Continued challenges for new riders
November 21, 2009 at 7:42 am #23441
” A change of direction results in a lean, a lean does not result in a change of direction.”
This is false on both counts, but unnecessary to his (otherwise correct) argument. I personally think understanding why this is wrong is really important to your understanding, scientific or otherwise, of how your bike steers. As with any argument, you can disprove it by contradiction: finding any single case where it fails.
Try the following, either on your motorcycle or (preferably) on a bicycle.
1) At VERY slow speed (slow walking speed), turn the handlebars but do not lean the bike. You will find that you CAN (don’t have to) steer the bike directly (not counter-steering) while keep the bike completely vertical. The reason both direct steering and verticality hold is that you are steering your bike like a car or trike. Both tires have a (mostly) flat surface is in contact with the ground, and the only way to change direction is by changing the orientation of the front tire’s contact patch.
2) At speed greater than 10 mph, try to lean the entire you+bike package without changing direction. You can’t! The reason is simple. If a bike is leaned, it HAS to turn. The explanation is really simple: bike tires (both motorcycle and bicycle) are rounded. The circumference of the middle of the tire is larger than the circumference of the edge of the tire.
That means that if you roll the tire one revolution on its side, the inside of the tire will travel less distance on the ground than the outside of the tire. The only way for that to work is if the tire rolls in an arc. Voila! Turn.November 21, 2009 at 10:00 am #23449
“2) At speed greater than 10 mph, try to lean the entire you+bike package without changing direction. You can’t! “
Yes, you can. Three examples:
1. Leaning against a steady side wind while going straight.
2. Going straight on a side-way slope – in effect you’re leaning against the ground, rather than being perpendicular to it.
3. Set up body position (hanging off) while counter-steering to go straight prior to executing a turn. The bike would be leaned while going straight.
You’re using the “rolling a cone” example that David Hough used in Proficient Motorcycling; it is technically correct but on a tire where the contact patch width is what, not even an inch wide, the inner and outer diameter difference at the contact patch would account for a very small amount of turning effect relative to steering angle. The coning effect has more to do with needing to add throttle to maintain speed in a lean. The above is not a real argument against the correctness of the statement you cited.
Back to the statement you felt was incorrect: “The fact is that counter-steering, or direct steering, results in a change of direction, not lean. A change of direction results in a lean, a lean does not result in a change of direction.” Note that it’s a cause-and-effect statement, i.e., what happens first, and what follows. Does direction change happen before or after the bike leans?
The statement is actually correct in physics, i.e., direct changes first, then bike lean follows as a result of direction change, but the semantics is tricky and you need to think it thru. The whole thing has to do with equilibrium of force. This is the sequence as I see it:
1. Steering (turning the handle bar) causes tire contact patch direction change, and the friction (i.e., traction) between the tire and pavement causes a change of direction of travel. (Imagine no friction/traction between the tire and pavement, such as when you’re skidding on ice – no amount of leaning will result in a change of direction. Right here it should be clear that direction change is from steering, not from leaning.)
2. The change of direction of travel results in centripetal force wanting to pull the bike/rider to the OUTSIDE of the turn -> As a result the rider/bike has to lean toward the INSIDE of the turn to counter, or balance out, the outward centripetal force. The point is if there’s no direction change first, then there’d be no centripetal force, and you wouldn’t be leaning the bike to counter the centripetal force.
Hope this makes sense.November 21, 2009 at 11:47 am #23450
First off, I think we agree…for the most part. Second, I think I definitely over-simplified things. You’re absolutely right that there is a complex equilibrium of forces that must be maintained, and it’s certainly not as simple as I made it out to be.
I think you’re still missing my point which is simply that change of direction can be brought about without lean, and that a leaned bike will change direction. That point is a direct contradiction of the line I cited. If I, for instance, go to a big empty parking lot and get myself into a nice 25 mph circle, I can, with a sticky throttle, take my hands off the bars and keep going around in that nice tight line. No steering input whatsoever and the bike keeps going in a perfect circle. Whatever combination of forces is at play, the bike goes in a circle if it’s leaned over substantially.
As far as your examples of ways to lean a bike without turning, I think it’s fairly straightforward to say, as you suggest, that opposing a certain amount of turning force with another force, either a strange normal from an inclined surface, wind, or displacement in body weight of the rider, may yield cancellation. If you chain a moving car to a barge also in parallel motion in an adjacent canal and try to turn the car away, nothing will happen. But that’s not conclusive proof that the action of turning away is not responsible for turning impetus. All you’ve done is show that some additional force can be introduced to cancel out or counteract whatever cornering force would normally be causing a change in direction. Also, I’m not sure what roles tire profiles and deformation behavior play in the examples you gave, but I wouldn’t be surprised if it had something to do with it, especially in the case of pre-corner setup.
Again, I didn’t mean to get into a physics boxing match (one I’m horrifically unqualified for), only to point out common-sense error cases in the cited statement.November 21, 2009 at 2:56 pm #23451RabParticipant
I don’t see a problem with any of what you’re saying, so long as you’re not *paralysed* with fear. Many of us have been where you are now.
