Fastfwd01

I'm browsing the forum over at Weight Weenies and they seem to talk A LOT about stack and reach over there. I've not picked up much on that here really. I'm in the market for a new bike and this gives me pause for consideration of how it should impact my choice. I might believe this is something that a bike shop would be best equipped to determine, but they are obviously going to only direct you toward the brands they carry.

I have been measured at one bike shop and was put off that they claimed they had a 'program' that would tell them what bikes were the best fit for me and it turned out the 'program' was their malware riddled computer being used to pull up bike manufacture websites and comparing their bike geometry graphics to my measurements one by one possibly based on what they had in stock I might guess.

I have short legs and a long torso. I know one of the suggestions was the Trek Emonda. I'm guessing this falls into the 'long and low' more aggressive race geometry being a good fit for me. I know I was only looking at endurance geometry bikes at the time and I wasn't really wanting to hear that.

I'm pretty clueless how he was judging my measurements against those geometry graphics and I'm gathering different manufacturers follow different principles for their sizing vs. reach. Cervelo for example seeming to more strictly adhere to proportions of reach for smaller sizes. It concerns me a little that I might have an unusual body type.

Is there a good online resource for learning more about this or is this something that most generally can be fitted with different stem if there is an issue?

rpenmanparker 

Stack and reach will invariably determine bike fit. And your riding style will combine with your measurements to determine what stack and reach you require. Stem length and angle, steerer spacers, where you prefer to have your saddle, your handlebar choice are all modifiers of the required stack and reach. Study up a bit more and find a shop you have faith in. If you are still concerned, perhaps investing in a professional fitting before and after your purchase would be worthwhile.

Some folks just work off their current bike and the understanding of how it works for them and compares to the new bikes under consideration. Over a period of 32 years and through many bikes, that has always worked for me.

chaadster

I think Robert's explanation above is confusing and misses the mark.

First, stack and reach do not describe fit, but frame sizing.

Fit is about your position on the bike, and where things (e.g. bars, seat) need to be for you to be comfortable.

Stack and reach tell you how a frame is sized, which gives those knowledgeable enough to know where the seat and bars need to be, an idea of how that's going to happen. Specifically, which stem rise and reach, and seat post extension. Even seat post layback and seat position relative to BB are described by measurements other than stack and reach.

The benefit to knowing stack and reach is not to do with fit, but rather to better understand how frames compare in size, as traditional sizing designations (i.e. seat tube length) never told us much, but is even less relevant today than ever (due to things like compact geometry and new tech that make shaping and building frames more fluid).

So rather than thinking Size 54c (which tells you zippo), think stack and reach. If all frame builders used stack and reach, getting a bike closer to your ideal size would be much easier.

Up North

FYI - if you like the Emonda it is available in H2 fit which is more endurance than speed which is H1 fit. You can check out the geometry of both on Trek's website. It boils down to size of head tube - H2 longer head tube than H1.

chaadster

If longer HT is all it is, that's pretty...well, weak. The thing about stack is that all you need is some combo of longer steerer, spacers, or higher rise stem.

If all Trek is varying between the two geometries is stack, that's purely cosmetics (the irony being that fewer spacers supposedly looks racier, but racers do it to get into a more aggressive position, the opposite of what a taller HT does).

Fastfwd01

I might not have this right, but I'm possibly catching fewer spacers makes for a stiffer headtube?

chaadster

Stiffer head tube? I don't know how that would work, if not completely opposite due to the HT being shorter.

If you mean front-end stiffness in general, that I don't know, though it's certainly possible. I'd guess it would be a negligible point of difference on such a modern bike.

bt

stack and reach? the first numbers I look at when choosing a frame.

nemeseri

The emonda H2 geo is pretty much an endurance frameset. Quite high stack and short reach. I'm short so I was struggling to get as low as I wanted on that frame. It's a very sweet ride though.

You should compare your current bike's reach and stack measurements and compare them to the bike in mind. It will help you pick between sizes.

Very important though that bike manufacturers tend to measure things slightly differently. So you should ride the bike before buying.
For example my size 50 emonda has a 374mm reach on paper and I use it with a 100mm stem. While my caad10 in size 48 has a 368 reach, but even with a 110mm stem the reach is shorter than on the emonda. My specialized Allez in size 49 has a reach of 380mm and with a 100mm stem it's still shorter than the emonda.

So ride them first!

bruce19

Is it accurate to say that frame size for traditional bikes (along with TT measurement) works well as a starting point but the advent of slopping TT frames "created" the need for a more precise measurement criteria/system, thus stack and reach?

chaadster

I don't think there's much accurate in that statement, because the phrasing is awkward, the term "traditional bikes" needs definition and is arbitrary at best, and the use of quotations around the word quoted raises questions as to what you're meaning to say there.

