Originally Posted by Commodus (Post 14436062)

Setback is set in stone, or it should be. No matter what purpose you are putting the bike to. Finding this position on my racing bike, after much trial and error and finally getting a pro fit was a complete revelation in both power output and comfort.

Originally Posted by Brian Ratliff (Post 14436104)

Think about it. Yes, you probably want the three contact points to be fixed relative to each other; however, there is no reason why you can't rotate the whole constellation around the bottom bracket to get a different position. There are plenty of riders who fit their saddles further back and their bars slightly higher and closer to create more power for climbing. Plenty of riders who have a bike with a longer, lower, more saddle forward position for flat races and sprints. Most time trialists and triathletes move their bars down and away to accommodate the much steeper seat tubes of modern time trial bikes.

Fit is all about getting the constellation of contact points right; position relative to the ground is a different story all together.

Originally Posted by ColinL (Post 14436029)

use them together and you have your handlebar position. very simple X-Y coordinates.

Originally Posted by rruff (Post 14436197)

No you don't. Look at my explanation and example above. Two frames with the same Reach can require stems of different length, if their Stack is different. If Reach was defined at a fixed height and not allowed to vary with Stack, then you would use the same stem length with every frame that has the same Reach.

Originally Posted by Commodus (Post 14436161)

Sure, but setback determines the balance of your body on the bike relative to the force you're outputting into the pedals. If I set mine up with too little or too less, I get lesser or greater amounts of my weight on the seat and my hands, shifted from my feet. Even disregarding comfort issues, if you are not balanced on the bike, you can't transition properly - you have to shift your weight to stand for a climb, or a sprint, and then shift it again to sit back down. Impossible? Of course not, but isn't the point of fit to optimize your position on the bike?

Of course if you don't have to transition, this becomes a far murkier discussion - hence your very valid examples of TTs and flat races.

Originally Posted by bored117 (Post 14435737)

In all honesty datlas, I want to see you on bike just to further my understanding of bike fit. When I looked at your bike I assumed you are pretty much all legs... Wondering if my assumption is right :)

Originally Posted by Brian Ratliff (Post 14436241)

Your weight balance does not change significantly until we start talking about massive changes in position; on the order of several inches. A TT position (non-UCI legal, which is typical in the amateur ranks) shifts the center of gravity of the rider forward by over two inches. That kind of shift can affect bike handling, but it certainly is rideable. Smaller shifts of less than an inch can't really change very much. A shift of 10mm in saddle is only a change of 1% in weight distribution between wheels.

As far as standing and stuff on your bike, if little changes affect your ability to move around on the bike, you have issues besides mere bike fit.

Originally Posted by Brian Ratliff (Post 14436241)

Your weight balance does not change significantly until we start talking about massive changes in position; on the order of several inches. A TT position (non-UCI legal, which is typical in the amateur ranks) shifts the center of gravity of the rider forward by over two inches. That kind of shift can affect bike handling, but it certainly is rideable. Smaller shifts of less than an inch can't really change very much. A shift of 10mm in saddle is only a change of 1% in weight distribution between wheels.

As far as standing and stuff on your bike, if little changes affect your ability to move around on the bike, you have issues besides mere bike fit.

Originally Posted by Commodus (Post 14436279)

Based on my own experiences, my researching regarding fit, the endless 'favourite saddle' threads here on BF and what I've seen on various events and group rides, these 'little changes' affect everyone.

But if you don't think so, I can certainly understand your indifference toward STA, and bike fit in general.

Originally Posted by Brian Ratliff (Post 14436459)

People are in the mindset that each contact point is independent. I'm saying they aren't. You want a lower position but you don't want to affect your power production, you don't just move your bars down. That would close your hip angle and affect your power. You increase the stem length and move your saddle forward and (slightly) up at the same time so your hands, feet, and saddle say in the same position relative to each other. Your power production says the same but now you are in a lower position.

Originally Posted by ColinL (Post 14436488)

Uh, how did your feet move? They didn't.

That's the reason we don't touch saddle setback. Even if you move your cleats, this changes the fulcrum on your foot, which can not only affect power but also comfort and even cause problems with your plantar fascia or achilles.

Originally Posted by Brian Ratliff (Post 14436528)

Your feet go around in a circle. A circle has no top or bottom. Why is this hard?

Originally Posted by Commodus (Post 14436541)

Cuz this particular circle does have a top and a bottom, and more importantly for cyclists, it has a front and rear.

Originally Posted by Brian Ratliff (Post 14436556)

So then, do you make position adjustments when the ground slopes upward? However do you manage if you have to get off to change your saddle setback every time you go up a steep hill? Does your circle-with-a-top-and-bottom crankset reorient itself when you get out of the saddle? However does it know when to do this? You push a button or something?

Originally Posted by Brian Ratliff (Post 14436528)

Your feet go around in a circle. A circle has no top or bottom. Why is this hard?

Originally Posted by ColinL (Post 14436636)

really? take 3 pics of yourself on your bike with your saddle where it is now, and then with the saddle bottomed out fore and then aft on the rails with your feet at the 3 and 9 position. it will change your knee angle tremendously.

some people are super sensitive to fit, but if you really size your bike like that Brian, you are either missing out (as Commodus said before) or you're performing well but strangely insensitive to fit.

Originally Posted by ColinL (Post 14436670)

are you taking lessons from Campag4Life? :lol: let's simmer down.
...

Originally Posted by Brian Ratliff (Post 14436637)

So you are saying the front and back of the circle are dictated by the frame? Are recumbent riders just screwed then? Where is the front and back of their pedal circle?

Originally Posted by Brian Ratliff (Post 14436214)

You are hung up on using stack and reach separately to compare frames.

Originally Posted by Brian Ratliff (Post 14436459)

You want a lower position but you don't want to affect your power production, you don't just move your bars down. That would close your hip angle and affect your power. You increase the stem length and move your saddle forward and (slightly) up at the same time so your hands, feet, and saddle say in the same position relative to each other. Your power production says the same but now you are in a lower position.

Yes, your hands have more weight on them. True. But this is not a fit issue, this is just a consequence of gravity. Fit is about biomechanics. Gravity is gravity. Rotate the position up if you want less gravity on your hands.

Originally Posted by datlas (Post 14438773)

ok, i finally got my 10 year old to take a picture of me on my bike so i can demonstrate how the bike in question fits me.

I had to hold onto the obligatory white garage door with one hand, but i think you get the idea...this is my "jra" position, what i do 75% of the time. If pulling at the front, i bring my forearms down parallel to the ground.

http://i1228.photobucket.com/albums/...s2/photo-1.jpg