Shimming a 25.4 post to 27.2

Anyone done this? The question is whether the shimmed smaller post would create a potential to damage the frame. I’d rather not do this since it’s a brand new KH - and it’ll probably be the last uni I can afford for a very long time. If there’s even the slightest hint that it would cause porblems the thing to do would be to save up and just get the larger post.

So far I’ve found:

The problem…
My wife has short legs. Very short legs. Extremely short legs. I just got her a KH24 because she complained that the trials was too small. I’ve got the seat on the KH24 absolutely pegged at the bottom and the pedals in the 127mm holes, so it’s set up to be as low as it possibly can go. Shes about on her tippy toes when she bottoms out on a revolution. Yes, that short. Yes, you probably have a 6 year old that can ride a 24" uni.


  1. Cut an inch off the frame. I really don’t want to do that.
  2. The adjustable portion of the post adds about 3/4" to the overall height. The hope is that replacing the adjustable post with a non-adjustable post will be enough. Even that’s not a given.
  3. Leg extension surgery.

We have a non-adjustable post we used on her trials, but it would need to be shimmed up from 25.4 to 27.2.

I’d also be very interested in trading our KH adjustable 27.2mm post for any 27.2mm non-adjustable… if anyone is interested. Our 27.2mm adjustable post has about 5 inches of post left, so it would still be ideal for a 36er.

The shim should not do anything negative to your frame. I’d say go for it, it’s gonna end up cheaper than a new seatpost! Koxx-One unis used to come stock with a shim (29.2-27.2), I dont know if they still do, I dont know if they’re still produced!

Also. if it stills doesn’t work, cutting the frame off a little bit would be the only good solution, I’ve done it myself because my friend was too short for the KH20 Longneck I sold her. If you have a dremel to do the job it should be really easy. We can’t really notice a difference, except that it’s about 1" lower than the original Longneck.

I am running a shim on my kh long neck as we speak! and k1 still shims their frames

I used a short bit of electrical conduit to shim the post on my giraffe. It only goes about half way around the seatpost and I had to put a lip on the top edge to stop it from falling in when installing it. It’s been on there for years with no negative effects.

If you have access to some scrap metal bits, you might be able to make due without buying something for it.

The Conundrum comes with a pack of shims, many Ti frames are shimmed, so no it’s not wierd and it will work, though it may allow the seat post to move around a little more.

It’s okay to cut your frame, but honestly I’d spend $65 and buy a Nimbus II frame, cut it down instead of ruining a KH frame. I cut down a Nimbus II frame for my son’s short friend, at the time she was 4’10", so I cut off a couple inches, renotched the back, and it’s worked well ever since!

How about that, 4’10" is exactly what we’re dealing with.

Thanks all for the input.

I never would have thought about getting a nimbus frame for cutting down. Thanks for the suggestion. Yeah, I’d rather preserve the KH frame… and one of the features of the KH frame is actually contributing to the height problem. There’s loads of clearance between the 3" duro wildlife and the top of the frame. Almost makes me wonder if I can cram my 26" wheelset in there :wink:

Since it’s the cheap route I’ll check my LBS for a shim today or order one online. I’m still not convinced that 1/2 - 3/4 of an inch will make too much of a difference.

Did your son’s short friend grow? Looking to offload a short frame? :wink:

She grew, but she won’t give up her frame, I’ve asked :stuck_out_tongue:

Also what seat has she got the Impact Naomi seat is a good 1-1.5" shallower than a KH free ride (and far more comfy imho), a one piece post will save an inch and a bit coupled with a Naomi saddle and you are looking at up to 3" lower!

Older KH24s and KH26s were the same size with different brake locations, later KH24 frames where shorter and kh26s were taller to fit bigger 3" tyres I believe

I have chopped a frame and re slotted it before, only took 15 minutes to do.

Another more expensive option would be to get a Schlumpf and gear her 20" up to a 30" :stuck_out_tongue:

I never would have thought about swapping seats to get a lower profile. She currently has a KH Slim.

I have one of those in my bits box as it wasn’t thin enough and I didn’t like the fabric cover but it is pretty thin already, you will only save about 10mm swapping to a Naomi

Oh and I went out with someone who was 5’10" she had a little booster seat cushion for her car :stuck_out_tongue:

You mean 4’10"?

And yeah, I joke about that from time to time - that is when I think I can get away with it. Weight and age are the only thing keeping her out of a booster seat. :smiley:

Of course the day she gets her much anticipated KH24 and discovers that she’s not tall enough to actually ride the thing is not a good day to joke about height. :wink:

Here’s a picture:

Yeah, that’s a 24.

Lol yeah I meant 4’10" :stuck_out_tongue: my Mrs now is about 6’ or something silly (much taller than me lol)

It looks like a 36er :stuck_out_tongue:

That post swap will save you 2", a one piece post can slam flat against the seat mounting plate but I think you will have to chop the frame a few inches as if she is riding MUni you still want a bit of room to lift yourself off the saddle. It is a painless process, just drill a hole under the existing slot by the amount you want to trim the frame buy then using a hacksaw make two cuts in line with each side of the existing seat split down to the hole you drilled, then lop the top off the frame, give it a tidy up wit ha file and you are done :slight_smile:

Could also go to thicker pedals and like 145 cranks

Currently at 127mm (spirits). I told her to get some platform shoes. That didn’t go over too well.

Get her a MUni penguin :smiley:

UDC used to sell these shims but I don’t see them on their web page anymore.

I have two of them 22.2 /27.2 & 25.4 /27.2 that I have used on my KH uni’s for dropping in spare seats with short posts for shorter people that I am teaching to ride.