Influence of ST< on Top Tube length

[e-RICHIE]

For whatever reason, the concept of achieving proper setback/seat tube angle confuses the crap out of me. I would think (and maybe I'm way off here) that proper steback would be achieved when you are able to place the saddle in the center of the rails and and that spot is the point at which the combination of "comfort" and efficiency of pedal stroke are maximized. That being said, I would think that choice of seatpost amongst any of a number of other things could have a significant effect on this.

i agree. and atmo non-setback seatposts look gay, so they don't get on the menu.

I don't know why I have such a hard time wrapping my head around this concept, but I do. I am further mystified about how one designs a frame around setback without seeing the individual the frame is designed for in person, because I would think that femur length, etc. would/could have an effect on this. I would think for every indivdual there would be some differences in where the "best" setback would be.

agreed. the rider and the position precede a setback. you can't design a frame
without the rider - unless, of course, you are making industrial stuff.

[Dave Kirk]

But what about the 'extended forearm to end of middle finger from the nose of the saddle' reach method.

That one of course is completely and utterly valid.. it's the only thing I use to size.

Sarcasm if not obvious.

dave

[Andy A]

I heart this thread already. I am with Shawn G in that its taken YEARS for me to finally grasp (with my body) what is put so simply in words. Now that I feel like I get it physically, I am now trying to wrap my head around the concepts I've read for so long, put so many ways...this thread is awesome. I know its all about finding that foundational ideal starting point of proper position for power/efficiency/comfort/FLOW... and the setback concept seems at the core of it all once that position is determined. Which will be different for everyone... and start to influence every other of the dozen variables... oy.

[e-RICHIE]

I heart this thread already. I am with Shawn G in that its taken YEARS for me to finally grasp (with my body) what is put so simply in words. Now that I feel like I get it physically, I am now trying to wrap my head around the concepts I've read for so long, put so many ways...this thread is awesome. I know its all about finding that foundational ideal starting point of proper position for power/efficiency/comfort/FLOW... and the setback concept seems at the core of it all. Interested to hear how slacker setback gets you there, and how it influences everything else.

to really grasp this, you must see a rider on a bicycle, and then erase the
picture of the bicycle. the position, assuming it's correct or near so, is a
starting point for conceptualizing what lines connect which points underneath.
it's really not that hard after you've logged in a few thousand fast miles and
made a bunch of frames. there are no formulas and no shortcuts. oh and by
the way, there are no formulas and no shortcuts atmo.

[swoop]

website fit calculators are the devil's instrument.

[zank]

website fit calculators are the devil's instrument.

These things exist? I'm living in the dark ages.

[72gmc]

how long ago did cc drop their online fit calculator? If I remember right it had 'french fit' and 'eddy fit' options--not a knock on cc at all but I do still have the numbers it spit out for me, somewhere.

[Shawn G]

i agree. and atmo non-setback seatposts look gay, so they don't get on the menu.

Noted. But I would think that using a setback post would require the builder to use a steeper seat tube angle to achieve the same saddle setback one would get by using a zero setback post, no? But based on my very limited memory, the bikes I often read guys raving about being so well balanced (Merckx, Pegs and I believe often yours) tend toward a shallower (< 73 degree) STA. Wouldn't a shallower STA combined with a setback post put a riders knee way behind KOPS (if one was looking at this) in most cases? Or is this the goal?

Shawn G

[zank]

Noted. But I would think that using a setback post would require the builder to use a steeper seat tube angle to achieve the same saddle setback one would get by using a zero setback post, no? But based on my very limited memory, the bikes I often read guys raving about being so well balanced (Merckx, Pegs and I believe often yours) tend toward a shallower (< 73 degree) STA. Wouldn't a shallower STA combined with a setback post put a riders knee way behind KOPS (if one was looking at this) in most cases? Or is this the goal?

Shawn G

See Dave Kirk's note regarding KOPS above.

[e-RICHIE]

Noted. But I would think that using a setback post would require the builder to use a steeper seat tube angle to achieve the same saddle setback one would get by using a zero setback post, no? But based on my very limited memory, the bikes I often read guys raving about being so well balanced (Merckx, Pegs and I believe often yours) tend toward a shallower (< 73 degree) STA. Wouldn't a shallower STA combined with a setback post put a riders knee way behind KOPS (if one was looking at this) in most cases? Or is this the goal?

Shawn G

if you really knew me, shallow would be the operative word atmo.

[Andy A]

yes, yes, YES. that's where i am, finally feeling it on bikes that fit me best, that i feel best on when riding hard. i am more aware of the 'me' and less about me fitting the bike. bike needs to intersect theandy, i don't care how it gets done.

to really grasp this, you must see a rider on a bicycle, and then erase the
picture of the bicycle. the position, assuming it's correct or near so, is a
starting point for conceptualizing what lines connect which points underneath.
it's really not that hard after you've logged in a few thousand fast miles and
made a bunch of frames. there are no formulas and no shortcuts. oh and by
the way, there are no formulas and no shortcuts atmo.

