Member Contributer emoyer Posted June 18, 2014 Member Contributer Share Posted June 18, 2014 On Saturday I took the MSF Advanced RiderCourse, and one of the range exercises is designed to help riders get the feel of braking in a curve. You ride a circle of 75 foot dia at maybe 15 MPH or so, and at one point you apply some brakes and see how the bike reacts. I thought the bike would want to fall inward when doing this, because as speed decreased from the braking there would be less centripetal force holding the bike up. But, repeatedly, when I braked, the bike leaned LESS. Is this really the way it works, or do you think I was subconsciously doing something else with my body position or the handlebars that made the bike stand up? To make things even more confusing, when I asked the instructor about it afterward, he said it depends on the bike, and he's had students report both more lean and less lean when applying the brakes in the curve. I'd be grateful if someone could make all this a little clearer for me. Thanks. Link to comment Share on other sites More sharing options...
TNRabbit Posted June 18, 2014 Share Posted June 18, 2014 It's basic physics. You & the bike are in an arc, & when you brake the forces try to pull you out of the arc. Braking while maintaining a turn requires additional steering input in order to stay on your line. ....and it doesn't depend on the bike.... Link to comment Share on other sites More sharing options...
Member Contributer MBrane Posted June 18, 2014 Member Contributer Share Posted June 18, 2014 This is part of what is happening when you target fixate on something, and run the bike straight off the road while braking. It's also big reason why on the street you should get all your braking done before you turn in. Of course if you lock the front mid turn you will surely lowside, but as long as you have traction braking forces tend to make the bike stand up. Some are worse than others (Buells), but they all do it. Link to comment Share on other sites More sharing options...
The Phantom Posted June 18, 2014 Share Posted June 18, 2014 I thought the bike would want to fall inward when doing this, because as speed decreased from the braking there would be less centripetal force holding the bike up. But, repeatedly, when I braked, the bike leaned LESS. Is this really the way it works, or do you think I was subconsciously doing something else with my body position or the handlebars that made the bike stand up? Centripetal force. If you're turning left you're forcing the bike into an arc, but the bike actually wants to continue straight ahead (body in motion tends to stay in motion and all that). Note that the centripetal force is stronger than the gravitational forces that are always acting on the bike, but not as strong as the force being exerted on the bike via your steering input. When you brake you're giving some of the power back to the centripetal force, which then becomes stronger than the steering input force you're applying to make it go left - even if you don't alter your steering input - so its natural tendency then is to go in the direction it wants to go in - which is out of the arc, and in a straight line. Ergo, the bike will stand up. There's also some stuff going on with the wheels (centrifugal forces there) which act as gyros to keep the bike balanced - braking forces upset those forces as well. All bikes will do this given equal parameters - same speed, same radius of arc. But if you go a bit slower there is a point where the bike isn't going fast enough to have those centripetal forces overcoming the gravitational forces acting on it - in reality the centripetal and gravitational forces are pretty much balanced - and upon braking the bike will then fall into the arc rather than out of it. Good on you for doing the advanced rider training, and for asking questions Link to comment Share on other sites More sharing options...
Max1 Posted June 18, 2014 Share Posted June 18, 2014 Its one of the reasons they tell you to do all your braking before hitting a curve. I've had bikes that you could brake into a corner, all had rear drums brakes. There are a lot of people who have or recommend their own techniques for corner braking. Most of us have had to drop the anchors at some stage into a curve & usually with interesting results, )like throw in an impending pothole, a bit of gravel, rain & then the bike not only stands up half way through a corner, but you now have a tank slapper). Link to comment Share on other sites More sharing options...
Member Contributer Switchblade Posted June 18, 2014 Member Contributer Share Posted June 18, 2014 That old center gravity thing every time ... Link to comment Share on other sites More sharing options...
Member Contributer Havagan Posted June 18, 2014 Member Contributer Share Posted June 18, 2014 http://www.motorcycleforum.com/showthread.php?p=1112569 Link to comment Share on other sites More sharing options...
Member Contributer Rush2112 Posted June 18, 2014 Member Contributer Share Posted June 18, 2014 Applying brakes while banked over can be done and should be learned... good on you for taking the course. In addition to the other comments when applying front brakes the steering geometry changes more dramatically by steepening the rake angle and shortening the trail. If your VFR suspension is set up to stock settings you will continue to under steer and the bike will stand up unless you add additional steering input. If the suspension is tuned to have quicker turn-in and is near the limit of just barely under steering it may transition to over steering while braking and will want to fall into the turn when braking. This may be why your instructor had opposite feedback about the same inputs from students on different bikes. I find gently using a little rear brake makes the bike squat and doesn't change the steering geometry as much and reduces the amount of tendency to stand up in the turn... care must be taken not to use up all the grip between braking forces & turning forces; tires only have so much grip, exceed that and you'll have a whole new set of issues! Edit: My comment on the back brake is strictly during moderate to mild street riding. When riding near the limits the front brake is doing the work along with appropriate steering inputs... As Lint's shared video below points out... Nick's trail braking & riding techniques saved my cookies; I practice them almost every ride! Link to comment Share on other sites More sharing options...
Lint Posted June 18, 2014 Share Posted June 18, 2014 3 time World Champion Scott Russell and Yamaha Champions Riding School on trail braking: I personally trail break and I have no issues whatsoever. In fact I have had to stop quickly in a curve and it saved me. Link to comment Share on other sites More sharing options...
