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  1. #1
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    Q factor - such a concept as too *narrow*??

    Thought I would post in the fat bike forum since Q factor seems to crop up when it's considered too wide on some... fat bikes, of course. That said, is there ever a time when Q factor can be too *narrow*? I ask since 120mm BB are too wide for my preference. Though "trail" Q-factor of 178mm seem quite comfortable and sometimes ? preferable to anything narrower. The observation is totally a personal preference that reflects how I like my body positioned not only while spinning uphill for extended periods, but also how I want to be positioned to feel stable when descending through narrow passageways and when the trail gets bumpy.
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  2. #2
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    I realize that everyone is different, especially when it comes to bike fit, but.... If I ride a 68mm bb bike all summer, after a couple of rides on my fatbike in the winter, my knees complain a little. Every time, I've been able to consciously correct the problem by making sure I wasn't keeping my knees the same distance apart that they would be on a bike with a narrower bb. I focus on making sure my knees are over the pedals instead of in between them.

    Just mentioning as a possible solution for people experiencing problems with fat bike Q factor. It's not going to solve the issue for everyone.

  3. #3
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    Q factor can be to narrow if your feet hit the frame or you can't run a tire combo that you want. I have don't like Q factor over 200mm. It causes issues with my hip and I don't like the bike handles with my feet for far out.

  4. #4
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    Quote Originally Posted by Bacon Fat View Post
    Q factor can be to narrow if your feet hit the frame or you can't run a tire combo that you want.
    Yeah, when it comes to the question of "too narrow", I think that this is probably the best answer you're going to come across as a generality. Some people might have a minimum Q criteria for comfort, but that's so intensely personal that it will vary.

    The narrow extreme will be road race bikes. But you're looking at major tire size restrictions there, obviously.

    My body personally doesn't seem to mind varying q factors. But I still have preferences. Riding a fatbike with a 121mm PF bb shell (same as 100mm threaded) and a 177mm rear hub width as my year-round trail bike, I occasionally run into width limitations. As in, my bike is too wide for the trail. It's typically some sort of choke point because of rocks. It's not frequent, but I do run into it a few times a year, and has me thinking about moving to a narrower plus bike for my typical trail bike purposes and using the fatbike for more limited riding. I've not encountered a q factor on a bike that's too narrow for me outside of tire capacity reasons.

  5. #5
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    For me the main problem with a wide Q-factor is increased pedal strike from the extra width.

    It's not just the overall width but the fact that when you are pedalling in tough conditions, eg steep climb, the bike tends to rock from side to side, and this translates into lower ground clearance when the bike is canted over, so the pedal even strikes low obstacles.

    What the optimum Q-factor is I do not know, but I suspect if you looked at the gap between your left and right footprints when running comfortably, you'd be pretty close.

    As a singlespeeder I don't have a comfort issue with Q-factor because any time I'm working hard I'm probably out of the saddle, and so thrusting straight down.
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  6. #6
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    Some good responses here, thanks. Sounds like the issue with Q-factor still has to do when it's too wide not too narrow. Agreed on a wide bike being the bottleneck on some trails.
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  7. #7
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    Road & 'Cross bike q-factors feel uncomfortably narrow to me vs a standard mountain bike, and I feel it negatively affects my ability to produce decent power. Q-Factors over 210 mm start to feel too wide to me, I find I have a hard time transfer my weight quickly from pedal to pedal when standing and trying to accelerate, and at this width my knees start to get pretty sensitive to cleat set up.

    Even out side that range though, I find I've still been able to enjoy riding.

  8. #8
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    Quote Originally Posted by Velobike View Post
    What the optimum Q-factor is I do not know, but I suspect if you looked at the gap between your left and right footprints when running comfortably, you'd be pretty close.
    That is exact

    IME , too narrow doesn't exist.
    We are designed to apply force straight downward not with an angle.

    Of course , design may vary a little from a manufacturer to another
    "There is a big difference between kneeling down and bending over" -FZ

  9. #9
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    It seems that for me, if I am clipped into the pedals on a fatbike (I do usu. ride flats) that I need to point my toes out. That means cleats need to be moved (or shoes dedicated to the cause).
    But yeah, I forget the wide Q-factor until I pedal strike a tree root on the downstroke.

    I think shorter people generally have a little more trouble with wide Q-factors.

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  10. #10
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    Quote Originally Posted by Fleas View Post

    I think shorter people generally have a little more trouble with wide Q-factors.

    -F
    I guess I've been lucky then.

    5'8" here and ridden some pretty wide Q-fatbikes with no issues.

