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  1. #1
    Senior Member
    Join Date
    Feb 2010
    Houston TX area
    My Bikes
    Trek 1420 triple, Mercier Corvus, Globe 1 700, Surly Disc Trucker, GT Avalanche, GT Grade, GT Aggressor, GT Helion, Mercier Corvus
    1 Post(s)
    0 Thread(s)

    Seat tube angle to center of bottom bracket distances for different leg lengths ?

    Are there any charts that show for different seat tube angles and different leg lengths (upper and lower leg leg lengths) where the ball of the foot ends up on the pedal stroke?

    this one is difficult for me to put into words but let me try a description: I want to get a Surly Disk Trucker for a 62 cm frame it has a 72 degree seat tube angle. Is there any chart that shows for a particular leg part length how far back the saddle should be behind the center line of the seat tube to get the ball of the foot over the center line of the crank

    Disc Trucker | Bikes | Surly Bikes

    I want to ride in a nearly upright position and will adjust stem and handlebar selection to get me well above the saddle height to get an upright position.

    My premise is that seat position should only be used to adjust where the foot is over the pedal and not to adjust for reach length.

    I need an engineer to do some math for math for me

  2. #2
    Senior Member
    Join Date
    Jul 2005
    17 Post(s)
    0 Thread(s)
    I do not know of any such chart. It's really not that pressing an issue for most people. Surly's market for the disc Trucker is people who are going to be riding in an rpm range of between 60 rpm and 90 rpm. KOPS is nice to achieve and I like it because I emphasize spin in my riding and am frequently up at 100 rpm cadence. This is on my commute mind you. Most people are riding well behind KOPS and are fine with that. Well, a lot aren't but it isn't the KOPS that is at issue, its reach as you obviously know but they don't want to spend the $$ for new stems and/or bars or seatposts to get their reach right, KOPS or no KOPS. If the Trucker has a 72* seat tube angle you will have to work at getting to KOPS with a 62cm frame! I would think a zero setback seatpost at a minimum. Well it would be hard for me. You might be taller than me. There actually is an app that will measure how far back you need to sit to achieve KOPS, its called "Plumb Bob".


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