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Forward pressure on outside bar to maintain turn...?


Pillowes
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Hey guys, first post here after being long-time reader.

What do you guys think of this post? Specifically, this picture near the end of that first post. 

image.png.045d7a47e8329fc1c6d8ba5ba7cc4ade.png

Each line from bottom left towards top right represents curves of different radii. X axis is speed and Y is basically how much pressure you're holding on the handlebar to maintain a turn. Negative values on Y axis represent inside handlebar forward, 0 represents no bar pressure ("neutral steering"), and a positive Y value represents forward pressure on the outside bar.

In a separate image that's not in the above link, but still originating from Vittore Cossalter's very interesting book "Motorcycle Dynamics", it states handlebar pressures with and without hanging off 0.05 meters. With the hang-off, pretty much all turns apparently start to need "outside bar forward" pressure.

image.png.845a43a96b81f2e28513880c008df4e5.png

Do you guys feel this is accurate in your experience?

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I don't see anything here that I would disagree with, personally.

It aligns with my experience that a rider who hangs off can hold a tighter arc (or go faster on the SAME arc) than a rider who doesn't, because they don't have to lean the bike over as far.

Regarding bar pressure IN a corner (not initial steering pressure, but maintained bar pressure while the bike is already on an established arc), I personally wouldn't be trying to manage the steering torque to achieve a particular arc at a particular speed. Instead, I would manage the SPEED, for a given corner, to achieve "neutral steering" (no bar pressure). On a well setup sportbike with good (and warmed up) tires and good suspension, If the bike was tending to want to "fall in" to the corner (tightening its arc), that would indicate to me that I could carry more speed in that corner, so I would enter the corner faster and/or roll-on the throttle in the corner to create some acceleration to stabilize the line. If the bike was tending to go wide, that would tell me that I was carrying a bit too MUCH speed for the corner. Adding steering torque in the corner (pressing on the bar) restricts the ability of the front end to move, as it needs to, to accommodate the irregularities in the pavement. I'd be concerned that restricting that movement means I'm fighting the bike and compromising my traction by not allowing the front end to work as it should. I would not typically try to correct a bike drifting off line to the outside by adding bar pressure; I would either slow down until the line was under control, or use a hook turn position (hanging off more forward and to the inside) to correct the line without trying to force the steering.

In practice, it is not often that we ride a constant radius arc at an exactly constant speed, in most cases we would be planning an line that would straighten the corner as much as possible, making decisions about how much speed to carry in and how much drive we could get going out, rather than trying to set a fixed arc and keep the speed exactly constant, so I'm not sure how useful, on a racetrack, the above data would be other than to illustrate that neutral steering IS possible and that hanging off DOES make a difference.

Of course different types of bikes (cruisers versus sportbikes, for example) would have different steering characteristics and a cold or very worn and profiled front tire could change handling quite a bit - as an example, in my experience a very cold race-slick front tire will want to make the bike "stand up" in the corner, and you really do have to maintain pressure on the inside bar to maintain an arc, until the tire warms up.

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