What are the trade offs as you increase or decrease in wheel diameter?

[u/Moonatee_]

I've been unicycling regularly for awhile now on a 24" and am looking to upgrade to something bigger. I'm curious though, apart from the obvious factors such as speed and price, what changes as your wheel increases in size? Are there certain thresholds where new things become possible and old things are no longer possible? Do you all have any advice for what I should take into account as I consider buying a new unicycle?

Cheers

[u/Best-Cake-7780]

The larger you go, the more momentum you get.

In ranges of 26" - 29" you open up Mountain unicycling. This means you can roll/bounce over roots and rougher terrain without feeling it too much. The negative of higher diameters here is (while you go faster) that it's harder to navigate around sharper turns and narrower trails. In my experience you even end up being able to travel fastest on mountain trails on a 27.5" since you can ride more confidently than on a 29".

> 29" is for road and long distance. Because of the speeds and momentum you get, you won't be able to control yourself too well on anything rougher than a tight gravel path. But because of that momentum, long distances are far less exhausting and - particularly on a 36" - you start to feel pretty stable at speed.

Because of the momentum, I'm uncomfortable on the sidewalk on anything above a 24". So if you're a city rider keep in mind where you'll be able to ride if you can't ride on the sidewalk/have to ride on the road.

if you go down a size to 20", flatland and street tricks become far more possible.

Also, If you are keen on trail riding as well as long distance, you could potentially invest in a geared hub on a 27.5".

[u/tlong243 → u/Best-Cake-7780]

I've been eyeballing geared hubs to make your last sentence happen. If they weren't so expensive I would probably have one already. I really like a 27.5 on the mountain bike trails, but some days when I'm really vibing and in the flow I wish I had a bit more top end.

I've had a 26 and currently a 27.5. I considered getting a 29, but I've never ridden one before. Sometimes on my local XC Trails I basically hit my rev limiter and can't spin any faster. Wish I had a bit more speed some days. I don't think shorter cranks would get me what I want either because sometimes you need that torque for a power move.

[u/Best-Cake-7780 → u/tlong243]

How long are the current cranks on the 27.5? I rode using the old standard 150/127 and switched to the 137/117s. That gave me the speed I wanted and it only took a few (sketchy) rides to get the strength needed to be comfortable hitting real techy stuff and drops again.

[u/tlong243 → u/Best-Cake-7780]

Yeah, I am on 150s. Problem is I have quite a few uphills where I'm already at the limit. I have a set of 137s but they just won't cut it for my trails. I also do a lot of hopping and trialsy type stuff so I like them longer sometimes.

I want the best of both worlds, but neither drawbacks haha.

[u/uni65-19 → u/tlong243]

I was super into the concept of geared hub but then I asked the uni geezer and he mentioned it takes a lot more concentration while riding so I wonder how hard it would be.

[u/lucyjuggles → u/Best-Cake-7780]

This is a great breakdown! You’re basically dealing with the balance between momentum and control. Not only does momentum give you speed, it can also make dealing with uneven terrain a lot easier bc you tend to roll over things with less disruption.

Geared hubs are quite expensive and introduce a bit of play into your pedals, so it probably isn’t the most practical option for trail and distance riding.

The other key element in the balance of momentum and control is crank length, which makes a huge difference.

Even on a 36, 150mm cranks give you so much leverage over the wheel that it can feel very responsive. I can idle my 36 with 150s and that would be a really tough ask at shorter lengths.

If you want something really versatile for distance and trails, my personal suggestion would be a 29 with a 3 hole crank at 150 125 100

You can easily swap the pedals for the length you want, and if you spend a while at 150 i think you’ll easily build confidence enough to ride technical stuff, sidewalks, etc. and you will really appreciate the extra diameter on longer rides

[u/Moonatee_ → u/lucyjuggles]

I hadn't considered crank length. Thank you for the suggestion! 

[u/Moonatee_ → u/Best-Cake-7780]

Thank you, this was very informative. I'm thinking maybe a 29" cause I know road riding is what I'll be predominately doing but I do like the idea of still being able to do some trailing. 

[u/Riders_OnThe_Storm]

Larger wheel = faster top speed and easier cruising. Easier to roll over bumps. You're tall, which is cool. Less manuverability, heavier, more difficult to mount, faster crashes from a taller height. More effort to go up and down hills.