DC City Hauler

I'm bike shopping and am not sure what frame size I need. Ordinarily, I'd just go to a bike store and try some out. But they are closed. I've seen all sorts of advice online after googling, but I was wondering if there was a forum consensus. Do I measure my inseam length? If I have a bike that sort of fits, do I measure part of that? It's a hybrid that has a different geometry from what I'm shopping for, so I'm not entirely sure how indicative that would be of anything.

Thanks.

Phil_gretz

https://www.competitivecyclist.com/S...ulatorBike.jsp

You don't really want to know "frame size" at all. What you want is a set of frame measurements that you can use to compare different manufacturers, different geometries, and otherwise apples-to-oranges comparisons that you'd be making.

Have a friend do the complete measurements on your body, plug into the calculator, and get a printout of the bicycle dimensions that will be a good first approximation of a fit for you. That's the way to do it.

bruce19

One thing to understand is that you can fit a range of sizes. They are Competitive, Eddy and French. (You can do a search for details). I use the Guimard - LeMond sizing method. When I do the measurements, my inseam of 32.5" is converted to 82.55 cm. This is then multiplied by .665 and the resulting product (54.9 cm) is the frame size. I've been using this method since I began cycling approx. 40 years ago. One caveat....thanks to the move to sloping TTs to save production cost (at the expense of precise fit), you will have to measure the actual bike virtually.

Kapusta

I go by frame stack and reach. Google it.

If you can find a calculator to figure that out (or get the measurements from a bike that fits you well) I would go by that.

DC City Hauler

I find sloping TTs ugly. Maybe I'm just old.

Litespud

back in the mists of time, I used the Competitive Cyclist calculator to mail-order a frame. Worked out fine, and that original frame size has been the basis for for sizing all subsequent frames

cyccommute 

If you like the way your current bike fits, just measure it and get something similar. Although I haven't looked at the geometry of every bicycle from every manufacturer, I have look at enough of them to know that for a given "size", they really don't vary that much in all the major proportions that people seem to think they do. A minor difference isn't going to have that much of an effect on the rider, either. A hybrid is fitted more like a road bike. A mountain bike has a smaller frame but the proportions are used for someone larger. For example, a 58cm (23") road bike and 19" mountain bike will have the proper proportions for someone around 6' tall ± 3". Someone 5'9" will be right on the edge of both bikes being too large and someone 6'3" will be right on the edge of the too small and should go down or up a size, respectively.

But a Trek or Giant or Specialized or Jamis or etc. will all be about the same proportion independent of the brand or even model of bike. Even a bike with a sloping top tube with a corresponding shorter seat tube will still be proportioned like a bike with a horizontal top tube.

Or just use the geometry of a bike that you like to ride now. If you've ridden for any amount of time, chances are that you'll like just about anything that fits about the same way. We adapt to bicycle quite well.

"Frame stack" is kind of a new way of saying "standover height" which I've been flamed for suggesting is a good way to find frames that fit. All it is is the standover height minus the bottom bracket height. And that's pretty much the way that every shop I've ever been to checks to see if the frame "fits" you on a preliminary basis. Lots and lots and lots of people have told me that there is one specific measurement that is used for sizing frames...one person was adamant that the "one" measurement is the head tube length...but when I've walked into a shop, I've never heard anyone start with top tube, reach, bottom bracket height, or even top tube length. They all have a customer stand over the bike and lift the front wheel. If there isn't any space between the frame and the sensitive bits or if there is too much, the shop person will move on to a different size and do the same test.

Only afterwards do they start talking about reach and other measurements.

Kapusta

Frame stack is NOT another way of saying standover. They are two completely different measurements. All they have in common is they are vertical.

Standover matters when you are standing over the bike. Stack matters while you are riding the bike.

Two frames can have the same standover with drastically different stack heights, and vice-versa.

I got an in depth professional Serrota fit a few years back. I came away with a data sheet showing the optimal frame size. It gave a lot of info in terms of bar width, saddle angle, height and setback from BB, distance and drop from saddle to hoods, cleat placement, crank length. It also gave optimum stack and reach as measured to the base of the stem.

You know what is NOT anywhere on the spreadsheet? Standover height.

