Page 42, "Steering head Rise and Fall"

DH says that the steering head rises and falls when the bars are turned. "When you turn away from center, the steering head drops. When you turn back to center, the steering head rises."

I invite all our honorable forum participants to check their bikes to confirm this for themselves. Except for some radical chopper front ends, nearly all bikes will have the low point of the steering head occur at center. (Oh, Tony Foal, where are you when I need you most?) Because radiators, tupperware, front wheel & mud guard can make this measurement so difficult, try bringing the steering head cap nut under the garage door header. Measure from the top of the cap to the door header when the bars are centered and again when the bars are at full lock. If the low spot for the steering head isnt dead center, post up the make, model and year of that bike. (Edit; Drat. I forgot about hub-steering bikes. I dont know if the steering head changes on those bikes. Nor am I familiar with BMW's telelever system. Earle's Leading Link designs may differ too. The above observations ought to hold true for standard telescopic forks.)

While all y'all are at it, check all the two wheelers in your stable and let us know if you have any ordinary bicycles that are similar. Dont forget to check the scooters.

I believe DH got this steering head rise/fall bit bass-ackwards. One of the reasons the bike's bars tend to self center is that the steering head is lowest at that point betwwen the stops.

I predict that steep raked sportbikes will have as little as 1/4 inch rise/fall difference. While cruisers may be as much as an inch difference. Standards will be near a half inch. Dirt bikes will have the most variance. Yet all bikes will have the low points of steering head fall at centered bars. (Home-built extended telescopic front ends will be different, or tend that way.)

This could be a two or three person job for those of us with luxo-potomuses. Keep in mind that this is a difficult measurement to take. Repeat your efforts. Get any assistants to take measurements too. Dont tell your assistants what the measurements should be. Let them do it blind.

Page 41 top. Page 40 bottom: DH writes about "hands-off riding".

If the bike naturally wanted to turn because "Gravity actually helps turn the front end away from center and resists the front end returning to center. (Page 42); riding "Hands-off" would be near impossible.

If the steering head did not drop when the bars are centered, there would be no other place of stability except at one or the other fork stop.

I can see why many riders do not understand how the bike's geometry works. The riders' eyes glaze over due to this unfathomable inconsistancy. And they move on to more understandable things. And they never trust themselves to speak of these things. (Edit; If I told you that you could climb a slight slope on a standard bicycle using nothing but a little body weight shift and waggling the forks from side to side, would you believe me? Modern fork geometry permits this. When two or more bicyclists know this, they can race each other up garage ramps using the technique. Very strenuous and screaming good fun.)

That steering stuff is pretty hard core mechanics. The mensa masters around here will have a field day with me if I got this wrong.

(Edit: page 40; DH covers his butt with a sort of disclaimer that his understanding of bike machanics is based on 30+ years of arm-waving discussions and napkin scribblings. Its not like the hard data/science wasnt available at the time?  Thus DH offers us his OPINION of how things really are. Do you think that DH did any checking for himself on his own bike before commiting such opinions to print?)

nobody rides half as well as they know how.

Now that you know about steering head rise and fall, anybody want to trust "Mass Shift" on pages 42 and 43?

nobody rides half as well as they know how.

From Foale and Willoughby, Motorcycle Chassis Design (Osprey 1984, out of print):

With a normal motorcycle (i.e., with positive trail) held vertically, the steering head will drop as we turn the handlebar to either side... The greater the rake angle, the greater the drop...

This drop tends to work against the self-centering effect of castor because, to return deflected steering to the straight-ahead position, we must lift the considerable weight supported by the steering head. While this effect is detrimental to balance (hence another reason why trials bikes have steep head angles), and to directional stability while travelling in a straight line, it helps to steer the wheel into a corner when banked over, thus reinforceing the self steering effect of trail mentioned earlier.

One of my complaints about Proficient Motorcycling is chapter organization. Chapter 2, Motorcycle Dynamics, includes both arcane details of steering geometry, such as you cite, and practical instruction on steering skills. Keeping in mind readers, purpose, and use, I would expect many readers to look for cornering technique in a dedicated chapter. Embedding it with the background theoretical material makes it harder to find, and it also gives the reader the impression that he's got to understand chassis geometry before he can steer a motorcycle.

Glancing at the bookshelf behind my desk, I count 18 books about riding that I have bought and read over the past 25 years or so. Many are dedicated to better lap times or to the finer details sportriding. But for getting from Point A to Point B safely and confidently via public roads, Hough's are the best.

The main thing that distinguishes Hough from the rest is his focus on street riding. While I'm mainly a sport rider, the fact is that most of my riding--most of everyone's riding--is in traffic on public roads. I recently analyzed fatal sportbike crashes in the SF Bay Area and found that only a few occurred on the twisty rural two-lane roads that are sought after by sport riders. Most were in situations where a cruiser, a tourer, or a scooter would be just as likely to crash. The rider error that caused or contributed to the crash didn't have anything to do with esoteric issues such as line selection, body position, push-vs-pull countersteering, or trail braking. Rather, the riders made basic mistakes such as poor judgment when passing, failing to maintain control on a straight section of road, not anticipating other motorists' actions.

Apparently, I am blown out of the water on this one.

I am surprised others didnt jump on this error. Now that this error is apparent, I guess that I can't have fun with "Mass Shift".

Ya think anybody on this forum got excited and measured their own bikes?  One of the great aspects of PM is that we have bikes at hand and can check stuff for ourselves.

A proficient rider tends to understand a great deal about the motorcycle and how it is supposed to function. That understanding is best when it comes from the rider's hands-on checking for himself. That direct experience armors the rider against the mis-statements and errors of others. And the rider's self confidence is correctly enhanced at the same time that his self doubt is banished. All of which takes time. And each of us has out own route to proficiency.

Your perspective that DH mixes arcane details with basic MSF instruction is spot on. I can see how upsetting that might be to some  readers of the book. Yet some students like to know about the what&why that instruction is based on. I dislike rote instruction as the only fare to learning. Getting the balance is pretty hard to do.

Even the great MCNews gets it backwards every once in a great while. Tony Foal had to clarify some confusion about Dan Gurney's Alligator lean angle a while back. I expected a hailstorm of letters about that error from the proficient riders/readers of the rag. Alas, it was a weak hailstorm. Proficient riders/readers of MCNEWS are happy to forgive the occasional error. But, we are not about to forget nor forego a chance to tease each other about our humanity.

Thanx for the fun, DataDan.I had hoped a few more would join in. We seem to be the only ones consistantly awake on this thread. Although, I am pleased that the view count continues to grow. We have some sort of audience. A participatory audience would be more fun. 

nobody rides half as well as they know how.

Anybody feel uncomfortable with that statement/opinion? Anybody got an alternative or varying opinion?

If a biker was to have an "emergency maneuver", what might that be and what part of it makes it 'emergency'?

If you think that DH is dead-on correct, you can post that too.

nobody rides half as well as they know how.