Dumb crank question!

So I got my new 140 mm cranks in the mail today and am in the process of removing my 127’s off the Sem XL which I did fine with my new crank puller. But now, it seems like a stupid question, but how do the new cranks go on? What makes them snug in there tightly like the first set of cranks?

The orginal cranks were obivously quite compressed on to the hub hence the need for the crank puller but should I have purchased some other specialized tool that assists with putting the new cranks back on… or is there something I just don’t know about this… DUH, yeah right, for sure there is something I don’t know or I wouldn’t be asking you guys right?! LOL

Anyhow, what do I need to do to put the new cranks on?

I’m going out for a ride on my 20 inch while there’s still daylight and hopefully when I’m back there will be some suggestions for me here… thanks in advance.


some will tell you to lightly grease the square tapers, I dont really know if it’s good or not. then push one onto the correct side, tighten the nut down as tight as you can. Then I hammer then on with a block of wood protecting from damage, then tighted the nuts again. Mr. Childs will give you a more enclusive view, but this is a start.

whenever i’ve changed cranks, i’ve just placed them on and then when you tighten the bolt, the crank naturally slides into a snug fit,
are they splined or just standard coterless?
if you do get them on then just a small point, don’t do them up as tight as you can, tighten them to 40 pounds (if you have a tourte wrench)

i know this won’t help, but get back to me with more details


Search for tips on installing cranks. John Childs has posted his recipe several times. His requires a special tool for one part of the process. I don’t always grease the tapers, especially if I’m putting aluminum cranks on a steel axle but that doesn’t mean I’m right. John ALWAYS does.

1.) Put the LEFT crank on the LEFT side of your uni.
2.) Put the RIGHT crank on the RIGHT side (they are marked L and R).
3.) Place a piece of wood on the HARD (concrete) ground or floor (the pieces of wood are to protect your cranks and should be centered under or over the axle).
4.) Balance the uni on the board on one of the cranks (center the axle, not the crank, on the board).
5.) Place another piece of wood over the other crank (center over the axle).
6.) Smack the top piece of wood with a hammer (HARD) DIRECTLY over the CENTER of the AXLE.
7.) Flip the uni over and do the same thing.
8.) Install nuts or bolts, whichever are appropriate, and tighten.
9.) Install the LEFT pedal on the LEFT crank and the RIGHT pedal on the RIGHT crank. They are marked L and R. The LEFT ones are LEFT HAND THREADED and will seem to go on backwards. As you look at the outer edge of the LEFT pedal toward the LEFT crank the pedal axle will turn COUNTER-CLOCKWISE to tighten.
10.) Ride a short distance and retighten the crank nuts (bolts) until they no longer require tightening between rides.
11.) NEVER ride a uni with LOOSE cranks or pedals!

I have a dumb question myself. I just got a crank puller for x-mas.
How do I take a crank off with it.
AKA I dont have a clue how to use it

Let me know


Thanks for your suggestions; the cranks are on - used the ‘sandwich between two pieces of wood and wack with a hammer’ technique. I’ve gone for a test ride and all seems fine so far.
Just one curious thing (I posted this earlier but it hasn’t appeared), the Dotek cranks look like they flare out somewhat especially when compared to the Sem XL cranks. Is this a feature of the Dotek’s? I don’t think they are installed in any way incorrectly though of course this is my first shot at installing cranks. Anyways, cranks on my other uni’s seem to be parallel to the frame but these new cranks flare out from the hub toward the pedal. Any ideas?


This “flaring” is referred to as “Q” for some reason. I haven’t seen any quantification of the “Q” factor of cranks and am constantly hoping that some educated person on this newsgroup would just come out and say it so I wouldn’t have to research it.

I have 140mm Dotek cranks on Blue Shift and they have very low “Q” especially when compared to Lascos. The Doteks are almost perpindicular to the axle but not quite. I have some 140mm steel Schwinn cranks which have a slightly higher “Q” than the Doteks and, actually, I would expect those to be similar to your Sem cranks.


