Road Cycling - A different thought on frame sizing.

After measuring and studying hundreds if not thousands of customer’s measurements over the years as a custom frame builder. I came to the conclusion that although human bodies are all different; they do follow certain rules of nature.

Tall people are not scaled up models of short people. Most of the height difference is in the legs; body length differs by a lesser proportion.

If you have long legs then you also have long arms. Short legs; short arms. This makes sense since most animals are four legged; why should we be any different?

Leg length is a combination of the inside leg measurement plus the length of the foot. Length of the foot is important because when pedaling the toe is pointed downward at the bottom of the pedal stroke; so the foot becomes an extension of the leg.

People, who have a short inside leg measurement for their height, generally have longer feet. (Bigger shoe size.) It is as if they were designed as a much taller person, but their heel got turned further up their leg; making a short leg, long foot.

Imagine two people both six feet tall standing side by side; one has a 34 inch inside leg, the other a 32 inch leg measurement. Because they are the same height it follows the one with the shorter leg has a body 2 inches longer; he also has longer feet and shorter arms than the other guy. They can both fit on the same size frame, (59 cm. center to top i.e. 57 center to center.)

They will both have close to the same seat height, because the short leg guy has a longer foot so his seat needs to go higher than his inseam would suggest. They can also use the same top tube length and handlebar stem, because one has short body long arms; the other long body, short arms; making their reach the same. Minor adjustments in seat height and stem length may be called for.

It has occurred to me that with these compact frames on the market now and only available in small, medium, and large; customers are only ball parking frame size anyway. It has long been my opinion that frame size is linked to the overall height of the rider more than any other measurement because of the rules of nature I have just spoken of.

So I have just formulated this based on my own frame sizing chart. If you are 5’ 3” to 5’ 5” frame size equals Height divide by 3.3. For people 5’ 6” to 5’ 10” frame size = Height divide by 3.2 and if you are 5’ 11” to 6’ 4” frame size = Height divide by 3.1

A example would be someone 6’ 2” = 74” divide this by 3.1 = 23.87 in. (61 cm. measured center to top. i.e. 59cm. center to center. A person 5’ 7” = 67” divide this by 3.2 = 20.93 in. (53cm. center to top. i.e. 51cm. center to center.) The easiest way to convert from inches to centimeters is to get a tape measure with both on and simply read across.

Reach which is top tube plus stem length; is frame size center to top plus 10cm. If you want something more accurate go to the chart on my website (Link below) go to ‘Bicycles’ page 6 ‘Bike tech.' That chart was derived not by any mathematical formula but by records of custom frames built over many years. Most people find it pretty accurate. The above is an attempt to come up with a simple formula that comes close to this. Please don’t change your position based on this alone because this is new thinking.

What I would like to know from everyone is; is this of any help or does it complicate things further and also does it come close to what you are riding now?

No, thanks for the great post. And the chart.

Most LBS use standover. I'm 5' 10", 30 " inseam. The Chimp. Don't know what size my bike is. I just ride it.

The most important part may be the rider. My body hurt like *&$@ until I got stretched out. Now, I ride fine.

I don't wear shoes and pedals, like to move my feet around, use differant muscles.

For me this supports my own experience a lot better than most of the other guidelines I've tried. I'm 5"11" and can't remember my inseam (shoe size 10.5 - 11), but every time I measure inseam and use the latest guide I'm looking at, I come up with a frame size of right around 55 cm - which is what I'm riding. The problem is that I always feel "cramped" no matter how high I set my seatpost (max. now).

When I used your formula I come up with a 58 cm c-t size and intuitively I was planning to just toss the 55 cm I keep coming up with and go to a 57 on my next bike. I think you're onto something. BTW, I have over 23,000 miles on two nearly identical frames that are 55 cm. and have always felt like they were a bit too small....its not like I'm on a new unfamiliar bike, or inexperienced.

I'm 6' 0", 35" inseam and I ride 61cm frames. Your chart says 59. Maybe on some frames a 59 would work, but not anything I ride.

Geometry can a have a huge effect that you do not account for in your measurement. Top tube length and head/seat angles can change fit significantly.

Also, while the reach may be the same on long and short torsoed riders, weight and musculature distribution is not. That also may influence ideal top tube length.