And when I worked with the shop to find frames to fit me, their primary criteria was looking at the stack and reach. They also took into account head angle for frames that would require much in the way of spacers, as that affects the reach. Everything else (including standover) just needed to be “good enough”. And the reality was that any size from one or two larger all the way down to the smallest they offer would have been fine for standover. Of course there were other “critical” numbers (like bb height, CS length) but those are primarily handling related, not fit related.

If you think standover height is a good way to size a bike, fo for it, but I doubt you will find many fitting pros who would agree it is as good a method as stack and reach.

deadlocked

I’m trying to figure out the proper size as well

cyccommute 

Definition of frame stack:

Add the bottom bracket height and you have standover. Same measurement. From the same place.

Standover matters when you have to get on the bike. Stack may matter while riding but if you can comfortably get on or off the bike, it won’t matter if the stack is perfect.

Only if the bottom bracket height is different.

That’s because everyone seems think it doesn’t matter. Tell that to small people who are put on bikes that are too big for them because no one makes bikes the right size for them. For years, my 5’ tall wife had to endure bikes that were 3” to 5” too tall. Try riding when you can only straddle a bike on your tiptoes and then tell me that standover doesn’t matter.

I’ve bought many, many bikes. I have never...not once...had someone ask me about stack or even reach. I’ve been in a lot of shops and seen people”fitting” bikes and not a single one has every been asked about frame stack. Going back to bikes for small people, especially for mountain bikes but also small framed road bikes with 700C wheels, the top tubes are often too high where the small rider has to stand. Shocks push the front higher and leave even less room. We “normal” sized people don’t have to deal with that. But it is critical for lots of others.

Standover is a place to start. It’s the easiest way to screen a lot of bikes. Bikes are more about how they feel than a list of numbers.

DaveSSS 

Stand over height is not even listed on most geometry charts and it is NOT stack plus the BB height, because top tube sits lower than the top of the head tube and it's most often sloping down. The BB drop, but not height is included in most geometry charts. I use only the stack height as the indicator of the vertical frame size when buying a new frame.

Kapusta

Yeah well, that's only because you know what you are doing.

Kapusta

Uh, nope. completely different measurements from different places at BOTH ends of the measurement.
Stack: BB to top of head tube.
Standover: ground to top of top tube at some point, usually either at the halfway point or where a person is expected to stand over the bike.

These don't just differ in the bottom part of the measurement, but the top part as well. And the top can vary based on the slope of the top tube as well as the distance from the top tube to the top of the head tube. And all of these combined can vary a LOT between models with the same standover.

This is a logical fallacy based on an appeal the the extremes. I never said stand over does not matter AT ALL - nor would any bike fitting pro. It is simply a limiting factor in some cases. But it is NOT what determines optimum frame size. I can easily clear the standover test with any 54cm road bike with compact geo I've swung a leg over. So according to standover, I can fit anything below that. 48, 50, 52, 54. Not much help, is it? In fact, I end up fitting best on most 48-50cm frames. Standover would never tell me that.

As far as people who have issues with stand over... you are talking to such a person... at least I used to be. For MTB frames, I was early to the short-stem / long frame reach party. So back in the early/mid 2000s, frames that had the reach I wanted (usually large) were tight on the stand-over (especially since I liked big tires and long forks). On one frame (Heckler) I had zero, on another (Azonic Saber) I was had about negative one inch. You know what? It never mattered. The only issue I ran into was that the longer seat tube limited how long of a dropper post I could use. The bottom line is that there was no way I would have sacrificed the reach I wanted for some more stand-over. Of course, not having enough standover freaks some people out. If I were one of those people, I would NOT size down on those frames, I would look for a different frame altogether. Now, with reaches getting really long in newer fraome, I am on smaller sized frames, and this is never an issue.

As far as your wife (and other who are very short)... yeah, the bike industry has often done a terrible job with making bikes to fit small riders. That does not change the basics of fit, though.

Whether or not they are talking about this to you is irrelevant. Any shop worth a crap will prioritize fit ON the bike, and stack and reach is at the heart of that. IF you find that the frame with the correct ON BIKE fit has too little stand-over for the customers comfort, they should NOT go to a smaller frame. They should abandon that model altogether. I am sure many do simply size down, but that is for reasons other than the customer's best interest.

