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

[BC1100S]

I've never under stood why it is standard practice to hang your butt off the seat when cornering ...But I see riders, even racers doing it well before reaching the above limits. Why?

Chicks dig it.

 

[nickrides]

Order Lee Parks book Total Control
Read it and your questions will be answered.
Obviously you don't want to learn something from your peers on this basic topic.

 

[OGOBRacing]

Ditto to the above post.
All I can add is getting your position right and off the bike a bit gives you more room for error at any speed other than slow, tight maneuvers. You don't have to be 10/10 to gain an advantage by using it.
Trust me.

 

[36654]

Thanks for your thoughtful experiences and examples of professionals who train this technique.

However I'm not convinced that it really does any good (from the hard physics perspective) for other than those who are running hard in corners 10/10s or very close!

I mentioned the 2 conditions of where I do agree it helps, running our of tread on the side of the tire due to lean angle and keeping a foot peg out of the pavement.

Moving your butt to the side, moves the center of mass of the motorcycle off (not a good thing) the vertical center line of the motorcycle. This put side loads on the wheels (wheel flex effects) and side loads on the front forks and rear suspension ( more flex effects which could lead oscillations, source of tank slappers, etc). In most cases this movement also causes the center of mass to Raise (move higher from the ground) as it is the riders mass on top of the bike that is moving. This also is not a good thing (think high side).

I do agree it gives the sensation of falling into the corner, inadvertently or more easily counter steering so for most if "feels" good.

I do not believe that the feel good benefits out weigh the negative effect of side loads and higher center of mass.

Am I missing something?

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.

 

[Paul_F]

Order Lee Parks book Total Control. Read it and your questions will be answered.

As well, take an advanced riding course.

I've never regretted taking part 1 & 2 courses with Lee.

 

[cabnfvr]

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.

 

[BC1100S]

Obviously you don't want to learn something from your peers on this basic topic.

Obviously you have a holier-than-attitude. This rarely (If ever) results in the target of your comment being open to further advice from you.

 

[nickrides]

Ya Know BC 1100 I've asked for advice on this forum many times.
I don't argue with those kind enough to take the time needed to give me advice.
But you've stated your opinion.
Ride Safe.

 

[BC1100S]

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.

When you're on a K1200S, EVERYONE is going to be holding you up.

 

[PoorUB]

We were riding up Beartooth Pass a few years back on my Harley. My wife was with, we were packed heavy for a two week trip. We stopped at the vista coming up the north side. When we were going to leave a gent on a CVO Road King asked to go first as, "I like to take the corners hard and I don't want anyone holding me up!" I told him I doubted I would not hold him up, (I like to roll along through the switch backs too), but he insisted so I let him go. About a mile up the pass my wife was asking me WTH was with this guy? Even she was wondering why he was so slow. I was riding his butt waiting for him to take off and he never did. We finally got a safe place to pass and I blew on by him and didn't see him again until later that day at gas station. Never did talk to him although I was dying to. I told a riding buddy about it and he laughed because he knew the guy and he was pretty full of himself. My buddy laughed and said he wished he had been there.

Now I feel I should add, I am certainly not the fastest or best rider out there, but I believe better than average. I have had my butt handed to me a couple times on those same roads. Never on a Harley, but a Goldwing 1800 and a Victory Cross Country rolled by me pretty easy one day. Both were solo riders and both are better at cutting curves than a HD bagger with mama on the back!

 

[vtbob]

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!

 

[36654]

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 , 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.

 

[PGlaves]

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.

 

[vtbob]

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 , 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.

 

[36654]

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

 

[cabnfvr]

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.

 

[alancoles]

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.

 

[ncpbmw1953]

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.

 

[cabnfvr]

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.

 

[alancoles]

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.