Finally, I'm not convinced that extra foot length is equivalent to extra height, especially as crank lengths change.

Interesting. It does seem oversimplified, but using that formula for me, it spits out the same frame size that other forumulas generate and that I ride. Hmmm..



Most LBS use standover. I'm 5' 10", 30 " inseam.
At 5'10", a 30" inseam is a bit short... So, according to Moulton's theory you should have big feet. I'm guessing average for that height is size 10 (?)... What size shoe do you wear?

Very insightful. I'm a 53, and it kind of sucks because most bikes come in 52 or 54.

I wonder what his theory on penis size is.

Works for me, almost too well. I'm 5'10 and 1/2, so I fall between 3.2 and 3.1. The first gives me a 56, the second a 57. I fit either pretty well with the right stem. I think I have very average proportions though, so I wouldn't be a good test case.

Dave, I think your chart is pretty close. It is hard to compare TT lengths without knowing STA though. I am 190cm tall, 90.5 inseam and my bike has a 60cm TT with a 12cm stem and a 72 STA. You would put me on a 57 TT with a 13.5 stem. If your bike had a steeper STA then we would be very close.

My wife rides a bike at her height of 161cm which has a 51 TT and a 9cm stem which is what you suggest. Her STA is 74 degrees (maybe 74.5).

Obviously, years of observation have given you a pretty good handle on what works for most people.

What I would like to know from everyone is; is this of any help or does it complicate things further and also does it come close to what you are riding now?Anecdotally, the formula seems to work pretty damn well for me. My custom is about a 58.75 ST and a 58.5 TT with a 14 stem (which seems a little long now that I'm less concerned about having a flat back and being stretched out). I'm 6'1" with a long torso, long arms (35.5 sleeve), and (I think)shorter-than-average barefoot standover of 33.75" (with a 13 shoe) and the formula spits out a frame size of 59.812885. Coincidentally, I just bought a frame that measures 60cm unconventionally, because it uses the top-of-top tube as "theoretical center" - which means that actual center is almost right at the formula length (top tube has very narrow profile). Gonna have to think about what this is telling me in concrete terms, but I do feel better about the frame size choice I made! :D

I wonder what his theory on penis size is. :roflmao: You want the truth? You can't handle the truth! ;)

What I would like to know from everyone is; is this of any help or does it complicate things further and also does it come close to what you are riding now?

Your chart puts me on a 54 which is exactly what I have now. My shoe size is 1 1/2 sizes larger though ;)

I wonder what his theory on penis size is.
Traditionally isn’t that linked to shoe size? ;)

Im 5'1" was riding a 50C, now a 47C it fits much better. Also works with your theory.

dave,

sounds good to me. how're u measuring reach though? you're not just saying that everyone should get 10cm stems are you? if so, that's a good starting point, and hard to go wrong, but not ideal...

sd

From what I've been reading it seems that you can get a good "fit" from a frame geometry that is compact (and therefore maybe a bit smaller than traditional frames) by adjusting the stem length/height and the saddle position/height. Of course, the frame size still has to be within "the ballpark." I know that is the theory of compact frame manufacturers and although I'm not endorsing this theory, it does seem to make some sense. The exception(s) would be if the frame was either too large (making these adjustments impossible) or grossly too small, placing the center of gravity somewhere it shouldn't be which can have an effect on weight distribution and/or rake and trail which affects handling.

dave,

sounds good to me. how're u measuring reach though? you're not just saying that everyone should get 10cm stems are you? if so, that's a good starting point, and hard to go wrong, but not ideal...

sd
No that was not what I meant. If the frame size is 59 then the combined top tube length and stem would be 69cm. It could be a 57 top tube with a 12cm stem or a 58cm top tube with an 11cm. stem. I am not talking of custom frames here I mean stock frames which could be any top tube length.

On the compact frames with the sloping top tube the only way you can estimate where the handlebars should be is to measure horizontally across from the seat post combining an imaginary top tube length plus the stem length.

Your sizing nailed it for me. 6 feet even, 32 inseam, big feet, knuckles dragging on the sidewalk when I walk.

