycles. Here is the link:
Be the first on your block to won a 52" unicycle!
(They do not list inseam requirements.)
Scott
Sem Abrahams has the tallest unicycle record at 114.8 ft set in 2004. Lots of info and video can be found at …
As for the largest wheel, I’ve seen several large wheels (60"+) also at Sem’s. One of them requires blocks on the pedals for him to ride.
Carl
Thanks, Scott, I totally missed that! Looks like the ultimate SteamPunk Uni. I wonder if it would be bearable to ride for my 3 mile commute? And now that I see it’s several hundred dollars less than my estimate, it almost seems affordable. . . .
This thing is crazy!
uniShark,
Tom Miller of The Unicycle Factory makes them when requested. He once told me big wheels are his favorite because they ride so smooth.
Very cool! I think Foss has something similar, but not that big. Downside-for me anyway-is the solid rubber tire, and of course, a rim that large is inherently fragile. I believe 36" is the largest pneumatic unicycle tire made. Hard rubber is just too impractical for any serious distance riding, unless you are on a super smooth, controlled track. But it would sure be fun to ride one around at the beach! 
Hard to tell from that pic, but it must have the shortest seat tube imaginable! Looks like he’s literally sitting on the tire!
Here’s a link to John Foss’ world famous Garage Page featuring many big wheels:
Hard to tell without knowing how big Leo is, but I’d guess in the range of 45-55", more on the high side of that.
Because he has a life. Occasionally. 
The Unicycle Factory (mentioned above), Indiana. 765-452-2692. Not sure how much they cost these days, but with Tommy Miller it’s more about when than it is about how much. I’m sure he builds them cotterless now (mine is oldschool cottered). And no, you don’t need a splined axle with such a fragile wheel.
That biggest one is still the record holder to my knowledge. It was built by Steve Gordon/Gordon Moore, and has a 73" diameter.
Yes. I’d much rather do any long ride on a 36" air tire than my 45". Now that the 36" tires are available, that unicycle is relegated to parades and the occasional show. It’s great for spins, terrible for bumps or “real-world” outdoor riding. Not that they couldn’t be used for ultra-long rides, like Wally Watts going around the world in the late 70s.
The 63.5" unicycle on my Garage Page was basically built with the fork legs welded to the steel Schwinn seat base. Meanwhile, it appears Leo’s cycle has some sort of cantilevered seat, with the fork going up behind him…
Wow… so glad that I found that pic because I’m learning a great deal of info re: large wheel history. I had no idea you had that large collection of big wheels John. Looking at the “garage page”, I saw the following quote:
“Currently the largest unicycle wheel is 73” by Dave Moore and Steve Gordon in Southern CA. Photo taken by Göran Lundstrom."
So John… do you know if this unicycle is still in southern cali? I would love to meet it and it’s owners/makers!
Thank-you for all the feedback guys. The pic that I started this thread with looks like highly customized and quality work… would be interesting to throw a noose around this guy and drag him over to unicyclist.com for a q/a on his build.
In Japan last year I saw Chinese rickshaw wheels that were 48" +.
After some research I found a supplier in China, but the cost of shipping a bulk order, and the fact the tires were a solid rubber I didn’t go any further.
But they are out there.
Ridable Replicas in Alameda, CA makes a number of interesting cycles, including a few big wheel unicycles.
As mentioned above, it’s in Sem’s garage in Livonia, Michigan. Probably not for sale either. 
I forgot to mention those. There’s a Japanese version that has been used for unicycles in the 80s and 90s. I think they were 43" wheels, with wide tires like a Coker and also wide, ultra-durable, ultra-heavy steel rims. They were, after all, intended for industrial use, even though a human had to pull them! We saw some of these rickshaws, which are still used as a touristy thing, in Japan in 2004.
Sem Abrahams also had a unicycle made from one of those wheels, when I visited his family in Holland in 1983. It had really short cranks on it, like 110s or something, so was hard to mount but really cruised once you got it going, as long as the road stayed flat! 
I knew a few other people who had had unicycles made from those wheels, but they were expensive, and possibly a very long wait when you needed a new tire or tube. IUF founder Jack Halpern had one, and it was used for the (current) 100 mile Guinness record in 1987.
@johnfoss
Do you know where I can find any more info about the world record for the largest/biggest size wheel for a unicycle? Thinking of trying to break it with my long legs…