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  1. #1
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    Bike fitting, Q-factor, knee pain

    Been trying to solve knee pain issues and am now thinking Q-factor might be a significant part of it. Had my regular ride in the shop for a week and rode another bike. Found my knee pain seemed to be eased, even gone. I've been tinkering with getting the right fit on both these bikes for a year. Seat height, fore and aft, stem length, etc. One difference between the two bikes I had not looked at was Q-factor. Measured and lo and behold, difference of about 10mm. Many internet posts tell me this might make a difference, including the great Sheldon Brown, and mention medial pain (which I have), etc. And (not that this is always a good guide - it seems logical: if your feet are further apart than your hips while cranking there's more strain on the knee). So firstly, I'm looking for feedback on that point.

    Its amazing to me since I've had knee problems and been asking around (from my GP, an orthopedic surgeon, a physiotherapist, and countless bike shop mechanics and salespeople) on the one hand how there seems to be a pretty standard set of replies (adjust your seat height, spin more) on the other how much contradictory info there can be about hardware - whether crank length or Q-factor are important when it comes to knee pain, for instance. The last word always seems to be, 'go to a pro fitter'. So secondly, what should a pro fitter do? I bought these two bikes new (been going second hand most of my life) and thought with a new bike I'd get a fit, get the right thing, etc. First bike (a Fuji Touring 2012) guy sold me. $1,000 CDN. Fit would be extra. Second bike, a Devinci Silverstone SL3 cost about $1,500 CDN. This time I got measured up, but my options for a bike were S,M,L. So why the measuring? This shop was better and let me swap out handlebars months after buying trying to get me comfortable, but in both cases the fit was basically, raise or lower saddle height til it looked good. I know what I spent is not a ton of money in the bike world (though for me, a lot) but what is a reasonable expectation for a fit from your local shop when buying a new bike? And what would a pro fitter do and for how much more money? I would have gladly spent some more money on fitting machines or cameras filming my movements if I could then get choices in crank length and Q-factor if it would mean saving my knees. Do you have to spend $10,000 before these kinds of options?

    Hoping I have my problem solved. Happy riding.

  2. #2
    Bluebird of Hapiness Marcus_Ti's Avatar
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    Lots of things can cause knee pain.

    Me for example, I have more than a bit of natural turn out and flexibility at the hips...I'm most comfortable with Speedplay pedals and tons of angular float in the cleat. Lock my feet forward and parallel and I'm not happy on the bike

    Knee pain can also come from too low a cadence.

    Can also come from too low a saddle.

    Can also be a stance issue (Q-factor).

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    shop mechanics and salespeople are just that...you want to consult people who know cycling and biomechanics. Further it could also be some odd biology on your part, see bike fitter/builder extraordinaire Zinn puzzled by this guy: Technical FAQ: A perplexing foot problem - VeloNews.com
    Last edited by Marcus_Ti; 07-31-15 at 09:39 AM.

  3. #3
    Senior Member Retro Grouch's Avatar
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    I doubt you'll get much help from me, just more questions. I consider myself to be a continuing long term research project with a sample size of one.

    After I broke my hip I found my range of motion on that side to be compromised. I've switched to some really short cranks (148 mm and 152 mm) on a couple of my (recumbent) bikes and found them to be much more comfortable. I'm planning to convert another bike to a 165 mm compact double tomorrow and I'm really excited to see how that feels. I'd like to convert my beater bike to 165 mm cranks, but I can't find a (cheap) 165 mm triple crankset with mountain bike bolt circle diameters.

    I've not had an issue that I could attribute to Q-factor yet. I too have toes that point outward more than most to the extent that skiing was quite difficult for me. I had to be constantly aware of keeping my feet parallel. One winter I checked the tracks I left while walking and running in the snow and found my left and right footprints to be quite close together. I surmised that meant that smaller Q-factors would be better for me. My delta recumbent tricycle initially came with cranks that had a pretty wide Q-factor. They never felt uncomfortable in either my knees or hips but I always thought they "felt" inefficient. My new 142 mm crankset is better but, if I could, I'd like to reduce the Q factor even more.

    For practical purposes, Q-factor is one of the more difficult and expensive things to change on a bicycle. There are commercially available gizmos to spacer your pedals out to give you a wider Q, but you have to juggle BB, crankarm and even frame designs to reduce the Q dimension significantly.
    My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.

  4. #4
    coprolite fietsbob's Avatar
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    Q factor reduction is requiring going back to old cranks with straight arms

    that come at a right angle from longer square taper spindles , you can lose chainrings and use shorter spindles then

    Now, All most universally the crank arms are made curved , wider at the pedal than where they meet the BB spindle..

  5. #5
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    Are you a larger or broad shoulder/hips person? Everyone thinks of length but width must be fitted too. You should should have handle bars with width fitted to your shoulder width for example.

    I am 6-2 and fairly broad shouldered. I was having knee pain on my road bike with ultegra cranks, but the crank width cannot propely fit all peoples stance width. I finally figured out to fit it with pedal extensions to widen my feet position, and the pain immediately went away forever. Simple solution eliminated the latetal stress which was the cause of the problem.

  6. #6
    Newbie mjw353's Avatar
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    I had a very similar knee pain issue as the OP.

    After purchasing a new road bike, I began experiencing mild intermittent knee pain during moderate effort rides. My pain was mostly frontal (below the patella) but would also be accompanied by lateral pain.

    Like the OP the Q factor of the new bike was different than the old. Switching to speedplay zeros, allowed me to adjust the cleats' centerline offset so my knees could track vertically. Changing the stance width in conjunction with the increased float of the Zeros eliminated my lateral pain. However had further adjustment been needed beyond what the cleats alone could achieve, the pedal spindles can be changed to a different length.

    I also had a Retul fitting done at ERO-sports ( in the LA area ) During the fit analysis, adjustment to saddle height and Fore/Aft position cleared up the frontal pain. I would highly recommend a dynamic fit session with a certified fitter. In my case the saddle adjustment was less than a centimeter. Had I tried to find that position on my own, I'd still be looking for it. The number of adjustments that can be experimented with on these rigs is literally infinite, and changing the bike's configurations takes only seconds.

    There are several systems out there, although I only have experience with the retul rig:

    http://www.retul.com
    http://www.gurucycling.com

    ERO Sports - Home

    HTH

    cheers,
    -m

  7. #7
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    My experience was identical to allroader55-- persistent knee pain, bought extended pedal spindles (+12mm) and the pain went away completely with no other fitting changes. I have large feet (size 14 US) so the spindles were intended to give shoes clearance from the chainstays-- the complete removal of knee pain was a surprising and welcomed bonus.
    "Get a bicycle. You will not regret it, if you live. --Mark Twain

  8. #8
    Newbie Willard45's Avatar
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    I too had persistent knee pain while riding for long distances. I tried using extended pedal spindles for my riding, but it doesn't help me to get rid of my pain and finally had to consult my physio in Mississauga at Physio Now clinic for physiotherapy. I had no other choice and had to do something to reduce the pain and start my riding again. I searched for many options nad heard this is the best option for persistent knee pain. The treatment really worked for me and I had no longer suffered from knee problems. First try changing the spindles and if it doesn't work, then consult a physio.

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