What diameter for making your own hubs for the C5 brake kit 2nd Gen??

[ryeguy2006a]

I am looking to make my own hubs for the C5/C6 brake upgrade kit for my 2nd Gen 1976 Trans Am. I am going to have the machine shop turn down my rotors once I cut them off, but I need to know what the diameter is that I need to get them cut to? I know that it needs to fit over the rotor, but don't have one yet to find what the diameter is. Any help would be great. I have searched many times on this forum but cannot seem to find the answer that I am looking for.

I am going to slowly build my own kit, I just purchase some 17" rims and used the template from Kore3 to see if it would fit under my rims and it will. I am going to piece together a kit and this will be the start of my car transforming into a PT car.

Thanks,
Ryan

[shep]

They need to be turned down to just under 6 inches if I remember correctly.

[prosuperstar]

I just modified some 3rd gen rotors last week for c5 brakes. Are you using 3rd gen rotors? If so I can measure mine tomorrow morning and let you know

[John Wright]

measure the little recess on the backside of the C5 rotor...the hub just needs to be a smigit smaller than that so it will sit flat.

...same with the rear axle flanges if you are using C5 rotors back there.

pointing to the recess on the rear rotor...front is similar
https://static1.pt-content.com/images/pt/2010/09/edgethathitsaxleflange-1.jpg

[astroracer]

Hey Ryan,
I am doing the same thing for my BadAst Project. I will be turning the front hubs down to 5.75 or 5.81 diameter.
I don't want to hijack Ryans thread but I have a pertinant question also.
I am in the process of ordering rear axles also and want to verify the C5 rotor register diameter. What diameter do you guys order for the C5 rear rotors? I measure the rotors at 2.75 I.D. But need to know what works for fitment of the rotor to the axle.
I "borrowed" Johns pic from above so you know what I am asking.
https://static1.pt-content.com/images/pt/2011/08/29au11_rotorregistrydiavi-1.jpg
Thanks guys!
Mark

[Apogee]

C5/C6 rotor register diameters are nominally 70.5mm [2.776"], however most center bores on the rotors will measure somewhere between 2.778-2.786 depending on the manufacturer. FWIW, C5/C6 wheels have 70.3mm center bores so don't assume that they're the same as the rotors.

As for the flange diameter of the hubs, we cut ours to 5.94" with a .12 x 45 degree chamfer on the face. This maximizes the material around the wheel studs which gives more options with respect to wheel stud knurl diameters and fits in all known C5 and/or C6 front rotors. The C6 rotors are less forgiving due to their being a heat dam design, so we size for the worst case scenario to maintain universal fitment as much as possible.

Tobin
KORE3

[ryeguy2006a]

Ok, great that is just the info that I needed.

[csouth]

I know the OP's question has been answered. I have a GM A body with tall spindles, so I was wondering what you would use to cut the rotors back? Plan on buying the brake kit from KORE3, but if I could save the money on hubs that would be great.

[prosuperstar]

your gonna have to use a lathe to get the outside diameter correct and concentric

[csouth]

Isn't the lathe used at the end to get the precise cutting?

[John Wright]

Here's what a 3rd gen Camaro rotor looks like when I had 2 of them turned down to make hubs for my 2nd gen camaro. Chucked it up and used a parting tool to remove the rotor from the hub.

https://static1.pt-content.com/images/pt/2010/04/C5hub-1.jpg

https://static1.pt-content.com/images/pt/2011/09/C5hub2-1.jpg

https://static1.pt-content.com/images/pt/2009/10/C5hub11-1.jpg

[80 MONZTA]

I know the OP's question has been answered. I have a GM A body with tall spindles, so I was wondering what you would use to cut the rotors back? Plan on buying the brake kit from KORE3, but if I could save the money on hubs that would be great.

I have a bench top size lathe and could not chuck up a whole S-10 rotor in it, so I used a 4 1/2" angle grinder with a 1/16" thick cutting wheel to slice off the rotor section from the hub. Looked the same as John Wright's pic's (well, except they were junk-yard rotors and had typical angle grinder cuts instead of nice and smooth). :razz:
After the parts are separated, then you need to have them finished in a lathe. Before I cut mine apart, I asked someone with a brake lathe if he could do this for me. He said he could probably do it, but was extremely nervous about the rotor section spinning and damaging his machine as it broke free. That is when I decided to just break out the angle grinder and do it myself.

[a67]

Another method of removing the rotor from the hub is to drill a series of holes. IIRC, used a drill bit around 1/4" and when done gently whacked the rotor with a hammer. Being cast it easily cracked between the holes and the rotor section fell off.

Then finished up in the lathe.

Bob.

[csouth]

Thanks guys, you've all been a great help. Buying parts and installing is easy, but doing it this way will save me some money and teach me some things...