Saddle setback questions...

[scottcw2]

How do y'all determine your ideal saddle setback?

is it based on where your knee is in relation to the pedal spindle?

does it depend on your riding style?

does anyone use Bontrager's center of gravity method - http://www.sheldonbrown.com/kops.html?

What are the advantages/disadvantages of knee before/behind/above the pedal spindle?

Thanks.

[RPS]

Scott, I stopped measuring my knees over the pedal spindles a very long time ago. I now base my saddle setback on what feels right and comfortable to me. With the exception of my TT bike, my CG is very close to being over the BBKT. Works very well for me.

[Climb01742]

i second doing it by feel.

[scottcw2]

Scott, I stopped measuring my knees over the pedal spindles a very long time ago. I now base my saddle setback on what feels right and comfortable to me. With the exception of my TT bike, my CG is very close to being over the BBKT. Works very well for me.

BBKT = bottom bracket?

[Dave]

Placing the saddle too far forward can place an excessive amount of weight on your hands.

I've experimented quite a bit with saddle fore/aft and found that placing my knee behind the pedal (up to 2cm) allowed me to apply a bit more torque, but may reduce my top cadence a bit. I'm spinner and carry plenty of low gear to permit spinning up the steepest climbs, so I now tend to keep my knee over the pedal spindle or up to 1cm back.

Moving the saddle too far back can foul up the weight balance of the bike. With my saddle far back, the weight percentage on the front can drop to 42% or less. I think my bikes corners better on a technical mountain descent with around 45% on the front. If you never descend a mountain you may never notice the difference.

[RPS]

BBKT = bottom bracket?Yes.

A good way to check is to hold your position as steady as possible and slowly place all your weight on your legs. I do it with the cranks at 3 and 9 position. If I lift my butt off the saddle and hands off the bars at the same time, then I'm balanced over the bottom bracket.

And although I have different bikes set up differently (some more aggressive than others), they all seem to center me directly above the BBKT. May not work for many, but works for me.

[terry b]

I use a home-built jig to place the tip of the saddle 75-80mm behind a vertical line drawn throught the center of the BB (at my ideal saddle height.)

This practice has saved my tired, old knees. Used to do it by guess/feel and it messed me up on more than one occasion. I got to that number with a lot of riding on a "golden" bike that I in turn measured the heck out of.

[bcm119]

Trial and error.

I've always approached it with the idea that your setback determines how efficiently your legs produce power. The further back you sit the more your glutes and hamstrings are engaged... sitting forward uses the quads more. The trick is to find the sweet spot that uses all these muscles "equally", which will depend on your femur length, flexibility, build, etc. I've found theres no magic formula-- trying very small adjustments and listening to your body is the way to go. It takes patience.

[mcteague]

I started trying the knee over pedal setup, using the front of my kneecap rather than the bump below, and then just pay attention to what I am doing. If I keep sliding back on the saddle I move it back. Sitting on the nose too much, move it forward. Your body will tell you what it wants.

Tim McTeague

[SoCalSteve]

I use a home-built jig to place the tip of the saddle 75-80mm behind a vertical line drawn throught the center of the BB (at my ideal saddle height.)

This practice has saved my tired, old knees. Used to do it by guess/feel and it messed me up on more than one occasion. I got to that number with a lot of riding on a "golden" bike that I in turn measured the heck out of.

Thats the key...Finding that "one" right bike, the one that fits you better than all the rest. The one you can do a long ride on at a fast pace and still feel comfortable in the saddle at the end of it...The one that you look forward to riding day after day.

Thats the one that you find every relevant measurement and come close with all your other bikes (if not 100% the same).

Steve

[TAW]

Experience is a good teacher, you find out what feels comfortable and feels most efficient. It's probably also a good idea to check your position in the mirror when making changes. This winter I was on the rollers and noticed in the mirror that my cleat positions were different due to some loosening of the screws. You'd want to make sure that you're not adjusting too much or doing anything completely out of whack.

[MadRocketSci]

Trial and error.

