Advertise on Bikeforums.net



User Tag List

Results 1 to 12 of 12
  1. #1
    serenity NOWWW! amahana1's Avatar
    Join Date
    Jul 2004
    Location
    Northern Iraq
    My Bikes
    custom surly SS, several others in the works
    Posts
    319
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    What is Q factor

    I have seen this in a number of threads. I have done a search trying to find what is it exactly with no luck. Also, I have seen BCD used, what is BCD?
    In his surreal surroundings among the clouds, this was his flight! Until, he saw the master caution light.

  2. #2
    BIG RING Bikeophile's Avatar
    Join Date
    Apr 2005
    Location
    Hamilton (Formerly Toronto)
    Posts
    799
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by amahana1
    I have seen this in a number of threads. I have done a search trying to find what is it exactly with no luck. Also, I have seen BCD used, what is BCD?
    BCD = Bolt Circle Diameter. This is the distance from bolt hole to bolt hole on a Chain Ring.


    Q Factor as per Sheldon Brown:

    Q-factor
    In Fit-Kit terminology, this is a factor based on the relative length of the femur compared to the rest of the leg. A large Q-factor is interpreted as an indication that the rider in question needs a frame with a shallower seat tube angle.

    Also, another name for the tread of a crank set.

  3. #3
    Retrogrouch in Training bostontrevor's Avatar
    Join Date
    Sep 2004
    Location
    Knee-deep in the day-to-day
    Posts
    5,484
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

  4. #4
    serenity NOWWW! amahana1's Avatar
    Join Date
    Jul 2004
    Location
    Northern Iraq
    My Bikes
    custom surly SS, several others in the works
    Posts
    319
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    ahhhhh, i see..much appreciated!
    In his surreal surroundings among the clouds, this was his flight! Until, he saw the master caution light.

  5. #5
    King of the Hipsters
    Join Date
    Jan 2005
    Location
    Bend, Oregon
    My Bikes
    Bianchi Pista
    Posts
    2,125
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    In its most common usage, Q-factor simply refers to the side to side distance between the pedals.
    How far apart do the pedals place the rider's feet.

  6. #6
    Direct Hit Not Required BlastRadius's Avatar
    Join Date
    Nov 2003
    Location
    San Bruno, CA
    My Bikes
    Pinarello Galileo, Bianchi Alloro, Guerciotti Cross Force, Iron Horse Hollowpoint MKIII
    Posts
    6,190
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    As said above... but, the Fit-Kit definition is not commonly used.
    Usually Q factor is tread.
    http://www.sheldonbrown.com/bridgest...ne-1991-13.htm

  7. #7
    serenity NOWWW! amahana1's Avatar
    Join Date
    Jul 2004
    Location
    Northern Iraq
    My Bikes
    custom surly SS, several others in the works
    Posts
    319
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    So am I right to assume (great article by the way) that you want your crank-arm pedal spacing, bb spindle to be as close to your natural spacing as possible? Generally speaking, a low Q factor is preferred?
    In his surreal surroundings among the clouds, this was his flight! Until, he saw the master caution light.

  8. #8
    Direct Hit Not Required BlastRadius's Avatar
    Join Date
    Nov 2003
    Location
    San Bruno, CA
    My Bikes
    Pinarello Galileo, Bianchi Alloro, Guerciotti Cross Force, Iron Horse Hollowpoint MKIII
    Posts
    6,190
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I definitely feel better with low-profile cranks than wider tread cranks.

  9. #9
    Immoderator KrisPistofferson's Avatar
    Join Date
    Oct 2004
    Location
    POS Tennessee
    My Bikes
    Gary Fisher Simple City 8, Litespeed Obed
    Posts
    7,596
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Goodness! I always thought "Q factor" was OCP related! As in: "I wanted that carbon fiber kickstand, but it didn't have a high enough Q factor."
    Quote Originally Posted by Bikeforums
    Your rights end where another poster's feelings begin.

  10. #10
    likes avocadoes
    Join Date
    Nov 2004
    Location
    oakland, ca
    My Bikes
    heh, like that info would fit here...
    Posts
    1,125
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Bikeophile
    BCD = Bolt Circle Diameter. This is the distance from bolt hole to bolt hole on a Chain Ring.
    mostly right. BCD is the diameter of the imaginary circle that runs through the centers of the bolt holes.

  11. #11
    BIG RING Bikeophile's Avatar
    Join Date
    Apr 2005
    Location
    Hamilton (Formerly Toronto)
    Posts
    799
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    yeah i guess i could have been more specific...thanks!

  12. #12
    Retrogrouch in Training bostontrevor's Avatar
    Join Date
    Sep 2004
    Location
    Knee-deep in the day-to-day
    Posts
    5,484
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Generally you want a narrower Q.

    Though I've got a set of old Sakae cold forged cranks that when mated to my track bike's BB seat so deep that I have to move the ring to the outside of the spider to get a proper chain line. The cranks have very little flare from the spider, so I'm basically looking at like a 45mm-from-center tread and that actually feels too narrow for me to get decent power.

    Modern cranks have much higher Q factor, both because they're designed to provide clearance for bikes with wider rear triangle spacing (as much as 140mm on some mtb's) than old road (126mm) or track (120mm) bi kes. On top of that, cold forged allows for a slimmer profile than the less expensive manufacturing techniques that are popular now.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •