Let's talk stack and reach

I can certainly buy that and would agree.  What would you say is an allowable tolerance for reach before we start getting too short or too long?  

Agree but for the sake of the discussion, what is defined as "acceptable"; 10mm, 15mm, 20mm?  Assume a fairly adjustable cockpit rather than something completely locked down.  

Is a Shiv L acceptable at 565 / 425   or 6mm more stack and 7mm less reach?

B2 at 556 / 420   3mm less stack and 12mm less reach?

Boardman TT9.0 at  530 / 450  29mm less stack and 18mm more reach?

None of those would be any good. The numbers from the fit should be to the pad. Fit bikes should be to find the relation between all the contact points, meaning where you make contact with the bike. The numbers quoted are frame stack & reach, or to where the stem connects to the frame.  So what you're doing is trying to figure out a combination of frame, stem, and bars to get to the coordinates from the fit session.

I did it the lazy way, after I got fit (RETUL) i had the fitter send me a list of bikes in my prive range that would work.  It was a very specific list (i.e.,. "old" Felt geometry), but addressed the reach with a specific stem length.

And do know that the stem length is also an effective length. An earlier post was brought up about knowing the bars to be used. The pads can be at a different location relative to the bar clamp, and would need a different actual stem to arrive at the same final position. I switched bars and went from a 120 stem to a 90 as the new pads were right over the clamp whereas they were behind on the old set. It will also matter towards stack as some may put the pads on top of the aero sections, whereas others may have them directly on the base bar.

You say it was the lazy way, but I know you did a lot of thinking on this one...

Question:  did the fitter include what cockpit to use for each?  I would imagine (as said above by several - Ben and others), that a difference in the bars could materially affect the fit of a bike, possibly moving one from a bike that "would work" to one that wouldn't.  Was this a consideration, or did you have a hyper adjustable bar set in mind?

Just curious...  Thanks.

Matt

Now we are heading where I was hoping this would go  

Matt - My impression from talking with the fitter was that his recommendations included a consideration of the "stock" cockpit as I was looking at complete bikes.  I only say this because when I settled on a bike, he mentioned that the bars would be perfect for me.  A lot of folks put the 3T aura bars on my frame, I'd be curious to know if that would make the frame unsuitable for me.

As a sidenote, rode the bike last weekend at a 70.3, haven't yet had the frame bike for a fine tuning so re-created the fit best I could.  Very comfortable and very fast.   Big believer in a proper fit (after 8 yeears in the sport!    )

Chris

Ok so this where it gets a bit muddy for me.  My fitter gave me all the numbers but the deciders at the end were stack and reach.  We found those and then we pulled up every bike imaginable and looked at their published stack and reach numbers as well before deciding on the proper bike.  So are you saying straight stack and reach doesn't work?  Extrapolate please.  

As a follow up, too, my fit changes significantly over the season.  I have a long torso (flight surgeon said, "God cheated you out of your legs, but at least you won't break them both when you eject" ) and am happily on a 54cm P2C.

Over the course of the season, though, I dropped my bar - jeesh - almost 2 cm from when I transitioned off the road bike early spring to my late season, super-sprinty (and at that point still comfortable) fit.  Note that I also had to change the seat position a bit to accommodate (mostly to avoid getting speared in the prostate - moved it forward and tilted the nose ever so slightly down along the way).

I suspect that at the start of next season, after a winter on my road bike, I'll need to raise the bars maybe a cm or so and work my way back down.

So, this clearly complicates it a bit, unless you get fit more toward the middle of the season (so it can go either way a bit) or you have your all-season-long fit dialed in and you don't change.  Many people do manage a more aggressive fit as the season progresses, though - just something to consider.

Pros and AG super-elites (you know who you are), maybe not so much.  Shlumps like me, more so.

Matt

Since you have all the numbers it sounds like you should take another look at what they mean. In the first post you listed a stack of 559 and reach of 432. But is that frame dimensions or to the pads? My response of "None of those" was if those dimensions were to the pads, but if those were meant as frame size then you want to look at some other numbers. You want to know to the pads and then figure out the other pieces to reach that. The specifics of each piece all depend on each other. If the bars you like are rather tall (ie the pads are on the aerobars instead of the base bars), you would need to do at least one of the following as compared to using a lower set of bars: use fewer spacers, use a more down-angled stem, use a frame with a lower stack. So the questions as asked aren't quite how you want to look at this. Take a look at what you need to do to get to the fit coordinates given to you. Getting the dimensions of some of the parts could be a little tricky, but maybe one of the other guys would have better info than I do on that.