Weight Distribution on a Bicycle: How Does It Affect Suspension Response?

[Hodgie]

Hey guys,
I'm currently doing a project on bicycle suspension response.
My query is how is a cyclists weight distributed over the two wheels of the bike. I realize it is going to change depending on the position of the cyclist. I'm just concerned with a "normal" recreational position. I am just would the weight on the handlebars be negligible, are is there a ratio between weight into the saddle and weight into the handlebars?
thanks//

 

[minger]

Assuming no acceleration, this problem can be easily solved by summing moments and forces with a free body diagram. Below is my surely failed attempt at an ASCII free body diagram.

       v
^----------------^

Where the v is the force applied by the person, and the ^'s are the wheels. You can sum the moments about any wheel to find the reaction at the other. Sum forces to find the reaction at the other wheel. Since all forces are in the vertical direction, you don't need to worry about vertical distances, only horiztonal.

If we denote $$l_f$$ as the distance between the front wheel and the rider, and $$l_r$$ as the distance between the rider and the rear wheel, and $$W$$ as the weight of the rider, and $$R_f,R_r$$ as the front/rear wheel reactions respectively, then:
$$W l_r - R_f(l_r+l_f) = 0$$
So
$$R_f = \frac{W l_r}{(l_r + l_f)}$$
and
$$R_r = W - R_f$$

ooooo, just seen that you're concerned with weight into the handlebars. Um...you could get into a comfortable riding position, take note of the angle that your arms make, then measure the force with a food scale or something. Find the vertical component and add it to the free body diagram. Subtract it from your weight so that the sum of the downward forces equal the weight. Rinse and repeat.

The horizontal force on the handlebars should cancel out with your butt/feet and doesn't need to be calculated for. I've also assumed negligible weight for the bike.

 

[Hodgie]

Thanks mate, great response##