DIY bike fitting

[lph]

heh-heh. I can see myself approaching my dh saying "Hi, honeeeeyyyy - would you like to measure my gonies tonight?" I've been waving measuring tape around all week as it is.

But my problem was really this: I'd like to compare the distance from where I sit to the bars (both vertical drop and horisontal reach) on all my 3 bikes, to see how different they are (or aren't). But measuring from the saddle is a bit tricky, as the saddles are different lengths, and I don't sit on them the same way. But can't I assume that if each saddle is fitted in the same way*, each saddle, or more precisely, my actual sitting point, will have the same vertical and horisontal distance from the pedal on each bike?

In that case I can use the pedal, or bottom bracket axle since all my cranks are the same length, as a starting point instead of the actual saddle.

(*in my case knee-over-pedal-spindle and heel-on-pedal-plus-a-little)

[HillSlugger]

The measurements I've been using for transferring the setup from the professionally fit bike to the others:
1. center of crank to seat top
2. setback of seat measured as the distance the nose is behind the crank center, measured using a plumb line down from the seat
3. distance from the seat nose to the bars and to the hoods

I've tried to make them as close as possible and it's worked out pretty well.

[Wahine]

If you have had a bike fit and you are just trying to replicate that on different bikes that have similar geometry, the way that MD suggests will work well because it will minimize the effect of seat tube angle which changes the knee over pedal and reach significantly.

If you have a willing participant, the best way to measure your joint angle is to do a brief film of you spinning on a trainer and freeze it with your pedal at dead bottom center (DBC), on a mountain bike or a road bike, that is when the crank is in line (at the bottom of the stroke) with the seat tube. It is not the same as true bottom center, that is the 6 O'clock position. Then you can use a compass to measure the knee angle. The knee angle should be 35 to 40 deg off of straight. Note that this is a different measurement than if you do the measurement statically. If you take the measurement by freeze framing while the person is actually pedaling the ankle movement changes the knee angle and makes it a larger degree of flexion. I like this movement better because is maximizes the fit while taking into account habitual ankle movements.