But the whole "what do bike shops do" argument is utterly moot here. The OP states in his first post that he can't do an in-shop fitting. He is going to need to look at geo numbers. And suggesting that he should start with stand-over is silly. How do you even do that? Measure inseam, subtract X inches and find the matching stand-over? What exactly is "x" in this case? I've gotten great fits with wildly varying standover clearances.

cyccommute 

You sure about that? I’ve check random bikes on the Trek, Specialized, Giant and Cervélo sites. All of them list the standover height.

Look at the definition of “stack” that I posted. The stack measurement of a frame can be all over the place. Giant, for example, measures stack to the top of the top tube (or vitual top tube) and they measure standover to the same point. It seems to be a very squishy number.

cyccommute 

Not everyone goes to the top of the head tube. I’ve seen measurements to the top of a virtual top tube as well. And going from the bottom bracket to the top of the head tube is going to make the measurement vary by only a very small amount...a few mm at most. That’s hardly critical.

As for the standover, it may vary due to a sloping top tube but the standover should be slightly higher than the virtual horizontal top tube. In other words, the proper frame fit should be the same as the frame stack. You might get away with being on a larger frame because you can physically stand over the frame but if you are stretching to do so, the other proportions are wrong and for a larger frame and a larger person.

You certainly seem to imply that standover doesn’t matter as do so many others. I’m also not saying that the standover is the end all of parameters to consider. It is certainly the one of the first things to consider.



Do you really think that every bike shop employee has every stack and reach for every bike they sell memorized? Does someone come in to a shop and the employee looks at them and says, “you need X stack and Y reach? Do you think that the average customer would even know what those measurements mean? Bike nerds, maybe...I have no idea for myself and I’m about as nerdy as they come...but the average first (or even third) time buyer?

How about used bikes? My co-op slings out used bikes like a greasy spoon at the docks on a shift change. We never know what bikes we are going to have and I guarantee that no one at my co-op has ever even measured stack and reach. We certainly don’t have 50 years of stack and reach data memorized or even available. The way the co-op employees sell bikes is to eyeball the customer’s height, pull out a frame about the right size, have them straddle it, lift the front wheel, and see if there is clearance. After a little fiddling with the saddle height, the customer is sent out to ride it.

That’s exactly every interaction I have ever had with any shop where I’ve purchased a bike. I have never heard anyone talk about stack or reach. People are asked how the bike feels but there is never a discussion about something that would confuse most people. I can usually tell the shop personal more about the bike they need they know.

I’m actually very unparticular with fit within a range. I can pull a bike of the peg and if it is a 19” mountain bike or 58cm road bike, I can ride it without really needing anything changed on it. I can tell if the bike is too small or too large, of course but if the bike is in that size range I can ride it all day lone.

Did I tell him to start with standover? Go back and reread what I wrote. I said to measure the bike that he likes and start with something similar. I never said anything at all to DC City Hauler about standover. It’s a measurement that he can do and should likely consider but I didn’t say to ignore everything else.

Kapusta

Anyone who understands what stack is goes by the top of the head tube. I am sure you can find SOMEONE who does it otherwise, but that is not what the essentially universal understanding of the term means.
I don't understand what you are saying here. But IFyou are implying that the difference between where you measure standover to and where you measure stack to are not that different, this is simply wrong. Just on my 4 bikes alone, the difference in hieght between where you measure stand-over to and where you measure stack to ranges from 1-1/2" to 7". That is a massive (and inconsistent) difference.

Again, this idea that stack and standover are in anyway relatable or that one can be used as a proxy for the other is complete and utter nonsense.

I THINK you just explained why stand-over is a bad way to size a frame.

I never said that. Nor implied it. It is far down the list, though. It is just a "good enough" box to check that is irrelevant in at least 95% of cases for a bike properly fit by stack and reach.

Come on, that is ridiculous. Why would they need to memorize every stack and reach? Do they need to memorize every stand-over height? Of course not. If the bikes are there, just get on them.

For the umpteenth time, this is moot, though as the OP can't go to a shop of try the bike in person, and needs to look at measurements.

However, if you are going to ORDER a frame, a shop worth it's salt WILL find out those numbers to know if it fits.... as the shop I worked with does.

And the fact that the average customer does not understand proper bike fitting and the nuances of geo is not a valid argument against it.

