Thursday, September 21, 2023

A Search For "Gravel" Geometry": Part 3 - Is This Really New?

Okay, so far we've looked at how geometry can be a tradition, a myth, and how the "human factor" can adapt differing geometries making anyone saying that "this" geometry is THE geometry for any particular bicycle an erroneous statement. We also know that manufacturing, fashion, and popular figures in sport can influence what geometry might be baked into a bicycle at your local retailer. 

But certain things are better than others, so where do you look to find out what works? Well, you need to think about what you want to do with your bike, and then you need to think about how your rides might look, and of course, where your rides will take place in terms of terrain. 

never thought about anyone else but myself when I was thinking about a "gravel bike". I was thinking about long rides. I was thinking about stability, comfort, and all that on crushed rock roads, which we have 70,000+ miles of in the State of Iowa. I never was what you'd call a "roadie", having come from a mountain biking point of view, but before that, a rider that just wanted to ride a bicycle wherever I could go. In Iowa, that means gravel, pavement, and some dirt. 

My cycling as a youth was all over my small Northeastern Iowa city. I enjoyed bikes that I could ride no-handed for blocks upon blocks. It was easy, and the bike was friendly, not a hassle to pilot. Why ride a bicycle if you have to fight the bike just to get down a road, be that into a wind, on a rough surface, or on gravel? I figured that I wasn't the first person to have done this, or to have thought about this. So, I searched online years ago to see what sorts of bicycles riders used in the early 20th Century. 

A page from "Bicycling" magazine from the 40's detailing Willie Honeman's track bike.

A few things were becoming evident in my searches. The front end geometry was going to be numero uno in importance here. That, more than anything else, was going to determine how my "ideal gravel bike" would handle. 

My research pointed to a bike with a slightly slacker head tube angle, a healthy amount of fork offset, but nothing crazy, and a lower bottom bracket coupled with a bit longer than road bike chain stay length. Everything would be wrapped around some poofy tires, 42mm at least, and there would be room for mudguards too. 

That was all derived from older road bikes, but the discovery earlier this year of a page out of "Bicycling" dated from the 1940's kind of opened up my eyes to another source of geometry ideas that I had not considered before - Track racing. 

Nowadays a track bike isn't what it was back in the 1930's, when a man by the name of Willie Honeman was a track cycling champion, and neither were the machines like they are now back then. If you read the article correctly, the head tube angle is not some crazy steep degree. It is 72° and the bottom bracket drop, which is hardly anything on a modern track bike, is a healthy 75mm on this older design. The seat tube angle is 70°, rather slack, but that was still not uncommon in the 1930's.  Chainstays? About 430mm. Perfect for a 42mm tire. Well....not a track racing tire, but you know what I was thinking now. 

And the kicker? That is a 58cm top-tube on this frame. That's my size. 

And so what? What does this have to do with a gravel bike? Well, in old school track racing, which could be a multiple day affair, stability was prized. That also is reflected in the fork offset on the Honeman bike which is approximately 38mm. You had to be able to hold a line, especially no-handed. You could not be fighting the bike, because all the rider's energy had to go into moving forward and not be wasted by fighting the geometry. All the things I'd want in a bike, this track bike design has also. 

It's interesting to note that in the article, Honeman recommends a slightly slacker head tube angle for rough road riding. So, right up my alley. And again, all things which were race and rider proven design. It only makes sense then that gravel bikes have a similar design to cover rougher roads with stability and less rider fatigue induced by bad angles or less comfortable geometry.  

But I gotta admit. A track bike wasn't where I thought I'd find my ideas being proven out. 

Next: On Saturday - The Honeman Sprinter


AnyAndAllRoads said...

The fork offset is stated as being 1 3/4 inches of rake. Which would be 44.45 mm of rake, which IMHO makes more sense than the 38 you listed. It also states that a slacker head angle and more rake (closer to 50 mm) would be better for a "road machine". Given that the "roads" back then were probably not that different than what a lot of us ride on gravel bikes nowadays, that makes sense, too. A 71.5 headtube angle with a 50 mm offset fork? Sounds like a lot of the latest gravel bikes!

Nooge said...

You’re right that track cyclists back then would have prioritized stability and low effort to hold a line. Back in those days 6 day races were a major attraction at the velodromes. In those races the riders were competing to see who could ride the furthest distance racing around the clock for 6 straight days. They could sleep but your competitors were still riding so they slept as absolute little as possible. They were zombies on bikes!