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Old 03-23-2013, 10:37 PM   #991
Coachgeo
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any know of Southern OH or Northern KY moto gymkhana groups or groups forming? Contacts?
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Old 03-24-2013, 07:23 AM   #992
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Originally Posted by Coachgeo View Post
any know of Southern OH or Northern KY moto gymkhana groups or groups forming? Contacts?
You can go to the AMGRASS site here and ask, http://amgrass.com/ I see a lot of the same members here but it is another resource.
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Old 03-24-2013, 08:17 PM   #993
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Hmm... that might be a good point there, fuelish.

Do we have any videos of people practicing in tight spaces?
It is always fascinating to watch top class riders tackle a course, but the videos usually take place in a pretty large area.

How about it ya all? What would be the smallest space that you can setup some kind of a course on?

My first instinct would be the GP8. That can be done, within just few meters, and there are great variations of it with just a couple of more cones.




Anybody else can chime in on this? As the season is warming up for me here in NYC, I'm starting to scout for new spots to practice at. After the hurricane this year, my main spot, the airfield is closed now. So back to square one.

Saw this video recently. This one is not about the space of the course, but I'm absolutely loving the quick transitions he is making at the beginning of the course. That Left/Right Right/Left is a beautiful thing to watch.

a driveway is big enough, dirt teaches very quickly too.

I like school parking lots before sunset. all it takes is some chalk or rocks. leave the gravel and slide through it, its another tool. decreasing radius then flip it to increasing.... and in between do tiny circles till my head swims. swim left, turn right till it swims right....

the most fun ? a perfect dirt bike slide on pavement. to cool off. mount cheap tires and chew on them until the edges chunk off. ya.



I still can't fucking drift for shit though. some day.
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Old 03-25-2013, 06:59 AM   #994
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I retook the basic riders course this weekend. A refresher for me, but I am selling my first bike to my little brother and wanted him to take the course first, so I took it with him.

Anyway, after watching a lot of the videos here, and otherwise being interested in the sport... The figure-eights of the MSF course were easy!

I tried telling the other students to watch me turn all the way around to look where I wanted to go. A couple did great, most kept looking at their front tire and the lines of the box. However, those little Eliminator 125s sure do not lean much Just have to use a little more body english
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Old 03-25-2013, 10:06 AM   #995
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Posted this in the noob thread with no response so I will give this a shot.

Is the sole purpose of counterleaning during u-turns so that we can do them at slower speeds? If so, why can't I just sit straight in the saddle and add a few mph to my speed and maintain the same lean angle and turn radius? Or might I even hang off and do a u-turn scraping the pegs and knee at 20mph instead of 7?

This is making me think the whole drag rear brake and counterlean business is a waste of time, just add a little throttle and you can maintain the same turning radius without having to mess with the clutch or rear brake or shifting your weight at all yes?

Unrelated, but riding crossed up should allow you to scrub in tires more safely than hanging off or riding straight up and down yes? The main factor in the lateral traction limit of the tires is the lateral G's not the lean angle? In fact, on a dual compound tire, you're probably more likely to slip if hanging off since you might not be all the way over onto the sticky edges of the tire? Are my presumptions correct?
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Old 03-25-2013, 11:16 AM   #996
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Hello there bumbeen welcome to the wonderful world of Moto Gymkhana.

Lots of questions there, but essentially we are aiming to rotate the bike in the quickest possible time whilst covering the shortest possible distance.

There are three main variations in body position, lean in, lean out and lean with (plus everywhere in between) and one of them will suit you and your bike much better than the others, so it's simply a case of finding which one it is.

It's a bit counter-intuitive, but the slower the bike is going the quicker we can turn it. In order to ride the bike very slowly with significant bank angle we have to have what we call the balance of the bike. Riders usually rely on the forces of inertia to keep the bike balanced, but with reduced inertia from going slowly we have to be very aware of the position of the Centre of Gravity otherwise the bike could fall over. Maintaining the balance of the bike is much easier if we have the throttle open and the brake on at the same time.

You are quite correct about lateral 'G' being the limiting factor, but this does increase significantly with bank angle so there is always a trade-off to be made and finding it is simply a matter of practice, practice and more practice. There is NO short-cut.

