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measuring PCD

Started by _nibbsy_ , Sep 18 2006 11:02 PM

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13 replies to this topic

#1 _nibbsy_

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Posted 18 September 2006 - 11:02 PM

I have just picked up a set of steel rims for my LH that runs HQ pattern while i save up and buy a decent set of wheels.
They are 15" in diameter and i think they might be commodore pattern cos they came with hub caps that look they are off a VR and i'm pretty sure HQ would have never had a set of 15" back in the day.
I was after a way to measure the PCD accurately and check out if they are commo or HQ.
Could someone also tell me which one is which, 120.5 is HQ or commo and if 120.9 is commo or HQ.
Thanks heaps
nibbsy

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#2 warrenm

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Posted 19 September 2006 - 08:19 AM

Commodore is 120mm
HQ/WB is 4 3/4" (120.8mm")

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#3 makka

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Posted 19 September 2006 - 12:40 PM

Commodore is 120mm
HQ/WB is 4 3/4" (120.8mm")

HQ/Chev is actually 120.65mm or 4 3/4"

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#4 _devilsadvocate_

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Posted 19 September 2006 - 01:07 PM

To answer your question.........any easy way to measure pcd is to measure the distance between the centre of adjacent studs.
Finding the centre of the wheel or measuring to it is not always easy.
Using some basic year 9 trigonometry:
The pcd of the wheel in inches will be (dist bw studs in cm/ 1.49)

pcd(in)= adj studs (cm)/1.49 (for five studs)

or dist bw studs (cm) = 1.49 x pcd

For a torrie wheel 4.25in(or is it 4.24) pcd, dist bw studs = 1.49 x 4.25 = 6.35cm

Hope this is of help

Edited by devilsadvocate, 19 September 2006 - 01:17 PM.

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#5 _HB1200_

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Posted 19 September 2006 - 04:12 PM

Ring around your local tyre/rim stores, they some times have a gauge that measures the distance between adjacent studs and shows the pcd on a sliding scale.

HB1200

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#6 _nibbsy_

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Posted 19 September 2006 - 10:58 PM

Using some basic year 9 trigonometry

I'm flat out remembering year 9 let alone trigonometry from it!!! :tease:

Thanks for the replies guys, i was thinking of just taking one down to a tyre shop and seeing if they can suss it out for me.
Cheers again
nibbsy

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#7 _devilsadvocate_

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Posted 20 September 2006 - 12:10 AM

Using some basic year 9 trigonometry
I'm flat out remembering year 9 let alone trigonometry from it!!!

Thats why I gave you the formula for pcd from stud separation, I only mentioned it being yr9 maths(which it is) as there would be those on this forum that would waste time challenging that it was plucked out of thin air etc
Anyway understand the prob, you have a rim with the holes for the studs and you have to be able to measure to near to an accuracy of 0.7mm and have difficulty actually deciding exactly on the centre of the holes.

One way to do this with the holes is measure the distance of the closest edge of one hole to the closest edge of the an adjacent hole and measure the distance of the furthest edge to an adjacent furthest edge, add the two together and divide by 2.
Id be confident of a correct answer using a mm ruler, but would be best done with a vernier.
Id imagine that a tyre shop perhaps might have something to help out.

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#8 makka

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Posted 20 September 2006 - 12:17 AM

One way to do this with the holes is measure the distance of the closest edge of one hole to the closest edge of the an adjacent hole and measure the distance of the furthest edge to an adjacent furthest edge, add the two together and divide by 2.
Id be confident of a correct answer using a mm ruler, but would be best done with a vernier.

or you could save yourself time by measuring to the closest side of 1 hole, and the furtherest side of the other........