Fajita Dave
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Posts posted by Fajita Dave
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Rear brake should not be used on the racetrack. PERIOD. (unless it rains but i'm not sure exactly).
"Backing it in" can be induced by locking up the rear, true. You can use rear brake, or drop the clutch abruptly on downshift. But this is not what you are seeing in MotoGP or moto2.
To prove it, go watch a few moto2 races and you can see that even on right hand turns, they back it in and don't use rear brake. It's obvious because now that almost all riders let their inside leg hang during braking, you can see the rear end of the bike "come around" while their right leg is dangling in the air.
"Backing it in" is a result of "threshold braking" combined with "trail braking".
If you and your bike weigh 500lbs, lets say when you sit on the bike on a constant speed there is 250lb on the front and 250lb on the rear.
During very hard braking, you would want 490lb on the front and 10lb on the rear. Just enough weight on the rear so it still sort of "follows" the front.
At times, you will see the rear tire skipping.
So once the rider start to turn the bike, the front end is gripping and turns, while the rear with 10lb of weight on it continues straight ahead. There you go - you are crossed up... Don't release the brakes enough, and you'll get more and more crossed up until you crash.
To sum it up, backing it in is not a stunt that is induced by rear brake like on your BMX bike, it's a result of going very fast into a corner with extremely aggressive trail braking technique.
Hope this helps.
Don't forget about Newton's 3rd law of motion. Every action has an equal and opposite reaction. When you try to turn the handlebars in one direction, the handlebars try to turn you in the other direction. Since your lower body should be locked onto the frame with your knees this twisting force is transfered to the frame making the rear end step out.
Of course if the rear tire has traction then everything stays in line. But when the rear tire has almost no traction there is very little keeping it from stepping out of line. So the result when you turn the handlebars is you end up turning the frame too.
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I started martial arts from a pretty young age and learned how to meditate. I don't meditate before or during a ride but its sort of given me the ability to just "flick the switch" into being calm. It only works when I'm riding motocross which I've done since I was 9. I'm extremely at home in the dirt on my dirtbike and its easy to fall into a solid state of focus. Its not quite that simple on a sportbike.
I haven't been on a road course with my sportbike yet but I do get a little tense when I'm trying to go a little faster on my favorit twisty roads. As soon as I feel that tension I have to just back off the pace a little bit and regroup. Focus on turn in points, throttle control and looking through the exit. After that everything starts to flow nicely again.
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Have you thought about getting custom fitted leathers? There is a company in VA that makes them but I have no idea what their name is anymore. It was 4 years ago when I looked into it. It could be a last resort and it would be an expensive option!
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DIsclaimer, I didn't mean to make this sound so "deep" but its the only way I can find to explain it!
noamkrief, I think you might be to worried about termanology. Every region and sport has its own termanology and I don't nessisarily think it should be the same between motorcyces and cars anyway. With a car your body has no influence on the machine other then the direct steering, shifting and petal inputs. I think things get viewed more from a mechanical "matter-a-fact" kind of way because its entirely up to the car's setup.
On a motorcycle the rider is an integrated part of the system and you become one with the bike
. With such a direct and important role that you have on the motorcycle your brain registers whats going on more as if it were happening to you personally instead of it being the vehicles fault. So you end up with termanology like "backing it in" or "loosing the front" because it feels more like that is whats happening to US instead of it simply being mechanical feed back that a car is giving you.As far as a mechanic not using a torque wrech goes. That is completely rediculous. I don't know how anyone could work on the top end of one of these engines without a torque wrech and not strip the threads out of everything. Spark plugs and cam journals are torqued to 8 ft/lbs on my bike and it seems like a rediculously small amount to keep the bolts in place. A little tighter and the threads will strip.
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The front wheel is always following the direction you're traveling in. So if you're turning left, the front wheel is pointing left. As Lnewqban explained it does depend on the tire profile as well. One thing for certain the only possible way to be turning left and the wheel to be pointing right (off the line of travel) is if the front tire is sliding. If that happens it wont be sliding for long before you hit the ground.
When a motorcycle oversteers the frame is what moves around the steering stem. It looks like the handlebars are turned in the opposite direction of the corner. In reality the handlebars haven't moved at all, instead the frame rotated around them while the front wheel continues to follow the line being traveled.
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I love the slow motion with those camera angles. You can pretty much tell everything he did to result in a tank slapper!