  11. #11
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    Few times a month while driving I come up behind a weekend-warrior roadie who appears to be riding bow-legged (rear view). Sometimes it's a physical disability where the pedal stroke seems very inefficient when viewed from behind. Sometimes it is a seat too low, sometimes a beer gut forcing the thighs wide to accommodate the low hanging obstruction. Some people naturally walk pigeon-toed or duck-footed which could also play a roll in this discussion. Ever see someone's crank arms or chain stays that are worn away due to heel rub?

    Everyone is different and what is comfortable to one may not be to another. Seen lot of debate that narrow is best for cycling. I can also recognize real life examples where narrow is not ideal. Relating it to running, when you start off on a sprint in most sports your base is wide, shoulder width maybe a little less and as you get up to speed your stride width narrows a bit. At either extreme are you fat biking or road biking, maybe. Is there a happy medium for your leg speed/power ratio, maybe.

  12. #12
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    Persoally, i agree that it is easy to adjust to different q factors and would add that, for every person who claims to be more sensitve and need the narrower, there's someone else who would do better with the wider. These are a great prduct:

    SHOP & PRODUCTS

    I suspect that the industry fascination with narrow q factors comes from roadies who want to be able to pedal through a turn, mountain bikers who dont want to have to time their pedal strokes, and from drivetrains becoming more integrated and component-specific, with less tollerance for adjustability and lateral variance. Otherwise, we wouldn't have needed the whole "boost" specific drivetrain standard. We could have simply lengthened the bb spindle like we used to, until we had the necessary clearance.

  13. #13
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    Quote Originally Posted by Clayncedar View Post
    I guess I've been lucky then.

    5'8" here and ridden some pretty wide Q-fatbikes with no issues.
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    -F
    It's never easier - you just go faster.

  14. #14
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    Built up my first "fat" bike a couple of weeks ago, Salsa Bucksaw with a PF122 bottom bracket. I am running Next SL cranks so the q-factor is about 200. Have ridden it on 1 - 3 hour rides with up to 2500 feet of climbing. I had no idea how this would work out for me as I had never tried anything other than a normal MTB q-factor. Well, I love it. No hip or knee problems at all. Actually feels much better than my regular MTB and feet always land square on the pedals.

    Opposite of the above picture, I am knocked knee. My knees almost always hit the top tube. Actually on my Specialzied, I cut my knee up on that stupid Autosag valve because my knees are in close. The Salsa Bucksaw is the first bike I do not always hit the top tube, brush it sometimes but not like other bikes. The wider stance also feels better on descending and standing.

    Just my experience. Have fun, Jill

  15. #15
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    I am also 5'-8"ish and shrinking and my gf is 5'-3" on her tallest days. No issues with wide Q-factors on our fat bikes (Bucksaw and Borealis). I am more comfortable with them than my narrow Q MTBs, which are gradually getting sold off.

  16. #16
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    I have wide hips, and have to put spacers in my road bike pedals to avoid having constant IT band and knee issues.

    My fat bike is a little wide, takes a bit of getting used to, but is comfortable.
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  17. #17
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    Quote Originally Posted by Fleas View Post
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    -F
    Yeah, I'm actually bowlegged

  18. #18
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    5'8" 190lbs here and I much prefer the Q factor of my fat bike. I feel a bit like a Bulldog on it, but no pain issues. I am not bull legged but I do have a wide backside and thick thighs and the wide Q factor allows me to feel like my legs work like pistons.
    Last edited by SalsaSalsa; 03-14-2017 at 06:49 PM.

  19. #19
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    Quote Originally Posted by SalsaSalsa View Post
    5'8" 190lbs here and I much prefer the Q factor of my fat bike. I feel a bit like a Bulldog on it, but now pain issues. I am not bull legged but I do have a wide backside and thick thighs and the wide Q factor allows me to feel like my legs work like pistons.
    Sounds a lot like me at 210 lbs.

  20. #20
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    I must be a bit of a Goldilocks here. I like to keep my Q-factor low on my fatbikes, around 180mm or so if possible. I use an 83mm bottom bracket to make that happen (my main fatbike is a custom Waltworks). I have also found that low-q mountain cranks (like the 156mm q Sram cranks) are not to my liking either as I get some knee pain with those as well. I much prefer the 168mm Q from them. So... I guess that means I only have about a 10-15mm window of acceptable Q factors.

    I'm 5'11" and have short-ish legs (32" inseam). My joints are pretty creaky, though. In contrast, my wife rides a Mukluk (200mm Q-factor) and has no problems at all. She's only 5'-3" but she's all legs so that probably helps.

  21. #21
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    The fundamental problem with Q-factors for fat bikes is derailleurs. Because the chain has to go through all sort of contortions there needs to be surplus clearance for the chain.

    A hub gear or a single speed allows for a narrower Q-factor but because bikes are built to accommodate derailleurs, the Q-factor has to be wider than need be..

    Single speed riding is a small group, and there's probably not a great deal more hub gear users either so I don't see this changing soon.

