The ideal handling bicycle
Mon, June 29, 2020 
Back in the early days of my framebuilding career, mostly in the 1960s. I was experimenting with head angles, fork rake, and trail.
It was in the days before electronic calculators, and computers, so I kept track of my progress with a graph drawn by hand on squared graph paper.
It looked something like the graph above, only it would have been in inches rather than centimeters. Today there are online trail calculators available.
Trail not only gives a bike stability and keeps it tracking on a straight line, but also gives it self-steering qualities.
When you lean into a corner, the bike will for the most part steer itself around the bend.
Because the bike and rider are leaning, the rider’s weight is being pushed outwards by centrifugal force.
However, there is an optimum amount of lean, too much and the bike will slide out from under the rider.
Therefore, there is an optimum trail, if a certain amount of trail is good, more trail is not necessarily better.
The amount of trail is not the same throughout a range of different head angles. The steeper the head angle the more sensitive the steering, therefore less trail is needed to have the same effect as it would on a bike with a shallower head angle.
In time I found there was an “Optimum Handling” line that I could draw on my graph, that would show me the fork rake needed for a given head angle.
Reading vertically down from where the fork rake line crosses the head angle line shows the amount of trail. As you will see, steeper angles, less trail, shallower angles, more.
The example shown 73-degree head, 35 mm. fork offset, and 67.3 mm. of trail, was my standard road geometry on the John Howard, Fuso, and Recherche frames I built.
I would build a track bike with a steeper head angle (75 degrees, 25 mm. rake.) making for more sensitive steering because it is designed to be ridden on a banked velodrome.
The banking has the effect of riding in a straight line, not cornering like a road bike. The rider needs a bike that he can physically steer around an opponent in a quick move.
Also, in the event of another rider falling in front of him, he needs to be able to change direction in an instant. This was also my thinking, when I built a criterium frame with a 74-degree head, and 30 mm. of fork rake.
However, my standard road geometry gave this same ability to lean into a corner, let the bike take you round, but if you needed to correct your line, or steer around an obstruction, you can physically steer the bike by turning the bars, and pointing the bike in the direction you need to go.
I have said before, my bikes had a little more trail than most others built back when I was building, and more than on bikes produced today. That is not to say I am right, and all others are wrong, it is just my design philosophy is different.
The handling qualities of a bike do not depend on the steering geometry alone, it is the design of the whole frame, weight distribution, etc., etc.
When I recently rode a carbon-fiber framed bike, it felt okay, but the steering was different. Not bad, nothing I could put my finger on, or nothing that I could not get used to, given time.
My philosophy has always been, build a good handling bike, put a novice on that bike and he becomes an adequate bike handler. Put an experienced bike rider on the same bike and he becomes a brilliant bike handler.
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Reader Comments (15)
Hi, Dave!
Personally i like the bikes having more trail, i feel comfortable the bike being stable. My bike has 72.5 head angle and 41.5 mm fork offset.
Yes, current bikes now have less trail. I don't understand why, also since the entire package (fork, wheel) got lighter, thus easier for the outside forces to act on the front end.
I like it stable, more trail ;-)
Best regards,
Mircea
All of my early bikes were high rake/high trail with 'soft' handling.
Then I built a bike on an Alan aluminum frame.
Holy Toledo, low rake, low trail and twitchy.
I did come to love that bike.
But to ride it no-handed you had to sit on the very back of saddle with almost no weight on the front wheel.
Now that I am older I find it a bit much to handle and have gone back to an older steel frame that is closer to Dave's handling line. It is a bit firmer but the steering is more 'normal'.
Dave, isn't a trail of 60 considered "neutral"?
I’m not sure Ed, it’s all a matter of opinion. I arrived at my figures by actual experiment, I rode bikes in the 1950s that had zero trail, in fact trail was thought to make the steering sluggish back then.
