## Kz vs. speed

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I would give me your opinion on an issue: I want to model one quarter of vehicle. The tire manufacturer provides Kz (vertical tire stiffness) for different pressures and camber angles, but does so for a given speed (125 Kph).

Kz varies linearly with speed (something like: Kz=a*V+b, b>0) and Kz increases if the speed is increased (a>0) but what I can know how much ¿? There any way to make a rough estimate. Knowing the type of tire, size or something else might be able to determine about this variation? I wonder if there is any way of knowing about what is the slope of that line knowing, for example, the dimensions of the tire or the type of tire (radial).

And...

If the graphics are deflecction (m.m) vs. Load (Kg), is not entirely correct to obtain the vertical tire stiffness of calculating the slope of the line (Load*9.81/deflecction). The force that causes a certain deflection is the weight + the effect of centripetal force, not just weight. What do you think about this

Thank you very much

Regards, delacf
delacf
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Joined: 23 Feb 2010

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Unfortunately this isn't something that can be easily guessed or estimated based on tire size or a few rudimentary parameters alone.

May I ask what you need this information for? I realize you're modeling a quarter car suspension, but how critical is the speed dependency? Can it not be assumed to be constant within the scope of this project?
Grip is a four letter word.

2 is the new #1.
Jersey Tom
127

Joined: 29 May 2006
Location: Huntersville, NC

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I would like to justify everything I do in my project but, yes, I think I could take the stiffness constant. The project is a Formula Ford. As we have no downforce, is not critical the ground clearance.

I have also curious

The most complicated to design a suspension I think it is to get the necessary data. "If I have to draw a line I have a point. If I have to draw a parable I have two points. Always missing information "

Thank you, Jersey Tom

Regards, delacf
delacf
4

Joined: 23 Feb 2010