He got the bike to a nice lean angle and started applying throttle doing a good job of not mixing the two. It looks like he applied a little to much throttle and the rear started to slide. This caused him to lift off the throttle and tense up on the handlebars which caused some headshake. The tense arms kept the headshake going for a while AND transfered it to the rear end (hense the rear bouncing all over the place too). If the rider's arms are relaxed headshake stays iscelatied to the front wheel unless the steering damper is very stiff. When he finally relaxed the bike recovered on its own. Suspension may have played a part but who knows what kind of condition its in.
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See the news feed on the Superbike School Facebook page for a great article about this, with a quote from Leon Camier:
"Leon: Yes, it's a balance thing. When you're hard on the brakes, a bike can easily get crossed up going into a turn and sticking your leg out gives you better balance when you're hard on the brakes. It depends on the circuit, bike and how hard you're braking as to how much you need it."
That sounds familure
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And sometimes they don't do it at all.
Yeah, at COTA Scott Russell mentioned that Mark Marquez only hangs his foot out when hes pushing for every thousanth of a second. Otherwises its always both feet on the pegs. He showed it too once he made the pass on his team mate later in the race.
Since GP racers have shown on telemetry that they can enter a turn every single time within 0.5kph when they're turning out solid laps. With such a critical and small margin for error they have I guess sticking your leg out in the wind could give you just the edge you need to slow down for a corner. If its worth one tenth of a second per lap its worth it for them.
Sitting here thinking about it now I wonder if its a balance kind of thing. I ride mountain bikes and used to ride BMX and I used to stick a foot out when doing stoppies because I could move my leg to help me stay balanced on the front wheel. These riders are pretty much riding into every turn with the rear wheel as close to off the ground as possible. Maybe it helps them control how the rear end lifts under hard braking? I'm can't imagine it would let them brake harder, but a little more control would help them be more precise with their entry speed and line.
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Is this a pic from your recent track day following CSS L1?
No, not me.
I'm still working towards that...
It's interesting to note that despite riding faster now than ever before, I'm yet to put my knee down. (Not that 'knee down' is a goal for me, it will just happen when it happens.) It's a funny thing that when you start riding effectively you don't use as much lean angle etc. Riding faster and faster, yet keeping more and more lean angle & safety margin in reserve... But that would be a subject for an entirely new thread...
If we separate the lock on part from this question and just look at the weighting, since both pegs are connected to the frame, doesn't that minimize the importance of where the weight goes?
CF
This may not be an accurate way to think about it, since a bike always has cornering forces applied - but... I visualise the red lines in the above diagram as an actual physical structure, say it was created out of steel tube. Now if you set it on the ground and try to balance on it - which peg will you use? You could probably succeed using the 'outside peg', but if you try to balance on the 'inside peg' leant over like that... not a chance. That's a very simplistic example relating to stability, but may not even be valid once you factor in cornering forces...
Great example with the barbell, Hotfoot. Makes sense to me.
I think one thing being left out here is that you're body weight isn't working any differently while cornering as it is while riding upright. I'm having a hard time finding a way to explain this but I'll give it a try. At a 45 degree lean angle you have about 1G of cornering force and as always 1G of gravity pulling you straight down. That means you're body weight is more or less pushing on the motorcycle the same way it does as if you were riding straight! So whether you push on the inside or the outside peg its having nearly the exact same effect on the rear tire. In other words pushing on the outside peg isn't pushing "down" on the rear tire, its pushing it out in the same way pushing on the inside peg would. I suppose you could torque the chassis a little bit but wouldn't it have the same effect as making a tiny counter-steer input? However, since your body weight is hanging off the inside that leaves you with nothing to push with on the outside. If you look at the rider's body position all of his weight is centered over his inside leg, that would leave him with nothing to push on with his outside leg without compermising his body position.
When you get into the realms of MotoGP that would add another dynamic to it. Cornering at 2G you are pretty much stuck to the bike even if you aren't holding onto anything. I suppose that might give you some ability to push on the outside peg no matter where your body position is. The only question I still can't answer is why? What would be the advantage?
I know when I lock my outside leg into the bike it "feels" like I'm weighting the outside peg. I know its only because my knee is jammed into the tank and my toe is pushing down on the peg but it does feel like I'm weighting the peg. Having my lower body locked onto the motorcycle this way really helps me get my arms relaxed mid corner and I immediately feel the bike cornering easier and sharper.
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I live in Virginia and have been on the blue ridge parkway pretty often so I know what you mean. Its easy to get drawn into the double yellow lines knowing that your tires are still in the correct lane. I just found that having a slight change in mind set helped me stay fully in my lane. Instead of thinking about where my tires were on the pavement I was thinking more about where my head was relative to the pavement in left turns. As I approached a corner I thought of what I needed to do to keep my head just inside my lane and didn't worry about where the tires were. Of course you need to make sure the tires stay on the pavement! However, if your head is close to the yellow line than your tires will definitely still be on the road.