Ahhhhh Harper, it pains me so to not be able to please you with pictures… so many opportunities to post pictures and so few digital cameras available… sigh…
Hang in there my friend, some day it will surely happen: Erin will post some pic’s and the country will have a national holiday to celebrate!!!

So, if I understood you correctly, and I remember you mentioned that the Dotek’s had a low Q factor when I first asked about 140 mm cranks and you replied recommending the Doteks, the Doteks should be lined up along the line of the frame, more or less, without much flaring out from the hub to the pedal. Right?

However, the Doteks I have DO flare away from the frame. They are out wider at the pedal compared to where they insert at the hub. All in all, is this a good feature or a problematic feature?

(still picture-less)

Just a few more thoughts to add to that last post…
yes, you are right, the Sem cranks do look like those Schwin cranks that you mentioned.

Also, does a high Q factor mean that the crank is quite straight and therefore turns the pedal very close in to the wheel?

And with a low Q factor does the crank cause the pedal to turn a little more out from the wheel?

just wondering…


to have a low Q-factor is to have your ankles closer together.i too have never heard a reason that the letter Q is used.

it is also used to describle the bandwidth of filters in electronics

and it seems equaly unexplaned in that field too.

Here is what I have found. The “Q” factor as it relates to cycling, is not a “factor” at all but a distance. It is more accurately referred to as the crankset “tread” which really suggests a distance. The “Q” factor, or crank tread, is the distance in millimeters measured parallel to the axle between the outside extremes of the cranks at the pedal attachment points. The easiest way to measure the “Q” factor is to remove one crank and rotate it 180 degrees and reinstall it. Then measure the distance between the outside extremes of the cranks at the pedal attachment points. The ways to reduce the “Q” factor are to reduce the axle length, make the crank as perpindicular as possible to the axle, and reduce the crank thickness at the pedal attachment point. A low “Q” factor in cycling is generally considered to be good except in mountain biking. As Dylan mentioned in this thread, a high “Q” might be beneficial in unicycle trials.

The “Q” factor, or “quality” factor, as it relates to resonant circuits in electronics actually is a factor and is the ratio of the reactive power to the dissipated power in the circuit. A high “Q” in electronics is considered good. A really good tuned circuit will have a “Q” of several hundred to a thousand. I have a bunch of quarter-wave, superconducting, resonant cavities as part of a booster accelerator at my lab in which the cavity “Q’s” run 200,000,000. They cost really big bucks though and are hardly pocket sized.

On a bike the Q factor is also a consideration in proper bike fit. Some people have wide hips and others have narrow hips. You want you legs to be pumping up and down in a plane and you also want your knees to be pumping up and down in a plane and not doing any side to side movement. Adjusting the Q factor on a bike can help with bike fit.

On a unicycle some of that would still apply but on a racing unicycle or a touring unicycle there is also the issue of minimizing wobble and that generally means that lower Qs work better. For trials and aggressive muni a higer Q is generally more stable. For a fast XC muni a lower Q might work better.

Re: Dumb crank question!

On Fri, 27 Dec 2002 18:03:55 -0600, Max_Dingemans
<Max_Dingemans.gdlh7@timelimit.unicyclist.com> wrote:

>some will tell you to lightly grease the square tapers, I dont really
>know if it’s good or not. then push one onto the correct side, tighten
>the nut down as tight as you can. Then I hammer then on

Max I think you’ve been lucky so far. If you use the nuts to tighten
your cranks you risk stripping the threads. It’s better to hammer
first and only then tighten nuts. This is consistent with Harper’s
posted manual which is excellent except for some excess capitalisation

  • but I have a slight (may I say SLIGHT) feeling that he made it by
    cutting and pasting so the caps may not be his.

Harper now has either of two sins to confess (or may choose to remain
silent): stealing content or shouting :slight_smile:

Klaas Bil

The average person falls asleep in seven minutes.

Sometimes my head is a resonating cavity and sometimes I’m just plain stuffed-up. Is the Q different in these two cases?

Instead of the hammer technique I use a torque wrench set to 35 ft-lbs. A little more expensive but much more repeatable. I’ve never had a threads problem.