    Maybe when bottom bracket gearboxes become the norm we'll see narrower Q-factors.
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  22. #22
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    Quote Originally Posted by GiantTurd View Post
    I actually prefer the wide Q-Factor too, for the first time my knees and hips don't hurt on really long rides. I have wide shoulders and hips, first time I rode a Fatty I was like , WOW, man my legs feel good! It has ruined riding road or traditional Q-factor bikes for me.
    Agreed. Similar stature here. Wide Q can be kind to some people

  23. #23
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    Quote Originally Posted by GiantTurd View Post
    I actually prefer the wide Q-Factor too, for the first time my knees and hips don't hurt on really long rides. I have wide shoulders and hips, first time I rode a Fatty I was like , WOW, man my legs feel good! It has ruined riding road or traditional Q-factor bikes for me.
    +1 and I am not particularly wide.


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  24. #24
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    [QUOTE=Velobike;13085059]The fundamental problem with Q-factors for fat bikes is derailleurs.
    Actually the issue is not the derailleur per se, but the multi-cog rear cluster sandwiched between the frame and hub. Extra wide rims/tires force wider frame dimensions near the BB, but the rear hub is wider still; snaking the chainstays into S shapes helps give crank arm and ankle bone clearance, but that interference dictates the wider Q factor.
    Q factor was thought to be important, as most average men have similar pelvic dimensions widthwise, and the principle is to keep the legs moving in parallel planes over the pedals, rather than splaying in or outward, especially when constrained by rigid cleats. Cleat float has helped a lot with knee issues, allowing some flex around the 'plane' concept, but efficiency drops too far out of this ideal alignment. Road and track racers are most affected by bad Q, but MTB trail riders on flat pedals may not experience the effects on rides of a few hours with much of it downhill. At least, not until it gets so ridiculously wide that more begin to suffer. Too late sorry.

  25. #25
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    Since this was bumped to the top I'd like to add recent experiences; I've had a FB since 2013 and in the last 2 years noticed that as I rode it more when I'd go back the the regular bike I'd get really tight IT bands and lower back pain within an hour. (all contact points on both bikes are within fractions of each other) As an experiment I added pedal extenders to the regular bike so that it matched the FB effective pedal width. Over a month in and no physical issues switching back and forth between the bikes.

  26. #26
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    Being a big guy (not just tall, but a large frame) the narrow Q factor bikes always felt weird and gave me odd soreness in my hips and knees. On the fat bike I feel like my legs are finally going straight down, not inward, and I feel great.

  27. #27
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    It must be summer, fat bike threads bumped from the grave, hashing out old arguments

    We need to talk about hub spacing next, then gearing (1x vs 2x), followed by brakes (hydraulic vs mechanical), then we can hit the biggie: Suspension or rigid

    I'll start: 177 hub spacing is the ideal width!

  28. #28
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    Quote Originally Posted by Nurse Ben View Post
    It must be summer, fat bike threads bumped from the grave, hashing out old arguments

    We need to talk about hub spacing next, then gearing (1x vs 2x), followed by brakes (hydraulic vs mechanical), then we can hit the biggie: Suspension or rigid

    I'll start: 177 hub spacing is the ideal width!
    Lol, ok I'll bite. After playing around with 157mm, 177mm, and 197mm rear hub fat, I can say that 177mm allows the most flexibility in the fat tire range. Going "just" 4.0" wide tire? Frames can take advantage of near DH 157mm Q-factor (within 5mm, see RaceFace compatibility chart) and allow a 4.0" tire to fit. Going wider? A true 4.4" wide tire will fit before the chain rubs in the largest rear cassette cog. Some say 4.4-4.6" is all most people need for any fat tire situation.

    157mm rear hub doesn't play well with any fat tire more than an actual 3.8" wide. Offsetting the rear hub 3-5mm and increasing the chain line the same amount can bring tire capacity closer to 4.0" but... why? Until 167mm rear hubs become a reality, move up to 177mm and there's a whole less thinking to do in set up. 157mm rear hub makes sense when the frame doubles as a conventional mtb or "plus" (2.6 - 3.25") bike.

    197mm can be made to work with a 100mm BB shell, which is great but a 100mm BB shell is a compromise for anything less than 4.0" as far as Q-factor is concerned. 197mm works for set ups that call for 4.0 - 4.8" wide tires most of the time. That means winter (i.e. mud and snow).

    Getting back to the Q factor topic and as the OP, through trial and error I find that somewhere between the trail-oriented Turbine (73mm BB shell) and fat bike Next SL (100mm BB shell) is where I *feel* the most comfortable. That conclusion is totally a personal preference. Narrower than 178mm Q-factor (Turbine and 73mm BB shell) and I feel less stable on a mtb; wider than 203mm (Next SL on a 100mm BB shell) and I find pedaling kind of awkward.
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