A key indicator of whether or not you have got it right is when you can rotate the bike through 360 degrees in about 2.5 seconds. Get a friend to time what you can do now and then see if any changes you make to body position or amount of throttle or brake make any difference. If you find some combination that's faster do more of it, but if slower, do less.
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Old 03-25-2013, 04:33 PM   #997
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bumbeen: coming from personal experience, riding this on the parking lot, its not that simple to just add or maintain speed and just leaning more, to turn quicker.

If your bars are not turned, you can lean all you want, but you will still be going wide, so the trick is to get the bars turned as much as you can, and preferably to a full lock so your turning radius is as tight as possible.

Adding speed to this, will wrestle the bars out of your hands, as the bike is trying to straighten front wheel, with more power from the rear wheel, pushing front wheel straight, as well as trying to stand up, rather than lean. With less speed, bike falls into the turn, and the front turns lighter and faster. But keep in mind that this is happening with bars at FULL lock to the side. Moto GP or street racers can lean their bikes to the point of knee dragging, but they are not twisting their bars to the full lock. At the speeds they are traveling they are covering much greater distance and wider radii than in Gymkhana, and the small adjustments to the bars are enough to put the bike into a deep dive for their purposes. In Gymkhana, we are traveling much slower and turn radius is much tighter, so we rely on the turn of the bars to get the bike turned faster, and then add lean to it, to decrease the radius even further.

But with slower speed, as motogymkhanaman is saying, you need to counter-balance the bike, so it doesn't simply flop on its side because there is so much lean, but not enough inertia to keep it stable at that lean angle and at that speed.

Also, adding more speed with front at full lock, can very well just start sliding the front wheel, as there might not be enough grip for that speed AT that angle of the bars.

However, knee down, doing tight circles is possible.



This might be exactly what you are saying, however for time attack, this is not the most efficient way, and you WILL lose time on the track, as he is still doing pretty wide circles compared to what you would want to do in a Gymkhana timed event.

In comparison to the above video, these guys turn the bike AROUND quickly.



Look at how much they lean the bike AND twist the bars. But the speed of the bike is minimal (from standstill). Yes they put their foot down, but that is exactly the point. There is no way for them to counter lean to keep the bike stable at that lean angle and that speed, BUT that is probably the tightest radius possible for that bike, which is the point of Gymkhana turns.

So to get the fastest turn-around, you are trying to get as close as possible to these guys, where the speed is enough to keep the bike counter-leaned without putting your foot down, and yet not too fast, where you can not twist the bars to a full lock for the tightest turn.

Vulfy screwed with this post 03-25-2013 at 04:53 PM
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Old 03-25-2013, 04:38 PM   #998
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I made this graphic a while back, and hopefully it shows a little bit clearer how much turn radius is dependent on lean AND bar angle.



As I was making this, one thing that struck me, was that when the bars are twisted fully to one side, the angle at which the bike is leaned, changes the location of the traction patch on the tire. So the more you lean your bike with full lock on the bars, the further forward the patch of the tire that is on the asphalt, moves, decreasing turn radius DRAMATICALLY.

But with that happening, rear wheel is pushing front tire which is almost perpendicular to it, at this point, so there is a fine balance in speed, where there is enough of it to keep the bike moving, but not too much, where rear overpowers the front, and starts to slide it, as the front can not cope with momentum that rear is delivering, to turn the bike in its direction...


I hope I'm explaining it clearly enough, and not making any major errors in my reasoning. I'm just trying to explain, what I've been feeling through the seat of my pants, on my bikes, when I do these exercises.
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Old 03-25-2013, 04:49 PM   #999
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Thanks! And this is why I asked here without going and trying it out myself first haha. I was thinking of doing twist 45 and lean 45 and just adding more speed so I wouldn't have to counter lean to hit my lean 45 mark. You have now created a bunch of other questions but I am indisposed at the moment to post them all! I will have to reply again when I am at a full sized computer.
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Old 03-25-2013, 04:56 PM   #1000
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Old 03-25-2013, 07:58 PM   #1001
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I like how they put that foot out real wide. I was watching(vids of) and have been practicing tight turns from a standstill. Handy for U-turns and turning right on to narrow streets. You can run over your foot, altho I just get my feet up as soon as I initiate the turn.
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Old 03-25-2013, 09:55 PM   #1002
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Originally Posted by bumbeen View Post
Posted this in the noob thread with no response so I will give this a shot.

