I use a combination of Stand over height and the Manufacturer's recommendation. In my case, with short legs, I choose the smaller of Giants two recommendation. Bikes that don't meet my requirements are removed from my short list. It works for me.

Reach can be fine tuned with handlebar stems, or the handlebar itself if necessary. Seat position should be used only to achieve the correct knee angle.

Waddo's wife is 1.59m high. That is 62.6 inches. The average height of adult females in the USA is 63.5 inches. Waddo's wife is about average height for an adult female in America.
https://www.cdc.gov/nchs/fastats/body-measurements.htm

Your child is that high? Unless you child is a teen who has already done their puberty growth, you might want to get them checked by your doctor for gigantism or other similar hormonal disease.


You don't seem to understand that:

https://cimg2.ibsrv.net/gimg/bikefor...d239985f4f.jpg

You can't size a sloped top tube frame by looking at the "seat tube length". You can see in the above diagram, there are five frames which are exactly the same effective size, but depending on the slope of the top tube on that particular random frame, the seat tube can be five different "lengths".

So if you go into a bike shop and say "I want an 18 inch seat tube frame", that is just meaningless LOL. :lol::lol::lol:


https://cimg5.ibsrv.net/gimg/bikefor...fc4fc9fc25.jpg

You're not getting it. Bike sizes are referred to by nominal seat tube length, but they function by total size like a jacket or shoe.

That's why you dont go by leg length or reach (whatever that means), but rider body size.


And there is no reason that a 5'2" rider would go up in size from 15" to 17"

It's actually called effective seat tube length.

Why do you keep quoting single number inch sizes as if we're still in the 1990s? You must be older than Jesus because it's been decades since even US manufacturers have quoted frame sizes that way. In the modern era you get a published geometry table, always in metric millimeters. The so called frame size is often just s/m/l/xl or some generic 1/2/3/4 scale, because your type of single number frame size quoting is dinosaur obsolete (for exactly the reason I attempted to teach you in my past several posts). We are well past the pre-historic era where most frames had similar geometries and a single seat tube number can be used for sizing.




https://cimg0.ibsrv.net/gimg/bikefor...aded3c38ff.png

https://cimg4.ibsrv.net/gimg/bikefor...f50c9cc243.jpg


Astounding lack of knowledge for someone who has the audacity to participate in this thread.

That is correct, nobody knows.

But if they already have a bike that fits them well, they have something to go by. The last three bikes that I bought (one as a complete bike, two as bare frames), I first looked at effective top tube on the manufacturer's geometry chart. I already had a couple bikes that fit me well, so I had base measurements to work with. Thus it was pretty easy to pick the right size. All three of these were ordered on-line. I first looked at effective top tube length or if that was missing on their chart, the actual top tube length. And then a quick comparison for standover height and bingo, I have the size I need.

Go back a decade and a half ago, I was trying to figure out the size I needed from Thorn by providing various body measurements to them. They decided I needed a size 610S. If this was still the world of "fist full of seat post" sizing, I would have said no to that size because the last horizontal top tube bike that I bought based solely on stand over height was in 1973 when I bought a Raleigh Grand Prix, size 23.5 inch (which today is 59cm). Thus, I knew that with a horizontal top tube, anything bigger than 59 would be too big for stand over. But the Thorn bike I was looking at that they said I need a 61 effective seat tube length, the frame had a sloping top tube and the other measurements on the chart gave me the trust that stand over height would be ok. That bike fits me just fine.

I mentioned earlier in this thread that my rando bike had too long of a reach, changed the handlebars earlier this year. That is one of the three that I bought on line based on top tube length. In this case, when I first built it up, I apparently measured the reach of the handlebars that I installed wrong, that is why I got my reach too long on that bike, a simple case of user error that I finally rectified this year. It was off by less than an inch, so fixing it was not urgent.

And the complete bike that I recently bought, I knew when I ordered it that I would need a different stem to adjust it for size.

You have a valid point that if someone does not have a well fitting bike to use for base measurements, you have to start from scratch. But my point is that do not just size only by seat tube length.

A lot of this discussion misses the fact that frame sizing is general and specific fit is accomplised with stem and seatpost.

Most road bikes that come in 2cm increments only change reach by about 1cm per size. Yet "normal" stems come 90mm to 130mm - a 4cm spread. You would have to get the bike size wildly off before it becomes unlikeable due to TT length.

Which is why the best guide to sizing is the manufacturer's height to size guide.

Saddle fore-aft affects pedaling mechanics and weight distribution. A 4cm change in stem length is a night and day difference in handling.

Stumbling into a frame size based on a meaningless seat tube length and then afterwards attempting to carry out fit with the aforementioned hack bandaids is dummy stupid and ass-backwards.

The seat tube is the only tube that can be freely adjusted on whim. Get the correct reach frame, and afterwards you can slide the seat post any way you want. Stumble into buying the wrong reach frame and you are permanently cucked and stuck with your dummy bandaids that screw up the rest of your fit.

Manufacturer's height guide is a starting suggestion at best. Two people who are the same height but have different torso/leg length ratio will need different reach frames.

You need to stop screwing with people. It's bad enough that you sabotage your own cycling with your farcically wrong ignorance. Don't mess other people up too.

"Mr I don't even know what the term reach means". Dunning Kruger gold award of the 21st century.

We are not in agreement, but it is unlikely that either of us will convince the other to change their position.

What is it you disagree about? This is all just discussion.

Ignore the noise from Yan, pkease.

Pick any frame with published geometry and a rider height and I will illustrate what I'm talking about.

Or, just keep being an insulting whiner that can't read.

Based on your lack of progress, it doesn't sound like the gulf in knowledge is bridgable. Good day to you.

You make Bike Forum suck just a little bit more.

