throttle and radius

This guy is considered a reputable riding coach in Greece. What he says in fluent Greek (please use English subtitles) is that mid-corner,once you touch the throttle the bike wants to tighten its radius. He mentions people telling him that their bikes want to open their radius and he tells them that its their unconscious actions that makes their bike open the radius because they can't handle the speed(!).

Any comments? Do motorcycles naturally tighten their radius once we open the throttle (maintenance or acceleration) while leaned?



go to 16:15

 

YCRS demonstrates that in every class, and its the complete opposite result

 

Wheels spinning faster means more gyroscopic effect, thus the wheels wanting to line up with the center of the earth (ie. stand the bike up and widen the radius). Grecian guy needs to re-read the great Greek physicists.

 

Maybe he's spinning up the rear on his scooter.

 

He's wrong or it doesn't translate well across languages.

 

I ask you: Is this the place to discuss operaring a motorcycle?

 

Kind of, not really. A spinning wheel wants to maintain the direction of its axis but not necessarily stand up. There are other physics at play, but gyroscopic effect alone doesn’t describe it. Maybe it’s time to break out those Greek physic books?

Edit: not saying this guy is right. I need to ponder what he’s saying a bit.

 

Yes and no. Didn't watch the video, but I think I get the concept. I argued against this theory with a certain professional club racer and realized that I just hadn't yet gone fast enough to experience it. Obviously if both tires are hooked up, and you add throttle, the bike will stand up and go wide 10/10 times.

It's only a thing at the very limit of traction, when the front end is doing the hard work and both tires are struggling for grip. When the throttle is opened, there's a sensation I call "hooking" when the weight transfers off the front, and both tires regain traction causing the bike to lock into the corner. It's a similar feeling to throttling through a rut on a motocross track.

Judging by the picture of a scooter in that video, he may be talking about something different, or is wrong.

 

Simply opening the throttle does not make the bike want to stand up. Run wide yes if there is grip at both ends. Exceed the rear grip and the bike will rotate but that's not the same as a slight opening of the throttle trying to make the bike tighten it's radius.

 

Its a yes and no. Yeah you can oversteer on exit with a 600 or 1000 if the suspension is setup right and you are on the edge of traction. However, adding throttle will take weight off the front pushing you wide so i like to say the answer is complicated.

 

I agree there are other forces at work. Amongst them, the weight transfer to the rear of the bike can stretch the forks a little, compress the shock, unload the front tire and push the bike wide. But unless the bike oversteers by spinning the rear wheel, it won't turn tighter.

 

This guy kind of explains the same thing, and shows video.

 

Maybe the bikes should come with instructional read outs on the dash telling you when to use which controls.

 

Not saying which side is correct but it is no where as simple as gyro effects. For instance one thing that could change when you apply or release the brake/throttle is the trail as suspension changes. That is just one effect of some very complicated (IMO) physics.

 

The scooter is on a different section of the episode.
He doesn't mention sliding the rear or anything similar.

What he says is,once you open the throttle mid-corner,the radius tightens because of:
1.the cog of the motorcycle moving to the inside of the corner
2.the front stops pushing and starts tracking because you unload it

among other things that he doesn't mention.

 

I think front/rear weight distribution and weight transfer can affect this. If you are straight up and down, and you hammer the gas, the front wheel does what? It lifts off the ground. Now, if you are leaned into a corner, and give it more gas, the same situation can occur, but along the axis of the lean(or rear axle). So I can see how getting on the gas can help tighten up the radius of a corner. Not saying I'm right, but just giving thoughts here. Motorcycle dynamics are very complicated, even more so than car dynamics in my view.

 

It's all greek to me..



<I'll get my coat>

 

without even clicking the vid, there are 3 ways to look at it:
1. corner exit in general: you open it up and the bike tends to go wide.
2. geometry change: once you open the throttle, you unload the front thereby squatting the rear and making the bike take a wider turn at lean
3. you start spinning the rear and thereby having the rear end step out, thereby letting you point the bike more towards the inside and maybe taking a slightly tighter turn. with a big maybe.

 

i asked my greek riding frens on FB, let's see what they say. (and no, not the crazy ones who think they are a greek god @Metalhead )