hub sizing question

Unicycles and Equipment
1

Here’s one for the “just wondering” category …

As I was looking through the Unicycle Source catalog (unicyclesource.com), I
noticed the pictures of the NK/Semcycle Deluxe and Suzue hubs. John D. has
included on the Semcycle Deluxe page a picture that shows it and the Suzue next
to each other, and it’s clear that the NK is quite a bit “beefier.” But it also
looks like its flanges and bearing attachment areas are wider than the Suzue,
and this brings me to my question–are wheels built with these two hubs
interchangeable? I know that the Telford uses both kinds of hubs, presumably on
the same frame, but they don’t look (again, from the picture) like they’d end up
with their bearings spaced the same width. Is there a standard width for uni
hubs, and if so, is it measured from flange to flange, or from axle tip to axle
tip, or what?

Peter

Peter Kittle Department of English CSU, Chico Chico CA 95929-0830 ph:
530/898-5305 fax: 530/898-4450 email: pkittle@csuchico.edu www:
http://www.csuchico.edu/~pkittle

2

RE: hub sizing question

> hubs. John D. has included on the Semcycle Deluxe page a picture that shows it
> and the Suzue next to each other, and it’s clear that the NK is quite a bit
> “beefier.” But it also looks like its flanges and bearing attachment areas are
> wider than the Suzue, and this brings me to my question–are wheels built with
> these two hubs interchangeable?

When you say wheels, do you mean the spokes/rim part? That would be a factor of
where the spoke holes are. I don’t know the answer there, other than that you
don’t re-use spokes when rebuilding a wheel.

> Is there a standard width for uni hubs, and if so, is it measured from flange
> to flange, or from axle tip to axle tip, or what?

Unfortunately there is not a standard, even among “conventional” unicycles. This
means some customization might be necessary if you change hubs. For years I have
been riding Miyatas with Semcycle NK hubs. The frame width had to be changed
slightly to accommodate the bearing locations, and I had to deal with problems
due to the very narrow space between bearing and flange on the NK hub.

>From a frame’s point of view, the difference between hub/axles is the width
between the bearing races. Too far off, and you may not be able to use it. I
bought a beefy wheel with re-heat treated NK hub from Telford for my Roger
Davies carbon MUni, and had to give it back because it wouldn’t fit my
non-flexible frame. I’m still waiting for a ‘next generation’ axle from Roger.
Most steel frames can be adjusted (bent) to fit the small differences in hub
size though.

Note that though the NK hub is definitely beefier (and heavier) than the Suzue,
the thickness of the center part of the hub is not as important as other
factors. Primary is the quality of the metal and the production process. In
this case, the advantage goes to the NK because it is heat treated. Also
remember where axles break, which is almost always between the bearing and
crank arm. Note this is almost the same width on the two hubs. Since that area
is limited by the inner dimension of the bearing, you can’t just make it
thicker without changing bearings and possibly your unicycle’s bearing
attachment method as well.

For ‘conventional’ axles for MUni, meaning they fit standard crank arms, I
personally rate the three axles discussed above as:
#3. Suzue - very good, strong & light, still holding up on my carbon MUni
after more than a year
#2. NK (Semcycle) - stronger, though a little heavier (a worthy tradeoff)
#3. NK re-heat treated by Telford Design - strongest conventional axle you
can get (that’s why the wheel Geoff made me was $200)

Ride on, John Foss, the Uni-Cyclone (reply to jfoss@unicycling.com)
http://www.unicycling.com

“Oh darn it. I meant to roll that!” - Kris Holm after riding off a cliff

3

Re: hub sizing question

Pete,

    Perhaps worth mentioning is how the crank arms attach to the axle.
    Excepting a one piece design, internal or external threads on each side
    of the axle provide the most common means of drawing the crank arm
    (assuming a cotterless style) tight over the square taper. External
    threading requires a small turned down protrusion (about 3/8" long) from
    each end of the axle which is male threaded to receive a hex nut. Most
    times this nut has an integral washer with serrations to prevent it from
    comming off. Internal threading requires a hole to be center bored in
    each end of the axle then threaded. A bolt can then be screwed into
    these threads to hold the crank arm on. I think the internal threading
    arrangement is stronger because you can use a hardened bolt to
    supplement the axle. If the depth of the threaded hole reaches through
    the taper and bearing surface (about 1-1/4") this adds strength to the
    axle at its weakest point.

“The Muniac”