Also I found that you really can't have much of a "line" through left turns. You more or less need to follow the curve of the road. Personally I feel its not as important to have that late turn in point when making a left turn on a two lane road. You already have a much better sight line through the corner compared to if it was a right turn so there isn't to much of an advantage by turning in later. Turning in as late as possible and using all of the road width does help you get through the corner with less lean angle.... but so does going slower. So just make sure you're going the appropriate speed.
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I think the most common problem I've seen especially after teaching a few people to ride is keeping their arms tense. Death grip on the handlebars, pushing on the bars and just keeping their arms tense I think is the single biggest factor that makes a motorcycle unstable. A motorcycle is increadibly stable when its geometry is left to do its own thing by a rider with relaxed arms, once you tense up that stability goes out the window when it counts most.
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I have done some drag with these smaller bikes.Wheelies seldom occur if launched properly, as there is no power wheelie.
I am sorry, i did not read that you were a coach.I am quite envious.You have in my opinion, the best litre and 600 there is today.The BMW has what....185+ ponies at the wheel? That's enough to take off!
My question was this - How exactly so you shift in high power bikes ( which you answered ).Further, i asked if pro's did it the same way you do - clutchless, or is there some advantage to using the clutch.
Dipping revs are a problem if you are out of the powerband to begin with, IMHO.As for your husband's wheelie issues, a few inches of wheelie, like 6 in or so isn't a problem.Leaning forward and slipping the clutch just a bit will help settle the bike.Trailing the rear brake is another option.
Which year's S1000 do you have? Also wheelspin is more a car problem.Does occur on heavy bikes, like cruisers i think.
You Madame, are right on all counts.Salute!!
I'm pretty sure pros will have a quick shifter setup unless its outlawed by the rules. So there would be no using the clutch.
If you up shift with the clutch I guess it depends on how much clutch you intend to grab. A while ago I noticed that on the street I barely pulled the clutch at all on up shifts. It probably wasn't disengauging the clutch enough for it to make a difference and shifting felt the same as if I pulled the clutch in all the way. When I shift near redline on my 600 it always seems to be a lot smoother without using the clutch.
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I wonder what his tires looked like to....
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The concept of moment of inertia sounds difficult, but it is not so much.
The bike+rider system always rotates around the combined or system's CG, either during hard braking-acceleration or during quick flicking.
Sitting on the bike, our body has a somehow rigid connection with the bike and; hence, there is one moment of inertia, which has a high value (the system has more inertia to be rotated).
Standing on the pegs, our body has a flexible connection with the bike (via our legs, knees and hips); hence, there are two masses connected by a flexible link.
That flexibility reduces the total moment of inertia because the smaller bike of the bike can rotate around its CG with certain margin of freedom respect to the mass of the rider.
Note that the value of the moment of inertia depends on the value of the mass, but also depends on the square of the distance that separates the CG and the pivot around which it rotates.
Standing on the pegs drastically reduces the moment of inertia or rotational inertia to flicking the bike or to perform a wheelie.
That is the answer I've been having such a hard time figuring out on my own! Primarily on my dirtbike I've always noticed that the bike seems to handle quite a bit differently while standing on the pegs. I mostly noticed this after I started trail riding recently instead of the high speed motocross I was used to since I was 9. It simply "felt" like the center of gravity of the motorcycle on its own was lower, however it makes perfect since that what I've been feeling is just a result of me "detatching" myself from the motorcycle it reduces the moment of inertia. Just to make sure I have this perfectly clear, the CG doesn't have any significant change you're simply changing the pivot point of which the motorcycle leans around. If I locked my legs to the motorcycles making the bike/rider system ridged again (like sitting on the seat) it will raise the MOI which is exactly what it feels like in practice on my dirtbike.
I definitely know you don't want a low CG on a motorcycle for cornering. Its way past my normal bed time so I'm having trouble thinking of how to explain it but cornering G's and gravity go hand in hand. When you maintain a lean angle that is the exact equalibriam of gravity pulling you to the ground and the cornering G counteracting gravity to keep the bike upright. Having a higher CG gives gravity a bit more leverage for pulling you to the ground while leaned over so less lean angle would be required for any given corner compared to a lower CG. Thats the basics of it anyway....
Thats why I come to this forum even though I don't post much. People let the facts do the talking instead of their egos!