What about used bikes? The OP is not looking at used bikes, he is looking at bikes he can get geo numbers for. Yes, used bikes with no info you will of course have to either measure them or try them on. As far as how your Coop does things..... so what? You get what you pay for and I am certainly not looking to your coop for bike fitting advice.

If you are not too particular about fit, then why are you giving advice about it?

I would be interested for you to answer my question regarding how the OP should determine his optimum standover, seeing as he needs to look at geo charts to figure out what will fit.

(6/3/2020: Edited to soften language)

Midou

Thank you for your advice guys

boobie

First, consider the type of riding you'll be doing. Get a general sizing, test ride all the bikes you can that are smaller and larger than that size, and don't rush the process. I see it too often that people buy bikes impulsively without having any comparison to any other bike. The first bike they hop on always "feels good" but there are many more out there to try. A lot of bikes ride differently and a bike that works well for one person isn't exactly going to be the right one for the other. Again, don't rush the process.

cyccommute 

Why should that be any more valid than going to the top of the top tube? In fact it should be less valid since the head tube height is the most variable part of the bicycle frame between brands. The top of the head tube can be flush with the top tube or can extend beyond it. The difference in how far the head tube extends beyond the top tube can cause the variance in stack that you describe between models and manufacturers.

Again, I didn’t say that stand over is the only way to measure a frame but it is a quick and easy way to gauge what works and what doesn’t.

And I never said that standover is the only measurement that matters. It is the first thing that bike shops check when a customer comes in, however.


I seem to recall someone saying something to the effect

Standover height doesn’t need to be memorized. The way it is “measured” is to have the customer, well, stand over the bike. Reach can be measure, crudely, by the customer using a cubit measure (elbow to finger tip) from the tip of the saddle to the handlebar. It’s not precise but it’s close enough.

I can’t see any way of measuring frame stack that doesn’t involve a tape measure and, to be accurate, a level to determine the virtual top tube.

And, for the umpteenth time, I never said otherwise. Back in post 7

I’m not stupid, no matter what you think.

Again, did I say otherwise? Although I have ordered lots and lots of frames from various places and have never used reach or stack to do so.

But the use of these measurements and the importance that you (and some others) place on them mystifies the bicycle fitting process. I guarantee you that the vast majority of people riding bicycles don’t even know that these measurements even exist. If the measurement isn’t known, is it all that important? Do you want to argue about angels now?

Are you sure that DC City Hauler isn’t looking for used? DC City Hauler said “I’m shopping for a bike...” That covers a broad range of possibilties.

As for the bikes, you said it yourself...you “try them on”. Again I have to keep repeating myself, that’s what every shop I’ve ever been to does. They have you “try the bike on”. If someone were to ask about reach or stack, I’m sure that any bike shop would find that out for the customer but I don’t it really comes up that much.

As for your comments about my co-op, they are doing what the rest of the industry does. Many of the paid staff come from other bike shops where they learned bike fitting the way everyone does it. Me thinks that your objections to my co-op’s practices has more to do with me than the shop.

And if you are so picky about fit, why are you giving advice about it? We may both be on the extremes but, honestly, I don’t hear too many (or any) people I know who run around complaining about the frame stack on their bikes being all wrong.

By following my original advice...measuring an existing bike. If DC City Hauler doesn’t have an existing bike, he (assuming a “he”) can measure his inseam and subtract up to 2” for a road bike geometry and up to 4” for a mountain bike geometry. As I pointed out above, standover height is provided for many of the new bikes out there...at least for 4 manufacturers. Three of those cover most of the quality bikes sold.

And, yet again, I did not say that standover is the only measurement to consider.

Phil_gretz

It's disappointing that we get so entangled with minutiae that the OP, DC City Hauler, cannot get a simple clear answer to his question, which was how to understand frame size (first) and how that relates to his fit (second).

I gave him the fit calculator, which answers the second question for him. What I failed to explain was that many production bikes have geometry charts that accompany them, which relate the "size" name to the actual dimensions of the bike. When one is fortunate enough to locate the geometry chart for a particular frame of interest, then it is easy to determine which is the "most likely fit" starting point for the frame. Without that, you have to actually measure the bike to determine the dimensions, and then compare those to your fit calculator results. This will tell you how close that particular bike is.

