Strange tire grip fact.

[taxonomy]

I am reading Tony Foale's Motorcycle Handling and Chassis Design. It's nearly an impossible read for the novice, which I surely am.

Anyhow, I thought I would pass this on.

Tires exhibit maximum grip when they are sliding about 10%. This is to say that a tire will deliver more forward thrust on an accelerating bike where there is about 10% slippage. That is the tire is moving about 10% faster than the contact patch.

This also holds true for cornering. So, the tire will deliver some amount more camber thrust when it's not hooked up completely. Weird, but true, if I am reading it right. Smarter folks feel free to chime in.

[dparker3975]

This tire grip fact sounds likes you are 10% closer to testing your frame sliders!

[e30addict]

same thing works under braking as well

10% slip under acceleration and braking. 6-8 degree slip angle when cornering.

Easier to achieve with cars than with bikes because of the obvious consequences on a bike. There's probably only a handful of people on the planet who can do it regularly on a superbike.

[taxonomy]

same thing works under braking as well

10% slip under acceleration and braking. 6-8 degree slip angle when cornering.

Easier to achieve with cars than with bikes because of the obvious consequences on a bike. There's probably only a handful of people on the planet who can do it regularly on a superbike.

I would imagine anyone off the front in MotoGP is working this limit.

Crazy.

A

[intergalactic]

I am reading Tony Foale's Motorcycle Handling and Chassis Design. It's nearly an impossible read for the novice, which I surely am.

Anyhow, I thought I would pass this on.

Tires exhibit maximum grip when they are sliding about 10%. This is to say that a tire will deliver more forward thrust on an accelerating bike where there is about 10% slippage. That is the tire is moving about 10% faster than the contact patch.

This also holds true for cornering. So, the tire will deliver some amount more camber thrust when it's not hooked up completely. Weird, but true, if I am reading it right. Smarter folks feel free to chime in.

10% is a wicked generalization, and things change depending on the tire, but yeah. Slip=grip. And depending on what the slip to grip curve looks like, you can get lots or very little notice that you are approaching or past the peak.

[taxonomy]

Hence "about". I was just surprised a tire delivers more thrust in slip mode than grip mode.

One thing that I think a lot of beginning riders don't get is slide does not equal crash.

[Paul_E_D]

I think what most people don't realize is that slip does not equal a detectable slide. I have watched bikes from EX500s all the way up to liter bikes laying darkies out of the turns at Loudon. Most times I mention it to someone they are like, Really? I didn't notice.

The tire is in slip stage well before you can perceive it. Once you feel a slide, you might be surpassing that optimum thrust zone.

[scubasteveRR]

[taxonomy]

I think what most people don't realize is that slip does not equal a detectable slide. I have watched bikes from EX500s all the way up to liter bikes laying darkies out of the turns at Loudon. Most times I mention it to someone they are like, Really? I didn't notice.

The tire is in slip stage well before you can perceive it. Once you feel a slide, you might be surpassing that optimum thrust zone.

There it is, people smarter than me. Hence, "slip angle".

I has suspected something like that. Slide is beyond slip, and way off the back of the grip bell curve.

[Stromper]

In real drag racing they say that number is closer to 33% faster

I thought that would be due to "adhesion" rather then rubber extruding into surface irregularities

[taxonomy]

In real drag racing they say that number is closer to 33% faster

I thought that would be due to "adhesion" rather then rubber extruding into surface irregularities

That varies considerably from the "meshing gears" idea that I had before I started reading this. My idea was basically that highest grip is static and that it starts falling off quickly when it exceeds that.

Turns out it isn't so.

[spydah]

It makes sense if you consider that tires are more sticky when they are warm, and when a tire slips there is more friction since it is moving faster than the surface it touches. More friction = more heat = stickier tire.

[e30addict]

That varies considerably from the "meshing gears" idea that I had before I started reading this. My idea was basically that highest grip is static and that it starts falling off quickly when it exceeds that.

Turns out it isn't so.