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This question doesn't have so much to do with cornering or sportbike riding but more of a general motorcycle physics question. On another forum that I visit the debate whether standing on the pegs lowers or raises the COG comes up often. Since there are a few people on here who have a good understanding of physics and more importantly the math behind it I figured we might be able to come up with some answers!!! There might be to many variables to come up with a good answer.
So does standing on the pegs lower or raise the COG??? Obviously this one has plenty of variables. Standing as high as you can would surely raise the COG (like you would on a dirtbike) of the whole bike/rider system but what kind of effect would it have? Or how about putting 100% of your weight on the pegs while still keeping your body as low as possible (as you would on a sportbike) like you're crouched behind the windsheild?
I don't know calculous but I try to have a good basic understanding of physics. Personally I would think moving where the rider's weight is placed on a motorcycle frame from above the engine at the top of the bike, to bellow the engine near the bottom of the frame would have a massive effect on the COG of the bike and change its handling pretty dramatically! This could make the bike much more stable and change lean angle / direction much quicker which could be usefull riding through a rock garden on a dirtbike. However, the rider will need to be standing for that situation which would raise the overal height (and COG). Resting weight on the pegs instead of the seat I would also think could help keep the front tire on the ground while powering out of a corner on the extremely powerfull modern sportbikes. That would let you twist the throttle a little bit more and power past your opponents down the straight away.
So what kind of effect do you think weighting or standing on the pegs has?
P.S. Changing how you hold yourself on the bike anywhere between your ankles to your hands can change how the bike reacts in any given situation. I think its even a make or break part of the riders techique to keep the motorcycle under control. That makes almost limitless variables so I'd rather keep that out of the equation for now!
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I think you're way to caught up in trying to lean lower, especially after 3 months of riding!!! Leaning lower and carrying more corner speed simply come with time and experience. It really does happen automatically if you practice good technique. Good technique lets the motorcycle feel rock solid and stable even if your pushing traction limits. Having that stable feeling motorcycle inspires confidence which usually results in you going into the corner faster and leaning it over just a little bit further untill something feels "unstable" again.
Forget about trying to hold a constant radius while accelerating. Reaching deep lean angles requires using the availible traction from both tires in a smooth, predicatable way (adding lean angle + throttle overwhelms the rear tire like Hotfoot mentioned... far from smooth or predicatable). If you're accelerating you need to make sure your line leaves you with the extra space for the widening radius.
Bottom line is you need to start with a good foundation. Leaning lower isn't a foundation, its the result of a good skills foundation that lets you lean lower.
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Are you saying that a 40/60 weight distribution will fix a sliding front tire while it's sliding? If the front tire is sliding due to corner entry speed exceeding the tires limits? Not the suspension being out of optimum working range.
Unless your already at your tires combined maximum lean angle (with the 40/60 weight distrubution) than there is always some wiggle room for unloading or loading one or the other tire. If the front is sliding chances are the rear tire still has some grip left to give out. So getting on the throttle will take some pressure off the front which lets it regain traction and stops the slide. Now more of that cornering load is shared by the rear tire instead of overloading the front.
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What about Pedrosa's crash at Philip Island? Same thing?
From what I saw it looked like to much lean angle. I'm pretty sure I saw parts scrapping just before the tires let go. Also he lost the front and rear tires in his wreck. Adding throttle and lean angle at the same time will make the rear kick our suddenly but doesn't have much effect on the front tire.
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T - Is your question about fault in the legal sense? Or in a less formal sense?
JK makes a good point about the lane splitting legality. However even in California isn't lane splitting resitricted to a very low speed? Like 20 or 25 MPH? I have to admit to a limited knowledge of the legalities of lane splitting but I would have to say even where legal, a rider is accepting an additional amount of risk.
Legally I don't know who is more at fault however practically I have to agree with the concensus and say the rider should have been aware of the increased risk and ridden accordingly.
I live on the complete opposite side of the country than California so I could be wrong. From what I've gathered lane splitting isn't "legal" nor is it "illegal" so its more or less tolerated. So the person at fault would probably be the motorcycle rider for riding to fast or to close for traffic conditions.
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Personally I'd say its 50-50, however, the rider put himself in a situation where he was going to fast in traffic with nowhere to go. The driver shouldn't have been acting like an impatient idiot either by darting around in traffic (just like the motorcyclist).
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If you want to see some video of it in the rain, let me know, I'll post some up.
