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fore/aft position???(9 posts)

fore/aft position???John445
Apr 30, 2002 5:12 AM
I know the theory in finding a good starting point for my fore/aft position on the saddle is to get the plumb bob directly over my pedal axle. My question is, where on my knee do I hold the string. I have read, the bony protrusion under the kneecap, also the bony protrusion on the inside of the knee. Anyone know a more exact point. These tests show I am too far back, but I have my seat all the way forward.

re: fore/aft position???Len J
Apr 30, 2002 5:29 AM
Sounds like you need a new seatpost. One with less setback.
What kind of bike? Seattube angle? Femur length?

Both the positions you mention are starting points, you need to find the position that is most comfortable, and powerful, for you. Most riders are between a few CM behind to ahead of the spindle. Mashers tend to be behind, spinners tend to be ahead.

A Couple of other things:

Make changes slowly, a few MM at a time, so as not to put undue stress on your body.

As you move the seat forward, you need to lower the seat a little to maintain a consistant height. Measure the distance from the center of the BB to the top of the post, and reproduce this as you move the seat forward.

re: fore/aft position???SteveO
Apr 30, 2002 5:36 AM
forward requires higher (at least until youre substantially forward of the bb)
Your right, flunked geometry! nmLen J
Apr 30, 2002 5:48 AM
re: fore/aft position???cyclopathic
Apr 30, 2002 7:49 AM
it is usually either kneecap or bony protrusion just behind (1-2cm), joint's rotating point.
variations allowed...C-40
Apr 30, 2002 8:30 AM
I've never had much luck with the knee placed directly over the pedal spindle. Too much spin and not enough torque in this position, for me.

It's not so important where you place the string, but that you be consistent when taking measurements. All this does is get you in the ballpark. From there, you have to go by feel. I just setup a new C-40 and used the plumb bob as accurately as I could (by myself) to set the saddle position to match my old C-40. I knew in the first 5 minutes that the saddle was further forward than normal, just by the feel. Moved the saddle back less than 1cm and it felt like what I was used to.
Seat tip relative to BB Centerjpa
Apr 30, 2002 11:20 AM
Once you have it dialed or if you have a second bike that is dialed measure the horizontal distance from the tip of your saddle to the vertical center line of your BB. Drop a plumbline from the tip of your saddle and measure to the center of the BB. Remember this measurement and BB to top of seat and dialing in a new bike or second bike will be cake!
only with the same saddle...C-40
Apr 30, 2002 1:11 PM
Saddles vary so much in length and shape that measurements from the tip of the saddle aren't valid unless both bikes use the same saddle.
re: fore/aft position???jswhern
Apr 30, 2002 6:03 PM
place your line on the tibal tuberosity just below your patella.