Brakes and wheels - V8 project

[Fast_Eddie]

I recently purchased a partially complete V8 project car and am having some problems clarifying the brake and wheel combination.

I was of the belief that it had HQ-HZ stud pattern and brakes, as the front rotors that came on the car (new)have been identified to suit these model Holdens.

However, when I took up the rear rotors (it has disc brake Holden axle tubes with a 9" Ford housing) to get machined, I was told they were past saving, and a new set were required. I've been advised that the rotors on the back were Commodore.

I was of the opinion that HQ-HZ and Commodore PCDs were different (ie stud pattern) - however the wheels - 15x7 Cheviot Hotwires - seem to fit properly on both the HQ-HZ front rotors and the Commodore rear rotors.

Is this possible?

Regards

Edward

[SRVLIVES]

HQ/WB are slightly different to Commodore. Here's a question I asked over on oldholden about this very subject.
http://oldholden.com/?q=node/27938

[cruiser056]

Fast Eddie,
                   I have HZ brakes on the front and VN brakes on a VN diff on the rear of my FE.  I am running HQ GTS wheels front and back.  Apparently there is a slight difference in the stud pattern, only a couple of mm.

                    So some of the older type wheels will fit both, but you may have some problems if you buy new wheels.  This is what was explained to me.

                     Hope this helps.

Michael

[FC-225]

There is 1mm difference between commodore and HQ PCD's.
So that makes it.05mm per side of the pcd,hence wheels and rotors will interchange.. Maybe not quite right but has worked for many years now...

AL

[blacky]

 I have just converted a commodore diff to HX type stud pattern by putting the axles in a mill and offset drilling the stud holes to the correct pcd and fitting oversize studs to correct this slight but potentially catastrophic difference. Took maybe an hour and around $30 to do .
 Cheap insurance I reckon.

[SRVLIVES]

Exactly Blacky!

I don't think people understand the dangers of this minute difference.

[Fast_Eddie]

Thanks guys - you've basically confirmed my thoughts - ie that there is a difference and yes, it matters.

I imagine that having the new Commodore rotors drilled and restudded to suit HQ would be the best way forward. Looking at the old ones, it looks like this is may have been what was done before? It explains the five holes.

[mcl1959]

To be exact, HQ and Chev have a 4 3/4 inch pcd (120.65 mm)
Commodore has a 120mm pcd
HQ and chev have a 7/16 inch diameter stud (11.1mm)
Commodore studs are 12mm diameter.
Most wheels locate the wheel nuts EXACTLY into a pcd which is set into the wheels.
Steel wheels are the worst since the nut starts easily and once it beds into the v shape in the wheel it bends the stud over to match the pcd of the wheel.  Slotted multifit wheels will be OK for logical reasons.  You may find that deep shoulder nuts which don't start on the thread until the nut is already inserted into the wheel will not even start on the studs at all if you put the wrong wheel on.
Commodore wheels will go onto HQ hubs but will bend the wheel studs every time you do them up and undo them.  Don't put HQ wheels onto a Commodore as tightening up the wheel nuts will not only bend the studs but it will jam the wheel on so hard you will not be able to get it off.  We have had to cut off a number of HQ wheels from Commodores because they simply would not come off any other way.
Funny thing is when one stud breaks, the rest go at the same time due to the shock loads.  Sometimes you can be lucky and one stud will remain holding the wheel.
In short it is advisable to run the correct pcd for the wheels you are using.  You may get away with it for years and then one day it will just go bang and your life may be in jeopardy because of one small shortcut.  

Ken

[fccool59]

that kind off clears some child hood confusion, I remeber being told when I was a kid that HQ wheels dont fit a commodore but a guy down the road had HQ sports rims on his commodore.

So i guess the statesman SL/E alloys are different to commodore SL/E wheels but look the same.

[Dr_Terry]

Hi Guys.

The Commodore SL/E alloys are 15" & the HZ Statesman SL/E's are 14". The offset is also quite different.

I'm stunned at the number of people that have Commodore rims on HQ-WB (or vice versa) & get away with it.

Dr Terry.

[Fast_Eddie]

Following all the feedback here (thanks!) I have looked again at the stud pattern/brake issue on this car, and have established the following.

The stud pattern front and rear is HQ. This has been achieved by using HQ rotors at the front, and using modified 9"axles with a HQ stud pattern at the rear. Therefore HQ wheels fit safely on the studs front and rear. I mistakingly thought the rear rotors were studded in the posts above.

However, mounting of the rear brake rotors remains unresolved. The car came with a Ford 9" housing that had the axle tubes changed to what I believe to be Commodore tubes to facilitate the rear disc brake set up.



Whilst the new Commodore rotors fit comfotably over the studs, what hasn't been contemplated is the way the Commodore rotors locate on the axles. This can be seen in the following photograph.



I believe that I am correct in assuming that the proper result should have the rotor centred on and bearing on the axle by the rotor closely fitting over the raised section in the centre of the axle. The above photo clearly demonstrates that the diametre of the centre of the axle is too small to achieve this.

Would an acceptable fix be having a ring machined  up with an inference fit that mounted onto the face of the axle, and allowed the rotor to fit comfortably over?

Any advice would be appreciated.

[FC-225]

Yes you are correct,the rotor needs to spigot off the axle centre. An interference 'ring' would be fine.
It is common practice to do that on VT commodore front rotors to retrofit to earlier commodore hubs.

AL

[Martin]

Please explain:   pcd?

Thanks.

Martin

[SRVLIVES]

Pitch Circle Diameter, simply the stud pattern.

[Martin]

Now I know.  Thanks, SRV

Martin