Maybe you should start commuting to work by motorcycle; one day a week at first. That’s one way to get lots of miles in traffic and experience will help you overcome your mental blocks.
Beware of falling into the trap of thinking (as I did initially) that faster, risk-taking riders (on the street) are necessarily better riders. Sure, there are some great and fast street riders out there, but most of the fast street riders I see out there every day are squids who are just too stupid to realize the danger they are putting themselves (and others) in.
One of the best motorcycling “skills” you can learn is to ride your own ride and not feel pressured into riding beyond your limits or competing with anyone on the road, or keeping up with other riders when it’s scaring you, or allowing yourself to get pissed-off with that dick-head car driver who wants to race you, etc. etc. etc.
Ride your own ride. No-one else cares if you’re fast or not…November 21, 2009 at 4:36 pm #23452
OK, eternal, I stayed up until almost 2 am to write the semi-nonsense I wrote (the physics/mechanics were not fully correct; I think I messed up by discounting the tire’s “coning” effect in a turn you mentioned, and I didn’t/couldn’t explain the steering geometry involved). I really shouldn’t have written what I did, because half truth like that (on the physics/mechanics part) only serves to confuse people. If anybody is really interested in the physics of this, read the following from James Davis on what’s happening during counter-steering (which talks about the tire “coning” thing):
A lot of this stuff is counter-intuitive and can make one’s head spin. When I first read them, I spent days thinking about it, finally put it all together and felt it make sense, but now, months later, I half-way forgot why again. Understands the physics satisfies the intellectual curiosity, but by and large it’s not necessary to ride the motorcycle.
Anyway, let’s not gunk up this thread with too much physics discussions. I’d like to get back on topic – share your experience on learning to ride. Thanks.November 21, 2009 at 10:27 pm #23457eonParticipant
Having an automatic I’ve not had to worry about hill starts (yet), but I have driven stick for over 15 years. I also learned how to drive in the UK where (shock) we have an actual test and hill starts is one of the things you are tested on. Roll back an inch and it’s an automatic fail. The principles are the same so here is how to do it in a car.
I’ll assume you have come to a stop facing uphill with your foot on the brake and the clutch pressed in.
1. Pull on the hand brake (what you call the e-brake here)
2. Foot off the brake making sure the hand brake is supporting the weight of the car
3. Give it some gas and ease off the clutch into the ‘friction zone’. We actually referred to it as the ‘biting point’ which I prefer. There is one point where the engine starts to bite and you can support the weight of the car with just enough gas and just enough clutch so that you are neither rolling back or forward.
4. At this point you can then ease on the gas, ease of the clutch and release the hand brake and away you go.
Replace hand brake above with rear brake on a bike and everything else should work the same (I imagine!).November 21, 2009 at 10:46 pm #23460BouncingRadicalParticipant
Motards are so badass!November 22, 2009 at 12:49 am #23446
Common sense tells you that chicken strips might be a bit more about machismo than skill, but one of the best pieces of advice on of the track-day instructors gave me was that, if anything, you WANT to have chicken strips…and go as fast as everybody else. The real mark of a good rider is that they can go the same speed as another guy (or faster) and lean LESS in the same turns.November 22, 2009 at 12:51 am #23462
Wise move. Sorry for the derailing!November 22, 2009 at 1:06 am #23455
I had an “interesting” experience with uphill start.
I bought my GS500 before I knew how to operate a motorcycle. The seller rode it to my garage and parked it there. The evening after I finished my MSF class (no M1 yet, and no riding gear other than the helmet, gloves and hiking boots), I started my GS for the first time and went for a ride around my neighborhood streets in the dark. After a while I decided to go up this small hill not far from my house. The hill was perhaps 400 feet high, with a county communications facility (bunch of antennas) on the top and a good view. The road going up was fairly steep; on a mountain bike I had to be in the lowest gear and strain to ride up that hill. I thought that first gear would be spinning the engine too high, so I decided to charge up the hill in second. That worked well until the first turn, which happened to be the steepest section and the sharpest turn (more than 90 degrees), so I had to slow down and down shift. I stalled the bike right there. Not panicking yet, I held the bike with both brakes, started the engine, let out the clutch and stalled it again. Tried it again, more gas, letting out the clutch quicker, stalled again. I started to worry. Tried it 3 or 4 more times, still couldn’t get it going. The headlight was getting dimmer, the battery was getting weaker, and I really began to worry. Being in the steepest section, I dared not let go of the brakes, and couldn’t put the kickstand down and get off, so I was stuck there in the dark, with a weakening battery, fearful of dropping the bike on my very first ride. I didn’t know what to do, so I stayed like that for a few minutes, and then finally decided to try duckwalk backwards down the hill while dragging on the front brake. That worked, and good thing I could flatfoot on this bike comfortably. When I finally reached a driveway on the right side of the road, I back into the driveway carefully, started the engine, turned left and rode downhill.
