The Bicycle: Evolution or Intelligent Design. Part III
Mon, December 8, 2014 
This is the final part of a three part series. If you haven’t already done so, I suggest you read Part I, and Part II first.
The slump in bicycle sales that lasted through the 1960s, ended during the 1970s spurred on by a bicycle boom in the United States. In America people were realizing that exercise was an important part of a healthy lifestyle. In Europe those who had given up on cycling in the late 1950s, were coming back to the sport after the initial love affair with the motor car had subdued.
If you remember from part one of this series, the standard racing frame of the early 1950s had a 71 degree seat angle, and 73 head angle. If you also remember that 2 degree difference, with the seat tube leaning back slightly from the head angle, benefited the framebuilder because when building larger (Taller.) frames, the top tube automatically became longer.
This old framebuilding design philosophy had not been forgotten among the older established framebuilders that had been around for years. However, no one was prepared to go back to 71 degree seat angles, so 73 seat, 75 head angle became the new norm.
The sales pitch made for this steeper head angle trend was that it made the bike feel livelier when sprinting. It also made a bike that was squirrely and sometimes difficult to handle. The other gradual trend that had happened in the period from the 1950s through to the 1970s was that racing cyclists were riding smaller frames. Frame sizes had shrunk as much as 5cm. or 2 inches.
Smaller frames were lighter, and stiffer. Improvements to aluminum alloys meant that longer seat posts and handlebar stems could be used, and of course this was necessary when using a smaller frame.
I initially got into framebuilding trying to build a frame that suited me. I am short in stature, 5’ 6”, I found that even with a 73 degree seat angle, I still found myself sliding forward in the saddle when sprinting or anytime I was making maximum effort. I came to the conclusion that a body will always find a natural position for any physical task. One where it can perform at maximum efficiency.
When you teach a child to ride a bicycle, you teach them to balance, and that is about it. They are seldom taught how to ride out of the saddle, and yet once they have mastered the balance part, you will see them standing on the pedals when the going gets tough, or extra speed is needed. It is the human body finding the best way to do the job efficiently.
The Ordinary or High Wheeler bicycle, had a simple efficient riding position. Not aerodynamically of course, but in terms of getting power to the pedals, the arms worked in direct opposition the legs. Over the years that followed in an effort to get the rider’s back horizontal to be aerodynamically efficient, the handlebars were moved further and further forward without lowering them a significant amount, and without changing where the rider was sitting.
It wasn’t until the trend went to smaller frames, that handlebars could be placed lower in relation the saddle. Today saddle to handlebar height difference is probably greater than ever, and I believe the riding position of today’s racing cyclist is the most efficient it has ever been.
The only time I see a lot of sliding forward in the saddle is on time-trial bikes, where the arms are once again stretched forward in an effort to gain the most aerodynamic advantage. It would seem to me that the saddles on these bikes should go even further forward. Although UCI regulations might prevent that happening.
Incidentally, the leisure cyclist who has neither the ability or desire to ride in an extreme racing position, often set their bike up with the handlebars high and forward, when lower but closer (Shorter stem.) might be just as comfortable and a more efficient position.
Getting back to the steep head angle trend of the 1970s. It was just that, a trend that really served no useful purpose other than to make something different as the racing bicycle was reborn after a long slump. The other reason was old established framebuilders clinging to this notion that, “The seat angle must be shallower than the head angle.” Because that is the way it has always been.
I never followed that trend though the 1970s. In fact I went the exact opposite, staying with the 73 head angle on most road frames, and on small frames especially, I made the seat tube steeper than the head angle. My customers in the UK were exclusively racing cyclists, and rarely questioned the geometry, all they cared about was, “How did it ride?”
Evolution has been happening in the bicycle business since its invention, and is still happening. Look at what happened in the last thirty or so years. The Mountain Bike began with a handful of enthusiasts downhill racing on trails in Northern California. When it went mainstream in the late 1980s, it appealed to mainly young adults who had grown up riding BMX bikes in the 1970s.
