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Sunday, February 22, 2009

Snow Bike Fit - playing with q-factor is fun!

One look at the bike above and you know this won't be a "normal" bike fitting.

I'm certainly not new to the world of snow bikes: I've worked and ridden with Mike Curiak for the better part of the last decade, so I've certainly been subjected to a few cold "over-night" rides on the groomed surfaces of the Grand Mesa.  I have consulted with Mike (BTW he owns the record for the fastest human-powered traverse of the Iditarod Trail, by bike of course, all 1100 miles in a little over 15 days), as well during this time for certain aspects of his training, any time he gets a wild hair to try something that should be nearly impossible by human standards.  

I've seen the numerous iterations and changes made to his current snow rig -- the indomitable Snoots made by the good people of Moots Cycles in Steamboat Springs, Colorado.  So I vaguely know the ins and outs of a true snow bike.

To say that this bike is "custom" is an understatement of the largest order.  Every single tube, feature, and add-on has been painstakingly developed in a partnership of ideas between Mike and master welder Brad up in Steamboat (Brad has his own snow bike as well). I think the low five figure price tag Curiak has estimated is exactly that -- a very low estimate.

A quick rundown of the features: 
  • The whole bike is (in Moots tradition) built of titanium
  • Only the front rack is on there.  The rear rack has been removed for simplicity during the bike fit.
  • The tires are 4 inches wide (Surly Endomorphs) built to snow-specific rims, of course.
  • The cassette and freehub body are 9-speed but only 8 gears are on there due to space requirements.
  • The rear hub is 165 mm spacing instead of the normal 135 mm for mountain bikes.
  • For that matter, the front hub is also spaced 165 mm so front and rear wheels are inter-changeable.
  • The bottom bracket (a Phil Wood square taper) is 155 mm end to end (instead of ~110 to 120mm  for road and mountain bikes).
  • In some of the pictures you will see brass fittings on the bottom of the bottom bracket and the back of the fork legs -- these are pet-cocks for fuel dispensation.  The fork legs and the seat tube (along with the big "box" above the crankset) hold fuel for his stove.
  • Custom made bar ends grace the cockpit, but they are usually hidden under large hand covers called Pogies to protect hands from the severe cold
All told, the bike weighs.... well, a lot, even unloaded. 

So for obvious reasons, Mike wanted to check out some position issues that had come up in a 300 mile "shake-down" race.  I mean, when your going to be pedaling and pushing  a bike for three straight weeks, peace of mind is a big deal.

So now to the fitting....

Numerous problems presented themselves.  First, I had never put a bike with that large of a rear-axle spacing on the Compu-trainer stand.  A 150mm spaced tandem was the biggest up to this point.  After lining things up and having the right skewer on there, it was clear that with a little finagling it might JUST fit, but the enormous tire would not clear any part of the flywheel.  So we decided to remove the flywheel completely and we could set resistance on the rear wheel by dragging the rear disc brake.  

With this settled, I began to work on the flywheel, only to find that it requires a T25 torx wrench for one side (fine, I got that) and, more problematic, a 4.5 mm size Allen key for the other.  My complete Park Tool Allen kit does not have a 4.5 -- UGH!!

Such is the frustration one frequently encounters with a Compu-trainer:  Spotty software compatibility.  Ear-clip heart rate monitors.  When you really have no competition I guess you just never have to work to improve anything in your product.  Hopefully, someday soon, someone will come up with a better set-up and I can ditch that thing on Ebay.  Cyclops?  Anyone, please?

So on to the next idea.  Curiak brought an old set of rollers with him for just such an occasion.  

This, I thought, was going to be interesting:  4 inch wide tires on rollers.  

For safety reason we did away with the handy Retul platform that rotates -- no need to introduce more potential energy into the situation -- and set the rollers up, quite literally, in the corner of the Studio.  This way Mike had an "out" when it came to balancing and trying to stop - he could just lean into  the wall.  Also, placing the front wheel in contact with the wall in front, compensated for the bikes desire to run itself right off the rollers, especially as he tried to start pedaling.

There was plenty of inherent resistance in the tire/roller interface, so we were able to leave the tension belt off the rollers completely.

With the logistical hard part out of the way, all we had to do was hook him up to the Retul LED harness and test him out.  No problem here except at the feet.  Mike uses Lake winter shoes that are 8 sizes too big and puts in extra liners and vapor barriers (the funny looking loose gray "socks" you see in the pictures).  

Finding landmarks of the ankle and toes was next to impossible, and the water-proofing gunk ("schmeg" according to Mike) all over his shoes made it difficult for the LEDs to stay in place.

(Wood screws help with traction when pushing a 150 pound bike into a headwind on glare ice)

Everything held up and after two back to back scans of his right side, we moved the whole set-up to the opposite wall and repeated the scans for his left side

So what we found was quite helpful.  Here is an example of the Retul file from his right side.

