I believe that was the angle used on Roman chariots. ;-)

just bumping this back up...I am interested in any answer as well.

I read it was done by trial and error from the early road racers. Steeper angles are nothing new and were also tried. Apparently 72-74 felt right, seemed the best handling balance and seemed to perform best. Realize this was often racing in Europe on cobblestone roads, etc. so the criteria may have been a bit different from today. However, 72-74 still remains the standard for road racing today and this seems highly unlikely to change. Steeper angles may seem logical for time trialing or triathlon but would make no sense for road racing.

"read it was done by trial and error from the early road racers"--
Do you remember where you might have read that? I would like to get the source for an article I am writing.

"72-74 felt right, seemed the best handling balance and seemed to perform best. Realize this was often racing in Europe on cobblestone roads, etc. so the criteria may have been a bit different from today. However, 72-74 still remains the standard for road racing"--
so who exactly today says this is the 'standard' and why exactly do other people follow it? Today when Trek, Giant, Kestrel, or whoever want to built a carbon road bike sculpture, do they say, 'let's build it with a 72-74 deg. seat tube angle because that what Joe's framebuilding down the street is using and we really should follow what he and everybody else is doing'?? If that is really the case, that is amazing.

Any additonal input is welcome....

---

---

Where would you want to swim ?

The seat tube angle and head tube angle are all about how the bike rides. The head tube angle will determine how "quick" a bike will handle. Now, there are other aspects of this - many kind of moot today. In the past when a frame builder made the frame and fork, the head tube angle was setup with the rake of the fork in mind. A given angle with a give numbers of centimeters offset on the fork would smooth out a ride. It used to be that flex in a fork blade was a good thing and the precursor to modern suspension forks. It seems today that if a person can watch his/her fork blades deviate 5cm from neutral on a rough surface they freak out and put on a stiffer fork. Not thinking that the flex may just have been put there on purpose.

As seen on this photo of a 1961 Paramount, the fork has quite a curve in the blades.



This type of tube curving is still used often in many higher end frames - for the purpose of damnpening a ride. Litespeed Ultimate (before the carbon seat stays) was a great example of a frame with curved stays that was intended to deflect and thus smooth out the ride. I cant think of any newer road bikes other than one off customs that take the rake and curve of a fork blade into consideration for dampening. Though I know of many with a jackhammer stiff fork..and a rider with a sore back.

As for the seat angle. That will determine how rapid the bike seems to go...pull that wheel in and you feel like a rocket (shorter wheel base, also altered by the rake of the fork). If you put to steep an angle on the seat tube, you will alter the virtual top tube length of the frame as you reaise the seat. To shallow you can hit the wheel into the frame. It used to be common that you could change your wheel base with the rear dropout adjustment screws (Sachs and Campy dropouts to name two) You could alter your wheel base as much as 3cm on some bikes....and yes you certainly could feel a small change.

So...seat angle - 73 degrees is about average...I tend to believe that it is due to a more common and consistant agreement between builders over the years of trial and error - the error possibly being that if you raised the seat 2cm on a frame with a 65 degree seat tube - it would also move back 2cm (potentially). Head tube...I think that the mass's have determined that it is best to come to damn near a standard there as well becuase not every builder has they money to OEM their own special carbon/carbon fork to put on their bikes (Like Pinarello and Gios do - but their forks "Mizuno" are heavy compared to other forks out there) Note, I said other - not better.

---

----------------------------------------------------------

What if the Hokey Pokey is what it is all about?

And another thing...am I the only one who can remember back in the day when Kestral was the first company to really make changing out your fork common? People would put on the EMS fork and then hit the front of their shoes into the front wheel if they were to pedal into a corner! They would shorten their wheel base a TON. I think that there were more speed shimmies and shoe - vs- front tire crashes than I would even like to think about.

---

----------------------------------------------------------

What if the Hokey Pokey is what it is all about?

Greg,

I have be interested in building (or at least trying) a frameset. In past research, I came across these titles:

"Custom Bicycle: Buying, Setting Up, and Riding the Quality Bicycle"

and

~"Design your own frameset..."

I remember from a couple reviews that these books are/were considered great references. If you can get your hands on these books ($$$$ because out of print), I bet they make reference.

( Steeper angles may seem logical for time trialing or triathlon but would make no sence for road racing)

Well maybe, Some frame builders make thier larger sizes with steeper angles,I belive Cannondale is one,while a slack seat tube angle will work for a shorter person,and taller person with long legs will be better off with a steeper seat tube angle to open the angle between the leg and torso,I have a 75 a76 and a 78 degree seat tubed road bikes.

Trial and error is how the standard geometry was devised. However, the head tube angles used to be "proprietary" and never published, with the exception of the independent testers. There are even a few builders these days who say that their headtube angles are proprietary.

