Adjustable seat post for 22.2mm frame

I recently purchased a KH Slim seat for my freestyle unicycle, replacing my worn Miyata seat. I like the Miyata because it is as close to flat and horizontal as any I know but it is getting harder to find replacements parts, plus the width in the back is too wide IMHO for seat in front transitions.

The KH Slim is the width I want and relatively flat, but is higher in the front since it is made for trials/street/flat ridiing for the most part. I would like an adjustable seat post similar to this for a 22.2mm frame so the seat can be tipped down in front to nearly even with the back. Having the seat higher in front makes seat in back transitions more difficult. I purchased the 25.4mm adjustable post by mistake and it obviously does not fit the smaller frame.

Any ideas on how to:

  • Modify the above seat post to fit a 22.2mm frame, or
  • Create a 22.2mm adjustable seat post myself, or
  • Find an adjustable 22.2mm seat post to purchase (do they exist?)

Of course the easiest solution is the purchase an Equinox or Eclipse frame with the larger seat tube size but finances do not permit such simplicity.

If you have a rail adapter you can we an old school bmx seatpost. Some of them had integrated rail clamps. 22.2mm is the same as 7/8" and it was the standard back then.

If you need a rail adapter put an ad on the trading post. I needed one a couple years ago and I had it in hand a few days after posting the ad for the cost of postage.

I’m no freestylist, but I could see a rail adapter being a deadly finger trap on a freestyle unicycle.

This is probably the most expensive solution to your problem, but here goes… you could try buying a 22.2mm rails-type seat post, AND the KH adjustable post, and use the KH seat adapter on the rails-type post bottom.

It probably won’t be a bolt-off, bolt-on solution… just looking at some images online, you may need to do a little tweaking of the rails post to change the angle of the bolt holes. Maybe a shim would be in order. I dunno…

…but if you try, do let us know! I’m still riding my 22.2mm Coker and would love an adjustable seatpost. For now, I’m fixed.

Kenny-

I once made an extension for a 25.4mm (which is 1") seat post by turning a 1" diameter aluminum rod to the ID of the 25.4mm seat post. I then epoxied the modified rod into the seat post using Armstrong A-12, which is a 50,000 psi epoxy. I think you could do the same by cutting the 25.4mm post up close to the tilt adapter. Then, epoxy whatever length of 22.2mm (7/8") tube you want into it. If the 22.2mm OD is too big to slip in, it can be turned down slightly as long as it doesn’t thin the wall too much on the 22.2mm tube. If the wall would be thinned too much, you could use 7/8" diameter aluminum rod. You can buy a 3 foot length of 7/8" diameter 6061-T6 aluminum rod for about $20 from McMaster Carr.

Hi Greg!

An interesting approach, and simpler than most I’ve come up with. Where does one purchase the Armstrong A-12 epoxy, and where is McMaster Carr? Is this a brick and morter store or online?

My other “best option” seems to be removing the top piece from the 25.4mm seat post, grinding the top piece to fit a 22.2mm seat post, and attaching the two. What I don’t know about this approach is how much material is available for removal on the top piece. I’ll have to get a flashlight and check it out.

My Conundrum uses a 28.6mm post. To avoid using a shim I took the top part of a KH adjustable post and paired it with a 28.6mm bicycle seat post made by XLC that used a similar adjustment system. The rounded part of the KH adjustable section that allows tilt was wider than the corresponding groove in the XLC post so I had the open up the groove of the XLC post to get the two to mate together well but it didn’t take much grinding and I haven’t had any problems with the setup since. Quite a few bicycle seatposts use this type of adjustment (e.g. Thompson) but I don’t know if any are made in a 22.2mm size.

My Conundrum uses a 28.6mm post. To avoid using a shim I took the top part of a KH adjustable post and paired it with a 28.6mm bicycle seat post made by XLC that used a similar adjustment system. The rounded part of the KH adjustable section that allows tilt was wider than the corresponding groove in the XLC post so I had the open up the groove of the XLC post to get the two to mate together well but it didn’t take much grinding and I haven’t had any problems with the setup since. Quite a few bicycle seatposts use this type of adjustment (e.g. Thompson) but I don’t know if any are made in a 22.2mm size.

