I have a real need for speed. I currently have a 20" and it does not go anywhere as fast as I would like. I want to get a faster one however I am limited on budget ($200 or less preferred but am willing to spend up to $300). Would it be better to buy a 29 inch and save on the money and not worry about the extra mph or splurge a little and buy the 36er? The biggest I have ridden is a 24" and that was only for about 200ft however I did not have too much trouble ridding it and I think the only reason I did was because the seat was raised higher then mine. So also think of how ridable it would be when responding when responding.
Save up and go for the 36er, its really very much worth it.
I went from a 24" to a 36er no problem. It may take some people a little practice but anyone who can ride a smaller unicycle can learn to ride a larger one.
If you get a 36", you will fall in love with it almost immediately! Then you’ll wonder what you did without one for so long!
+1 for the 36. Hands down. If you can ride a small one, you can ride a big one. It might take a few tries to get on the first time, but there’s no question that you’ll ride it, and if you ride it, there’s no question you’ll get good 'n comfortable on it and pine for more. IMHO 
+1 on all that.
Hawo cloakanddagger, i recommend saving up for either a Nimbus 29er or UDC coker or the absolute monster coker (36") if you want to attain some serious speed. Those links are from the Australian UDC by the way. But if you do end up getting a 29er, it will give some serious speed, just like the coker. Either way it’s a win win situation really. 
I should add that the purpose is to be able to keep up with most/all bikes.
Even a 36 will have real trouble keeping up with most bikes on normal roads. We had five geared unis, including two geared 36" unicycles on rolling terrain this weekend, and even the fastest among us were not able to keep pace with reasonable bicyclists on flats and downhills. The key to keeping up with bikes is to ride uphill.
But if that’s the kind of speed you want, you definitely want the 36" instead of the 29".
+1
Go for the 36". The best feeling in the world is jumping on and cruising around as fast as you can Its basically the same as a smaller uni, but you can go TONS faster. Its really exciting when you’re pedaling as fast as possible down a hill or beating bikers going uphill 
actually I did some tests today. I attached a little thing to the spoke of my front bike tire and counted the revolutions (one revolution for every time I here the thing hit the front fork). I timed it for a minuet and then counted the revolutions of my uni for a 1 minute period. Both times I rode at a decent comfortable speed. Needless to say the bike was much faster but here are the results.
@=revolutions
132@ 26" wheel 838.495feet/min 9.5 MPH
96@ 20" wheel 502.655f/m 5.7 MPH
96@ 36" wheel 904.779f/m 10.3 MPH
96@ 29" wheel 728.849f/m 8.3 MPH
So basically what this means is that if peddle at the same speed as my 20" I will acctully be FASTER on a 36er. This is an assumption so if anyone could spread some light on the issue that would be great.
Well not to thread jack, but I’m selling my brand new coker big one in case you’re interested. It’s here: [FOR SALE] New Coker BIG ONE!
The key to this is to ride with casual bicyclists who use hybrids/comfort bikes, not bicycle enthusiasts on road bikes. I hate going slow on my road bike(13-14mph is too slow) and I wouldn’t want to put my friends through that, but I have a few friends who find the pace I keep on my 36er to be perfect for a nice ride on a comfort/hybrid bike.
I can go faster than a lot of bikes on the cycle trails in the area though when I am spinning fast on my 36 or riding my geared 29er, but most of the bikes I pass are casual bicyclists. The road bikes go zooming by. Being a distance unicyclist…it is nice that you go slower than a bike because it means that your friends who don’t ride bikes/unicycles a lot can get on a bike and keep up with you for the most part. I have to ride slower when riding with my dad or with some of my friends, so it is usually me waiting up for them and not the other way around.
In short, the only two options you really have for trying to keep up with some bicycles is to get a 36 or a geared 29.
I don’t want to burst your bubble or anything, but nobody on a unicycle will keep up with “most/all” bikes. Sorry.
Even on a geared 36, you just can’t hold 28mph on flat ground, tailwind or not. Many of the rides I go on have large portions continuously at 30mph or faster. Riding in packs, bikes will always be faster than the fastest unicyclists. I suppose that in the future we might see an absolute monster rider on a wheel much bigger than 36" who could sustain 28mph or better on flat like a strong road cyclist (which I am not! i can’t do that on my bike without a big pack to pull me along with its draft…). But I’ll believe it when it happens, and that’s just asking for some serious injury from falling from that high up. Unless you gear up a 36 to higher than 2:1 or something. I have a feeling, though, that a higher gear-inch setup than 65 or 70" would just be too hard to push on the flats, and you’d only be able to get that kind of speed on descents, where bikes just hands-down become untouchable due to their aerodynamics and big gears.
If your goal is to only keep up with casual bicyclists, a Coker is definitely your best bet, unless you want to go geared. A geared 29er is also great for speed, but (IMO) a geared 36 still takes the cake. I can keep up with slower road bikers on my geared 36, but only the slower ones, and not if they actually are trying to go fast. 20mph for a road bike is a nice slow cruise for a whole lot of people, whereas it’s the fastest I feel like I can keep up for any time at all on my geared 36.
On my geared 36, I feel like I make quite a nice match for one of my friends on his track bike, but, again, only if he keeps it to a good aerobic cruise and doesn’t try to hold his best possible average.
If they’re riders that think their 5 mile ride to work broke all the records, then you’ll pass 'em on your Coker, though :). It’s pretty satisfying to pass folks when I’m on my unicycle, but it’s even more satisfying to momentarily keep up with a roadie (but never the fast ones), which usually only happens when climbing, where many of the gearing and aerodynamic advantages of bikes are lessened. Road bikes are just too efficient and easy to ride!
I started out my Cokering trying to keep up with the serious bikes, but in my drive to compete, I always got stomped. My fastest ungeared averages just don’t cut it, and my fastest geared averages won’t either, and I feel like I’m representative of a medium-level geared Coker rider. Definitely though, the door is open for a bigger better setup with a bigger better rider to push it faster and faster, but I doubt we’ll ever match the bikes.
Yeah I am more trying keep up with casual bikers. My brother likes going fast but he does not have a street bike yet. He goes about 13-15mph so I might need to speed up a little. Everyone else I ride with only rides at about 10 so the 36er is perfect.
How much is a guni? I have looked a little but havn’t found any yet.
They’re not cheap. You can probably jerry-rig one yourself for cheaper, but to get a geared hub from Florian Schlumpf is either $1056 or $1421, depending on whether you want the weaker road hub or the beefy, unbreakable MUni splined hub (which I think is totally worth the extra cash). After the hub, you gotta buy the rest of the uni, so the cost can rapidly approach $2000. My KH36 setup was about $1920ish total, but I paid less for the hub because the sucky dollar has only gotten worse since I bought mine.
I’d get a really nice ungeared 36 (anything with a nightrider, stealth pro, and 14-gauge spokes; everything else is up for debate IMO) and save money (if you desire) to pop a geared hub in there one day in the distant future. I say this based on my opinion that geared 36 > geared 29 > fixed 36 > fixed 29. Since the geared hub makes both a geared 36 and a geared 29 approximately equally cost-prohibitive, I’d go with a 36, get fastish on it, and save up to upgrade in months or years.