I checked the Co-Motion web site to make sure how they measure their frames. I'm riding a 57cm Americano, measured center-to-center. The hybrid I use for a sloppy weather commuter is rather smaller, but has more seat post and stem showing. My previous road frame was a 23-inch measured top-to-center (from 1975, when men were men and stock frames were available in 2-inch increments) tourer.

Well it puts me on roughly a 57.5 c to c frame which is pretty spot on. I ride a 56cm but its too small... most 58's I've tried are too big. I would need to go +10cm and maybe a little more on the reach, since I have arms to my knees but its definately very close.

hmmm, according to that my bike is too small. I'm 5' 3" with a 28.something inseam. I should ride a 19" correct? My current mtb is 18", and yet it feels fine.

Eh, as long as it works it's good enough for me.

What about me? I have a 38 inch (=96.7 cm) inseam. My height is 1.89 m. I don't know what that is in foot.

hmmm, according to that my bike is too small. I'm 5' 3" with a 28.something inseam. I should ride a 19" correct? My current mtb is 18", and yet it feels fine.

Eh, as long as it works it's good enough for me.
You are fine. I was referring only to road bikes; MTBs tend to run an inch or so smaller with more seat post showing. 48cm. which is just under 19inches, is the smallest size conventional road frame you can build. That is one with a level top tube and 27 inch wheels because at that point the top tube and down tubes merge together.



What about me? I have a 38 inch (=96.7 cm) inseam. My height is 1.89 m. I don't know what that is in foot.
This formula does not work for you because you are 6’ 2 ½” tall but you have exceptionally long legs; 38 inch inside leg. For you I would recommend a 64cm. frame center to top, which is 62cm. measured center to center.

Looking at frame geometry charts, it seems that all frames from the smallest to the largest, are built the same height off the ground (ie bottom bracket height). There is less than1cm difference between a tiny women's frame and a clydesdale and that distance is set to be correct for a medium frame.
Would it make sense to select a crank size proportionate to the leg, then design a BB height to give safe cornering clearance. This would mean that every rider has their pedal at the same height off the ground, but the BB would vary by several cm depending on their size.
If you look at v small frames, you see riders with the saddle and BB way too high off the ground. Imagine scaling up the smallest size to the largest with a proportionate BB height. (ie increase every dimension by 50%), It goes from 26.6 to 39.9cm

I figured it out once, and the actually difference between a 170mm crank and a 175mm crank is something miniscule like .4"... I don't think it really makes as big a difference as some might lead you to believe. As for cornering clearance, if you are going hard into a corner, your inside leg is probably up anyways, so it doesn't really matter if you have 167's or 180's... they won't strike.

Looking at frame geometry charts, it seems that all frames from the smallest to the largest, are built the same height off the ground (ie bottom bracket height). There is less than1cm difference between a tiny women's frame and a clydesdale and that distance is set to be correct for a medium frame.
Would it make sense to select a crank size proportionate to the leg, then design a BB height to give safe cornering clearance. This would mean that every rider has their pedal at the same height off the ground, but the BB would vary by several cm depending on their size.
If you look at v small frames, you see riders with the saddle and BB way too high off the ground. Imagine scaling up the smallest size to the largest with a proportionate BB height. (ie increase every dimension by 50%), It goes from 26.6 to 39.9cm
You have touched on the dilemma all frame builders face. Building a traditional road frame with a level top tube you can only lower it until it merges with the down tube and you are left with a tiny head tube. When you have reached this point the only way you can make the seat tube any shorter is to raise the bottom bracket. But as you so rightly point out the last thing a short person needs is a bike with a high bottom bracket.

However now it is acceptable to build a frame with a sloping top tube, building small frames got easier. As for crank length as ‘seely’ mentions in the post after yours; the difference between the longest and shortest length is not that great. Also the modern clipless pedals offer more ground clearance; so yes bottom brackets could be lowered. But to do so lengthens the down tube and the chainstays so you build a frame that is not quite as stiff. So it all really depends on what you are designing the frame for.

I'm 6'4", 36" inseam, and ride a 62 cm bike. I also have 180 mm cranks.
Tom

Isn't frame size a little bit related to the purpose intended for the bike - Comfort/long distance vs race/crit? Thanks for any advice?

Jim

Isn't frame size a little bit related to the purpose intended for the bike - Comfort/long distance vs race/crit? Thanks for any advice?