When I built road frames in the 1980s, the technology was there that I could have built welded frames. However, racing frames were traditionally lugged steel, hand brazed. A welded road frame was not acceptable to my customers. Sloping top tubes also were not acceptable to me, or my customers.
The Mountain Bike was a different animal altogether, not bound by any framebuilding traditions of the last 100 years. The welded frame was accepted, and lent itself to mass production in aluminum as well as steel. The BMX bike had been a basically a “One size fits all,” frame. The mountain bike became available in Small, Medium, and Large sizes.
The old school framebuilders like myself disappeared and the corporations took over. It was not surprising when the road bike made a comeback it would look similar to the Mountain Bike and be available in S, M, and L sizes.
The level top tube started out as a point of reference for the frame builder, but it also became a point of reference for the customer. If a person always rode a 56cm. frame, he knew what a 56 frame would look like, and you couldn’t sell him a 54 with a longer seat post, and different stem.
By radically changing the look of the road frame, it left the door open for limited sizes to become acceptable. Once again something that suits the manufacturer, not necessarily the customer.
In the 1980s, even with my knowledge of bikes, I could not have sat down and designed a road bike like today's machine. Even if I did, would it have been accepted? It had to evolve, and that is the way it has always been.
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Reader Comments (9)
Road frames with sloping top tubes just don't look right to me, all my road and track bikes have level top tubes. If I ever buy another road frame it will have to have a level top tube, the only frame I can see myself being interested in right now would be the steel Colnago Master because it seems that all carbon frames have sloping top tubes.
Even Lance Armstrong was a proponent of the level top tube when he rode a Trek, he didn't want a sloping top tube (I remember seeing him discussing this in a documentary some years ago). Why was a level top tube so important to him? Because it looks right!
Cracked pelvic bone! Thats what happened with a level top tube. Riding my 2004 Mercian Vincitore that I had built to my specs with the classic 73x71 from the dark ages. I skidded on some ice and went forward on the sadde and hit the level top tube OUCH! Now I do have to agree that bikes LOOK better with a level top tube, but sloping ones as on my 2008 Concorde Xblade for me been height impared (5' 3") IS safer. Now as to the comment about sliding forward when sprinting etc. AS I have said before I always ride with my sadlle as far back as possible, also level or with a slight back tilt. So I never do have this problem. I do think the saddle angle is important my prostate doc says this could also affect this problem? and I should have the saddle tilted down a bit? Of course women do not have this to worry about.
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Thanks Dave for this series, great information on frames, as ever!
Dave, Thanks for this series. I often refer to and share many of your tech articles as they are well written and explain the topic with real experience along with the physics.
I too prefer the level TT. It does look better because that is what I grew up with understanding was the convention.
You write:
I think it's neat (I ride with a low bar), and I'm glad to read that there's someone out there who's got a different perspective from Grant Petersen at Rivendell. He's written at least twice about how we ought to ride more upright because it's more comfortable, and we wouldn't need gloves. But I like the lower position; I put drop bars on my hybrid/commuter because I like to be out of the wind, and I feel like the lower position gives me more power (maybe it's my imagination, but I feel like I go about 1mph faster in the drops than in the tops, even with a tailwind).
You're glad to read that there's someone out there who's got a different perspective than Grant Petersen? You mean you are glad that mainstream thinking exists in published material about cycling? I don't get it. He's an outlier. You need to read more cycling fitting articles.
Also, Dave's perspective seems to be almost entirely limited to lightweight racing cycling, which is the real big difference. Both have blinders on, both have good ideas.
Did you ever fillet braze bicycle frames, Dave?
Would they have been accepted in the market?
Dave again I would say that you provided us with the best of knowledge regarding bikes. I often read your blog and comment on it. Thank you for being every time here to educate us on best bike available around.. cheers