I bought cheapie Craigslist unis for my boys after I learned to ride because they expressed interest. My oldest is almost 8 and will be riding soon. He can get 2 revolutions and can push a wheelchair up and down the street indefinitely. He can even fremount but can’t get more than 2 revolutions yet. So like I said he’s close.
I told him I would buy him a bigger uni when he learns how to ride. The seatpost on the 16 is most of the way up. He practices on a Sun 18 at school. When I look online Sun seems to be the only name brand that has an 18. Should I get an 18 or a 20 when he is ready?
19/20 would be better. The one extra inch will be well worth all the tire options. I can’t see it being too big.
Definitely 20. It will be easier to find tires, unicycles and replacement parts in this size, plus there’s a chance he will never outgrow it.
If there is 2"+ of seatpost exposed on the uni, he will fit either a 19 or 20.
If he wants to go into street/trials/muni, a 19 would be best. For freestyle or skill riding, a 20 is better.
19" have a few tyre choices but they are all pretty good. 20" has an insane number of tyres of mixed quality available.
Thanks all. I wasn’t even thinking of an 18 until I saw him on one. I will go with the 19 or 20 for longevity. Would the tire on a 19 make it harder to turn and maneuver for a 55lb little guy?
Definitely yes. I didnt think of that in my last post…
Trials unis are tough as hell, but are expensive and harder to maneuver. Putting on a higher volume 20" tyre would let him do bigger hops and drops without needing a different uni.
I would reccomend a UDC club to start off with (I dont know if the Sun or Torker unis have enough frame clearence for higher volume tyres). It is a solid 20" unicycle with a decent quality saddle. I would personally order a single or doublebolt seatpost clamp with it as quick release gives me nightmares. It is likely that you will have to cut the seatpost down a lot.
If he decides he wants to do hops and drops over ~1ft, you can replace the tyre with something 20x2.4 like an onza sticky finger. At the same time you should probably change the cranks for something stronger.
Thanks davejh. I have a very short seat post so that won’t be a problem. If he decides to get into big drops he will probably need a double walled rim along with new cranks. But I think I am getting ahead of myself as he can’t ride yet.
So I took him to the school playground to ride a little today. He is up to 7 pedal strokes now and he can feel how close he is. I raised his seat while we were at the school and mesured the seat height when we got home. With a slightly bent knee he is at 23 1/2". The 20" unis at UDC require at least a 25" inseam. I hate the idea of cutting the frame on a new uni so I think I will look for a Craigslist 20 to cut the frame on and get him a nicer 20 when his legs grow another couple inches.
Hi,
keep in mind that with a cut-down seatpost, the insteam will be equal to the fame height + cranks.
I looked to at one of the 20" uni at UDC as example (Impact Athmos) and the required insteam listed with cut-down seatpost is 24.6". But as it has 140mm cranks, you can still reduce the required insteam but going with 125mm cranks without cutting the frame.
On the upside, going with a 19/20 uni that is already designed to jump around will make it long lasting whatever your son decides is the funniest to do on a uni 
im going down to community circus this afternoon, they have a couple of club 20s and i will take a camera and tape measure with me…
From measuring my trials uni (with 137mm cranks) i believe that it should fit but i will provide evidence later today.
sorry, forgot my bag… will measure it up tomorrow morning
Buy it once, buy it right. Buy the new 20" and cut the frame. Your cut will be hidden beneath the seat clamp. Then all he will need is the appropriate seat post size.
My 4 & 5 year olds were on cut 20’s and still ride them at 6 & 7.
So I bought a 20" torker lx off craigslist today for when his big breakthrough happens. I put it in the attic so he doesn’t see it. I want it to be a surprise and I don’t want him to feel any pressure from me to learn.
The wheel looks straight, I noticed a little rust but nothing concerning. The bearings are tight but i have spares if it is more than just tight caps. What I failed to notice when I bought it was one of the cranks has been changed. One crank has a little q factor and the other has none, at least they are both 125’s. I have 125’s on my 26 right now I suppose I can put those on and get him 114’s when he gets comfortable on the 20. It looks like I only need to cut the frame down about an inch but I will wait till he is riding his 16 a block or so.
I thought hard about getting him a new uni but we seem to have trouble with bent rims in this family and l want to move him on to double walled rims as soon as he proves he is going to stick with it.
The LX is a good choice as it allows freestyle riding as well as some drops and such. The slightly wider tire will make a big difference if he gets into hopping and drops. A lot of kids on our unicycle team ride LXs, from elementary school through High School and beyond.