The only thing that I look at any more is effective top tube length. If that's in the ball park, I can ride off with other adjustments.

Yeah...the seapost @ 782mm is kinda throwing me a bit....that can be swept forward angle wise, and setback can be used to compensate, then the nose of my saddle no matter what has to be 91mm aft of the BB center (?), yada, yada, yada...I guess my reach = 492mm?

I'm a bit short bus here...

Basically you have the placement of the contact points on a finished bike, but you need stack and reach of a frame. You can achieve those contact point placements on a real frame. Then decide whether you did it in a way thst is pleasing to you. Stem length and angle, number of spacers, position of the saddle on the rails, amount of seatpost exposed, etc. If so, the that is the frame for you. Just record its specs and you are good to go. But suppose the stem is longer than you like by 1 cm. Use trig to determine how much more top tube or frame reach you would need to shorten the stem that much. Suppose the saddle is pushed all the way back on the rails. For every cm you want the saddle clamp closer to the middle of the rails take away 1 degree of seat tube angle. Or if the saddle is too far forward on the clamp, add seat tube angle. Same idea with head tube height, stem flip and spacers. When you are done, you will have the perfect frame design for you.

...not me. #notbibs

Not exactly. You aren't taking angles and spacer stack into account.

.
...as you may or may not know, I have to set up a lot of different bikes (mostly my own). About the only measurements i use in choosing parts like the stem and setting up the overall bike is the distance from the crown of the saddle down to the pedal surface where my feets go (measured along the seat tube), and the more or less center point of the saddle (right about where it clamps to the post.....this can vary from saddle to saddle and bike to bike) to the centerline of the bar (measured along the top tube).

For me, personally, everything else is fine tuning of the saddle position in relationship to the crank spin axis, saddle height and tilt, and maybe tweaking the bar angle a little.

I guess maybe I'm not as fussy as a real dedicated racer, but this works for me, mostly.

That I understand...

How do I correlate my data to that data?


I do need to ensure I preserve my saddle position in relation to the BB...I have used some web widgets to play with stem angles, length, spacers, etc..


This I do not know how to do. Trig? Ha! I was an ace in music theory, I slept through trig...

I'm trying to boil this down to a range of the standard parameters that'll work for me, with some limits set, such as stem length and spacer stack...

I'm pretty sure that most of the people at our shop's Computrainer sessions are triathletes.

Crown of the saddle? Where you place your ass?

Right, I'm not fussy either but as per my fit, on my existing frame I am not engaging my quadriceps when/where I need to on the pedalstroke for full effect, and I'm out of room for adjustment on the bike, I have to compensate when climbing...So, I do want to make sure I'm accounting for and ensuring I have the correct position over the BB...

brb...gotta go ride!

ditto

Those internet calculators will help you. Here's one: Stem Comparison Tool | yojimg.net

I used that jpeg as an underlay for a CAD sketch and came up with:

Eff. Top Tube: 523mm
Eff. Seat Tube (c-c): 653mm
Stem: 90mm
Head Tube: 240mm
Seat Tube angle: 74°
Head Tube angle: 72°

You must have very long legs and a very short torso, correct?

1-4" snow tonight and a high of 33 tomorrow with high winds. I gotta go, too!

Nothing like that off the shelf, that's for sure. Best ready-made frame would be a small endurance frame that would have a short top tube and a tall head tube. Then add lots of spacers and stem flipped up.

In the most basic terms, look back at the original pic you posted and notice that the measurements run from the center of the BB to the center point of the bar/stem interface. On a manufacturer's website, you will see "stack" and "reach" on the geometry chart. This point is generally measure from the center of the BB to the center point of the stem/steerer interface on a stock frame with a slammed tube. So you could consider the measurements on your picture to be "full stack" and "full reach" or something like that.

I hope that made sense...

The frame in that jpeg might be just a dummy frame for pasting stack and reach onto.

Maybe I'll do some trig on it after lunch.

Nope. I scaled it based on one dimension and everything else matched up (within a few tenths of a millimeter and based on my point locations selected by using the pixels in the image).

Thanks Billy. It's made a big difference to how my cycling goes, too. Machka has lost 25kg, and that has made a tremendous difference to her cycling, particularly climbing hills. That's why we are slowly getting back into LD riding.

The old saying is that "Fashion is for people who don't have a style of their own".

lol @ short bus

the reach you need is 401mm

reach is BB>HT center, so you have to come up with the difference with stem length / angle / spacers as mentioned by everyone above

that stack number is gonna tell you what kinda angle / spacer combination youll need

the seatpost measurement is to the top of your saddle so that can be effected by the height of your intended saddle. if youre using one you have you can measure it, add that to whatever the frame mfg says the ST length is and the remainder is your seatpost length. that 91mm depends on the saddle position and the setback on said post.

id +1 to it being a pain in the ass finding a production frame with suitable geo and it not looking fredly. and also +1 to [MENTION=2795]Trsnrtr[/MENTION] 's advice of ETT being most important. i dont know how to trig either.

Can we please get away from this serious bike stuff and get back to the nonsense?

I like to call it frame stack and reach vs. finished bike stack and reach. Or finished bike drop and reach.

Good job. How did you copy and save the jpeg out of BF? I didn't think you could do that.

Yes, this is pretty well how I do it for my and Machka's bikes. We both have bikes that fit us as close to perfectly as we think, and I have used those as the base measurement model for all the others.

That measurement from the crown of the saddle to the pedal at bottom dead centre takes into account the crank length, too, which the measurement provided doesn't. While 15mm doesn't sound like much between a 160 and 175 crank, or even 5mm between 170 and 175, it does involve moving the saddle up and down a little to compensate and that might have a knock-on effect with saddle angle, reach and bar height.