I've always approached it with the idea that your setback determines how efficiently your legs produce power. The further back you sit the more your glutes and hamstrings are engaged... sitting forward uses the quads more. The trick is to find the sweet spot that uses all these muscles "equally", which will depend on your femur length, flexibility, build, etc. I've found theres no magic formula-- trying very small adjustments and listening to your body is the way to go. It takes patience.

if you google "seat tube angle" you'll find some articles, mostly from triathlon sites, that talk about this. In their view, it's the other way around....forward engages hamstring and glutes, further back more quads. Seems to make sense, as if you're sitting directly over the BB then they'll be a lot of pulling on the upstroke from these muscles. Here are a couple of links and quotes:

http://www.tri-ecoach.com/art7.htm

Steep seat tube angles (75.5 to 78 degrees) put you further forward and benefit athletes who have well-developed hamstring muscles (runners).
http://www.slowtwitch.com/mainheadings/techctr/seatangle.html

The authors only guess at the causes for the enhanced ability to perform with the steeper seat angle, and posit about the,

"greater contribution of the hamstrings and gluteus muscles (Heil et al., 1995). Although muscle recruitment cannot be determined from the present results, alterations in muscle recruitment or activation patterns can have the effect of distributing muscular work over a greater muscle mass (increased contribution of the hamstring and gluteus muscles) that would theoretically reduced the work rate per individual muscle fiber (Coyle et al., 1988)."

It seems that saddle set back is trade between different things like comfort, handling, and performance. From the studies cited above efficiency improves with seat tube angle; however, long distance comfort may be compromised with more weight on the hands. There is an optimal set back for a given frame for handling, which again should be traded against the other two factors. That's where the experience comes in - what is important to you, and how much of each function can you give up to get it? Ie, if you ride on the flats all day for huge distances, does handling matter as much as performance/comfort? If you're scared sh*tless on technical descents can you say tolerate a bit more weight on your hands if you need to move your cg forward? Or if you only want to ride 30-50 miles as fast as possible, can you deal with feeling more aches at the end of the ride?

When I read stuff like the articles above I keep thinking of the Trek bikes; They have short setbacks for their sizes (effectively a 75 seat tube angle in size 56) coupled with long top tubes. Maybe they did help LA a little in the TdF with the spinning and efficiency. Probably doesn't make them more comfy, though.

[Peter P.]

After over twenty years of slamming my seat full rearward on the rails regardless of geometry, I just tried the KOPS method this year.

I never fully embraced KOPS because:

1. No one could agree on what part of the knee should be indicated against what part of the crank/pedal.

2. It required the assistance of a friend and I didn't want to bore my buddies with my anal sensibilities.

3. Whenever I casually tried setting my fore/aft using a string method, I always had to slide my seat forward, then I had to raise it. I always thought that raising my seat any amount above the "heels" method would result in a too high seat.

So, after buying Andy Pruitt's book and reading his method a bunch of times, I gave it a try and I'm very satisfied. Here's why:

If I set my seat height using the heels on the pedals method, it feels perfect just to leave my saddle full rearward. But for those last 20 years I always found myself scooting forward on the seat every minute or two and I knew I should be more settled on the bike.

Using Pruitt's method of determining saddle fore/aft, I discovered my leg length discrepancy is in my thigh, and if you follow his instructions you'll be able to see differences as little as 1mm.

After I tried Pruitt's method I was very satisfied as I'm squirming around the saddle much less. I honestly don't think it will improve my performance any though I can feel different muscles being used. It is certainly a comfort issue. I liked it so much I set up all my bikes this way.

I believe if you set your seat height on first go around using any particular method, you're at 90% optimum position. Then set your seat fore/aft using KOPS and you're at 95%. Then re-check your seat height and fore/aft and I'll bet you're so close to perfect as to not bother futzing with it.

Another good thing about these string methods they are easy to see the measured results you know; you can SEE whether the string is touching the end of the crankarm and measure it with a ruler. Methods like Bontrager's do have merit, it's just it relies more on intuition and it's hard to put a real number on it.