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Fit Calculators(5 posts)

Fit Calculatorscollinsc
Nov 29, 2003 2:05 PM
A while back I was playing with the Competitive Cyclist fit calculator. Just recently, I found my old results (which I guess I had never really studied before) and got to wondering, just what do they mean by "saddle setback"?

The whole business looks like this:

Fit Calculator Output (cm)
Seat tube range c-c: 54.3 - 54.8
Seat tube range c-t: 56.0 - 56.5
Top tube length: 56.4 - 56.8
Stem Length: 11.9 - 12.5
BB-Saddle Position: 71.8 - 73.8
Saddle-Handlebar: 56.2 - 56.8
Saddle Setback: 6.9 - 7.3
Seatpost Type: SETBACK

Lemond Output (cm)
Seat tube c-c: 54.5
Seat tube c-t: 56.2
Effective reach: 70.7
BB-Saddle Position: 74.0

How is "saddle setback" (and "saddle-handlebar" for that matter) supposed to be measured?
worthless dimensions...C-40
Nov 29, 2003 4:55 PM
The saddle setback is the horizontal distance from the tip of the saddle to the center of the bottom bracket. A plumb bob is dropped from the tip of the saddle to take this measurement.

The saddle to handlebar dimension would be a measurement from the tip of the saddle to the center of the handlebars.

Since there is no standard length for saddles and saddle width varies significantly, different brands of saddles will not place the rider in the same position relative to the bottom bracket, simply by taking measurements from the tip of the saddle.

None of these fit calculators can acutally produce very accurate frame dimensions, due to the inherent inaccuracy in taking body measurments. Most also have no way to determine an appropriate seat tube angle, because it is very difficult to measure the length of the femur.

You are better off riding a real bike that is close to the proper size and fine-tuning the fit over several hundred miles of experimentation.
pretty much what I had figuredcollinsc
Nov 29, 2003 8:07 PM
The variables involved in figuring out this value are pretty incredible. I must think though, that there should be some decent way of deciding where you should park you ass. KOPS doesnt cut it.

I am essentially wondering if there is a better way to decide if I should knock my saddle back that last half inch (on my straight shaft Thomson) or if I should experiment with some old Ritchey with setback.

I am expecting something similar to the "fine-tuning the fit over several hundred miles of experimentation" answer, which is fine, but a better starting point would be handy.
alternate opinionhudsonite
Nov 30, 2003 5:58 AM
I have been riding race bikes for a long time (30+years). Over time you make adjustments to 'dial in' the fit. So now my bikes feel right for me and I know what I like.

For grins I did the competitive cyclist fit calculator for myself and a buddy (also 30+ years on racing bikes). It turns out that the measurements that were spit out were almost bang on to our dialed in bikes. Particularly the saddle to bar and saddle to BB.

When I started the process I thought that they would be way off. When I finsished the process I had more respect for their fit calculator.

Now it is obvious that what it spits out is disjointed to bike/saddle geometries, but it has value if you know how to interpret bike measurements.

The CC fit calculator is a tool. As in all tools it has a place. But it does not remove the need for other fitting tools, including expereince and a 'brain'.
nothing wrong with KOP...C-40
Nov 30, 2003 7:54 AM
Setting the knee directly over the pedal spindle is a fine starting point, although taking this measurment requires help from an assistant to be very accurate. I've tried to eyeball it by myself and found the results to be pretty poor.

What I've found from many years of experimentation is that there is at least a 1-2cm range of saddle fore-aft position that will produce good results. I've placed my knee anywhere from a bit forward to 2cm behind the pedal spindle without creating any problems. The further back the saddle is moved, the greater the torque that can be applied to the pedals. I'm trying a further-back position now that I'm doing a lot of mountain climbing in Colorado. The further back position definitely favors a higher torque and lower cadence style. I still climb with a preferred cadence of 85-90, but I can drop as low as 70 if I'm riding a double and run out of gear.

Saddle height is also critical. Placing the saddle too high was my biggest mistake. A too-high saddle can significntly reduce cadence and power, since power = cadence x torque. If you move the saddle back, be sure to drop the saddle height .3cm for each 1cm of saddle setback.