930 front rotor bolt circle dimensions

[Harpo]

Can someone please tell me the bolt circle dimensions for the 930 front rotors? I want to make my own flat hat adapters.

Thanks

David

[Harpo]

I know the ID = 4.21 and the inner bolt circle is 4.96 with 5 holes. I have guessed on the OD of 7.0 and the outer bolt circle of 6.5 with 12 holes

[Harpo]

Can someone please tell me what the parts numbers are for the front & rear rotors I need for my 74?

Thanks

David

[Harpo]

Early or late?

[winders]

The custom hats I have on my race car use these rotors:

https://www.racecareng.com/item/1587482-60-vane-brake-rotor-rh-j-hook-125-1175?category=72152&brand=10615

They are an 8 x 7" bolt pattern that is pretty standard.

[winders]

I posted that because most people that do custom hats end up using the 8 x 7" pattern because there is a much larger selection of rotors available for that pattern.

[Harpo]

OK this is what I came up with. I will water jet the hat (flat) and wait for the rotors to arrive and hopefully I didn't screw this up.

[winders]

It's 8 holes on a 7" circle. That is 7 holes....

[Harpo]

After many operator and computer errors hopefully this will work

[winders]

Check out this thread:

Brake Rotor Hat Design Q's

[Harpo]

Thanks Scott good info. He is obviously way better at CAD than I

[Harpo]

This is a press in nut. Not to be confused with a riv nut. This is a class 10 nut with an HRC of 36. I didn't want a loose nut. The serrations and the clampload prevent the nut from turning (in theory).

[winders]

Why are you putting the nuts in the hat? I would think it would be better to use discreet nuts so they can be easily replaced as required.

[Harpo]

Scott, what is a discreet nut?

[winders]

A separate nut not attached to anything.

[Essexmetal]

Those look like prevailing torque (self locking) spline nuts. As with Scott I am a fan of a nut and bolt. With hats and rotors, whether floating or fixed I use K Nuts. They are light, strong, self locking and can handle the heat. Never had an issue with heat cycles loosening the clamp load, guess that is shared by having an equal quality bolt.

Unless Harpo makes some fresh hats he is stuck with this layout. I do not see any problems with it but would stay on top bolt torque if running some track days.

Harpo since it looks like all diameters are waterjet how tight is the pilot diameter for the hub and rotor ?

[Harpo]

I had made 6 of these hats so if this is a mistake I have others. This is just for the street so I don't expect the heat to be a problem. The fit to the hub is very tight.

I went with a full body bolt so there is no slop between the rotor and bolt and with this design the nut wont be moving either. I was looking for max shear and no movement within the entire assembly. I'm also planning on putting this nut in the hub so I can eliminate the loose nut there as well.

[winders]

I think that is a mistake. I don’t know of any hats that use nuts fixed in place. If it were a good idea, everyone would be doing it....

[Harpo]

The early 930 had a plate with internal threads

[bkreigsr]

Originally Posted by Harpo

The early 930 had a plate with internal threads

...never seen that. The early 930's came with 911 S calipers.

All the PET catalogs show the hats with nuts and bolts - floating or fixed.