Jim
Yes this is true; the frame I recommend on my sizing chart is for a racing position. If your riding style is more leisurely then you can go with a frame a centimeter bigger so there is less handlebar seat height difference. A tall person over six feet could go as much as two centimeters bigger.

I also want to remind you that I measured my frames center of bottom bracket to the top of the seat lug. This was standard for English framebuilders. Italian frames and most others are measured center to center. It becomes important when sizing or buying a frame or bike; if the bike dealer is talking center to center and the customer is thinking center to top; there is two centimeters difference. Watch for this if you are buying a bike on eBay; make sure that buyer and seller are on the same page on this one.

Also some people are confused over inseam; this is not your pant size. To be more accurate it is your inside leg measurement from crotch to floor without shoes. You can’t do this accurately yourself also when getting measured pull your pants up tight into your crotch and measure from the part that rests on the saddle. (In non medical terms, the little island between your equipment and the back door.)

Dave,
First off, it's a treat to have someone of your expertise on this board. I remember seeing one of your bikes in Bicycling Magazine. Small wheels, huge chainrings; at least I think that was your bike...

I like you theory. However, you adjust seat tube height for shoe size. If I understand proper pedaling technique, i.e., ankling, all feet should be level to toes up position at the bottom of the stroke which would obviate the need for a taller ST for longer feet. What am I missing?

regards,

So I have just formulated this based on my own frame sizing chart. If you are 5’ 3” to 5’ 5” frame size equals Height divide by 3.3. For people 5’ 6” to 5’ 10” frame size = Height divide by 3.2 and if you are 5’ 11” to 6’ 4” frame size = Height divide by 3.1

A example would be someone 6’ 2” = 74” divide this by 3.1 = 23.87 in. (61 cm. measured center to top. i.e. 59cm. center to center. A person 5’ 7” = 67” divide this by 3.2 = 20.93 in. (53cm. center to top. i.e. 51cm. center to center.) The easiest way to convert from inches to centimeters is to get a tape measure with both on and simply read across.

It bites a big one. the formula says 60 c-t, and I ride 58, or 57 c-c preferably with a 56.6 to 57 TT.

I'm 6' 0", 35" inseam and I ride 61cm frames. Your chart says 59. Maybe on some frames a 59 would work, but not anything I ride.

More proof you can't get closer that close with a formula. Your height and maybe a bit more inseam on a 57 c-c. I've been on 59 and 60 and even they don't fly.

Dave,
First off, it's a treat to have someone of your expertise on this board. I remember seeing one of your bikes in Bicycling Magazine. Small wheels, huge chainrings; at least I think that was your bike...

I like you theory. However, you adjust seat tube height for shoe size. If I understand proper pedaling technique, i.e., ankling, all feet should be level to toes up position at the bottom of the stroke which would obviate the need for a taller ST for longer feet. What am I missing?

regards,
Thanks for the kind words at the start of your post, and for the record the small wheel Moulton bikes are built by Alex Moulton in England and we are not related.

I thought “Ankling” went out in the fifties. The problem is people write books on cycling and they know nothing they just keep repeating what has been written in other books. There is even a drawing I still see from time to time in cycling books which shows the ankling technique. The drawing shows a cyclists leg and foot clad in dress shoes and bicycle clips on the trousers and no toe clips of course; this drawing must have originated in the 1930s

Thanks for the kind words at the start of your post, and for the record the small wheel Moulton bikes are built by Alex Moulton in England and we are not related.


Sorry about the confusion. Then was Fuso your brand name? I'm guessing here, I remember your name from somewhere...



I thought “Ankling” went out in the fifties. The problem is people write books on cycling and they know nothing they just keep repeating what has been written in other books. There is even a drawing I still see from time to time in cycling books which shows the ankling technique. The drawing shows a cyclists leg and foot clad in dress shoes and bicycle clips on the trousers and no toe clips of course; this drawing must have originated in the 1930s

Then are you advocating a toes pointed pedaling style? This conflicts with everything I have ever read, both old and modern. In fact, the only person I can think of that ever used that style successfully was that French guy whose name slips me at the moment (prolly couldn't spell it anyway)

Sorry about the confusion. Then was Fuso your brand name? I'm guessing here, I remember your name from somewhere...

