Advertise on Bikeforums.net



User Tag List

Results 1 to 11 of 11
  1. #1
    Older than dirt CCrew's Avatar
    Join Date
    May 2008
    Location
    Winchester, VA
    My Bikes
    Too darn many.. latest count is 11
    Posts
    5,345
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    172.5 to 175: Noticeable?

    Offered a deal on a 175 crank armed Ultegra to replace my crappy 172.5 FSA. Is the crank arm length really noticeable? I'll admit going in that I'm old and have cranky knees, and all my bikes are 172.5. Its a deal from a friend that gave him fits trying from 170, so although he's about giving it to me ($50) Id feel bad trying and flipping it if it didn't work. I'd ask to borrow it and buy it if it works, but it's about new and if I did that and it didn't work really wouldn't be "right" to hand them back.

    Thoughts? (not on the deal, just whether it's a huge/noticeable change)

  2. #2
    Senior Member zonatandem's Avatar
    Join Date
    Dec 2003
    Location
    Tucson, AZ
    My Bikes
    ariZona carbon fiber tandem & single
    Posts
    10,111
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    You will not notice . . .
    Once worked on a tandem whereby someone had mixed up the crossover cranks between stoker and pilot (pilot was 175, stoker was 170) neither rider had noticed!

  3. #3
    Guest
    Join Date
    Jul 2008
    Location
    Grid Reference, SK
    My Bikes
    I never learned to ride a bike. It is my deepest shame.
    Posts
    3,769
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It is a subtle difference. I have 170s on my old road bike and 180s on my mountain bike and I can percieve a difference when I think about it, but if I had just hopped on to a bike with without knowing the crank length it wouldn't be the first thing I would notice. 172.5 to 175 will be noticeable but not distracting.

  4. #4
    Senior Member
    Join Date
    Nov 2009
    Posts
    7,118
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    you probably wont notice.

    i have 172.5 on my fixed gear, 175 on my aluminum bike, and 180 on my steel bike.

    my "ideal" length according to one measurement is 177mm or something like that. some days i think i can feel the difference between the 175 and 180s but i cant tell a thing between the 172.5s and 175s

  5. #5
    AEO
    AEO is offline
    Senior Member AEO's Avatar
    Join Date
    Jun 2007
    Location
    A Coffin Called Earth. or Toronto, ON
    My Bikes
    Bianchi, Miyata, Dahon, Rossin
    Posts
    12,255
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    it depends on your leg length and flexibility.
    If you legs are long and you're flexible, then you're very unlikely to notice the difference. The only difference you might notice is that your cadence has dropped by single digits.

    If your legs are short, even for 172.5mm cranks, then you will most likely notice it.
    If your legs are short and you're not very flexible, then you will notice it.

    and even then, there are variations in how the legs are proportioned, so you might feel it, or not.

    For me, I notice I have a much easier time using 165mm cranks due to my limited flexibility.
    Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
    http://sanfrancisco.ibtimes.com/arti...ger-photos.htm

  6. #6
    Senior Member
    Join Date
    Jun 2010
    Location
    Pearland, Texas
    My Bikes
    Cannondale, Trek, Raleigh, Santana
    Posts
    5,721
    Mentioned
    7 Post(s)
    Tagged
    0 Thread(s)
    CCrew, My road bike's cranksets range from one 165 mm, two 172.5 mm and one 175 mm. If I jump from one straight to another I can tell the difference for the first few revolutions and then I adapt and it becomes a non issue. Your knees will have more range of motion, but work output will diminish a tad because of the added mechanical leverage.

    If they don't work, flip them and split any profit with your friend.

    Brad

  7. #7
    Senior Member
    Join Date
    Sep 2010
    Location
    Wyoming
    Posts
    69
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Ccrew,

    You mention that you have creaky knees. For this this reason I highly recommend that you not incrase the length of the crankarms. Longer crankarms cause your knee to bend more at the top of your pedal stroke. This "hyperflexion" (I believe that is the correct word) puts more strain on the knee joint. You may not feel the difference after a test ride or ever after a few medium distance riders but you will start to feel the pain in your knees the more your ride with the longer crank arms. Stick with shorter crankarms and higher rpms for the sake of your knees. I speak from experience.

  8. #8
    Desert Flatlander
    Join Date
    Jan 2009
    Location
    Buckeye, AZ
    My Bikes
    2001 Trek Alpha 1000, Micargi Tahiti NX3 'The Iron Horse', and many other cheap resale and family bikes.
    Posts
    80
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    If they don't work give your friend the opportunity to flip them. If they don't want to and you don't feel right about making a profit, then pay it forward and sell them for the same price. I like to flip bikes, when I have a friend that wants one I pay it forward and sell it to them for what I paid, with the free tune-up.

  9. #9
    Senior Member
    Join Date
    Feb 2009
    Posts
    4,149
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    My knees do not like 175's and are happy with 172.5. My leg length in bare feet is 33.75".

  10. #10
    Senior Member
    Join Date
    Jul 2005
    Posts
    3,193
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Yeah, when I went to 165's from 170's, my cranky old knees really liked it. You're going in the wrong direction. bk

  11. #11
    I have senior moments... bikinfool's Avatar
    Join Date
    Oct 2008
    Location
    Woodside, CA
    My Bikes
    Many
    Posts
    2,153
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Can only say the difference might be noticeable. I've used 170/172.5/175 on a variety of bikes. Used a 177.5 for a while on one bike and my knees said no. YMMV.
    suum quique
    Mountain bikes: Santa Cruz Hecklers (99, 02, 07), Santa Cruz Nomad, Moots YBB, Trek OCLV Pro Issue, American Breezer
    Road bikes: TST, Trek 2300 (Carbon/Alum)

Posting Permissions

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