We actually performed 5 different capture periods to get all the information we wanted.  I determined, first, that his seat was much too low -- I could actually just look at him pedal early on in the fitting and see this, but the Retul really helps to  quantify the asymmetries that a trained eye picks up.  What the system was integral in picking up was that Mike sits off to the left of his saddle and with the left hip scooted forward as well.  It was not severe - I have seen much worse positioning, but it was certainly worth paying attention to.

As I expected, Mike's lower extremities were very "quiet" even when pedaling with some effort.  His knees tracked very little in the medial-lateral direction, and they did so only at about a 1 degree angle off the vertical. His hips had only minimal to moderate movement vertically as well.  No surprise, since he often races many days in a row and has only had mild issues in the past.

After doing some further measurements on the bike it was determined that Mike's pedals were spaced unequally - his q-factor was increased on the right by a few millimeters.  This was feeding into his current left-skewed hip position.  

(Incidentally, Mike also noticed his rear wheel was 3 mm out of dish - this determination I left to him, since he is a master wheel builder and has built every wheelset I currently own.  By correcting this, his bike will track better in the snow -- every little bit helps especially when the bike is loaded.)

Normally, given the deficits noted by the Retul system, I would think about spacing the clients left pedal out temporarily with some washers to provide for a better proprioception to both legs.  ("Temporarily", because I don't believe in purely compensating for a functional deficit [Read here] )  Not a great idea for Mike's purposes - when you are riding for this long under the extreme cold conditions he'll face, you want to have as much interface with threaded surfaces as you can.

In this case, though, we are able to space the bottom bracket spindle back to center.  

A brief detour.....

As the bike industry strives for narrower and narrower q-factors on their bikes (just about to the point now where it can be a detriment to the average cyclist), this bike fitting reinforces to me that we sometimes have to ask ourselves "Why?".  Is a narrower q-factor better?  For everyone?  For anyone?

It is helpful to some, but my experience has been that about 3/4 of the cycling population does not benefit and are often harmed by it.  You have to ask yourself, 

"How does placing my feet closer together affect my back, hips and knees?"  

"Are my ankles going to act differently?"

"In what foot position (off the bike) is my hip flexor going to be the most coordinated (to get out of the way of the downstroke of the opposite leg)?"

There are a number of proposed reasons for having narrow q-factors out there (on the inter-web and otherwise) and they smack of the same type of reasoning that has pervaded (and perverted) bike set-up and fit for years:  

  • When we walk our feet have a narrow step width (they track in line with one another) then so should our feet on the pedals ..... the problem with this reasoning is 1. normal step width during gait is actually between 2 and 4 inches and 2. during gait one foot is completely unattached to the ground for slightly more than half the cycle.
  • measuring between the iliac crests (bumps on the front of our pelvis near the belt line) can give you an idea of what q-factor you should look for in a bike setup ..... we can't even guarantee an accurate seat height based solely on our inseam, so this one doesn't hold much water.  It's like determining spoke length for a wheel by measuring the diameter of the rim -- it might get you in the general ballpark for the correct length, but there are numerous other factors to consider (like hub flange diameter, hub spacing, lacing pattern, etc)
  • most of the references I have read begin, "Logic suggests...." or " seems intuitive that... a narrow q-factor would be optimal." .... As someone with a scientific heart, I really cringe when I read pronouncements like this.  
There is no research out there to tell us what is optimal, but what my years of bike fitting have taught me is that when we do get the research it will likely be very similar to the crank length argument (some articles show improvement with much longer cranks, some with much shorter - translation = everyone is different and needs to be addressed individually).  Many asymmetries see improvement with spacing the pedal out - I see it help every day.

One point I will stipulate is that a narrow q-factor makes pedaling out of the saddle easier since you don't have to leverage the handlebars as much since less bike "rocking" is necessary.  

A narrow q-factor often "pinches" the biomechanical cycle, rendering many cyclists more inefficient.  The simple case of Mike's (and many other's) bike, makes a simple argument that you shan't spontaneously combust if you have a wider stance on the bike.  (It may even help.)


A computational error when he was outfitting the bike with a new seat led to the low saddle height, and when we changed both these things, his symmetry improved significantly.

All told, it was a worthwhile endeavor -- the changes we made were small (as they so often are), but 10 years of doing this has taught me that even small changes can make a dramatic difference for a "normal" cyclist.  For Mike, dialing it's absolutely critical.

We were finished, and none too soon... within a 48 hours the bike was broken down, packed up, and on it's way to Alaska.

Happy riding (and pushing) Mike.


  1. What I find interesting about this is that Q-factor should actually be something that is taken into account with fully-custom frame builds. I don't think that expertise is there though.

  2. Good points! After my G-Fit/Retul, I am still tweaking somethings to resolve knee pain - usually my medial right articular cartilage. (I had surgery in '05 for it to little avail.) However, I have no knee pain on my mountain bike, so I am starting to experiment with Q-factor. Without going into a long narrative of my experience thus far, this does seem to be something that deserves as much attention as anything else on a bike.

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