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Thread: Why is it recommended to hang your butt off the seat when in aggressive cornering

  1. #31
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    Quote Originally Posted by 36654 View Post
    Bob,

    Relative to your two concerns; 1) modern wheels and suspensions on sport, sport touring & touring bikes are very stiff in the lateral direction and 2) shifting rider position to the side moves the CG laterally, not vertical.

    As someone said in some BRC curriculum, most real world turns will be completed with a body neutral (in-line with the vertical axis of the bike) position. When needed, for road speed turns, above ~15 MPH, the added rider lean will align the rider's body CG with the inside fork tube. A 2-, perhaps 3-inch shift in position. For low speed, police style turns, the side is to the outside of the turn to counterbalance the weight of the bike.

    Now, as you've observed, these modest shifts aren't the "hang-offs" some riders are doing. It's just a matter of choice. My riding area is similar to VT, so there's a few rural roads where these techniques can be fun and (IMHO) appropriate. Otherwise, it's countersteering with minor amounts of upper body lean to keep the CG inside of the bike vertical axis during a higher speed turn.
    Thanks for your beneficial reply. Good info!

    One small detail when the rider shift position to the side, say 3 inches, his C of Mass moves to the side describing an angle(3") for the new C of M vector to the tire contact point to pavement. If you do the math, this point ( the new rider C of M) is higher (the hypotenuse of that angle) than it was prior to the shift. So when shifting to the side, the rider must move down some how to keep the new C of M the same or lower than it was prior to shifting. This part of the reason I feel casual shifting of positions has no real benefit.

    I have ordered the Lee Parks book to learn what I can from it. PS His deer skin gauntlet riding gloves are great!

  2. #32
    Registered User 36654's Avatar
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    Quote Originally Posted by vtbob View Post
    Thanks for your beneficial reply. Good info!

    One small detail when the rider shift position to the side, say 3 inches, his C of Mass moves to the side describing an angle(3") for the new C of M vector to the tire contact point to pavement. If you do the math, this point ( the new rider C of M) is higher (the hypotenuse of that angle) than it was prior to the shift. So when shifting to the side, the rider must move down some how to keep the new C of M the same or lower than it was prior to shifting. This part of the reason I feel casual shifting of positions has no real benefit.

    I have ordered the Lee Parks book to learn what I can from it. PS His deer skin gauntlet riding gloves are great!
    Bob,

    You're most welcome. I know you know how to ride a motorcycle. Otherwise, you wouldn't ride an RS.

    Relative to the math, let me think about it before providing a final answer. But, my initial response is, the change in hypotenuse is an arc length (L) change, not a height change, y = L cos(lean angle). To turn the bike, you want the lateral position of CG (Bike and Rider) to be displaced from the centerline, x = L sin(lean angle). So, you can maintain the same vertical height (y), but increase lateral displacement (x) by shifting the rider CG relative to the bike (i.e., a larger "effective" lean angle). Speed must increase to keep the bike stable at the higher lateral displacements......faster turns with a smaller bike lean angle.
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  3. #33
    Quote Originally Posted by CABNFVR View Post
    Street riding should never include a need to hang off. The only time we had anyone riding with us "hang off" the guy was holding us up. We were 2-up on a K1200S.
    Just imagine how slow he would have been if he hadn't been hanging off in the corners.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
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  4. #34
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    Quote Originally Posted by 36654 View Post
    Bob,


    Relative to the math, let me think about it before providing a final answer. But, my initial response is, the change in hypotenuse is an arc length (L) change, not a height change, y = L cos(lean angle). To turn the bike, you want the lateral position of CG (Bike and Rider) to be displaced from the centerline, x = L sin(lean angle). So, you can maintain the same vertical height (y), but increase lateral displacement (x) by shifting the rider CG relative to the bike (i.e., a larger "effective" lean angle). Speed must increase to keep the bike stable at the higher lateral displacements......faster turns with a smaller bike lean angle.
    When you think about this, remember shift the rider C of M (200lbs) vector does not shift the bikes (500 lbs) vector so these are no longer in alignment. (if they were your radius statement is correct). It also produces a situation where the Combined rider/bike C of M is no longer aligned with the Motorcycles' or the riders as it would be if the rider did not shift his position. Have these three C of M out of alignment enhances destabilizing possibility.

    Yep, these unstablizing forces are NOT huge size( very small if riding at 3-5/10s, but seemingly totally unnecessary unless one is leaning so far to run out of tread or about to dig in a peg like racers.

