Scraping the Peg (The Physics)!!!

a7x3797 said:
We'll it doesn't lower the pegs, it lifts the rear wheel. As for a one inch drop at the swing arm, the pegs distance to the ground will change at a ratio to the amount you dropped it, if you think of a triangle where the front wheel is the point and the bases are the swing arm and another base at the pegs, you could find the delta value. Without measuring, I would guess somewhere between 1/2 and 3/4 if an inch, and since my calculations deemed one inch at the pegs to be ~2.5* angle, it would only affect the angle by up to 2* which is 5%. And that falls within my set tolerance.
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If you "lift" the wheel gravity demands the chassis falls. It is impossible to lower the bike and keep the same peg height, unless you raise the pegs. There are no two ways around it.

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Preeminence said:
Suspension characteristics (weight) absolutely have to do with your clearance. If you've got really soft suspension, your bike might be an inch or two lower in a corner than someone with really stiff suspension. Corner speed creates lateral g-force which, on a leaned-over bike, compresses the suspension.

That said, I scrape my pegs all the time at the track (even with the knobs removed) and the rear is still pretty stable. If you've got a 190/55 tire, you've still got a lot of rubber on the ground at a 43 degree lean angle. From what I've heard, your max (safe) lean angle is about 5 degrees less than your tire height number. So on even on a stock 190/50, you can go to 45 degrees and still be in pretty good shape. I wouldn't go wide open on the throttle, but you should be able to hold a constant corner speed.
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My model involved nothin but peg height clearence, that's what I was saying.
 
Hellgate said:
If you "lift" the wheel gravity demands the chassis falls. It is impossible to lower the bike and keep the same peg height, unless you raise the pegs. There are no two ways around it.

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Agreed, but if you read my response, it affects the angle by under 2* so for my simple model I said its negligible from bike to bike. I just applied it to my bike
 
Sometimes this forum pisses me off, if ANY of you would have actually read what mu initial post was saying you would see I was settin up a simple static model of the peg clearence from the ground vs if you remove the feeler. This model represents that if you sit I the bike, and fall to the side, here's how many degrees you would fall before the peg touched. I was interested in it and I thought I would share what I found. I'm a 3rd year mechanical engineering student at RIT in NY. I understand more there are more to this model than what I included but remember.... IT WAS A STATIC MODEL. so I don't care how the suspension is moving and weight distribution.

Maybe if some of you would stop trying to bring the thread poster down by repeating one guy's response 5 different ways, we'd have a forum where people can post without being shit all over. If you guys were so smart, you would understand my simplified static model where I stated I did not include dynamic motions.
 
a7x3797 said:
Sometimes this forum pisses me off, if ANY of you would have actually read what mu initial post was saying you would see I was settin up a simple static model of the peg clearence from the ground vs if you remove the feeler. This model represents that if you sit I the bike, and fall to the side, here's how many degrees you would fall before the peg touched. I was interested in it and I thought I would share what I found. I'm a 3rd year mechanical engineering student at RIT in NY. I understand more there are more to this model than what I included but remember.... IT WAS A STATIC MODEL. so I don't care how the suspension is moving and weight distribution.

Maybe if some of you would stop trying to bring the thread poster down by repeating one guy's response 5 different ways, we'd have a forum where people can post without being shit all over. If you guys were so smart, you would understand my simplified static model where I stated I did not include dynamic motions.
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Never meant to shit on anybody. It just seemed like you were saying that the numbers applied across the board when, of course, they can vary. I do appreciate you doing the measurements, though. I've been getting concerned with how much I'm leaning now that I've taken the feelers off, and it's good to know that I'm not that far over. If anyone wondering how far over you can go with the stock pegs, I actually just put together a little video of my clearance at a recent track day. Now I don't feel so bad about getting some race rearsets.
 
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a7x3797 said:
Sometimes this forum pisses me off, if ANY of you would have actually read what mu initial post was saying you would see I was settin up a simple static model of the peg clearence from the ground vs if you remove the feeler. This model represents that if you sit I the bike, and fall to the side, here's how many degrees you would fall before the peg touched. I was interested in it and I thought I would share what I found. I'm a 3rd year mechanical engineering student at RIT in NY. I understand more there are more to this model than what I included but remember.... IT WAS A STATIC MODEL. so I don't care how the suspension is moving and weight distribution.

