what numer of tire do i need four a 20 rim??[&:][&:]

 

The profile height number depends on the width and the width depends on the rim width, so... How wide is your rim?

 

its a 20 rim by 8 1/2"

 

ok, well any sport tire for a 20" rim is gonna have a low profile.

For Example: My rims are 18 X 8.5 and I have put on

Front: 245/40R18

Back: 265/35R18

Now, other than having a bigger radius, your numbers would be a bout the same. Although my back tires have a lower profile number the are VERY close to the same height as my front tires as the profile height is derived from the tread width.

I put wider tires on the rear because the look cool and provide more traction but it is not mandatory. Many people here go with 245s for the front and 275+s on the rear. There is really no set numbers though. Your best bet is to ask around in the 4.6L or V6 forums to get a good idea of what people have.

The end result will really depend on what make of tire you want as different makers have different sizes.