Depends on the tire. R comps are less forgiving then street rubber

[stoinkythepig]

I think what most people don't realize is that slip does not equal a detectable slide. I have watched bikes from EX500s all the way up to liter bikes laying darkies out of the turns at Loudon. Most times I mention it to someone they are like, Really? I didn't notice.

The tire is in slip stage well before you can perceive it. Once you feel a slide, you might be surpassing that optimum thrust zone.

When I think about how a bike is turned (pushing the handlebars away from where you want to turn) I'd guess that turning always involves some sliding, at least on the front tire. I have a 1:25 scale model of my 9R here at my desk and I cannot get it to turn (with the front wheel straight or) without sliding.

[SVRACER01]

Wirelessly posted (Instinct: TELECA-/2.0 (BREW 3.1.5; U; EN-US; SAMSUNG; SPH-M800; Teleca/Q05A/INT) MMP/2.0 Profile/MIDP-2.1 Configuration/CLDC-1.1)

this is why you countersteer...to slide the rear.

[stoinkythepig]

Wirelessly posted (Instinct: TELECA-/2.0 (BREW 3.1.5; U; EN-US; SAMSUNG; SPH-M800; Teleca/Q05A/INT) MMP/2.0 Profile/MIDP-2.1 Configuration/CLDC-1.1)

this is why you countersteer...to slide the rear.

I respectfully disagree. I think the front slides and the bike corners because it's following the path the side of the rear tire wants to take for a given angle of lean. I could be way off base though.

[taxonomy]

I think the "slide the rear" thing was a joke.

There is some element of scrub when steering, but I don't know if it's enough to really think of it as sliding on the order of full percentage points.

I'm also pretty sure that a model is going to be a pretty poor approximation given the complexity that's actually occurring.

[Ken C]

I too, was surprised to hear this when I read Foale's book.

It is as Paul says, that slip angle that produces the most grip is imperceptible to most mortals. If you saw the graph describing this effect, you'd see that the time when grip is optimal is of a pretty short duration. Once you exceed this peak, then you suddenly lose a huge amount of grip.

[Stromper]

You steer the tires out from under the center of gravity and that levers the bike into a lean

tires don't slide so much as the distort in a continuous wave

[Ken C]

True, but that's a different aspect of cornering. Slip angle deals with what happens after the bike is leaned and affects how much grip is present.

[butcher bergs]

The science of grip was explained to me with a boat prop as the example.

The prop acheives maximum forward thrust when there is slight cavitation occuring as this is when it is displacing the most amount of water. Beyond a certain point, when you have more cavitiation there is less forward thrust. The other end of the spectrum seems to be obvious, that being, if there isn't any cavitation then you are not displacing the maximum amount of water the prop can handle.

Make sense? Does to me.

[SVRACER01]

Wirelessly posted (Instinct: TELECA-/2.0 (BREW 3.1.5; U; EN-US; SAMSUNG; SPH-M800; Teleca/Q05A/INT) MMP/2.0 Profile/MIDP-2.1 Configuration/CLDC-1.1)

Wirelessly posted (Instinct: TELECA-/2.0 (BREW 3.1.5; U; EN-US; SAMSUNG; SPH-M800; Teleca/Q05A/INT) MMP/2.0 Profile/MIDP-2.1 Configuration/CLDC-1.1)

this is why you countersteer...to slide the rear.

I respectfully disagree. I think the front slides and the bike corners because it's following the path the side of the rear tire wants to take for a given angle of lean. I could be way off base though.

Maybe slide should be in quotes.
when a motorcycle corners at speed that requires you to countersteer the rear tire takes a wider line through the turn than the front,(unlike a car where the rear takes a tighter line than the front) i call this "sliding the rear". its way more prominant on a dirtbike than a streetbike.

[Stromper]

Thinking causes wrinkles

[Paul_E_D]

best post ever!

[Ken C]

Thinking causes wrinkles

No wonder the guy in the mirror looks like Yoda.