Monday, January 25, 2016

The Minutiae Of Millimeters And Degrees

When it comes to the geometry of bikes, and especially of those for gravel travel, long time readers here should remember my various posts on my take on the sort of geometry that makes for a better handling and riding bike. If you are fairly new here, I will just say that my take on gravel bikes began to form back in 2010, and since then, some folks have listened that had the power to make bikes based on these ideas.

Some folks have said that this all wasn't necessary, and that other bikes would do just as well at what it was I am after- the best handling and riding gravel bike I could get. While one can ride whatever the heck they want to, on any surface they choose, to deny that geometry is tweaked to meet highly specialized tasks in cycling would be ludicrous. That time trial bikes, cyclo cross bikes, and crit bikes exist, when one could do all of those things on a traditional road bike, is all you really need to understand that specialized geometry is prevalent in cycling, and has been for a very long time. I don't think I need to bring up mountain biking, but the illustration works there as well.

Secondly, my thoughts on geometry weren't something I made up, but were pulled from history. I knew that lower bottom brackets, slacker seat and head tube angles, mated with a longer offset fork were from early 20th Century road bikes that had to be able to traverse roads made of dirt and gravel. Precisely what I wanted to do with my bikes. In my mind, "settling" for a cyclo cross bike was just not an option, nor should it be.

My Twin Six Standard Rando has almost the identical layout that earlier bikes had
The bikes eventually came out- The Raleigh Tamland, and another which is in the same vein, the Twin Six Standard Rando. The lower bottom brackets, slacker angles, and room for big tires which make riding gravel more comfortable and stable were just what I was after. Still, many people rail against these ideas as something the marketing machine came up with to "invent a new category" that is not necessary, in their opinions. That's all well and good, but I knew those opinions were either based on illogical thinking, or simply misinformed.

Then I got wind of an article on the "Red Kite Prayer" site about old road bike geometry. The "Italian geometry" is something that I had heard about in years past. The lower bottom brackets, and the slacker head tube angles. These were the ideas I had drawn my inspiration from. While some may think my ideas were "unnecessary" or whack, if you take the time to read the article, you will find that many builders and professional riders knew otherwise. It's real, it makes a difference, and many people have never ridden a bike with this sort of geometry to know the difference.

In the end, is it all just "splitting hairs", and can't we all just ride one bike and get along? Of course it is, and "no", of course we can't. I'm grateful either way that the "gravel bike" exists and that we have the right tool for the job now.

3 comments:

james said...

GT,
I'm totally on board with lower bottom brackets, lower chainstays, and more front center, but head slack head tube angle I'm not so sure about. I recently acquired a bike made by Elephant, the NFE. It's 650B based with a low trail design. The head angle is 73 but with huge fork rake, around 6cm if I recall. This puts the trail in the mid 30's. The handling is outstanding on gravel and dirt.
I would love to here your opinion and thoughts, good or bad, on such a design.

Guitar Ted said...

@james- Low trail, (without any load on) equals less stability. On gravel descents, loose, deep gravel, and in softer conditions, less stability is not what I, or many other cyclists, want in a gravel bike.

If, however, you put a rack up front and carry a load regularly, low trail makes more sense. That said, I really am not in that category, and therefore I am not looking at anything low trail to make a good gravel bike. In fact, just the opposite is true for me. Think "fire road descending" for mountain bikes, and what that geometry looks like. Then the gravel road geo I prefer makes more sense.

I don't see a lot of folks front loading their bikes at gravel events either, so again, low trail doesn't seem necessary or ideal.

Sam Lewis said...

Great post and comments on RKP. All this talk about lower bottom brackets on gravel bikes but Richard Sachs is making CX bikes with 80mm drop. My old road bike (Spec. Roubaix) has about 75mm drop. If a gravel bike was designed for 40mm tires, I would think 85mm drop would not be unreasonable, but I haven't seen anything over 75mm. Never mind more cow bell, I need more BB drop!