Bullet
I'd love to see some just for the fun of it
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I wouldn't say the idea of quick turn revolves around turning in as late as possible, it's simply to go from fully upright to fully leaned over as quickly as conditions allow, you can choose to move your turn point back a good ways compared to a lazy turn in and apex later,which is very good for blind corners, or turn at the same point and use a lot less lean angle for the corner, or carry more speed into the corner. Your turn-point, line and apex can change depending on any number of factors
as for learning when to quick turn and when not to, can you think of a situation where you wouldn't want to set your lean angle as quickly as conditions allow ?
Thats very true and much more clear that I could ever say it!
Now that I think about it you definitely can't use quick turn in all situations. A decreasing radius turn is the first one that comes to mind. You can still turn the bike quickly when turning in for your apex but before that you just need to follow the curve.
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Ok I think I may have got the understanding but there is a question I have. Lazy turning is defined as slowly leaning the bike into the turn correct? Now quick turn is to turn in as early as possible and get to your lean angle faster so you can get back on the throttle correct?
My question is if you are to turn in as early as possible to get back on the gas, how are you to know if you are lazy turning or quick turning? Take for instance the GP guys seem to be more on the lazy cornering then the quick cornering until they hit the chicanes then they are flicking that thing side to side very quickly!
Am I getting quick turn mixed up with quick flick?
When you quick turn you want to turn in as late as possible. Slower turning forces you to turn in sooner. The purpose of quick turning is to turn in as late as possible which gives you a later apex through the corner. A later apex lets you get on the throttle sooner, be more aggressive with throttle in the exit and you can stand the bike back up sooner exiting the turn which lets you carry more speed down the straight away. A slow turn in will cause just the opposite as that along with possibly needing to trail brake and get on the throttle later.
I think the slow turn in rate you normally see in MotoGP is usually because of the extremely high speeds they enter turns. Its tough to quick turn at 130mph compared to 80mph. If they're using a defensive line to keep people from passing they normal use an earlier apex and trail brake which causes them to use a lazy turn in rate.
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Emergency braking: Practice, practice, practice. Here's what I do : If you don't have a a helper as mentioned, pick a spot up ahead and see if maximum braking will get you stopped before you get to that spot. Ignore the rear brake. It will just lock up on you and get you sideways in more ways than one. . How do you achieve maximum braking? Practice, practice, practice. Always 'cover' your front brake with 2 fingers. Be aware that if you slam the brakes on, you may lock up your front, and you will be on your ear in no time. Instead, gradually apply increasing pressure. This allows for weight transfer to 'plant' the front tire for maximum adhesion and THEN you can really get on the brakes harder. It's kind of a fluid motion. Here's another shameless BMW plug: These days, all BMW's come with ABS, some of them even have power boosters. My K 1200 GT will stop so hard it feels like running into a wall, without any risk of locking up the wheels. In race mode the S 1000 RR will brake hard enough to chirp the front tire!
All good advice but I think how many fingers you put on the brake lever is personal preference, and a pretty important detail that is overlooked! Personally I think the more fingers you comfortably get on the brake lever the better off you are. I used 2 fingers on the brake lever for a long time and it felt great with the huge amounts of braking power that sportbikes have, however, after I was getting better at reaching the limits of my bikes braking potential I noticed using 2 fingers on the lever was forcing me to get tense on the handlebars under heavy braking. You only have two fingers squeezing the lever to naturally it feels like you're squeezing much harder compared to 3 or 4 fingers. While braking with 2 fingers every time the front tire started to lock the handlebars would turn left because of the pressure I put on the right grip. The tense grip also made it MUCH more difficult to "feel" the amount of traction and to modulate the brake lever with the correct pressure. After that I started using 3 fingers and eventually went to using all 4 fingers on the brake lever. It lets me stay more relaxed / neutral on the handlebars and drastically improved how accurately I can apply brake pressure. I have a pretty light physical build so it could be very easy for someone with more muscle to be perfectly comfortable braking with less fingers.
As for wet pavement braking on track compared to street, I'd think it would be about the same. You just have a lot more space to work with on the track. I wouldn't recommend trail braking either!
. With such a direct and important role that you have on the motorcycle your brain registers whats going on more as if it were happening to you personally instead of it being the vehicles fault. So you end up with termanology like "backing it in" or "loosing the front" because it feels more like that is whats happening to US instead of it simply being mechanical feed back that a car is giving you.
Went Down Yesterday
in Cornering and Techniques
Posted
Target fixation is the worst SR in my opinion! Of course its hard to say looking at still pictures but you rode into the ditch pretty late into corner exit. Do you think you could have made it dispite your early apex and high entry speed if it weren't for target fixation?