bolt pattern for cutlass

[joe_padavano]

If you measure from the center of the the studs on our cars you won't come up with 4.75. It's called a bolt pattern not a bolt circle. Go back and read the link you posted. You have to go from the outside edge to the center of an opposing stud or you will have the wrong measurement. On four lugs you go from outside to outside, so if you used center to center it would be wrong also. I don't have a problem understanding this at all.

Actually you do. You need to go back and read the part in the link that says "NOTE: When measuring a 5-lug wheel the measurement is only an estimate". Also note that the picture shows a CIRCLE inscribed in the center of all five lugs. The diameter of that circle IS the bolt circle, which is 4.75" for an A/G body car. Since most people don't own a wheel gauge, the linear measurement shown is a method to get close. There is enough difference between 4.75" and 5" bolt circles that you can use that method. There is NOT enough difference between 4.75" and 120 mm, however, for it to be used.

Edit: The following is from the American Racing Wheels website. I would guess that they know what they are talking about:

"The bolt pattern or bolt circle is the diameter of an imaginary circle formed by the centers of the wheel lugs."

http://www.americanracingwheelsinfo.com ... attern.htm

 

[jrm81bu]

Look at the picture again in you first link again. I will agree that the measureing line does intersect the bolt circle. However the point that they intersect is betwwen two of the lugs. That is a point that you cannot measure. That is why you go from the outside of one the the center of the other. Also note that that same pic show measurinf from the outside to the center of an opposing lug, just like I've been saying.
If you so sure that the center to center measurement is the bolt pattern a g body takes, go measure your own vehicle and start scratching your head when it comes in at 4.5 give or take a 1/32". The 4 3/4 pattern comes from that measurement plus half the width of the stud which with 7/16 studs is an added 7/16. This will give you around 4 23/32(or 4.71875) which is why the call 4 3/4 an estimate.
If the correct way to measure a five lug pattern is center to center, we would all be running ford rims.

 

[jrm81bu]

How bout this Joe. The bolt circle(that runs through the center of all the studs) measures 4.75. However you can't measure the diameter because you have no reference point accross from any given stud to measure. The next best thing is to measure from the outside of one stud to the center of an opposing stud. But that is still not the center of one stud to the center of another, that won't give you the right measurement because it is not the diameter of the circle since it does not cross through the center of the circle.