I thought about this problem for a few days. I even mentioned this to a friend who’s been riding for 20+ years. It must have been so instinctive and natural for him because he had no clue what my problem was with uphill start. A few days later it came to me – I was stalling because I was letting out the clutch too quickly; my logic (false) of letting out the clutch quickly was to get the power to the wheel and get moving quickly so I wouldn’t slide backward down the hill. The magic words were “the friction zone”. The correct technique was to stay in the friction zone, throttle up and get the bike moving slowly without bogging and stalling the engine, before letting out the clutch all the way. Once I realized that, and with a little practice on my slightly inclined driveway, uphill start was no problem.
Sounds simple if you knew this ahead of time, and I knew how to do this in a stick-shift car. But being out riding for the very first time, I was just overwhelmed on that hill and couldn’t think this through. If you just read about a situation ahead of time, then you’re better equipped to deal with it when you actually encounter it.
I’m curious how others learned to do uphill starts. Did someone explain or show it to you, did you “just know” on your own, or did you have to figure it out the hard way like I did?December 9, 2009 at 9:35 am #23655XRayHoundParticipant
I never understood that. Rights come far easier to me, partially because on the street (in countries where you drive on the right, anyway) running wide in a right means you MIGHT wreck, running wide in a left means you WILL wreck. Other than that, you’d think I’d be built for left handers… left handed, left eye dominant. But nope, outside of the track I run rights way more aggressively than lefts unless I just know the turn absolutely by heart.December 13, 2009 at 7:22 am #23687Capt CrashParticipant
Inclines are CAKE!
Here’s the dealio!December 14, 2009 at 6:21 am #23692
As of last week I’ve ridden 9,700 miles, and finally went on a 60 mile ride in the rain on Saturday morning. It included some sections of expressway (50-60 mph), 2-lane country roads (40-50 mph), and a narrow and twisty road (15-30 mph). Locked up the rear twice:
The first time was when going about 50 mph on the expressway, got close to the intersection and the light turned yellow, hesitated for a moment on whether to keep going or to stop, then decided to stop at the last moment. Had to brake fairly hard, but in the wet I used less front brake and more rear brake, and fish-tailed into the intersection by about 6 ft. Kind of expected that, and I could have used a bit more front brake and a bit less rear.
The second time was when coming close to stopping to make a left. The rear locked up, skidded a few feet and did a slight jerk when traction was regained. That lock-up surprised me a little; felt like maybe there was some sand on the ground at the intersection.
In the straight sections I pretty much rode as fast as in the dry, but in the tighter corners I went maybe 5 mph slower, followed the slow-in-fast-out principle, and leaned my body to keep the bike as upright as possible. I kept the speed in check and avoided braking in the corners.
It was fun; wish it had rained harder, but I’ll get my chances, and needed to upgrade my rain gear. Temperature was mid-50s, much warmer than the clear but cold (low 40s) weather we had a few days before. The helmet visor didn’t fog up too much and the visibility was not bad. I realized that although my Rev-it Turbine overpants are “water-proof”, it’s the inner liner that’s water-proof; the outer shell is not and got soaked, along with the content in the pockets. Also, my leather gloves got pretty wet; not good. I just bought a two-piece rain suit, and I’m looking for a pair of water-proof glove covers.December 14, 2009 at 7:13 am #23693eonParticipant
Sounds like you had fun. It’s always rewarding when you push your envelope that little bit further.
Interesting that you have Rev’IT pants. I was seriously considering getting myself a full Rev’It outfiit, probably the Cayenne Pro or maybe the soon to be released Sand. Went off it completely when I realized the outer layer is not waterproof. Currently my Teknic jacket is completely waterproof but I was looking to upgrade the protection level. Probably going to just stick with that as it rains a lot here in the winter so being waterproof on the outer layer is important to me. So much so I’ve now decided to get a matching pair of Teknic pants as my current Tourmaster ones absorb water like you described. I guess the climate and rainfall patterns where you live makes a difference in what gear works best for you.
I should add that the summer rainfall here is on a par with the south west i.e. not very much at all. It’s just that we get 3/4 of our annual rain in 1/4 of the year. So I need different winter and a summer outfits.December 14, 2009 at 8:23 am #23695
I think the outer-shell of the “Turbine” overpants I have is mesh construction for the warmer weather. Its’ a very tight weave, but still mesh, thus soaks up water in the rain. Other models, such as Cayenne Pro and Sand, in Rev’It’s lineup just MAY have fully waterproof outer-shell construction. Double-check before you write them off. I got Rev’It pants because they have hip pads/armor, which aren’t provided by many other brands.
My rational of getting a cheap rain suit ($40 for jacket and pants) to wear over my regular gear is so that my more expensive gear don’t get dirty/muddy from the spray kicked up by cars. It’ll also add a bit of extra warmth. I don’t quite get why waterproof gear is that important since you can just wear a cheap rain suit over the regular gear, unless you’re touring and really don’t want to pack the extra rain suit. I guess I’ll find out if it’s really a lot of hassle to carry and wear the extra rain suit.
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