My friend just bought the Nimbus 29" Drak Mountain Unicycle. Rode it some yesterday. It is a beautiful machine!
The interesting thing though, is that it came with the new double quick-release seatpost clamp. (NOT the double-bolt specified on the website.)
Does this mean that the 29er is now using a different, larger frame? I ask because I may be ordering parts later on. … or does this mean that there now exists a 25.4 clamp, that is simply just not for sale?
Or has it always been a 25.4 sized seatpost with a thicker outside frame (27.2) and I just never knew it??
Clamp sizes are measured by the actual part of the frame that they clamp around rather than the diameter of the seat post. Thus, the size of the clamp will always be bigger than the diameter of the seat post.
Right, I just have confusion on how my Nimbus 24" Muni called for a 25.4 inch seat post clamp when I replaced my clamp, whereas this 29" says it’s the same size and yet is using a totally different sized clamp… so now if I order a 29" frame to build up a new Uni…and the frame is fitted for a 25.4 seat post… how do you know if the clamp will call for a 25.4 clamp (like my 24" muni) or a 27.2"?? There’s no specs, and it would seem like it just changed out of the blue…and I’m assuming not all frames follow the same logic (or ill-logic)
You could buy some caliper gauges and measure it. Only a few Pounds/Dollars. That’s what I have.
This type of thing:
Hey, now that’s useful!
Think that’s what I’ll do once I get to doin’ things.
(And on further reflection…I read now that the Oracle frame has this different sizing, too, so…maybe it’s pretty standard and I made this thread for nothing 
)
Thanks:p
Things have got more complicated unfortunately. Bikes have always specified the clamps by the frame size. Unicycles have been lucky that they only needed 3 sizes for ages… hence simple. These were the steel frames with 22.0 seatposts (25.4mm clamp size), 25.4 seatposts (26.8 clamp size) and aluminium frames with 27.2 seatposts (31.8 frame size). Then we got the eclipse and equinox frames that were 25.4 seatposts, but had 30.5 frames; also Oracles and QX that had 25.4 seatposts with 31.8 frames.
So that is why we are now seeing fuller descriptions on the clamps and frames.
Here is a quick list to help:
Cheap Chinese unicycles with steel frames and 22.0 seatposts = 25.4 clamps.
UDC, Nimbus and Qu-Ax with steel frames = 25.4 seatposts with 28.6 clamps.
Eclispe and Equinox (aluminium frames) = 25.4 seatpost with 30.5 clamps.
Oracle and QX with aluminium frames = 25.4 seatpost with 31.8 clamps.
KH and Impact (aluminium frames) = 27.2 seastpost with 31.8 clamps.
Roger