However, I think I know what you're trying to say, and it seems to be calling into question the comments I made upthread, so although you didn't quote me, I guess I need to make a defense of my comments!

Traditional frame sizing was based on length of the seat tube, but because of the customary practice of building a "square" frame, i.e. one where ST and TT were same length, it came to be a shorthand (I guess) for the combined measurements critical to fit.

It worked for several reasons:
- lack of variety in frame design
- less concern with concept of fit
- fewer options for adjusting fit (e.g. bar options)

As technology developed and attitudes shifted, everything changed in frame design and our approach to fit. Even before Giant commercialized compact geometry, builders were stretching TT lengths and playing with angles, so the ST sizing concept was blown as a useful tool, but rather than it getting dropped, we learned to adapt by brand, like in the way we all knew Lemonds had long TTs.

At the same time geometry was changing, components were advancing to make changes fast and easy, but also limiting in some ways (think ahead stems) and our approach to bike fit became more scientific. Tlogether with the preponderance of compact geo design, these elements really made talking frame size by ST length utterly ridiculous.

But what to use instead? S/M/L based schemes seem less ridiculous because it drops the pretense of specificity, but doesn't tell us any of the numbers we need for fitting, so what to do? It's back to the geo tables, then, but that's a lot of numbers and requires some math when comparing frames from different builders with different geometries to know who's M is more medium.

Stack and reach measurements tell us something no other measurements do: where the HT is relative to the BB. It's handy because if you know where you want your bars to be relative to the bottom bracket, your golden, and you can compare different frames more easily.

So S&R are nice to have, but they don't describe fit; you still need to know how you want a bike to fit and have the numbers to figure it out and give S&R meaning. It would certainly be good if all geo tables included the info, and we started to work from them as a baseline....but there's still the question, "what size frame do I need?" I don't think that's ever going to be an easy answer again!

MKahrl

I concur with most of what chaadster said but differ in that traditional sizing on traditional bikes was not as bad as described. When fitted at a bike shop or by anyone knowledgeable the equal seat and top tube frame dimensions got the majority of riders in the right zone. Adjustments to seatpost height, saddle setback, and moving the stem up and down got them there. Sometimes the stem length needed to be changed and that was a pain.

Keep in mind that bike buyers of the 1950's - 1980's were interested all-purpose 10-speeds with handlebars roughly level with the saddle. With the specialization of road bicycles to racing-style fit (low handlebars) and sloping top tubes it became much trickier to figure out where the critical contact points were. Not helped by buying bikes online without any sort of fitting.

therhodeo

What shop are you going to?

bruce19

First, what I posted was not meant to be a statement. It was a question. Thus the question mark. Second, it had nothing to do with anything you said. You are reading way too much into my question. I had a 10 yr. layoff from cycling and when I got back into it things had changed. One of those things was sloping TTs. The only time I had ever seen a sloping TT was when it was a "girl's bike." Everything I had ever seen/read said that to find the right size bike you should start with some formula based on your inseam measurement. (I think Greg LeMond's coach, Cyrille Guimard, said it should be .667 of your inseam in cm) As so many people have pointed out that is not the standard practice anymore. My question was really about the origin of stack and reach as a tool. Since horizontal TTs are no longer common, in fact kind of uncommon,, did stack and reach evolve as a more accurate way of fitting people to slopping TT bikes? Or something like that.

Fastfwd01

Schlegel was where they told me they had a 'program' that they could input my measurements that would tell them what bikes would fit me and there actually wasn't a program. I'm sure the guy might know how my measurements vs. bike geometries would be a fit, but it wasn't the first time I had encountered dishonesty at Schlegels.

rpenmanparker 

As shown by the first quotation above, I never said that stack and reach describe fit. I said they invariably DETERMINE fit. That is a truth that you should know better than to dispute. And one which is hardly confusing. One need not refer to them when trying on a bike, but they are nevertheless the underlying factors in determining fit. They are there whether you choose to refer to them or not. In the complete bike stack and reach are modified by saddle position, crank length, stem length and angle, steerer spacers and such, but the stack and reach are the fundamental determinants of fit. Stack and reach are to the frame what the relationship of the three contact points is to the complete bike.

rpenmanparker 

Think of it this way: Stack and reach were always there, and were always important. But the need to clear the horizontal top tube always used to trump considerations of stack and reach. Now that the sloping top tube gives us the freedom to fit bikes much more perfectly in the areas that really matter, stack and reach have assumed their rightful place as the main considerations.

chaadster

Fit is determined by where the rider wants the bars and seat to be. Stack and reach just tell you what it's going to take to get the bars in position.

