johngwheeler

One thing I've learned from reading bike specifications is that manufacturers' interpretation of frame sizes vary greatly, be they in cm or "t-shirt sizes", so I've started using geometry tables to get an idea of the true size.

I've noticed quite a variation in Stack and Reach sizes for the same nominal size between models, even within the same general category of bike (road race, endurance, CX, gravel etc. ).

My question is how much variation from a theoretical "optimal" Stack & Reach for an individual is typically possible through adjustments to saddle, stem, and bars?

I realise that this will be a bit subjective, and that for some people a big variation in something like stem length may be unacceptable, but OK for others.

An an example, let's suppose you found a bike you liked that was a bit large or small, or had some aspect of its geometry that was a bit different to what you'd like, but which is otherwise what you are looking for.

How much adjustment is possible to get the bike to fit you?

I'll attempt to answer my own question, based on what I know so far, but I'd welcome any corrections!

Reach not ideal:
shorter or longer stem +/- 2-3cm (maybe 70-130mm) ,
compact/longer bars with less/more reach to hoods +/- 1cm?,
move saddle forward (not ideal, I know) +/- 2cm

Stack not ideal:
Spacers under stem: +/- 3cm
Bar rotation angle +/- 1cm?
"Hover bar" +/- 2cm?
raise/lower saddle - very little adjustment from ideal without compromising power, knee health etc. - maybe +/- 1cm?
Crank length - +/- 5mm

Assuming the non-ideally sized bike is somewhere in the middle of the adjustment range of the above, perhaps there is possible adjustment of 5-6cm in "effective reach and stack".

Or you could just shop around for a bike that fits perfectly without changing anything....

I'd be interested if my thinking is on-track or way off course :-)

(BTW: my interest in this topic is because I've borrowed a bike that is a bit large for me, and I'm experimenting with the above to see if I can make the bike fit me - or to determine whether I should just find something else )

Dean V

A lot of adjustment.
I have ridden Giant TCR in Small, Medium, and Medium/Large. Medium the best but the other 2 sizes ok as well.
Same fit on all of them. Saddle height, setback, Hbar drop, reach, all the same.
130mm stem flipped up on the small. 100mm stem slammed on the M/L.

johngwheeler

Good answer! It's kind of what I suspected - there is a "best fit", but others can work with a bit of adjustment. I'm waiting for a shorter stem for the large (58cm) Fuji endurance bike I'm testing; I fit OK normally fit on a 54 or 56cm Trek Domane, but these seem closer to a 56-58cm on Specialized Roubaix, so there can easily be a 2cm variation between brands.

I imagine there are two key factors here:

1) Can the bike be set up to an optimal fit without compromising function (e.g. Saddle height / setback)

2) Do you prefer the feel of a larger or smaller bike in terms of handling.

wphamilton

Preferring smaller or larger frame depends on how you want to ride IMO.

I came to this when researching different kinds of fit, such as "French fit", "Eddy fit", "competitive fit" and so on. Among these various fits, or more accurately riding positions, the same person would prefer different sized frames!

Having the same position on the other hand, the difference between using a small frame with a longer raised stem and seat post, vs a larger frame set up with the same position, is going to be manifested mainly in how the bike handles. Shorter wheel base, body weight shifted forward relative to the front axle. Smaller frame is stiffer. It's going to feel just slightly different.

rpenmanparker 

I would compress your ranges of adjustability due to three factors.

First, there is no adjustability in saddle position if you want what is best for your comfort, performance and skeletal health. The saddle just goes where it goes to give you those results, and you have no other say about it.

Second, if aesthetics mean anything to you, I would say the stem angle should not be outside of the 6-8° range either up or down, preferably down. Again regarding looks, the stem length should not be more than +/- 1 cm away from these norms of frame and stem size: 52 cm/9 cm, 54 cm/10 cm, 56 cm/11 cm and 58 cm 12 cm.