    Why unstablize the bike for no benefit? That is my fundamental question.

    I hope Lee Parks clears this up for me.

  5. #35
    Registered User 36654's Avatar
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    Quote Originally Posted by vtbob View Post
    When you think about this, remember shift the rider C of M (200lbs) vector does not shift the bikes (500 lbs) vector so these are no longer in alignment. (if they were your radius statement is correct). It also produces a situation where the Combined rider/bike C of M is no longer aligned with the Motorcycles' or the riders as it would be if the rider did not shift his position. Have these three C of M out of alignment enhances destabilizing possibility.

    Yep, these unstablizing forces are NOT huge size( very small if riding at 3-5/10s, but seemingly totally unnecessary unless one is leaning so far to run out of tread or about to dig in a peg like racers.

    Why unstablize the bike for no benefit? That is my fundamental question.

    I hope Lee Parks clears this up for me.
    Bob,

    You're asking for an explanation at the free body diagram and equation level, I doubt you'll find that in the layman literature.

    Relative to your latest post, the assumption is the rider and bike are rigidly connected. Issues concerning separate masses and their relative stiffness and damping are dynamics problems. This is a quasi-steady state explanation
    Last edited by 36654; 12-03-2019 at 06:59 PM.
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  6. #36
    Registered User CABNFVR's Avatar
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    Quote Originally Posted by PGlaves View Post
    Just imagine how slow he would have been if he hadn't been hanging off in the corners.
    Great point! I never thought of that.
    "Have BMW. Will Travel"

  7. #37
    Dress for fall & avoid it AlanColes's Avatar
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    Quote Originally Posted by 20774 View Post
    I had heard that Valentino Rossi started doing it and others figured that if Rossi was doing it, it must help. In reality, I suspect that it doesn't really help all that much but it gives the rider some sense of where the pavement is...it just felt right. The Rossi leg wave or dangle.
    Kurt, it was started by motorcycle racers well before Rossi was even born. I can't recall who is attributed with starting it but read an article many years ago that identified the two racers that folks argue over which one started doing it.

    There are significant advantages to it, but not in all situations. I used to Club Race in the mid-late '70s and it was prevalent then.

    As far as I'm concerned, this is not something that should be part of anyone's daily riding and I don't care how well regarded the proponents are, I have yet to hear a convincing case for it. I'll explain in a post at the current end of this thread after I've had the opportunity to read them all.
    Regards, Alan - President BMWONS - BMWMOA/BMWRA/BMWONS/Airheads
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  8. #38
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    Quote Originally Posted by vtbob View Post
    but seemingly totally unnecessary unless one is leaning so far to run out of tread or about to dig in a peg like racers. Why unstablize the bike for no benefit?
    The presumed theoretical benefit is to reduce lean angle at the same speed which is going to come into play when there is road debris in mid-turn you didn't anticipate. Or in the extreme just to get you around the turn quicker w/o sliding out from extreme forces involved.

    For my street riding practices as I'm ultra cautious but still enjoy spirited riding I've tried three different approaches:

    1. Inside knee out, cheek just off the seat inside, upper body inside and down
    2. Neutral body/weight always aligned WITH the bike's midline--no change in position
    3. Body/weight ALWAYS VERTICAL, tipping the bike right/left but keeping the body perpendicular to the ground, not the bike. This is what dirt bike riders routinely do.

    #3 is always viewed as heresy in street riding whenever I've brought this up. It's counter to everything we've learned about cornering. Here's the thing: for sane street riding it's shockingly effective. You'll see the lean angle is clearly far greater than with option #1 for sure. But, what I'm not sure about and could be part of the discussion is the fact that with option #3 there should be more 'down' force on the contact patches than with weight hanging off to the inside, yes? Does that offset the benefit of less lean angle one gets from option #1? That calculation is beyond my skill level but would be interesting to know the answer to. One of the potential pluses of this contrarian method (#3) for street riding is that you are better able to get the bike to vertical quickly than if you're hanging off on the inside. I recall during the hard braking part of the MSF basic course we were reminded to avoid hard braking when leaned UNTIL you've moved the bike to a more vertical/neutral position. I've tried them both and quite frankly w/ my corner entry speeds which are only going to be 20-25mph faster than the posted corner speed either works fine. In the end when I'm riding as fast on the street as I ever care to option #1 always feels the safest.