In other words, fit is a mutable result, depending on rider desires. The same stack & reach measurements can accommodate a variety of fits.

I just don't see any useful cause to say that S&R determine anything, because except at the limits-- the point at which a frame just doesn't work and cannot be made to fit the rider and/or their needs either physically or in terms of performance and handling-- there are ranges of adjustment at the component level to get the rider in desired position.

Fit is not a set of points fixed in space, it still would not be determined by the frame, but by the rider.

therhodeo

Yeah I'm not the biggest fan of them. You might check out The Bicycle Store up almost to Memorial off the Broadway Ext. They're kind of an odd bunch (know more about bikes than dealing with people) but really know their stuff.

chaadster

Yes, I agree...and thought that's what I was expressing when I said traditional frame sizing worked for a variety of reasons, but I do appreciate the clarity of your simplified comment, specifically that it got riders in the right zone. Absolutely.

RollCNY

OP,
I am of similar build: short legs, long torso, long arms. When I use fit calculators, such as Competitive Cyclists, they spit out numbers that are outside of the realm of any production bike. Going from memory, they say something like a 690mm effective top tube and a 180mm stem for my 6'4" height.

Similarly, when I walk into a shop, they want to steer me to XL frames, or 63's, but I have had far better luck learning what works for me, and that is invariably sizing down. I ride 58/59cm frames, and use saddle to bar drop to get the length that I need. I have never seen an endurance frame that would work comfortably for my body proportions. The taller head tube puts the bars too high, and I end up sitting essentially bolt upright.

I would wager that if your morphology is similar to mine, you could sit on a stock "race" bike and not be uncomfortable. If you look at any models stack and reach by size inside a given model, they get taller much faster than they get longer. I looked at the Allez and Roubaix tables, and going from 49 to 61, reach grows by 2cm and stack grows by 10cm over that range. When you get to larger sizes, quite often bikes get very tall for minimal length, and getting a comfortable position for short legs and long torso/arms gets much more difficult, at least for me.

Good luck.

rpenmanparker 

Is there any reason to choose one size frame instead of another? If not, then stack and reach make no difference. If yes, then that reason is the stack and reach. If you like the fit of frame A and want to find a different brand B that will provide the same fit, you can do that by matching stack and reach. Stack and reach don't tell you what frame you must choose, but once you know what stack and reach work best for you, they will always put you right.

Roll's situation is a good example. Larger size just doesn't work for him, but he knows what does. If he always chooses on the basis of the stack and reach he has found suitable, he will always be happy.

Ergo, stack and reach determine (and reflect) one's optimum fit.

RChung

Close, but not exactly. It was really the invention of the triathlon bike.

79pmooney

My approach to bike fit is to first get the seat in the right position to locate my hips properly over the bottom bracket and cranks. (Sometimes this requires a seatpost with non-standard set-back.) Then I play with how much forward lean I want. (The compromise between comfort and wind resistance.) This locates my shoulders in space. Next is how much arm bend I want to ride with. Now I look at my arms as pivoting around my shoulders. This means my hands swing an arc. But for the small part of the arc that is of interest, ie where the handlebars should be, that arc closely approximates a line, a line that for me has a "slope" of 1 cm of headset spacer/1 cm of horizontal reach.

So I have now located that line in space and can define it as being located at one point in space X cms forward of the BB and Y cms above the BB. Anywhere on that line will give me the same back bend, shoulder location and arm bend. (The positions will not be identical, but over a 4' length of that line, very close in comfort and efficiency.)

This approach makes it possible to get a wide range of bikes to fit me well. Bars low and close (limit being my knees hitting them when I climb) or high and far forward. I pushed that aspect to the extreme on my old commuter which had a very high HT. Put a 180 mm stem on it. Got the shoulder position and comfort and it located my Zipper fairing far forward and high, a great place for it for Seattle winter commutes, often against winter storm winds.

Now what I am saying here IS NOT what anyone else's fit should be. That seat location and shoulder hence handlebar line still need to be determined. Once that is done, finding bikes that fit is just work with the bike specs. I draw the bikes on a CAD program where I have all my other bikes. I can the quickly see what seatpost I need to locate the seat and stem for the bars. (And see if the bike is feasible.) ( have also written programs and a spreadsheet to calculate stems and the weight distribution between the wheels.)

Ben

Fastfwd01

I am on the shorter end of the scale. 5'6" or possibly 5'5 1/2" - I think you understand my concern though. I'm going to have to read up more on this. I think I generally get the idea and it favors me going with a more race geometry bike, but how my measurements factor into the mix still eludes me a bit. I did plug some ballpark numbers into that Competitive Cyclist calculator yesterday and it gave me some dimensions, but my measurements were far from accurate.