Then are you advocating a toes pointed pedaling style? This conflicts with everything I have ever read, both old and modern. In fact, the only person I can think of that ever used that style successfully was that French guy whose name slips me at the moment (prolly couldn't spell it anyway)
Yes, Fuso was the production frame I made.

And for the second part of your question I am not an expert coach so I feel I should ask for someone else’s input on this one.

I'm 5'11" so going by your chart I'd need either a 56 (if dividing by 3.2) or a 58(dividing by 3.1). As always, I'd fall between a "medium" or "large". :(


I wear size 10.5 and inseam is 31"-32"

More proof you can't get closer that close with a formula. Your height and maybe a bit more inseam on a 57 c-c. I've been on 59 and 60 and even they don't fly.

Interesting. Are you measureing c-t or c-c? Do you prefer a steep head tube and relaxed seat tube? Long stem?

Well, I am 5'11.5 inches

My pants inseam is 29" Don't know my "bicycle" inseam, but it is short.

So, most of me is trunk and head.

My shoe size is 9.5 to 10 depending on shoe. I wear about a 33" shirt sleeve length.

I ride a 55 cm Lemond BA (1999) - with about 0-1/2" standover height. Fits me great, and I was fitted by an experienced fitter. Tough job fitting me!

Does this fit with your formula and theories?

Well, I am 5'11.5 inches

My pants inseam is 29" Don't know my "bicycle" inseam, but it is short.

So, most of me is trunk and head.

My shoe size is 9.5 to 10 depending on shoe. I wear about a 33" shirt sleeve length.

I ride a 55 cm Lemond BA (1999) - with about 0-1/2" standover height. Fits me great, and I was fitted by an experienced fitter. Tough job fitting me!

Does this fit with your formula and theories?
Half an inch under six foot with about a 30" inseam? Yes I would say that was a very difficult fit and looks like whoever did it for you did a great job. And no, this new theory I have posted here would not work for you.

Fitting someone like you, if the person doing the fitting went by your inseam alone it would indicate about a 51cm. frame. Now common sense should tell anyone that you can't put a person almost six feet tall on a frame that small. Your height would indicate about a 57 of 58cm. so yes I would say the size you arived at is a very good compromise, and the fact that you are happy with it proves it works.

Fitting someone like you, if the person doing the fitting went by your inseam alone it would indicate about a 51cm. frame.

Yes, that is what I get by using the "standard" formulas, and it obviously would never work for me! One reason I am never too anxious to refer folks to those "crank in the numbers" fitting pages on the web!

We decided that the least important measurement on a roadie was standover height, and it has never bothered me a bit. Also why we chose the Lemond with a bit longer TT.

Thanks so much for your feedback.

Maybe someday I will get a custom fit.

Interesting annecdotal stats Dave. I think they're interesting in terms of getting newbies on roughly the right size frame, but appart from that I think we have to be a bit careful here for a couple of reasons.

Firstly, I think 'frame size' is slowly becoming an irrelevent measurement. It was quite relevant when lugs were the only option, but now with bikes having sloping top tubes more often than not, we're getting into this realm of 'theoretical size' where things become even worse than the 'good old days' when all you had to contend with was 'Do you measure ctr-to-ctr or ctr-to-top'! It's got to the point where I prefer to know what the head tube length is/should be, because this is a great number when it comes to setting handlebar height - which is one of the 3 key contact points that we're ultimately interested in.

Secondly, I find top tube length pretty important. Even though I've probably only had a tenth of the road bike experience you have, I do realise that the relationship between the seat and the bars are critical, and this is largely based on top tube. However this observation comes with a couple of caveats -

1) The 'reach' figures ( top tube + stem length ) are variable because you can design 2 bikes that have identical reach figures, yet the numbers are all over the shop. For example, when designing my personal bike, I had the option of a 605mm top tube and a 120mm stem, or a 615 top tube and a 110 stem. Both would net the same result, but I had to allow for CG-Wheelbase as well, and knew that the shorter top tube and slightly longer stem would mate well with my chosen rake/trail/HA figures.

2) Flexibility is also a key component to top tube or 'reach' figures, and this cannot be established through averages. For example, I went with a shorter top tube, and a slacker HA/longer rake fork with a 120mm stem on my personal bike, knowing that my flexibility would increase as I got fitter. This would allow me to go with a longer stem or bars as I got fitter and increased my core stability, without adversely affecting handling.

