Carbon Base and Thomson Seatpost

I just got a Thomson Seatpost in the mail and realised that it’s for rail-type saddles(silly me :roll_eyes: ).

I’m getting this carbon base. Is there any way to make it fit the Thomson seatpost directly, without a rail adaptor?

Yes. Have you seen how Scott Wallis does the adapter for his CF seats? It’s custom for the Thomson seat post.

Someone here (Gerblefranklin? Catboy?) has fabricated a similar adapter for their KH style CF base. It can be done but requires some custom work and custom thinking.

Silly Ivan. I can’t help you. I barely even read your post.

Is it Kaycee you were thinking of?

Get a Rail Adaptor

Hi Ivan,

Very simple just get a rail adaptor. They sell them ant UDC and MDC.


Just wondering, why are the thompson seatposts made like this?

what do you mean? thompson seat posts are Bicycle seat posts first and foremost. have you ever observed the way bike seats and seatposts attach? bike seat posts attach to the rails of a bike seat. this allows for more strength, and way more adjustability than to have a seatpost bolt to a seatbase like with a stock unicycle.

thompson and de-rail is the way to go!

I assumed they were bespoke for unicycles.

nope. we’ve just adapted them to our sport. i notice that the freestyle end of the bmx crowd has too, in recent years. the reason is that the thompson happens to be one of the strongest, if not, the strongest post out there.

unicycling, in general, puts unique forces upon the seat/seat post area. and with trials/street/muni the forces a seat post has to take far exceed those of bicycling. not only does a seatpost have to take downward forces, but also upward and other weird-angled forces/stresses.

it’s a lightweight, strong, and well designed product, albeit somewhat costly.


Not that simple, actually. It’ll cost me 40 euros(because of the shipping) and will add 200 grams(assuming it’s okay to saw the brake lever off the KH rail adapter) of weight to my uni. 200 grams of weight mean nothing at all, but I still don’t want them.

And that Kaycee thread is interesting, but it seems he had a normal plastic KH base, not a cf one.

Maybe I could cash out for a Scott Wallis base(what with my new job and all…), but he says he won’t take orders till next year. Does anyone have a used Scott Wallis base they’d like to sell?

Sorry to be negative, but don’t hold your breath on that one. Scott’s saddles are the best, and precious few of them have been made.

It’s been done at least twice with a CF base. I just don’t have pictures and can’t find the threads where it has been mentioned. It can be done. But you’ll need to use some engineering smarts to come up with a design that is strong and robust.

Also take a look at this thread for ideas. It includes good pictures of the Scott Wallis CF base.

You could also rig up something similar to the KH adapter pictured there. Weld or epoxy a half cylinder to a KH 4 bolt plate. Rig up some way of attach and adjust the two adjusting bolts on the seatpost. I’d follow that route. Something where you use the KH 4 bolt plate and the standard 4 bolt holes. That will be stronger and also allow you to switch over the KH rails adapter if necessary or other compatible seatpost mount options that may come in the future.

The bigger advantage of going rail-less is that you won’t have to worry about your fingers getting caught under or between the rails. More friendly for trials and street style riding.

The concept JC describes is used on alot of BMX saddles, but with one bolt attachment into the center of the post, like the pic. You don’t have to use a serrated semi-circle mount, Scott Wallis’ is actually smooth and the 2 bolts provide enough clamping force.


Hmm, good idea. I’ve got a 4-bolt plate broken off my old seatpost. If I can attach to Thomson, it will make a very good seatpost.

I’ll be following this thread with much interest…

Wouldn’t a “tilted” (see picture) 4bolt post allow you to get a horizontal rear portion using the KH Freeride. And if so are there any that are ones longer than 250mm as I think that is what my KH 24 came with and it’s just barely long enough with a rail adapter.

Zack Baldwin and Ryan Atkins once rode with carbon fibre bases attached to thompson posts before the wallis base came around.

I don’t their exact methodology in constructing a means for the two to be attached, or how effective their results were. Zack rode his unicycle that way in Defect, and there are just a couple tiny shots of Ryan on the Semper alum. frame where he rode with this seat arrangement. So, I don’t know what the weaknesses were, if any. This was around 2004/5.

Maybe you could ask Ryan about it, or maybe someone will read this thread and post what they know.

Here’s a picture of what it looked like on Zack’s old uni. You can see that he constructed a carbon fibre piece for it to work on the outside, but I don’t know what he did to hold everything in place on the flipside. I jacked this from

Zack, Ryan, and I all did this. The way I did mine was I took the bottom plate of the thomson rail holder and sanded it until it fit the contours of the cf base. Then I drilled for the two bolt holes. I sandwiched two pieces of thick innertube between the plate and the base to keep it from scratching the cf. I was never particularly impressed by the results, but it did work. From an engineering perspective, i think the rail adapter is much stronger for a host of reasons.

Zack got that second piece of cf from a cf base he snapped a while back.

I actually do have an extra de-rail base right now (miyata foam, duct tape cover, kinport handle) since I’m only riding one unicycle, but damned if I’m ever gonna part with it. Right now it’s hanging on the wall in my dorm room as a piece of art. It’s very classy. When the day comes that I decide to rebuild my trials uni, I’ll have that seatbase ready.