BPM can't change the width

beginners
#1 
void Car::setup(){

    
xPos = ofGetWindowWidth()/2;
yPos = ofGetWindowHeight()/2;

r1=320;
r2=400;
x=100;



thisRadius = ofRandom(r1,r2);


fadeSpeed = ofRandom(0.00001, 0.00045);
addSpeed = ofRandom(0.1, 0.9);
x=ofRandom(-20,20);

}

`void Car::update(){
z=pSensor.BPM;
if(pSensor.BPM>0){
	width=ofMap(pSensor.BPM,60,180,100,10);}
if(pSensor.BPM=0){
	width=0;}



float timeY = ofGetElapsedTimef() *0.05;
 amplitude = thisRadius + ofRandom(-0.5, 0.5);
 

yPos = ofGetWindowHeight()/2 + amplitude * sin(timeY)+x;

float timeX = ofGetElapsedTimef() * 0.05;

float homeX = ofGetWindowWidth()/2;

xPos = ofGetWindowWidth()/2 + amplitude* cos(timeX);

}

void Car::draw(){

ofSetColor(y,y,y);

ofCircle(xPos, yPos, width);}

}

I wan to use a BPM sent by pulse sensor to control the width , but it doesn’t work ? why ?
I also use the vector of pointers , is it related to this problem ?

void ofApp::update(){
pSensor.update();
thisCar.update();
pSensor.update();

//y=ofMap(pSensor.BPM,70,120,200,40);//    it works , BPM can change the y
numCars =2;

//update the list of cars
for (int i =0;i<numCars;i++){
	
	carList[i]->update();
}

}

I can use the BPM change the numCars , but can’t interact with the car class (like width , )

#2

some mistake with ofSetColor(y,y,y);
it should be ofSetColor(0,0,0);
it still can’t work