Third, if you care where the tops of your bar are located, then bar design is no help. The tops don't change with different bar drop and reach. And, even regarding the hoods and hooks, if you like a certain style, brand, material, and weight, you don't have much choice in drop and reach. Those other factors pretty much lock you in. You can get some relief from the bar angle and place you attach the levers, however.

All in all, I recommend buying the optimum frame size that allows you to keep your parts choices right in the center of the ranges I have outlined. What is the point of doing otherwise?

Maelochs

Amplifying what Mr. Penmanparker says ... if you are going to buy a new bike, simply do not buy a bike which isn't very far from optimal.

Unless you have certain strictures---for instance, if you want a specific C&V bike which is hardly ever for sale ... but there, how could you buy all the adjustment parts? if you are buying a bunch of super-cheap bikes ... but better simply never to buy anything which isn't pretty much right in your range.

I don't care what others think about how my bikes look ... when they buy my bike, they can buy me the bike They want me to ride. I will use as many spacers and whatever stem length and angle suits me. Still ... if I am going to buy a bike, I will not bike which doesn't fit or isn't really close to being right on.

johngwheeler

Good advice; thanks! I think getting a bike that isn't already at the limits in either direction (too small or too big) is definitely to be recommended, just to have some latitude for minor adjustment. There is probably less adjustment in practice than my 5-6cm guesstimate. More like 2cm with stem changes and spacers.

However there can easily be 2-3cm variation in frame geometry for the same nominal frame size from different manufacturers, so it seems really important to have an idea of what geometry dimensions will work for the individual.

My personal experience is a bit limited, but illustrative. My first bike (Trek Crossrip 54cm) seemed just about right (I had tested a 56cm and 54cm, and both were OK, but the 54cm just felt a bit less stretched out and more controllable). My second bike (Giant TCX) was a medium, recommended by the LBS, and in-line with Giant's sizing charts for my height (177cm). However, I think I probably would have been better choosing medium/large because I have long legs for my height, and prefer to have less saddle-to-bar drop. My current test bike is a Fuji Gran Fondo (large, I think, but there are no labels on the frame) - this is definitely a bit too big, but may be correctable with a shorter stem.

I guess I got lucky with the Trek, and had a better experience at the LBS who had both sizes and let me try them. The Giant dealership only had the medium in stock, so this is what they wanted to sell!

I had a bike fit on the medium-sized Giant, and between this and my Trek, I probably have enough data to determine my optimal frame size. There is of course no guarantee that these will coincide with bikes that I am interested in, which is why I asked the question about the amount of available adjustment.

Thanks!

John

redlude97

this is why we use stack and reach now. No variation between manufacturers in terms of how these are measured so it is easy to compare

johngwheeler

I agree. Now I just need to dial-in my perfect stack and reach numbers for a given style of bike.

My next bike will be either an endurance road bike or a gravel bike (at the "road-end" of the spectrum), so I'm looking to determine the following:

1) My ideal reach for an "endurance riding position" with a medium-length stem (100-110mm). Something that gives me good control (elbows closer in to body) but reduces weight on my hands during long rides.

2) My ideal stack to get minimal saddle-to-bar drop (<2cm). I have long legs for my height (cycling inseam of 875mm / 34.4" for a height of 177cm / 5'9.5") so I need a reasonably high stack height to achieve the correct saddle height and a low bar drop.

I reckon reach = 385mm, stack = 590mm would be a good starting point for me, at 177cm/5'9.5"

John

redlude97

sounds like a good guru dynamic fit is money well spent. this will answer sizing questions for you for different riding types.

79pmooney

My take (and this is something I consider very important): First: stack and reach have nothing to do with the seat position. They are the dimensions to the centerline of the steerer tube at the top of the headset from the bottom bracket (and handlebar stack and reach is from the BB to the center of the handlebar tops).

I have a drawing of all my bikes with all the BBs located at the drawing origin. I know the distance the seat needs to be from the BB. Also how far back it needs to be. Also the handlebar stack and reach.

I may rotate this entire triangle forward, bring the bars also down for fix gears to get my position lower for upwind work. For bikes intended to be more of a cruiser, I rotate the triangle back.