I guess the bottom line here is this all illustrates the value of true custom bikes! Many consumers only delve into geometry as far as asking questions like "What's the head/seat angles? What's the frame size/top tube length?" without realising that it's a bit more complicated than that. This is exacerbated of course by many bike companies now only offering 5 'compact' ( I despise that term ) sizes, and not even bothering most times to inform consumers what fork rake they have spec'd.

Kudos on sharing your stats, Dave.

Firstly, I think 'frame size' is slowly becoming an irrelevent measurement. It was quite relevant when lugs were the only option
Lugs have never been the only option. Denver would have been an excellent candidate for a fillet brazed frame with a long, sloping top tube to better accomodate his short inseam and long upper body. Actually, he is one of the arguments for a compact frame design. In addition, lugs can be fabricated to custom angles if desired.




Even though I've probably only had a tenth of the road bike experience you have

Wasn't the first road bike your fabricator ever built for you the one you had built for yourself this year? Congrats! :)

Yes Don, Thylacine Cycles is a new company. Find a way to deal with it, okay? :rolleyes:

Anyway, anything constructive to add to the discussion, or....?

It becomes important when sizing or buying a frame or bike; if the bike dealer is talking center to center and the customer is thinking center to top; there is two centimeters difference. Watch for this if you are buying a bike on eBay; make sure that buyer and seller are on the same page on this one.

Also watch out how the size is measured. A Cannondale is measured c-t, but from center BB till top of head tube (not till absolut top!) so a 60 cm. becomes a 63 cm than. De Rosa is another example, they measure c-t on top of the BB (where the seat tube begins) untill top.

Well, I'm long-leg/short-torso and this formula comes out just a bit smaller than I like to ride. I am 174cm tall with an inseam of 85cm. The formula "says" I should be on a 54 or 55 but I ride a bike that is 56.5 c-t (55 c-c). If I went smaller, I'd have to use even more spacers to get the handlebars high enough and I'd probably also run into issues with hitting my knees on the back of the handlebars when standing.

Lugs have never been the only option. Denver would have been an excellent candidate for a fillet brazed frame with a long, sloping top tube to better accomodate his short inseam and long upper body. Actually, he is one of the arguments for a compact frame design. In addition, lugs can be fabricated to custom angles if desired.

I don't believe there wer many of those around in 1998-99?? At least I didn't see them. Interesting thought, though.

I don't believe there wer many of those around in 1998-99?? At least I didn't see them. Interesting thought, though.

Fillet brazing has been around forever. It's just brazing without lugs. It allows the builder to use what might be non-standard angles and geometry that standard lug configurations might prohibit. A sloping top tube used to be considered non-standard at one time. :)

Welding could be and is used to accomplish the same thing as fillet brazing. However, it used to be somewhat stigmatized because of it's association with cheap, heavier bikes, so was rarely seen on high quality bikes. But even standard cro moly tubing can be welded.

The use of sloping top tubes to accomodate a shorter inseam has also been around forever, but usually it is used to get standover height for very short people, mostly women.

The sloping top tube/compact frame with longer top tube combination is really ideally suited to someone like you.

An example of a fillet brazed frame:

www.classicrendezvous.com/British/Taylor_Jack/JTaylor_Martinez.htm

I don't believe there wer many of those around in 1998-99?? At least I didn't see them. Interesting thought, though.It might also depend on what you were looking for. Investment cast lugs and fillet brazing are very labor intensive and, I think, considered the highest form of a framebuilder's art. So you don't generally see this on any true production bicycles.

It might also depend on what you were looking for. Investment cast lugs and fillet brazing are very labor intensive and, I think, considered the highest form of a framebuilder's art. So you don't generally see this on any true production bicycles.
Fillet brazing is a skill that requires a lot of practice; it is a balancing act with liquid molten brass. Done right surface tension will allow the brass to hang in the corner of the joint while at the same time all flowing together. The end result is a joint that requires only a minimum of clean up after.

