How to determine the PCD of a set of wheels.

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neilrr

MB Enthusiast
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Jul 20, 2004
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Car
Various.
Which are off the car.

Non Merc wheels, I think they are (4 x) 108 but not 100% sure & need to be.

Any suggestions?

Ta!
 
Easy to measure accurately on a piece of paper, but how to do it accurately on the actual 3 dimensional wheel?
 
Easy to measure accurately on a piece of paper, but how to do it accurately on the actual 3 dimensional wheel?

Try a ruler ? On the back of the wheel.
 
Get a marker and build the diameter up with tape till it is a snug fit in the wheel hole , hold a piece of card on the back of the wheel and spot through two of the wheel holes without moving the card , remove the card and measure the distance between the two dots.

Kenny
 
PCD pitch circle diameter is the circle that will pass through all the holes on a circle through the centre line of all the holes so the above will only be true on a four bolt wheel, measuring across two holes on a five hole wheel will not give true pcd

Try this site www.westerntowing.co.uk for info on how to calculate the pcd,


More info
 
Which are off the car.

Non Merc wheels, I think they are (4 x) 108 but not 100% sure & need to be.

Any suggestions?

Ta!
Very easy with 4 holes.
Tape measure to the opposite hole. Inner to inner, or outer to outer.
 
Thanks to everyone for their suggestions.

Isn't it half way between the inner to inner & the inner to outer measurements?

rbmsrk.jpg
 
Yes Kenny, the pcd is the diameter of a circle on which a number of holes are equally spaced on the centre of the circumference ie the centre of the holes is on the circumference of the circle.

Hope this explains, if you measure, on a four hole wheel, from the outside edge of one hole to the inside edge of the opposite you will get the correct diameter
 
Yes Kenny, the pcd is the diameter of a circle on which a number of holes are equally spaced on the centre of the circumference ie the centre of the holes is on the circumference of the circle.

Hope this explains, if you measure, on a four hole wheel, from the outside edge of one hole to the inside edge of the opposite you will get the correct diameter

I was just thinking about the pitch of the holes and the similarities measuring them from certain points, apologies.

I will return to my corner now.

Kenny
 
In my last picture the ruler is centred (as near as can be) at 100m & the middle of the opposite hole appears to me to be at 208mm, giving a PCD of 108. Is that correct?

I know it's not a terribly accurate or scientific way to measure, but what else could it be?
 
I read your pcd as 108mm. Edge to edge is easier...you are not guessing the centre of the hole.
 
I was just thinking about the pitch of the holes and the similarities measuring them from certain points, apologies.

I will return to my corner now.

Kenny

Your diagram perfectly describes why they are all the same.
 
The left hand number on the rule is at 92mm and the right hand is at 200 as far as I can tell with shadows not making it perfectly clear.

Subtract 94 from 200 gives 106 PCD, but you get idea, difficult to tell from here if it is 106 ish or 108.

Do you have access to a digital vernier? Put wheel onto car studs or push to wheel bolts through two holes and measure outside diameter, subtract the stud diameter to give pcd
 

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