Kenny-

I don’t understand the description of your other “best option.” Were you going to take the tilt adapter off of the 25.4mm seat post and alter it some way?

McMaster Carr is online at www.mcmaster.com/

The catalog is pretty easy to search. They deliver pretty quickly and they have J-B Weld epoxy which is much cheaper than Armstrong A-12 and perfectly adequate for the job.

Also, I have Armstrong A-12 at work and at home, I probably have some 7/8" aluminum rod at work, and I have a lathe at work.

I lied. I have no such material at work.

Yup. I’m thinking of detaching the top piece from the seat post and machining or grinding the place where the seat post attaches to fit 22.2mm. Looking at it with a flashlight there appears to be enough material on the top piece to maintain strength after grinding for freestyle use. I would hesitate to do it for any other style of riding, maybe distance. I have a friend with a metal lathe so will report back after this weekend.

It works!

Here is how I did it:
[LIST=1]

  • Obtain a 22.2cm seatpost, I cut the top off an old one.
  • Thread a long bolt into the top piece of the adjustable seatpost.
  • Insert the bolt into a metal lathe.
  • Machine off the 24.5mm seatpost.
  • Machine the attachement nub down to 22.2mm.
  • Use the lathe spindle to push the 22.2mm seatpost onto the nub.
  • Apply a bead of superglue between the 22.2cm seatpost and the top piece. [/LIST]

    Voila! This assumes you have access to a metal lathe and someone who knows how to safely use one. In my case I found a friend who has one in his basement.

    Adjustable222Seatpost.jpg

  • Cool project, Kenny. I hadn’t thought about Super Glue. It has really good shear strength as well as tensile strength. For your cylindrical surfaces all of the stress is shear (rotation of the post or extraction of the post). Let us know how it works out after it’s banged to the ground a few times.

    Somehow I don’t think superglue is going to handle the torsion forces your seat might experience in a UPD.

    KH redesigned his seatposts to include an alignment pin between the bracket and the seatpost. Why not do that here too? Just drill a hole through the seatpost and your ‘attachment nub’ and put a pin in there…

    Actually, Kris’ first improvement was to add a pin. Then he made it two pins. People (like me) still broke those, so now it’s one forged piece. No way superglue is going to hold. You probably could drill on either side, tap it, and use a set screw though. Alternatively, you could drill all the way through and use a long, thin nut and bolt to hold it from turning. Not sure how much room there is for that though.

    I’ve been concerned about superglue as well but haven’t had a chance to take it out for a whirl, the weather in Seattle is yucky right now. The Macy’s Holiday Parade this Friday, which SVUC is riding in, will be a soggy one.

    My next step if it twists is to install the pin but I like the idea of set screws or a bolt all the way through. Will have to think about it.

    Kenny-

    There is this thread from 10 years ago that discusses a new, black Torker with a strong wheel. Buried in that thread is a discussion of making the seat post extension the way I described. I am attaching a photo of the finished product. I eventually gave that Torker, with the extension still on it and two bent cranks, to Steve Howard. He rebuilt it for his daughter. The insertion length of 3" is long compared to what you had to work with.

    Edit: The seat post modification discussion begins on the second page of the thread.

    FullLength.JPG

    Just a thought…

    Would it be possible to use a 27.2 KH adjustable seat post and fit the 22.2 seat post INSIDE it? (after cutting it down and drilling it out)

    The newest adjustable posts have an oval internal cross-section but the older ones are still round, and the approximately the right size to put a 22.2mm post inside. However, this doesn’t really solve anything because you would still have to choose glue or pins and it would weigh more.

    Wow, who knew this thread would garner so many creative responses!

    Anywho, I tapped two sides of the seatpost and inserted screws coated with locktite. We’ll see how that holds. I may put in two more so I have one in each cardinal direction, I’m afraid pulling up on the seatpost may loosen something.