I also play with handlebar position based on my experience that there is, for me at least, an optimum place for my shoulders for good, comfortable and aero forward lean. Also an optimum elbow bend; too much gets tiring, too straight leads to injuries and control issues. That means my arms can swing through an arc without moving my shoulders. The small portion of that arc that are reasonable handlebar positions for me are very close to a line of "slope" 2 cm horizontal, 1 cm along the line of the steerer. (Very convenient for me. A -17 degree, ie horizontal, 130mm stem with a 1/2cm spacer is the same as a 120mm -17 stem with no spacer.) Different positions along this line feel different, but I see virtually no difference in either power or comfort. Closer and lower is probably slightly more power (and slightly better traction out of the saddle on very steep slopes, longer and higher is more aero and more comfortable on long climbs.

This handlebar line gets rotated along with the seat for the fix gear low position or laid back comfort. I also raise this line a little for comfort bikes, being quite aware that I will pay for that if I have produce long term power.

So, johngwheeler, in answer to your question as it relates to various bikes: I put prospective frames on the drawing. Then I sketch in a stem between that frame and my handlebar line. Do I like that stem? Is it a stock stem even? The bars have to land on my "line". That is non-negotiable. I will have a custom built if I really want "that bike" and my drawing says it will require a 155cm -25 to get there. (I also check the weight balance between the wheels. I will not pay thousands for a bike with a poor weight balance. I consider it a fact of life that the used stock bikes I buy as commuters and city bikes will require huge custom stems (often 180mm) and weight balance will be poor. But I don't own or ride those bike for pure joy. New or over $1000, the bars have to be on that line and the weight balance needs to be good.

Sucks having far from "average" proportions. And it sucks (or was it a true blessing) that I was arm-twisted to buy an unusual race bike that fit me to a "T" when I was 24 yo. Changed my life (and standards) forever.

So a long answer. But in short, yes, I take stack and reach very, very seriously. Completely make or break when i look at a bike. Nothing else measures up in importance.

Ben

Maelochs

This needs to be a sticky .... https://www.competitivecyclist.com/S...ulatorBike.jsp

motosonic

This is fantastic! Thank you!

rm -rf

This Stem Comparison Tool is very useful along with stack and reach. It shows the change in horizontal (reach) and vertical (stack) position of the bars with different spacers, stem lengths, or stem angles.

Otherwise, it's hard to estimate what effect different stem angles will have.

~~~~~
Bike fit
I've had a couple of paid bike fits over the years.

One had the computerized video that calculated leg angles, knee position through the whole pedal stroke, etc. I was on one of those fully adjustable fitting bikes, so we could easily reposition the saddle and bars anywhere in space. It was helpful, and I was a fairly new road bike rider who didn't really know the best setup.

Years later, when I was shopping for a nice road bike, I wanted to fine tune the fit before picking a frame size. After this session, I used stack and reach compared to my current bike to get a bike that would put me in the middle of it's range of adjustments.

The fitter put my current bike on a trainer mounted on a swivel platform, and did a few measurements, but mostly watched from different angles as I pedaled. We made a few somewhat minor adjustments that were quite helpful. This was good.

It's interesting how both high tech and/or an experienced eye can get good results.

Wheever

Oh! Thanks for posting that! I just replaced my -7° stem with a -6° and fudge it by subtracting a 5mm spacer, and could feel the difference more than I ever would have thought. Turns out I need to add back 2.5mm to make it exact. Cool! Thanks!

rpenmanparker 

Many folks now never even look st the nominal size anymore. They just seek whatever bike has their optimum stack and reach. Good idea.

caloso

Exactly.

johngwheeler

Good advice. I am now drawing up a list of bikes to try based on stack & reach, and only mapping them to the manufacturers' sizes to be able to ask for the right size in the LBS. I have found that there are bikes that are nominally 54cm,56cm & 58cm that would all probably fit me fine (e.g. my 54cm Trek Crossrip has a reach of 396mm and wheelbase of 1043mm - longer than some XXL bikes!)