[jerk]

balancing the rider's weight between two wheels should be what determines setback and top tube length. no one cares where your knees are. you need weight on your feet to pedal a bicycle and you need a proper amount of hip flexion to pedal a bicycle and you need the bike to be balanced and ride right. so you set the cleats up on the shoes in the right place, put the seat in the right place and the handlebars in the right place- and everything works.

long femurs are genetic gift most good cyclists are blessed with too but that has nothing to do with anything regarding proper bike design.

jerk

[Curt Goodrich]

balancing the rider's weight between two wheels should be what determines setback and top tube length.

jerk

Precisely. And I'll add that that no plumb lines or size cycles or fancy fitting studios are necessary to get there. Common sense and historical context trump gadgetry and there's not need to reinvent geometry and fit.

[GrantM]

to really grasp this, you must see a rider on a bicycle, and then erase the
picture of the bicycle. the position, assuming it's correct or near so, is a
starting point for conceptualizing what lines connect which points underneath.
it's really not that hard after you've logged in a few thousand fast miles and
made a bunch of frames. there are no formulas and no shortcuts. oh and by
the way, there are no formulas and no shortcuts atmo.

what e-Richie does is connect the dots...

The rest of the discussion is about where the wheels go.


-g

[GrantM]

balancing the rider's weight between two wheels should be what determines setback and top tube length.

jerk

On a custom bike, the wheels can go anywhere you want
independent of fit... that's the tricky part. On a stock bike,
changing the fit changes the riders position relative the wheels.

This is why i'm such a firm believer in made to measure bikes.
Fit the rider to their contact points, and set the wheels where
they need to go so the bike rides properly.

-g

[steve garro]

But what about the 'extended forearm to end of middle finger from the nose of the saddle' reach method? That one of course is completely and utterly valid.. it's the only thing I use to size.

Sarcasm if not obvious.

dave

sweet! let's ALL start using cubits! steve.

[steve garro]

Precisely. And I'll add that that no plumb lines or size cycles or fancy fitting studios are necessary to get there. Common sense and historical context trump gadgetry and there's not need to reinvent geometry and fit.

thanks! i've watched some "pro fitters" come up with positions on a size cycle that would be very hard to replicate in reality, and probally impossible to ride. steve.

[GrantM]

Noted. But I would think that using a setback post would require the builder to use a steeper seat tube angle to achieve the same saddle setback one would get by using a zero setback post, no? But based on my very limited memory, the bikes I often read guys raving about being so well balanced (Merckx, Pegs and I believe often yours) tend toward a shallower (< 73 degree) STA. Wouldn't a shallower STA combined with a setback post put a riders knee way behind KOPS (if one was looking at this) in most cases? Or is this the goal?

Shawn G

the saddle just needs to be "where it needs to be". Set back post or not,
it's just an appendenge that either has the correct range or not....

Balance is a personal thingy.
guys like swoop and me have the short femur curse, so our saddle isn't set far back.
It's about the individual, not the frame. "bikes" are neither balanced, or unbalanced,
their rider's are. So there is no generalization about this brand or that brand that
is worth anything in the abstract. A great bicycle is one that the rider has their
position in harmony with the geometry.

[jerk]

On a custom bike, the wheels can go anywhere you want
independent of fit... that's the tricky part. On a stock bike,
changing the fit changes the riders position relative the wheels.

This is why i'm such a firm believer in made to measure bikes.
Fit the rider to their contact points, and set the wheels where
they need to go so the bike rides properly.

-g

there's a really narrow range of wheelbase, front center and chainstay length measurements that still allow a bike with 700c wheels to handle right. that's the problem with made to measure bikes....most people/bike fitters/portlanders/bikeshop rats/frameforum people drafting'em don't get that part....i think in 90% of cases you're better off trusting the stock geos from the builders that already did their homework and put the wheels in the right place. move the fit around a bit-make sure its not at an extreme and it'll work. rarely does one hear complaints that their pinarello/eddymerckx/even trek madone handled like shit.

there are very few people designing bikes i'd actually trust to design bikes.

jerk

[Shawn G]

Maybe I've been starting from the wrong starting point all along.
It seems that most "fitters" put you on a bike based on the position you have, not the position you should have. You walk into a shop, they set you on a bike and ask "how do you feel?" Tough to know how you feel if you don't how you are supposed to feel, I think.

I proposed a version of the following in a PM earlier. Hopefully, said individual won't be upset with my introducing it for discussion here...Based on the above discussion, if I understand it correctly, one wouldn't design a bike based on a pre-determined set of angles and dangles because that is what "feels right" to the buyer, rather one should design a bike around the position a rider should have (for the variables provided by the buyer) thereby guaranteeing that in the end the bike fits like it should vs. what the buyer may think it should fit like?


Shawn G