Wheel PCD

[_Rob_]

im in the process of buying a new single rear wheel as one of mines damaged. the wheels ive got on at the moment are rondell 18 x 9 ET35 with a 112PCD.

 

now IIRC the Supes PCD is 114. the guy i was ordering my wheel off said i must have some 'variable wheel bolts' holding on my wheels, otherwise they wouldnt fit properly.

 

my question is, does this 112PCD cause me any negative affects? shall i buy another wheel the same, knowing the PCD is wrong? or shall i buy a full new set with the correct PCD? and what the hell is a variable bolt??

 

cheers guys...

[Jake]

Variable wheel bolts are a bodge to get the wrong wheels onto to your car.

Don't use them. Buy some other wheels with the correct PCD.

[_Rob_]

i dont get what they do...

 

surely if the wheel is the wrong PCD it wont fit the hub! the diameter of the PCD for the wheel is smaller than that of the hub. the bolts would then have to some how make the PCD of the wheel bigger...wouldnt they?

[connor66]

Rob,

 

The reason your 112 PCD wheels fit onto a 114.3 PCD stud pattern is because of hole clearance...the diameter of the holes in your wheel are greater than the diameter of the studs.

 

If you measured the diameter of one of your studs, it would be 12mm (actually slightly less but we won't get into that), the diameter of the holes in your wheels will be in the region of 14~15mm. It is simply the clearance between a 12mm stud and a 14~15mm hole which allows it to fit.

 

Problem is, because of the discrepancy in PCD's, none of your studs will be in the centre of the corresponding hole in the wheel, which could be bad news.

 

Imagine a 12mm diameter circle drawn on a piece of paper, now imagine a 14mm circle drawn from the same centre point...there would be a nice uniform 1mm gap all the way round (the difference between a 6mm and 7mm radius). Now imagine moving the 12mm circle up until it touched the 14mm circle...there will be zero gap at the top with a 2mm gap at the bottom, ie. the circles will be offset and not central to each other - this is the effect you'll have when fitting your wheels.

 

Draw a 114.3mm circle and a 112mm circle on a piece of paper from the same centre point. Now draw a line straight up from the centre point to the outside circle. Where the straight line intersects the outside circle, draw a 12mm diameter stud... where the straight line intersects the inside circle, draw a 14mm diameter wheel hole (or whatever diameter holes are in your wheels)...this "mismatch" in the positions between the 12mm stud and the 14mm hole are exactly what you will have all the way around the hub. Each stud will be on the very outside of each hole in relation to the hub centre.

 

Problem is, if your wheel nuts are conical shaped (as mine are) and the holes in your wheels are conical shaped (on the side where the wheel nuts go), they are designed to be exactly in-line and central to each other, ie. the cones on the nut and wheel make contact all the way round when tightened together. Imagine them tightened together when the stud and wheel hole are not properly lined up (as in the case of a 112 PCD wheel on a 114.3 PCD stud pattern), they will only make contact in one place...not good.

 

Hope that was relevant / of some use

[MKIVDreamer]

very well described!

 

I'm guessing that this will also put the studs under stresses that they are not engineered to take and could end up bending (best case) or shearing (worst case).

 

Do what has already been suggested - sell your wheels and buy some which have the correct PCD.