  9. #39
    Registered User CABNFVR's Avatar
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    Why is everyone trying to make this so complicated? Leaning off was started by racers in order to get more speed in a turn. How does this equal more speed? Simply because leaning off allows the bike to remain more upright and therefore faster (since hard parts are not dragging). Now the professionals are all over the place and as others have alluded to on this thread it really is now a science. Push, lean, rise up, get down, leg out, elbow out and all that and more depending on which turn they are in. Add to this the many racers who now drag an elbow in the turns and we street riders may need to just take a step back and rethink the necessity of any of this.

    Today's tip: If you're into a turn hot hot hot (to quote a really good rider friend) then you may want to consider moving your mass (can leave the m off if you prefer) to the inside of the turn. This will keep hopefully the bike from dragging hard parts and will hopefully keep you out of the woods.
    On the street you'll still look stupid but survival beats image all day long.
    "Have BMW. Will Travel"

  10. #40
    Dress for fall & avoid it AlanColes's Avatar
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    Quote Originally Posted by akbeemer View Post
    In an interview Rossi said the first time he stuck his leg out was on the last lap of the first F1,500cc race he won. He was racing for the lead and fighting for position going into a corner and said he stuck his leg out to break the concentration of his opponent. He said years later Team Yamaha asked him to stop lowering his leg. He resisted so they had him do several laps in a practice session keeping his leg on the peg and then the same number of laps while lowering his leg. The lap times were essentially identical.
    Kevin, I believe this is because it is a move that originated in dirt-riding, motocross, etc. Some have incorrectly interpreted the idea as a move to have an out-rigger sort of thing to support you if you go down. Nothing could be further from the truth, although many GP racers will stick their foot leg out to the side in the wet in an effort to do just that - not very good for their ankle if they actually go down. Every sport has plenty of things that are done out of tradition or superstition that have little or questionable benefit and more to do with habit, superstition, or unfounded beliefs.

    As I understand it, the motion of sticking one's foot/leg out was to have the top of your heel about level with the front axle. This was done entering a corner with one's body as far forward as possible and the leg acting as an extension of that in an effort to get as much weight on the front wheel as possible for traction. In the dirt on a turn that has been chewed up (very low traction) with a very light bike with knobbies, the amount of weight transferred may well have a beneficial effect on front-end bite/traction. On smooth racing pavement with sticky racing slicks, the amount of weight transfer compared to the level of traction available would likely be quite negligible. This is likely why in the rain one sees far more GP riders kicking their foot out towards the front axle than in the dry.
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  11. #41
    Dress for fall & avoid it AlanColes's Avatar
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    Quote Originally Posted by CABNFVR View Post
    Why is everyone trying to make this so complicated? Leaning off was started by racers in order to get more speed in a turn. How does this equal more speed? Simply because leaning off allows the bike to remain more upright and therefore faster (since hard parts are not dragging). Now the professionals are all over the place and as others have alluded to on this thread it really is now a science. Push, lean, rise up, get down, leg out, elbow out and all that and more depending on which turn they are in. Add to this the many racers who now drag an elbow in the turns and we street riders may need to just take a step back and rethink the necessity of any of this.

    Today's tip: If you're into a turn hot hot hot (to quote a really good rider friend) then you may want to consider moving your mass (can leave the m off if you prefer) to the inside of the turn. This will keep hopefully the bike from dragging hard parts and will hopefully keep you out of the woods.
    On the street you'll still look stupid but survival beats image all day long.
    Agreed.

    As far as I'm concerned, this is not something that should be part of anyone's daily riding and I don't care how well regarded the proponents are, I have yet to hear a convincing case for it, except for the situation several have shared here of finding one's self going into a corner too hot, etc., and need the benefit of additional cornering clearance.

    Before I get a ton of irate posts, let me explain. On the track one is trying to find every 1/10th to 1/100th of a second and maximum performance is critical. On the street, survival is critical not maximum performance. If you are leaning off the bike in normal street riding than one of two things are happening:
    1. you are travelling at a speed well above the posted limits and therefore this does not fit the definition of "normal street riding". It might fit the definition of "your" typical street riding, but that doesn't make it "normal street riding". ;-)
    2. you are leaning off when it isn't necessary and are actually not learning how far your bike can actually lean with you in a standard riding position

    #1 is fine (aside from any legal, safety, socially-responsible issues)
    #2 is very problematic. First, you are likely to actually become a very slow and hesitant rider if you are hanging off the bike at legal speeds or say 10-20 clicks above. At those speeds, the bike should have plenty of cornering clearance unless you are riding a few of the showier HD models. H-D's touring models often have more cornering clearance than many of their styling models.