For those of us who have been at this for decades, it's sometimes easy to "eyeball" a frame and determine if it's close. But with modern compact geometry frames, this isn't an exact science. Some argue that it's easier because fewer sizes are needed to fit a wider range of riders. This may be true.

Of course, the OP did not give any further information about what style of bicycle, from what era, from which manufacturer he's trying to size, so we're whispering in the dark, apparently.

Kapusta

Which is EXACTLY WHY you measure to the top of the head tube. It BECAUSE it varies so much. The top of the head tube is going to determine how low the bars can go, or in the other direction, how many spacers you are going to need. The top tube does not tell you squat about any of this. It also matters because for people who actually think reach matters (you know, the entire professional bike fitting world) reach is measured at a the specific stack hieght. if you need to add spacers to raise the bars, the reach gets shorter.

Also, this variance you just described (which I have been constantly pointing out myself) is yet another reason that Stack is NOT at all the same thing as stand-over. Remember, my response to you was to the comment....

Its not.

The vast number of people also do not understand anything about how derailleurs work, or what weight suspension fluid they have, or what size bearings their bike uses, what saddle tilt works best for them, or even the width of their handlebars. Does that mean that stuff does not matter? It is the job of a pro (or really ANYONE giving advice on something) to understand and take into account what the average person does not.

What your coop does in this regard is of little interest to me.. What you describe is NOT what the rest of the industry does, unless you are talking about big box stores. No respectable bike shop I have frequented would have someone straddle a bike, lift the front wheel, and send them on their way. I mean, maybe for a kids bike or a town cruiser that might work, but for a mtb or road bike that someone plans to spend a lot of time and miles on? That is unacceptable in my view, and not what a good shop does. If this is what members of your coop do in their retail bike shops for their day jobs, that's pretty weak.

Herzlos

Most online stores will have a sizing guide for the bike that should be pretty accurate (since the manufacturer determined it), and is likely to be better than just the frame length along because that's just a factor.

Extreme example, but my 17" framed MTB is actually bigger than the 20" frame I replaced it with, because it's longer and the top tube is a lot more lower. Both are a Large, though.

downhillmaster

Fit-weenie cat fights are the best!

DaveSSS 

Stack height should be measured from the center of the BB to the top-center of the upper headset bearing. Any other measurement is wrong. There is a correlation between saddle height, stack and saddle to bar drop. I use that fact to get the correct stack height, so I get my preferred 10cm saddle to bar drop, without using a big stack of spacers or a high rise stem. For my saddle height of 72-73cm, I need a stack height of 525mm with the most common 15mm headset top cover and a -17 (horizontal) stem. Producing a small saddle to bar drop can be a problem. If I wanted only a 4cm drop, I'd need an endurance frame with a 20-30mm taller stack, 20mm of spacers and a -6 stem.

Frame size numbers or letters are meaningless.. Use stack and reach to find the right size. Reach can only be compared at one stack height. If one frame has a 20mm shorter stack, then subtract 6mm from the reach before comparing. I look for 370-380mm.

Standover height is rarely a consideration these days, with sloping top tubes. I never pay any attention to it and most brands don't include it in there geometry charts.

cyccommute 

I’m curious as to how you walk into a shop and size a bike? Do you take your own tape measure, level, protractor, and spreadsheet then measure all the bikes your are interested in? How do you accurately measure “from the center of the BB to the top-center of the upper headset bearing” in a showroom setting? You have to run an imaginary horizontal line from the middle of the headset bearing, then drop a plumb line from that imaginary horizontal line, and measure the distance. Kind of difficult and time consuming to do.

Or do you scour catalogs and keep a data base of stack measurements for every make, model, and size of bikes available?

Alternatively, if a sales person were to ask the average cyclist what their “stack” is, they would likely get a blank stare as well. I’m not the average cyclist and I can’t tell you what the stack is on any of my 10 bicycles nor the 28 others I no longer own.

You may not pay attention to it but when it matters, lots of people pay attention to it. In fact, every shop I’ve gone into starts with standover to quickly screen frame fit. Asking about stack measurement is likely to get you a blank stare and/or the sale person heading for the catalog…probably while grumbling about the bicycle equivalent of rivet counters.

You are incorrect that most brands don’t include standover in their geometry charts. You just don’t pay attention to them.