Maybe if some of you would stop trying to bring the thread poster down by repeating one guy's response 5 different ways, we'd have a forum where people can post without being shit all over. If you guys were so smart, you would understand my simplified static model where I stated I did not include dynamic motions.
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I think you started a pretty good thread. It was neat to add some geometry and put the ideas down on paper and post them. To my memory (which is not that great :gaming:) I believe you are the 1st to ever do this. So that's pretty cool.
I appreciate the effort and enjoyed reading it. Don't let people stating you made a mistake on anything get to you...........EVERYONE makes mistake - like the lean angle on your bike? IF EVERYONE DROVE PERFECTLY 100% OF THE TIME - Every race would end in a tie. :lol:
So keep posting...........add some more juice to it and some pics and you will have one Hell of a good thread going. LOL If you really want to have some fun - throw a question out to the masses and see what everyone else has. :D
Thanks again for starting the thread. Now get to work on some more..............please :D
 
Op what do you weigh? Im about 195 and have never touched a peg. I dont have much in the way if chicken strips. Im not by any means an awesome or probably even a good rider when you get down to it. Never had a class beyond basic safety or been to a trackday. I'm just trying to figure out how guys drag pegs all the time and I don't yet if I don't have any strips I obviously get the bike over pretty far...
 
Sebastian F7 said:
Op what do you weigh? Im about 195 and have never touched a peg. I dont have much in the way if chicken strips. Im not by any means an awesome or probably even a good rider when you get down to it. Never had a class beyond basic safety or been to a trackday. I'm just trying to figure out how guys drag pegs all the time and I don't yet if I don't have any strips I obviously get the bike over pretty far...
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No offense to anyone, but I would have to say that it has to be improper technique. Fully agree with you about having very little chicken strips and never scraping. Most likely not enough throttle to keep the fork extended while leaned over (reduced ground clearance). And/or counter-weighing in turns (proper technique for slow turns, but bad for normal speed stuff).

Of course the other theory could be that folks who scrape on street are taking turns at 3 times the posted limit.. then I can see scraping even with good form.
 
a7x3797 said:
Sometimes this forum pisses me off, if ANY of you would have actually read what mu initial post was saying you would see I was settin up a simple static model of the peg clearence from the ground vs if you remove the feeler. This model represents that if you sit I the bike, and fall to the side, here's how many degrees you would fall before the peg touched. I was interested in it and I thought I would share what I found. I'm a 3rd year mechanical engineering student at RIT in NY. I understand more there are more to this model than what I included but remember.... IT WAS A STATIC MODEL. so I don't care how the suspension is moving and weight distribution.

Maybe if some of you would stop trying to bring the thread poster down by repeating one guy's response 5 different ways, we'd have a forum where people can post without being shit all over. If you guys were so smart, you would understand my simplified static model where I stated I did not include dynamic motions.
Click to expand...

We aim to please, so please aim...

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Erci said:
No offense to anyone, but I would have to say that it has to be improper technique. Fully agree with you about having very little chicken strips and never scraping. Most likely not enough throttle to keep the fork extended while leaned over (reduced ground clearance). And/or counter-weighing in turns (proper technique for slow turns, but bad for normal speed stuff).

Of course the other theory could be that folks who scrape on street are taking turns at 3 times the posted limit.. then I can see scraping even with good form.
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I usually aim for at least 2x when I'm going for it.
 
My fat ass got yelled at yesterday by TWO coaches at Team Promotion for scrapping my pegs through the paint on the apexes of the NY Safety Track.

They said exactly what was said here- body position, body position, body position. They told me to knock it down 10 mph and I'd be smoother through the lines, and as a result faster, through the turns.

While I'm not a third year engineering students, I did graduate from Smoothie King College and I learned- Smoother is better!:rmwl:

BTW, OP- Great work on the math!
 
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