Steve Bauer had the infamous 69 degree seat angled bike. Andy Hampsten even toyed with the angle of his seat tube, settling on anywhere between 71 and 72. Some crit bikes have parallel 73.5 or 74 degree head and seat tubes designed for the typical American criterium racing. This has (thank God) changed.

If I ever got my bike frame company started up, I would even have "proprietary" seat and head tube angles for every single size of bike I built. I would do it for pure mystery and fun. There are optimal seat and head tube angles for almost every size of bike, and many have their own beliefs on this subject, including oxymoronic positions on the subject.

I was one of those idiots who changed out their fork for a too-short Kestrel. I loved that fork on other bikes. All I did was ride them and try to fix them in those days.

I was so proud of my Kestrel fork as I was the first in my club team that had one. They had a good laugh when I would buy it in a crit, especially since I was on a short bike, anyhow.

As was I Bunnyman, as was I....it was on a Guerccioti (was that the spelling?)...I had black scuffs on my shoes (White and Red Time shoes)...I had to stop pedaling for corners...bike handeled for crap...I would not tell anyone though cause I had the Holly Grail for forks...the now seemingly heavy Kestral EMS...and I was cool.

---

----------------------------------------------------------

What if the Hokey Pokey is what it is all about?

"The seat tube angle and head tube angle are all about how the bike rides. The head tube angle will determine how "quick" a bike will handle"

---this part I understand: the connection between fork rake, trail, head angle, and wheel size; and the choice of all of these based on fork material, fork design, desired comfort, handling, and expected road surface.

"As for the seat angle. That will determine how rapid the bike seems to go...pull that wheel in and you feel like a rocket"

---here is where I am confused: the seat tube angle need not have any connection to the head tube angle; just look at tri bikes with big differences between those angles. And if seat tube angle for road bikes is just based on handling, why is there such an AMAZING industry agreement on the choice of this angle (it barely varies more than a few degrees all the way from hardtail mountain bikes, hybrids, full load touring bikes, to TourDeFrance rocketsleds) in spite of vastly different bike uses, rider body positions, and different frame materials. Is there any science to it at all?

Or is it all based on marketing and "looks"--curiously, the seat tube angle seems to very closely match the head tube angle (within 1-2 deg.) on most of these bikes which are designed for totally different purposes. Or is it just that most (all?) bike companies figure it is "safer" (i.e., more sales, less research, or $ investment) to "just do what everyone else is doing"??

Any thoughts from folks in the industry?

As for seat angle...as I said...mostly because the mfg's need to make a bike that will fit more than one person - so if that angle it too slack, the seat will go back as much as it goes up. That will alter the virtual top tube length. So yes, they do it to cater to the mass of riders out there. That is the smart thing to do in business. If someone wanted a bike with a 45 degree seat tube I am sure a custom builder could come up with something (like the old BMX bike called the "Quad Angle")

---

----------------------------------------------------------

What if the Hokey Pokey is what it is all about?

--so, making sure I got this right, you are saying that most bike companies make the seat tube angle the same or very close the the head tube angle so raising or lowering the seat and/or stem allows the top tube (or virtual top tube) to stay constant. So there is no physiologcal / ergonomic / efficiency / power reason for road bike seat tube angle? Is that right? That also seems amazing. One would think that the position of seat and cranks should be based more on comfort and power output for the type of riding the frame will be used for.

You know - recumbants are faster on flat roads than our "uprights". VERY slack seat tube angle!

---

----------------------------------------------------------

What if the Hokey Pokey is what it is all about?

well, if you lay on your back on a skateboard (the slackest angle of them all) and point it (and you) down a very steep hill, you will go even faster than a recumbant! But seriously, who do these bike companies consult when they slap together a frame?

>But seriously, who do these bike companies consult when they slap >together a frame?

Well, uh, many years of experience. Many pros and elites. If you build enough bikes for riders the likes of Merckx, Van Looy, Van Impe, Anquetil, Pou-Pou, Lemond, Indurain, Armstrong, Scott, Molina, Welch etc, you come up with a working philosphy manifested in frame philosophies like Colonago's, Derosa's, and yes, even our beloved Slowman's Quintana Roo steep angled tri bikes. Sometimes they try to move outside of the box established. Sometimes that effort fails, sometimes it works. I daresay that for every successful attempt at a bike frame, a company probably experiences at least one failure. The basic bike frame has not changed significantly since the advent of the modern safety bicycle, though, and isn't likely to change much in the future. I'd be hard pressed to believe that anyone except the most uninitiated amateur simply slaps together a bike frame without putting serious thought and research (including consulting REAL riders) into what they are trying to accomplish.