Is the sole purpose of counterleaning during u-turns so that we can do them at slower speeds?

*I'm not sure, sometimes the tires tell me its a good idea

If so, why can't I just sit straight in the saddle and add a few mph to my speed and maintain the same lean angle and turn radius?

* the tires felt greasy, so I leaned it, it worked (crap tires)

Or might I even hang off and do a u-turn scraping the pegs and knee at 20mph instead of 7?

*try it, you'll fall down, (some) tires give up at that speed

This is making me think the whole drag rear brake and counterlean business is a waste of time,

*ok, but it works, and you'll have to turn like a ship otherwise

just add a little throttle and you can maintain the same turning radius without having to mess with the clutch or rear brake or shifting your weight at all yes?

*radius just went from ship to mega barge

Unrelated, but riding crossed up should allow you to scrub in tires more safely than hanging off or riding straight up and down yes?

*lots of stuff happening, oversimplification, yes, I think so, depending on bike and rider height

The main factor in the lateral traction limit of the tires is the lateral G's not the lean angle?

*we need a volunteer, a rope, and some gforce doodads to test this theory, I'm passing on all but observation and saying "ooooooouch!"

In fact, on a dual compound tire, you're probably more likely to slip if hanging off since you might not be all the way over onto the sticky edges of the tire?

*there is no "sticky" edge. there is "greasy" and "fell down", and they're really close together

Are my presumptions correct?

*test em and see, no one will knock you for trying. we'll all learn something, I say prove it and shows us!
lots of questions...tried to answer what I understand.


what you have to remember is these two turns were easy, that next one has twice the speed to dissipate,, and the one after that is definitely going to slide the rear, and maybe the front a little. it changes from turn to turn, entry and exit, tighter or looser. I watch a very determined msf instructor makes 24' circles at 15 mph or so, hanging off, bike straight up, gaining speed now and again. very cool to see the persistence and improvements from curiosity.

IF he failed, what will happen ? a highside ?

what happens if he fails counterleaned ? a bike slide, and roll away from the back.

either way, someone will have to sweep the pavement before the next rider. I'd prefer to not get tossed myself, if I can help it.




time yourself dragging brake, tight radius, then try the boat turns. I bet 5 seconds at least difference on gp8. :)
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Old 03-26-2013, 01:36 AM   #1003
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Ok here's what I think, still not to a real computer... On vacation in Hawaii so posting from the phone.

Turning radius is determined solely by steering angle and lean angle of the bike. If you are at max steering lock and max lean angle, you will turn in a certain radius. If you are counter leaning and doing this max lean and max lock at 7mph. That means if you try it at 12mph you will not be able to counterlean because you need more weight on the inside of the bike to maintain the force from gravity to balance against inertia wanting to throw the bike out of the turn. Therefore you may sit straight in the saddle to provide enough force from gravity to counteract the increased lateral force. Given this increased speed, we have increased lateral load on the tire, making you more likely to slide out. I don't think this changes your turning radius or am I wrong? Turning radius is determined by lean angle and steering lock. A specific riding position, steering angle, and lean angle fixes your speed and turning radius. Yes?
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Old 03-26-2013, 02:34 AM   #1004
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"A specific riding position, steering angle, and lean angle fixes your speed and turning radius. Yes?"

All true, but we have to take the tyre slip angle into account. The faster we go when leaned over, the greater will be the difference in angle between the direction the tyre is pointing and the direction it is travelling.

To demonstrate zero slip angle spin a coin on its edge and as the energy decays you will see that the lean angle of the coin begins to increase and it will start to roll around its circumference. Irrespective of the lean angle the coin will not move from its starting position.

When we ride the bike we can get our wheels into a similar lean angle to our spinning coin, but due to the energy pushing us forward, instead of the wheel rolling around its circumference it has to slip along the ground instead.

The Moto Gymkhana rider takes advantage of this by minimising the slip angle through precise control of the speed.
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Old 03-26-2013, 04:42 AM   #1005
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The very first guy in this vid does amazing considering he is on a ZRX. NOT a light bike by any stretch to be tossing around like that.
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