Cornering Forces

[asinn0007]

Hi Everyone,

 

I had some questions about the look, push, and roll technique. Please stop me anywhere that I am mistaken.

 

1) Suppose my tires are capable of 1.2 g's of turning force (traction).

 

2) 45 degrees lean angle usually indicates 1.0 g of turning force.

 

3) One can turn at 1.0 g's of force at 100 mph.

 

4) Once can also turn at 1.0 g's of force at 45 mph.

 

5) Would the lean angles for 3 and 4 be the same 45 degrees?

 

6) Would only the radii for 3 and 4 necessarily be different?

 

7) What happens if I go into a turn at a 45 degree lean angle and roll on the throttle while maintaining the same lean angle? Do I increase the G force without changing the lean angle? Or does the lean angle subtly increase (centripetal force) to counter balance the increasing centrifugal force of the turn?

 

8) In 7 above, does the bike want to stand up or under-steer (widen the turn)?

 

9) Should the effective lean angle be calculated from the center of gravity of the rider/motorcycle unit (if the rider hangs off)?

 

Thanks,

 

Andy

[Adam06]

Wow, that sure is a technical question Andy. Might leave this for the physics experts out there. I just ride bikes

[harnois]

Hi Everyone,

 

I had some questions about the look, push, and roll technique. Please stop me anywhere that I am mistaken.

 

1) Suppose my tires are capable of 1.2 g's of turning force (traction).

 

2) 45 degrees lean angle usually indicates 1.0 g of turning force.

 

3) One can turn at 1.0 g's of force at 100 mph.

 

4) Once can also turn at 1.0 g's of force at 45 mph.

 

5) Would the lean angles for 3 and 4 be the same 45 degrees?

Yes.

 

6) Would only the radii for 3 and 4 necessarily be different?

Yes.

 

7) What happens if I go into a turn at a 45 degree lean angle and roll on the throttle while maintaining the same lean angle? Do I increase the G force without changing the lean angle? Or does the lean angle subtly increase (centripetal force) to counter balance the increasing centrifugal force of the turn?

Seems to me that either the lean angle has to subtly become more severe or your radius has to subtly get bigger, or some of both.

 

8) In 7 above, does the bike want to stand up or under-steer (widen the turn)?

I've seen this discussed a lot on here and other forums and I think in Keith's books - the general question of what effect do throttle inputs have on lean angle. Based on that reading and my own experience, the slight throttle roll-on does not make the bike want to stand up nor lean more. It also does not make it under-steer, quite the opposite, the slight throttle roll-on helps the bike around the turn for a lot of reasons.

 

9) Should the effective lean angle be calculated from the center of gravity of the rider/motorcycle unit (if the rider hangs off)?

Yes. That's the main reason for hanging off, to get more effective lean angle without leaning the actual bike.

 

I'm just a guy who rides bikes and likes reading and thinking about motorcycle physics - not claiming to be an expert on it.

[asinn0007]

Gentlemen,

 

Thank you for your time answering this question. Thanks for the details, Harnois. I trust your and Adam's first hand experience much more than that of any theory, paper calculations, or computer models.

 

Regards,

 

Andy

[kawdude636]

what a question(s).... I know that if I twist the throttle to WOT my bike MOVES!!!

[hubbard_28]

I have near zero idea what you're talking about, so I'm just trying to figure this out. You're talking about lean angle and G-forces, but why isn't speed more of a factor here? If I'm taking a slow (30 mph turn) at 45 degrees, and a medium speed (85 mph turn) at the same lean angle, isn't there going to be a much bigger difference in G's the tire is handling?

[Fajita Dave]

I have near zero idea what you're talking about, so I'm just trying to figure this out. You're talking about lean angle and G-forces, but why isn't speed more of a factor here? If I'm taking a slow (30 mph turn) at 45 degrees, and a medium speed (85 mph turn) at the same lean angle, isn't there going to be a much bigger difference in G's the tire is handling?

 

Theoretically no . A 45 degree lean angle is always right around 1G regardless of the speed you are traveling. The only thing that changes is your turning radius. Think of it this way, if you start a corner at 40mph at a 45 degree lean angle (1G) and accelerate to 80mph while still at a 45 degree lean then how many Gs are you generating? The reason why your turning radius increases as you go faster is because it would take more G forces to keep you in the same radius as a slower corner.

 

The reason why race cars like a F1 car produce more Gs the faster they go is because they generate more downforce. That downforce at higher speeds gives them more grip to hold the extra Gs. We don't have any downforce so it doesn't change at higher speeds.

 

Like it was said above a 45 degree lean angle needs to be calculated by where the center of gravity is when you're hanging off. The bike might only be at a 40 degree angle but because of your body position its cornering more like its at a 45 degrees (probably not that drastic though). Thats why you can corner faster when in the hang off position.

 

If anyone sees that I'm wrong about anything please correct it. I still have plenty to learn!