Get the joint just a little too hot and the brass will just keep running inside the tube; or it will drip off onto the floor; or worse still land on your feet and burn holes through your sneakers and your foot. Get the joint not hot enough and the brass just lays there like heaps of dog poop, and after hours of filing you are left with a joint that is full of pin-holes and craters. And the only thing you can do is start all over again.

A response to Thylacine Post # 40

Thank you for an interesting and enlightening post. It seems to me that everything has changed and yet nothing has changed. You still have two wheels spaced roughly the same distance apart; what has changed now is that a frame builder/designer has more scope as where they can place the rider. Where you place the rider affects the rider’s comfort, the efficiency of the rider getting power to the pedals, and the way the bike handles. This is no different than it’s ever been. I can see opportunities for framebuilders who know what they are doing, and I can see the potential for a lot of mistakes by engineer designers who know little about bikes.

And what does anyone use as a point of reference anymore? It’s easy for the framebuilder who can see the whole picture, but what about the average rider and even the bike store owner fitting that rider, it must be as confusing as hell. There has always been more to frame design than seat tube, top tube, and “What angles is it?” But when a rider bought a new frame if the size and angles were about the same, s/he knew what they were getting. Now as you point out two frames that appear to be the same can be totally different.

I agree, it must be very confusing for the newbie or the shop owner who is trying to juggle the customers needs as well as his/her own needs to move stock, economic reality and all that.

Personally, I've had a road bike in my stable every year for the past 15 years, and although I'm really a mountain biker pretending to be a roadie, I can see some big holes in the current road design/geometry paradigm. There's a shift starting to happen now though, and you can see it with the new Specialized Roubaix models - longer stays, more rake, higher bar position - many of which I've experimented with on this big orange bike of mine.

For someone like me, many of these changes are changes that the MTB scene went through in the past 5 years or so. For people of your experience though Dave, it's probably deja vu - this 'new' emerging geometry is not much different to the classic bikes ( I'm guessing ) of the 70's or something.

Do you know where this obsession with short, low and steep came from? Was it just people's obsession with 'percieved' 'quickness'?

Do you know where this obsession with short, low and steep came from? Was it just people's obsession with 'percieved' 'quickness'?
I never followed fashion and that policy worked for me over the years; if I designed bikes today I would do the same. Fashion should only dictate the overall look; a sloping top tube is an example; choice of different tube diameters would be another. When you start changing geometry for the sake of fashion; what are you achieving apart from a temporary marketing ploy? And you are not doing anything that hasn't been done before.

So to answer your question about short, low, and steep. (We are talking road bikes?)

Short: Shorter is stiffer, but should never be taken to extremes. Lengthening the chainstays is only making the drive section less stiff. You may add marginally to the comfort, which for recreational riders would be a plus.

Low: By this I take it you mean low handlebars in relation to the seat height. An efficient riding position is one where the arms are in direct opposition to the legs. When making a maximum effort legs are thrusting downwards with more power than your body weight. The only thing holding you down is your arms; power is transmitted from the arms through the shoulder and back muscles to the legs. When you need extra power you get out of the saddle; this is a natural reaction, even a child will do it even though no one has taught them to do it. You are doing this to not only get your body weight over the pedals but also to get your body closer to your arms so you can get a direct pull on the bars. Like lifting a heavy weight you need your arms close to your body, and if you hold the weight at arms length it will put a strain on your back. So too if your arms are stretched out too far ahead; the result will be back ache on a long ride. Arms need to be low and as near to the body as is practical; taking into consideration comfort and the rider’s ability to handle the bike.

Steep: I never believed in steep head angles; steeper seat angles in the case of smaller frames to achieve a riders position as outlined above. It has been established for many years that the ideal head angle for a road bike is 73 degrees. You can go to 74 degrees for criterium bike (with a shorter fork rake) and 72 degrees for a touring bike or an extremely small frame where you need to make the front end longer. But if you go steeper than this you make a bike that is squirrelly and twitchy in it’s handling; especially when you get out if the saddle to sprint. Any shallower on the head angle and the bike will feel sluggish or like a wheelbarrow when you sprint.

My advice to any framebuilder, or even a large manufacturer; find out what works and stick with it. If it goes against fashion then only give your customers as much information as they need; I wouldn’t advertise the fact that I was against fashion. Customers will flock to you when the word gets around that your bike handles and rides better that anything else.