I will never understand internet forums. You both (you know who) have a vast useful knowledge of bikes and touring that has been helpful to many others. That you disagree is not as important as conveying that information.

You are making the assumption that bicycle designers are idiots. A 43cm frame isn’t going to have a top tube from a 58cm bike. The reach doesn’t vary all that much within a brand’s frame sizes nor does it vary all that much from brand to brand. There is the caveat of mountain bike frames vs road frames where someone might try to put someone on the same frame size as they might ride in a road bike…for example, a 15” mountain bike is not the same frame size 43cm road bike…because people do that all the time.

While the seat tube length may not match the “frame size” as well as it did in the past with horizontal top tubes, the “frame size” says that there is a certain proportion of lengths of the various geometries of the bike. Someone who is around 5’ tall isn’t going to fit on a 50mm frame although, in the past, they were presented with that frame and told to “get used to it”. Hell, at some points, the smallest frame (or the only frame) available was a 55cm (22”) bike that was called a ‘27” bike’. My wife learned to ride one even though it meant that she had to hang her leg over the top tubes at the knee and do the splits to get her foot to the ground.

At this point in time, you’d have to have a really bad salesperson to “stumble into buying the wrong…frame”.

If the persons in question were close to the top or bottom of a certain frame size, that could be true but, for the most part, two people of the same height are going to fit on the same frame size. Minor adjustments to the saddle and stem will fix most variances.

​​​​​​​How many bikes have you sold? How many bikes have to fit to someone?

Blah, blah, blah.

See posts #27 and #36.

Good day to you.

The average height of a 12 year old child..boy or girl…is 54 to 64” (137 to 162cm) with girls being a little bit taller at that age. As shown above, most adult females don’t get much taller than a child of 12 years old.

You seem to be missing the point that most women in the US have an average height of a 12 year old child.

You are completely missing the point. “Frame size” harkens back to the days when the seat tube length was actually, say, 15” (43cm) long. Yes, the actual “seat tube length” varies today but a frame that is marked as a “43cm” is going to have similar proportions…including reach…of that old 15” frame.

And note, that in your diagram, the reach doesn’t change just because the seat tube length does.

“I’ll take ‘things that people don’t say anymore’ for $500.” No one really said that back when frames used horizontal top tubes. They asked for a certain frame size. Salespersons would..and still do…ask for the person’s height and perhaps inseam as a starting point for fitting a bike. They most certainly don’t ask for the person’s “reach” because even experienced cyclists probably don’t know what their reach is.

As someone who regularly sells bikes to people, I start with height and inseam. I have them stand over the bike and see how much room they have to avoid smashing and delicate bits on the bike. I then have then sit on the bike and see how “stretched out” they are (in other words, the “reach”). I then have them ride the bike while I watch them. I might suggest a different bike if they say they feel too stretched out or if I see that they look too stretched out.

That picture is what far too many adult women have had to deal with in the past. Things are better today but only slightly since bike manufacturers still cater to adult males for the most part.

I got my wife an XXS Specialized Sirrus. It came with 700C wheels which is really dumb on a small bike. Since it has disc brakes is it was trivial to swap to a 26” wheel. I also had cranks cut down to 140mm to better fit her leg length.

https://cimg9.ibsrv.net/gimg/bikefor...6df59fe54.jpeg

https://cimg1.ibsrv.net/gimg/bikefor...6215c5d3c.jpeg

That works.

If you start with height and get reach later, or reach first and then height, you are covering both bases.

And since they likely know their pants inseam length, for what you are doing that is a logical starting point.

A few years ago I saw my niece's carbon road bike in her garage. I asked her why she had her seatpost turned around so that the seat clamp was in front of the post instead of behind. She said that was the only way to get her bike to fit her well. She bought that bike over a decade ago from a high end bike shop, the bike shop sales person was most insistent that she needed that size frame for her inseam length. Later she met a guy that later became her hubby, he is the one that turned her seatpost around so that she did not have to be stretched way out to ride the bike. They do not make stems short enough to fix her bike fit.

Her bike frame is a size that would fit me perfectly, but she is three inches shorter than me. But apparently we have the same inseam length.

Point being that there are too many sales people that only sell bikes based on seatpost length.

The bike the OP asks about comes on size 15", 17", 19". 21", etc.

So what are you insulting me about?

You already made a comment responding to this exact post, which gave you an infraction and your post got removed by the mods.

Be smart and don't restart it.

While bicycle companies use centimeters for road bikes, they still list frame sizes in cm. For example the Specialized Tarmac SL8 Pro is listed in frame sizes of centimeters. Of course those are for a virtual seat tube length. The actual length of the seat tube is 380mm which isn’t close to 58cm. However, the rest of the geometries match a “58cm” frame. If that example isn’t enough, the Allez is listed by frame size as is the Roubaix and Aethos. Electric bikes seem to be the outlier in the Specialized line.

It looks like Trek is using S, M, L, etc. as is Giant. But I’d bet if you walked into a dealer for either one and said you regularly ride, for example, a 58 cm bike, they would pull out a large for you to test.

Long legged people are problematic but I would probably put her on a smaller frame and use a long seat post rather than put her on a tall frame and try to retrofit it. All of my bikes have much more than a fist full of seatpost showing. Mountain bike riders are used to having a lot of post showing and it’s not really much of a problem. Even with my ample frame, I haven’t bent a post in years.

Agree, she needed a smaller frame.

My rando bike (below) is a horizontal top tube bike, I would have just slightly a bit more than a fist full of seatpost on that one if I did not have the stem mounted there to push my Carradice bag further back so it does not hit my legs as I pedal.

https://cimg3.ibsrv.net/gimg/bikefor...ae2116b979.jpg