Primo seat-post question.

It says it’s 22.2mm. The same diameter as the coker seat post tube.
I CANNOt for the life of me get it on.

please and thank you


22.2mm in the BMX world tends to be closer to 7/8" which is 22.225mm. Some unicycle frames are actually closer to 22.0mm rather than 22.2mm. The combination of the Primo seatpost and a small frame will make for a tight fit. What frame do you have?

If it is a tight fit in the frame a bit of sandpaper on a wooden dowel (or something similar) can be used to sand down the inside of the frame to get it to fit. Some frames have excess chrome plating and other junk inside the seat tube that makes things a tight fit. Sanding that away will fix things.

My Primo in my Coker frame was everso tight. Unlike JC I used brawn over brain and forced/twisted it in to place.

Hello Chase,
Good luck, my post was tight. So your Primo adapter fits the seat rails?

There are also wire fitting brushes used for plumbing. A proper size fitting brush can be used to clean out the inside of a frame. Hardware stores and home improvement stores (like Lowe’s or Home Depot) carry fitting brushes.

Sandpaper wrapped around your finger or a small dowel also works.

You can also combine that with wrapping a piece of sandpaper around the seat post and whacking away on that for a while. Not sure whether that material comes off faster or slower than what’s inside the seat post tube, but I had one that wouldn’t fit, and after some time working away on the seat post, it did.

Don’t forget to grease both post and tube up good before trying to insert it. If you don’t, you run the risk of not being able to get it back out.

I have had this problem with my seatpost before, even though it is not a Primo. All I had to do was use a little grease and really pound it in.

Ladies and Gentleman, we have now eclipsed the hilarity of the broken nipple thread! Congrats.

Aside from a light “cleaning” of the inside of the seat tube, I’d lean more towards sanding down the Primo post than the frame itself. Posts are cheaper than frames…and the post is more than likely thicker tubing than the frame and can take the loss in thickness a bit better. Using a mallet to drive a post in is never a really good idea, it will deform the frame tube and fatigue the metal…and fatigued metal tends to break. Good luck.

Has anybody tried the Primo post with a Sun 28" frame? Sounds like that post might be too big for it. I need rails on this uni, but even a regular 22.2mm seat post makes for a pretty tight fit.

yeah, it fits just fine.
just a bit tight in the seat post.


Primo seatposts are made of very hard steel, so it will likely be easier and quicker to sand the inside of your frame than the outside of your seatpost to make it fit.

I just picked up a Primo post and for some reason it doesn’t fit my KH rail adapter. The grooves in the clamps are too far apart for the rails. I could probably force it in there if I tighten it really hard but it’ll bend the rails outward. Is this normal? I was using the adapter on a Thomson post before this and it fit in just fine.

The Primo comes with two sets of guts (the parts that clamp to the seat rails). One set for standard rails and one set for oversized rails (as used on some BMX saddles). Could you be using the wrong set of guts? The KH rail adapter has standard size rails.

I’ll also say that the guts on some Primo posts are cheeply made. Some Primo posts come with better guts than others. I’m not sure why. It’s the same post and generally the same price, yet they all don’t have the same guts.

I had the same problem using the Primo post with my T7 handle. It looks to me that I got two pair of the same wrong size guts.

Here’s a crappy picture of what’s going on. I get pretty much the same result with the oversized guts. The metal is very rigid and I’m not sure what will happen if I try to clamp it down as is. So I guess my options are:

A)Return the post, buy another Primo (because I can’t find any other 22.2mm), and hope the new one fits better.
B)Grind out the grooves of the guts so that they can actually hold both rails.
C)Bend the rails out to reach the grooves as they are.

Option B might take quite a while to do and the grooves would no longer be shaped the same as the rails. Option C seems like it would ruin the integrity of the metal and cause the adapter to fail at some point. Option A seems like a waste because I bought it from UDC and they’ll probably send another one with exactly the same problem. Chrashing, how did you get around this issue?

I suppose that could happen. A visit to your local bike shop (preferably one that carries BMX) will clear that up.

You can buy upgraded alloy guts or upgraded steel guts that will fit the Primo seatpost and a bunch of other brands that are all basically made the same. The upgraded guts are actually machined and are sized better. Your LBS should be able to find some better guts in one of their catalogs.

Since the Thomson post fit you know the rails on the adapter are sized and spaced correctly. Don’t bend them out. You’ll weaken or break the welds.

Something is wrong with the Primo guts. Look for some replacement guts that will fit the Primo post. There’s bunches of different brand posts that are all basically the same. Some have better guts than others, but the post itself is pretty much the same. Your LBS may be able to find upgraded alloy guts that will fit. If not, you can find other 22.2mm (7/8") BMX seatposts that have alloy guts.

Standard rails are 7mm. Oversized are 9mm. The KH rail adapter has 7mm rails.