Lint Posted June 18, 2014 Share Posted June 18, 2014 Taken from the post in this same forum. Here is an explanation of exactly why your bike stands up in a curve. http://www.cycleworld.com/2014/05/28/the-brake-light-initiative-treatise-on-motorcycle-control-using-your-braking-skills/?cmpid=enews052914&spPodID=020&spMailingID=20890912&spUserID=NzM4NjMwOTI0MDQS1&spJobID=321612328&spReportId=MzIxNjEyMzI4S0 #2 BLI TENET: Be able to light up your brake light midcorner The reason you’re shaking your head right now and grumbling, “This guy’s an idiot. My bike stands up when I grab the brakes in a corner,” is because you are practicing the wrong verb: grab. A grab loads the forks quickly, and the bike wants to stand up as the front tire bites. If this same grumbler can eaaase on the brakes, the fork and tire will load smoothly, the bike will slow, and the radius will tighten. Because you practice this smooth initial squeeze on every ride or drive, you will be able slow your bike midcorner, tighten the radius, and miss the truck in your lane. You will save your life, have more fun, ride in more control, and help grow our sport. Grabbing, stabbing, hammering, throwing, flicking, flopping, tossing… Those verbs need to be eliminated from your motorcycle-riding vocabulary because they add lean angle, braking, or throttle points too suddenly, throwing you past the limits of a tire’s grip. We have a problem in this sport. Bikes and tires are better than ever, yet riding at trackdays and on the back roads isn’t improving. My friend Ray Ochs, head of Rider Training at the Motorcycle Safety Foundation, plans to work with me on this Brake Light Initiative, for all the reasons stated in this article. The BLI is aimed at giving veteran riders and new street riders one more tool to enjoy motorcycling and to survive this immensely satisfying but potentially risky sport. I leave you with this simple premise: By better controlling our motorcycles, we will enjoy riding more and grow our sport. Link to comment Share on other sites More sharing options...
Member Contributer zupatun Posted June 18, 2014 Member Contributer Share Posted June 18, 2014 grabbing more front brake in a turn changes multiple things at once...the tires are slowing down, you are compressing the front forks more (changing trail, wheel base), the front tire is now gripping more as you are increasing load on it and making a larger contact patch and the momentum of the bike changes, the rotational inertia of the wheels are changing as their speed changes, centripetal force of the bike moving around the arc of the turn changes...as you slow down, MOST people push both hands on the bars, stiffening up rather than allowing the bike to "relax" and follow the natural tendency of the bike to lean more or stand up...you are "resisting" more...remember you are squeezing the brake lever...what is important is the "net" of all these effects...most of the time the bike wants to stand up... If you understand all the inputs under your control in addition to pulling on the brake lever--body position, weighting pegs, pushing or pulling on the bars, lowering the CG by getting your butt and shoulders less "over" the bike and more beside the bike, using the rear brake...you can affect the path of the bike to not run wide...no matter if it "feels" like it "wants" to run wide or not...AND as long as you are not exceeding the grip of the front and rear contact patch available you will continue to go around the corner... One thing I think Keith Code does is distill what options you have with your $10 bill...at any one time. If you don't practice it as in the MSF brake light begins to elucidate here, you will always "feel" the bike is "standing up"...rather than reading the situation and reacting with a set of inputs that brings the net result toward tightening your line and making the corner under braking. I can say I have felt both...and it takes a few laps at a track-day to get back to "control" while trail braking...to where it doesn't "feel" like runnign wide, but it feels like "control" while braking deep into a turn...and easing off and gettting back on the gas (and then it feels like you are drifting out while on the gas!"... Without practice, most of us don't intuitively react with all the inputs in our potential control...we only feel the final net sum of our unpracticed reactions as "running wide when I I brake into a turn"!...and most of us never will unless we attend a trackday or school under controlled conditions. Most of the time I can't listen to Keith Code or drink the CSS cool-aid, but he does know a thing or two...and in this case I concur. Matt Link to comment Share on other sites More sharing options...
Member Contributer emoyer Posted June 23, 2014 Author Member Contributer Share Posted June 23, 2014 My thanks to everyone for all the input. It is very helpful. Lots to think about and work on, and yet another reminder of how much I have to learn. Link to comment Share on other sites More sharing options...
Member Contributer zupatun Posted June 23, 2014 Member Contributer Share Posted June 23, 2014 My thanks to everyone for all the input. It is very helpful. Lots to think about and work on, and yet another reminder of how much I have to learn. If you can afford a little less than $200 you can usually do a trackday/classroom sessions at places like New Jersey Motorsports Park and learn in a controlled environment. Look here for trackdays around the US: I have been to trackdays and classes (Jason Pridmore's Star School) at New Hampshire International Speedway, ThunderHill California, Mid-Ohio, BeaveRun (has a new name)... http://www.sportrider.com/sportbike-riding/track-day-organizations CAUTION: Trackdays and Classes are known to cause or re-inforce addiction to riding motorcycles! Take classes or trackdays at your own risk. In some victims this has led to racing or an addiction to Vintage Racing (even more insidious!)...YMMV! Matt Link to comment Share on other sites More sharing options...
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