On the stock Coker I generally had a problem with my right foot drifting off the pedal. With the wider GB hub I haven’t seen that problem yet. This is probably due to the leg/hip/Q issues that John Childs so clearly described.

Re: Re: Dumb crank question!

I wrote it as a stream, picturing how I would do it while guessing what Erin has as her resources and assuming that she didn’t know that cranks and pedals were L-R. Then I changed the order of the last three steps and editted some of the middle steps to clarify them. I think I have written it before. I know JC has but he always includes a step to grease the tapers and one to squeeze the cranks on with a big c-clamp.

HOWEVER, I will confess to BOTH of these SINS and any others you require. I SUBMIT, prostrate, before the Nederlands inquisiton.

Re: Re: Re: Dumb crank question!

And a well done set of instructions it was.
You can certainly get the cranks on tight without greasing the tapers. The grease just helps get more consistent results every time.

I like the block of wood and a hammer method better than the C-clamp. I started using a C-clamp because I live in an apartment and didn’t want to disturb the neighbors at 11:30 at night by pounding my cranks on (I usually do my unicycle maintenance late in the evening).

We really need to make a FAQ for the newsgroup that covers maintenance issues and some of the other common questions. Unicycle.com has a FAQ but it seems to be geared towards beginner questions and purchase questions than some of the stuff that frequently gets asked in the newsgroup.

Hi all,

With appreciation to John “Loctite” Childs, here is his recipe. I archived it from MUniac.com

From john childs at muniac.com on or near November 14 , 2002

Here is my recipe for installing tapered cranks on my unicycles. Before I started using this recipe I had problems with cranks getting loose on my. Since I started following this recipe my crank problems have gone to almost zero.
Put a little grease on the taper. This lets the crank slide on fully on the taper and gives you more consistent results when pressing the crank on. Don’t get any grease on the threads, nut, or on the area of the crank where the retaining nut clamps down. Press the crank on using either a large C-clamp or a 2x4 and a hammer. Get the crank seated as far on the taper as it will go without using excessive force. Put Red Loctite on the threads and nut. Tighten it all down. Do the same for the other crank.
The purpose of the Loctite is to keep the nut from backing off on its own due to vibration and other forces. As long as the nut doesn’t back off, the crank will stay tight.
Here are three threads from RSU about getting cranks to stay tight.
crank comes loose all the time!
Red or Blue Loctite?
Loose Cranks


There is a classic teacherism. The dumbest question is the one that was never asked.

I always wondered why I never ended up with bloody ankles. This was do to riding with cranks with high Q factors. Oddly, I had a Sem XLW with 150mm Bicycle Euro cranks on them. These flare out a bit, but have a small Q factor. I also have a pair of MOnty 158mm cranks, which by the way are not perpindicular to the wheel plane( this answer is for a previous thread “way back when”) and flare out a bit more than the Bicycle Euros.

I prefer the larger Q factor myself, it creates some wobble, but I don’t ride fast any way, so I don’t mind.

I tried John Childs C-CLAmp method, but one problem. One, you need a beefy beefy C clamp. The ones you buy at Home Depot, for 17 bucks bend. John had mentioned this, but I thought I was buying a beefy one. YOu need to go to a store that sells nothing but tools to find one.

One last thing, just to add to the differences on mounting the cranks. I use a rubber mallet on the wood, but have used it directly on the cranks them selves with a piece of wood on the ground.

Good question, Erin.:slight_smile:

Re: Dumb crank question!

“john_childs” <john_childs.gepqz@timelimit.unicyclist.com> wrote in message
> And a well done set of instructions it was.
> You can certainly get the cranks on tight without greasing the tapers.
> The grease just helps get more consistent results every time.

This is similar to torque on a bolt. When you look up specs on how much to
torque a given bolt, the fine print at the bottom of the sheet will state
that the threads need to be clean and lubricated. This is for consistency
and avoiding galling of the mating surfaces that can occur at the high
stress levels needed. You don’t want galling to occur so that you can get
everything apart.

Just don’t lube any threads where you will be applying Loctite.