    To my mind, proper riding style for public roads is a) stay in your lane and b) keep your butt in the centre of the seat or just a slight "cheek shift" while cornering. Think about the idea of having a safety margin. There are far more unknowns and hidden hazards on public roads than on any racetrack. If you are already "hanging-off" the bike and one of those jumps in front of you, what do you have left?

    I think everyone should practice sliding their butt (half of it) off the seat and slightly dropping a knee so that they understand the procedure and get comfortable enough doing it, but reserve that action for an emergency that could save your life. If you are doing this as a regular riding posture on public streets and not always riding at highly illegal speeds then I think you are not using the existing cornering clearance that your bike naturally has and therefore in an emergency situation you will not have a good idea of what cornering you actually have and you'll have very little reserve.

    I have watched riders go down on public streets from both situations, not realizing that they had more cornering left because they appeared to be the ones always hanging off the side when it wasn't needed, and those that weren't aware of the extra clearance available if the did hang off the side properly. It is never nice to see, especially when injuries are involved. I hate seeing a motorcycle go down in front of me and have seen it happen to too many riders. Learning to understand and get comfortable with the limits of your bike goes a long way towards avoiding such a situation. Leaving a safety margin on public streets should be a no-brainer. The first and #1 improvement/farkle anyone should do with their bike is getting the rider into a good riding course (safe riding, performance riding, etc.). That one action has the ability to make any rider quicker, safer, and more aware. It will also definitely increase one's enjoyment of and appreciation for riding.
    Regards, Alan - President BMWONS - BMWMOA/BMWRA/BMWONS/Airheads
    Current: 2019 R1250RT / '06 Ducati ST3s / '91 R100GS / '86 R80RT / '75 R90S / '73 850 & '70 750 Commando Prev: '14 R1200RT / '04 R1150RT / '81 Honda GL1100 / '77 Suzuki GS750 / '73 Norton 850 Commando

  12. #42
    Registered User rogerc60's Avatar
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    Quote Originally Posted by ncpbmw1953 View Post
    For my street riding practices as I'm ultra cautious but still enjoy spirited riding I've tried three different approaches:

    1. Inside knee out, cheek just off the seat inside, upper body inside and down
    2. Neutral body/weight always aligned WITH the bike's midline--no change in position
    3. Body/weight ALWAYS VERTICAL, tipping the bike right/left but keeping the body perpendicular to the ground, not the bike. This is what dirt bike riders routinely do.

    #3 is always viewed as heresy in street riding whenever I've brought this up. It's counter to everything we've learned about cornering. Here's the thing: for sane street riding it's shockingly effective.
    I found this recently posted on another forum. Confirms your approach #3.

    https://youtu.be/rDJZjdKai24

  13. #43
    Every on track or on road riding school I am aware of teaches to shift your weight to the inside of the corner/curve. (In the dirt it is different.) The various propositions include dropping your shoulder, pointing your elbow, pointing your chin, weighting the inside peg, and indeed (gasp) shifting location in the saddle, slightly, or moreso. Now I read here on this forum the experts who know more than the teachers I have had or have read: Pridmore, Code, Parks, etc.

    Each of you have the right to pick who you choose to believe. You can even attempt to explain mass and other physics problems. But at the same time I know which credentials a person will have that I choose to believe. Carry on the conversation. If not valuable it is at least humorous.
    Paul Glaves - "Big Bend", Texas U.S.A
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  14. #44
    wanderer
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    Quote Originally Posted by PGlaves View Post

    Each of you have the right to pick who you choose to believe. You can even attempt to explain mass and other physics problems. But at the same time I know which credentials a person will have that I choose to believe. Carry on the conversation. If not valuable it is at least humorous.
    Well said.

    I, however have always been one to question the status quo, the established fact, when I see clear flaws. I question my premise, try to seek out well thought out arguements that would disprove my contention. Answers that the fall in the category "the book says so" or the like hold very little credence for me.

    While I respect experts, listen to experts, I do not defer my judgement to theirs with out quantitive (not subjective) proof.

    So far, in this case, I have found no such quantitive proof.

    And I do find this conversation both informative and humorous!

  15. #45
    Quote Originally Posted by rogerc60 View Post
    I found this recently posted on another forum. Confirms your approach #3.

    https://youtu.be/rDJZjdKai24
    Pretty cool. The dirt bike rider was able to corner faster and tighter than the sport bike riders.

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