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# Pacejka magic formulae

## Pacejka magic formulae

(OP)
Can anyone explain me how to compute tyre forces with the Pacejka formulae ?

### RE: Pacejka magic formulae

I don't understand your question. You just plug the coefficients and the operating parameters of the tyre into the formula and the forces are the answers.

Here's a website that may help.

I haven't checked it but it looks OK.

Incidentally you should be aware that there are several magic formualae, with different numbers of terms.

Cheers

Greg Locock

### RE: Pacejka magic formulae

(OP)
In fact i'd just like to know how to calculate the long. and lat. forces just having the coefs. I don't know that there are different formulae.

In my data
A coefs range from a0 to a13 with a111 and a112
B from b0 to b12
C from c0 to c18

and also am0 to am9 and bm0 to bm3

Thanks

### RE: Pacejka magic formulae

I don't know enough about the history of the magic formula to identify exactly which has 62 coefficients. Wherever you got your coefficients from should have the equation, they are pretty meaningless otherwise. I have not seen a111 and a112 in the literature I have read.

Cheers

Greg Locock

### RE: Pacejka magic formulae

(OP)
So can you give me just one formula with the numbers of coefs ?

Thanks

### RE: Pacejka magic formulae

Sure, I've posted the formula and some results from AVEC 92 paper 923063. It does not nominate coefficient values. I suggest you put your values in and see if you get similar looking curves. It might be a good idea to post your coefficients here as well.

http://www.geocities.com/greglocock

Look in the gallery, most of the way down

Cheers

Greg Locock

### RE: Pacejka magic formulae

(OP)
Sure i'm going to get the curves.

Un fortunatly the coefs for a Michelin tire are no longer available on the site i'v found them...

Anyway i'll try with other coefs.

Thanks a lot

### RE: Pacejka magic formulae

(OP)
So here are my coefs:
a0:1.9
a1:16
a2:1440
a3:1800
a4:8.65
a5:0.14
a6:0.165
a6.1
a7.051
a8.018
a9.06
a10:-2.35
a111:-2.35
a112.37
a12:-14.9

with these coefs Sv=(a111*Fz+a112)*gamma*Fz+a12*Fz+a13

if you want a plotter for pacejka you could download the simulation racer at www.racer.nl and you will get a pacejka plotter in which you can alter the coefs.

Send you my curve.

### RE: Pacejka magic formulae

(OP)
Do you have the longitudinal formula ?

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