In the 1960s I experimented with bikes with as much as nine centimeters of trail. Those bikes steered horribly and wandered all over the road when climbing out of the saddle, By the 1970s I had arrived at the sweet spot for me.
Many people agree with me, but some do not, it is still just my opinion. 60 mm. is a nice round number, that sounds good to many people. It is a bit like helmets prevent 85% of injuries, it sounds about right to most people, but can not be proven, because it is not factual, just an opinion.
Now bikes are made by large corporations, I think fork rakes have increased to avoid toe overlap and potential lawsuits from people who have no business being on a proper racing bike. As a small business I never worried about being sued, I never had enough money to make it worth a lawyer’s while.
Dave
Dave, would you say a bike that is easy to confidently ride no hands meets the attributes of good handling? If it's scary to ride no hands, could it be bad geometry, misalignment or just an inept rider, and how to tell the difference?
John B,
I always designed and built bikes to go around corners fast. Riding "No hands" was never a consideration.
Dave
Dave, have you experienced this type of geometry?
longer top tube
shorter stem
steeper head angle
smaller fork offset
normal trail
all for the same placement of handlebars and front wheel in relation with the bottom bracket. so bottom bracket, wheels, saddle, handlebars, all in same position.
thank you & best regards,
Mircea
A comment above asks, "isn't a trail of 60 considered neutral?"
Long time successful framebuilder Tom Kellogg of Spectrum Cycles (whose business is near closing so his web article may not be available much longer) published an article which concluded 56mm of trail to be neutral. He laid out his argument well.
You can read it here:
https://www.spectrum-cycles.com/geometry.php
If you read the article, it sounds like Dave's frames should have handled poorly. But they didn't otherwise he would not have been so successful.
If you look at the numbers of the overwhelming majority of road racing-style bikes sold today, they DO fall within a millimeter or two of that 56mm.
One reason I am intrigued by Dave Moulton's frames is their high trail figures. I've always wondered how they would handle. My only frame of reference are the "neutral" trail road bikes I've owned.
My mountain bike however, has a higher trail figure and I do love its self-steering qualities as well its maneuverability.
If I ever have extra money burning a hole in my pocket, I'll have a custom frame built with that high-trail geometry and see for myself.
Peter,
There is absolutely no need to go to the expense to have a frame built to my geometry to see how it rides. I built over 2,400 FUSOs, and there are hundreds of them still out there that can be picked up at a very reasonable price.
Or go to the Dave Moulton Bikes Facebook Group and ask anyone there what the ride is like. You may even be able to borrow one to test ride.
Dave
Mircia,
I don't really understand the question, but if you go over to bike-cad you can dabble in frame design https://www.bikecad.ca/
Dave
Dave,
there are two directions to go when same placement of: wheels, bottom bracket, saddle, handlebars.
one where the head tube is slacker, and one where the head tube is steeper.
i am asking about the second one, where: steeper head angle, longer top tube, shorter stem, smaller fork offset, normal trail.
what would be the pros and cons about this geometry, how the bike would perform?
(again, very important when compare, same placement for: wheels, bb, saddle, bars)
best regards,
Mircea
hi, Dave! is there any possibility to show you a couple of photos (sketches i did) regarding the different directions of geometry but keeping the same placement of the most important points: wheels' axis, bb, saddle, bars.
this is my email: mirceaandreighinea@gmail.com
thank you!
Mircea
Mircea,
What you are describing is pretty much like the standard geometry of most Italian built frames in the mid 1970s and early 1980s. If you read my Three Part Series: The Evolution of Frame Design http://davesbikeblog.squarespace.com/blog/2009/10/5/the-evolution-of-frame-design-part-i-the-wheelbarrow-effect.html
It will answer many of your questions. My email link is on this page center column. davesbikeblog[AT]gmail[DOT]com
Dave
Thank you for this explanation of trail.
Best read on this topic I've come across.
yeah, you wrote well. Now I understand why my hands are hurting while cycling. thanks, mate for sharing this geometry.