Replacement seat post

Hi all. I gave my grand daughter an old Norco 24" unicycle. The seat is terrible. I was given a better newer style seat, It has four holes to bolt it onto a seat post. The existing seat post is a straight pipe clamp on type with a 19.5 mm tube diameter. There is a replacement seat post on Amazon sold by Fun with a diameter of 22.5 mm. Does anyone know if it would fit into the unicycle neck?

A 3mm difference is pretty large for a seat post. 22.2mm and 25.4mm don’t work interchangeably unless you shim the smaller diameter post, but you are trying to fit large into small and that won’t work any way you do it.

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Let’s call on our in-house historian :wink: by gently rubbing the lamp :rofl:
@johnfoss : any memory of uni with smaller seatposts diameter than 22.2mm? Or is it just a mis-measurements of the top part where the clamping happens?

When you say the saddle is bad is it in bad shape or just uncomfortable? If it’s just uncomfortable take the cover off and fill it with some memory foam. After all hopefully she will use it to learn and move on to a better unicycle. If it is trashed maybe you should look for more modern used unicycle. They are out there, I have bought all my unicycles on the used market ranging from 20 inch up to 36 inch and got some very nice deal.

This is one of those situations where photos would be handy. Based on the description of the post, it’s definitely and old unicycle, probably from the 70s or earlier. Not great seats, but some were fine for learning on. Probably your easiest way to go in this situation is to fix up that seat if you can. Or go in eBay and see if you can find old unicycle seats on there, but that would likely involve buying an entire old crap uni just to get the seat.

To work with the new seat you purchased, you need a seatpost that will fit the old uni. Of the dimensions you gave, it’s not clear which is the one that fits inside the uni frame. Probably the 22.5, and the smaller diameter is the top of the post where the seat clamps on. Correct? has this post, at 22.2mm:
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That’s a common post size, but if you’re sure of your 22.5mm measurement, don’t order that because old unicycles used some different sizes. Does the uni have a set screw in or below the seat clamp? Some had those to help keep the post from twisting, and that might indicate it’s a skinnier post.


If the original seat post is steel and if you or someone you know can weld it is relatively easy to weld on a curved plate with 4 holes that matches modern saddles.

Lots of well thought out replies to my query. The uni is a five hour drive away so not easy to get to. After reading your comments I had the seat post carefully remeasured. I’m pretty sure now that it is 13/16"/20.6mm not 3/4" as I previously stated.
The new Sun seat post is 22.2 mm dia. So it’s 1.6 mm dia larger than the old post. I’m thinking that with the clamp backed right off, the old unicycle neck may recieve the new post. I will be going to visit her soon so I’ll try it then.
If it doesn’t fit I’ll cut the top plate off the new post and weld it onto the old post.
Thank you for your help folks I’ll let you know how it goes.

1.6mm bigger wont fit, even with the clamp loosened. I have to ream the seattubes on the frames I make from 27.2 to 27.4 because otherwise 27.2 seatpost wont fit in! Dont even bother trying to fit the bigger post, you could do more damage. I was going to suggest to cut the top plate off the new post and weld it on the old post.

jaco_flans, ok good to know info, I’ll jut weld the top plate on and hopefully be done with it.